ES2727860T3 - Outside machine cooling device - Google Patents

Abstract

An outdoor unit of a refrigeration system, the outdoor unit comprising: a multi-stage compressor (20, 150) that includes a plurality of compression mechanisms (21-24, 151, 152) connected in series, in which the refrigerant discharged from one of the low stage compression mechanisms (21, 22, 23, 151) is aspirated and compressed into one of the high stage compression mechanisms (22, 23, 24, 152); an intermediate heat exchanger (41, 42, 43, 161) located between two of the adjacent compression mechanisms (21, 22, 23, 24, 151, 152) and configured to cause the refrigerant to flow from the compression mechanism ( 21, 22, 23, 151) from low stage to the high stage compression mechanism (22, 23, 24, 152) to exchange heat with outside air to be cooled; an external heat exchanger (44, 162) configured to cause the refrigerant discharged from the compression mechanism (24, 152) of the highest stage to exchange heat with outside air; and a housing (121, 163) having a lateral surface on which an air intake port (123, 164) and an upper surface on which an air outlet (124, 165) is provided, and which it houses the compression mechanisms (21-24, 151, 152), the intermediate heat exchanger (41, 42, 43, 161) and the external heat exchanger (44, 162), where the intermediate heat exchanger (41 , 42, 43, 161) and the external heat exchanger (44, 162) are arranged along the suction port (123, 164) of the housing (121, 163), and the external heat exchanger (44, 162) is located above all intermediate heat exchangers (41, 42, 43, 161).

Description

DESCRIPTION

Outside machine cooling device

Technical field

Prior art

The present invention relates to outdoor units of refrigeration systems, and in particular to a refrigeration system that performs a refrigeration cycle of a multi-stage compression type.

An air conditioner that performs a two-stage compression refrigeration cycle by using carbon dioxide as a refrigerant as described in Patent Document 1 is known as a refrigeration system that performs a multiple compression refrigeration cycle. stages through the use of refrigerant that is activated in a supercritical region. In this air conditioner, the refrigerant discharged from a compression element in a previous stage is cooled in an intermediate cooler to be sucked into a compression element in a subsequent stage, so that the temperature of the refrigerant discharged from the element is reduced compression of the subsequent stage and, therefore, the heat dissipation loss in an external heat exchanger is reduced.

In an air conditioner described in Patent Document 1, as illustrated in Figure 20, an intermediate cooler (a) and a heat exchanger (b) on the side of the heat source are housed in a source unit of heat (c). The intermediate cooler (a) and the heat exchanger (b) on the side of the heat source are arranged on a side surface of the heat source unit (c). The intermediate cooler (a) is located above the heat exchanger (b) on the side of the heat source. A fan on the side of the heat source is provided above the intermediate cooler (a).

In Patent Document 2 an outdoor unit of an air conditioner is described. The outdoor unit of the over-blown air conditioner has a box-shaped body and is equipped with an apparatus such as a compressor disposed on the lower body plate and a blower installed in the body such that it is located in front of a hole formed on the surface of the body, the three complete side faces of the body and the upper part of the other side face being provided with suction holes, respectively, and heat exchangers being provided within the body along them.

Appointment List

Patent Document

[Patent Document 1] Japanese Unexamined Patent Publication No. 2009-150641

[Patent document 2] JP 2003279076 A

Compendium of the invention

Technical problem

In the heat source unit (c) of Patent Document 1 configured to aspirate air from the side and blow the air upward, that is, from a so-called upward blow type, the air flow rate is higher in a higher position than in a lower position, as illustrated in Figure 21, and, therefore, the intermediate cooler (a) located in a higher position has a high heat exchange efficiency. Therefore, the heat source unit (c) can be reduced in size by placing the intermediate cooler (a) in an upper position.

Since the pressure of the refrigerant flowing through the intermediate cooler (a) is lower than that of the refrigerant flowing through the heat exchanger (b) on the side of the heat source, the density of the refrigerant flowing through the intermediate cooler (a) is less than that of the refrigerant flowing through the heat exchanger (b) on the side of the heat source. Therefore, as long as the mass flow rates of the refrigerant flowing through the intermediate cooler (a) and the heat exchanger (b) on the side of the heat source are approximately equal, the volumetric flow rate of the refrigerant flowing through the intermediate cooler (a) is greater than that of the refrigerant flowing through the heat exchanger (b) on the side of the heat source. Even when the number of refrigerant paths is approximately identical in the intermediate cooler (a) and in the heat exchanger (b) on the heat source side, the flow rate of the refrigerant flowing through the intermediate cooler (a) is greater than that of the refrigerant flowing through the heat exchanger (b) on the side of the heat source and, therefore, the loss of refrigerant pressure in the intermediate cooler (a) is greater than in the heat exchanger (b) on the side of the heat source.

As described above, reducing the size of the intermediate cooler (a) to reduce the number of refrigerant paths has a problem of a large loss of refrigerant pressure in the intermediate cooler (a). On the other hand, an increase in the size of the intermediate cooler (a) in order to reduce an increase in the pressure loss of the refrigerant also has the problem of an increase in the size of the heat source unit (c).

Therefore, an object of the present invention is to reduce an increase in size of a heat source unit with a reduced degree of increased loss of refrigerant pressure in an intermediate cooler.

Solution to the problem

In accordance with the present invention, in an outdoor unit of a cooling system, an outdoor heat exchanger (44, 162) is located above all intermediate heat exchangers (41, 42, 43, 161).

In a first aspect of the present invention, an outdoor unit of a refrigeration system includes: a multi-stage compressor (20, 150) that includes a plurality of compression mechanisms (21-24, 151, 152) connected in series, in which the refrigerant discharged from one of the low stage compression mechanisms (21, 22, 23, 151) is aspirated and compressed into one of the high stage compression mechanisms (22, 23, 24, 152); an intermediate heat exchanger (41, 42, 43, 161) located between two of the adjacent compression mechanisms (21, 22, 23, 24, 151, 152) and configured to cause the refrigerant to flow from the compression mechanism ( 21, 22, 23, 151) of low stage to the compression mechanism (22, 23, 24, 152) of high stage to exchange heat with outside air to be cooled; an external heat exchanger (44, 162) configured to cause the refrigerant discharged from the compression mechanism (24, 152) of the highest stage to exchange heat with outside air; and a housing (121, 163) having a lateral surface on which an air intake port (123, 164) and an upper surface on which an air outlet (124, 165) is provided, and which it houses the compression mechanisms (21-24, 151, 152), the intermediate heat exchanger (41, 42, 43, 161) and the external heat exchanger (44, 162). In this outdoor unit, the intermediate heat exchanger (41, 42, 43, 161) and the external heat exchanger (44, 162) are arranged along the suction port (123, 164) of the housing (121, 163), and the external heat exchanger (44, 162) is located above all intermediate heat exchangers (41, 42, 43, 161).

In the first aspect, in the multi-stage compressor (20, 150), the refrigerant discharged from the low-stage compression mechanism (21, 22, 23, 151) is aspirated and compressed into the compression mechanism (22, 23 , 24, 152) high stage. The intermediate heat exchanger (41, 42, 43, 161) is located between two adjacent compression mechanisms (21, 22, 23, 24, 151, 152) of the compression mechanisms (21-24, 151, 152) and is configured to cause the refrigerant to flow from the low stage compression mechanism (21, 22, 23, 151) to the high stage compression mechanism (22, 23, 24, 152) to exchange heat with outside air that has of being cooled The external heat exchanger (44, 162) causes the refrigerant discharged from the compression mechanism (24, 152) of the highest stage to exchange heat with outside air.

The housing (121, 163) has the lateral surface, on which the air intake port (123, 164) is provided, and the upper surface, on which the air outlet (124, 165) is provided, and it houses the compression mechanisms (21-24, 151, 152), the intermediate heat exchanger (41, 42, 43, 161) and the external heat exchanger (44, 162). In the housing (121, 163), the external heat exchanger (44, 162) and the intermediate heat exchanger (41, 42, 43, 161) are arranged along the suction port (123, 164), and The external heat exchanger (44, 162) is located above the intermediate heat exchanger (41, 42, 43, 161).

The air taken in the housing (121, 163) from the suction port (123, 164) is subjected to heat exchange in the intermediate heat exchanger (41,42, 43, 161) and the external heat exchanger (44 , 162), flows into the upper space in the housing (121, 163) and is expelled through the air outlet (124, 165).

Here, the outdoor unit of this aspect is of a so-called upward blow type, in which air is drawn from the suction port (123, 164) on the side surface and blown up from the air outlet (124, 165). Therefore, the velocity of the air flow is greater in an upper part of the aspiration port (123, 164) than in a lower part of the aspiration port (123, 164). The pressure of the refrigerant flowing through the intermediate heat exchanger (41, 42, 43, 161) is lower than that of the refrigerant flowing through the external heat exchanger (44, 162) and, therefore, the density of the refrigerant in the intermediate heat exchanger (41, 42, 43, 161) is lower than that of the refrigerant in the external heat exchanger (44, 162). In view of this, when the mass flow rate of the refrigerant flowing through the intermediate heat exchanger (41, 42, 43, 161) is substantially equal to that of the refrigerant flowing through the external heat exchanger (44, 162), the flow rate Volumetric of the refrigerant in the intermediate heat exchanger (41, 42, 43, 161) is greater than that of the refrigerant in the external heat exchanger (44, 162). Even when the number of refrigerant paths in the intermediate heat exchanger (41, 42, 43, 161) is equal to that of the external heat exchanger (44, 162), the flow rate of the refrigerant flowing through the heat exchanger intermediate (41, 42, 43, 161) is greater than that of the refrigerant flowing through the external heat exchanger (44, 162) and, therefore, the loss of pressure of the refrigerant in the intermediate heat exchanger (41, 42, 43, 162) is greater than the loss of refrigerant pressure in the external heat exchanger (44, 162).

The external heat exchanger (44, 162) located in an upper part of the housing (121, 163), where the air flow rate is high, has a high heat exchange efficiency and can be reduced in size. On the other hand, the intermediate heat exchanger (41,42, 43, 161) located in a lower part of the housing (121, 163), where the air flow rate is low, has a low heat exchange efficiency . Therefore, to increase the Heat exchange amount, the intermediate heat exchanger (41,42, 43, 161) must be larger than in the case where this exchanger is located at an upper part.

For this reason, the size of the outdoor unit does not increase even if the size of the outdoor heat exchanger (44, 162) and the intermediate heat exchanger (41, 42, 43, 161) increases.

An increase in the size of the intermediate heat exchanger (41, 42, 43, 161) increases the number of refrigerant paths in the intermediate heat exchanger (41, 42, 43, 161). Therefore, in the intermediate heat exchanger (41, 42, 43, 161), the flow rate of the refrigerant in each refrigerant path decreases, resulting in a decrease in the loss of pressure of the refrigerant passing through the refrigerant travel The flow rate of the refrigerant flowing through the intermediate heat exchanger (41,42, 43, 161) is originally high and, therefore, a decrease in the flow rate due to an increase in the number of refrigerant paths produces a relatively large reduction in pressure loss.

On the other hand, a reduction in the size of the external heat exchanger (44, 162) reduces the number of refrigerant paths in the external heat exchanger (44, 162). Reducing the number of refrigerant paths increases the flow rate of the refrigerant in each refrigerant path, increasing the loss of pressure of the refrigerant that passes through the refrigerant path.

However, since the flow rate of the refrigerant flowing through the external heat exchanger (44, 162) is originally low, a certain degree of increase in the flow rate due to the reduction in the number of refrigerant paths causes Relatively small increase in pressure loss resulting from increased flow rate.

Therefore, by arranging the external heat exchanger (44, 162) above the intermediate heat exchanger (41, 42, 43, 161), the loss of refrigerant pressure in the intermediate heat exchanger (41, 42) can be reduced , 43, 161) with a reduced degree of increase in the size of the outdoor unit.

In a second aspect, in the outdoor unit of the first aspect, the multi-stage compressor (20) includes three or more compression mechanisms (21-24), the intermediate heat exchanger includes a plurality of intermediate heat exchangers (41, 42, 43) and the intermediate heat exchanger (43) of the highest stage is located above the other intermediate heat exchangers (41, 42) and below the external heat exchanger (44).

In the second aspect, the multi-stage compressor (20) includes the three or more compression mechanisms (21 24), and the refrigerant discharged from the low-stage compression mechanism (21, 22, 23) is aspirated and compressed into the high stage compression mechanism (22, 23, 24). Therefore, the intermediate heat exchanger includes the plurality of intermediate heat exchangers (41, 42, 43), the intermediate heat exchanger (43) of the highest stage being located above the other intermediate heat exchangers ( 41, 42) and below the external heat exchanger (44).

The pressure of the refrigerant flowing through the intermediate heat exchanger (43) of the highest stage is higher than that of the refrigerant flowing through the other intermediate heat exchangers (41, 42) and, therefore, the refrigerant densities in the other intermediate heat exchangers (41, 42) they are lower than that of the refrigerant in the intermediate heat exchanger (43) of the highest stage. In view of this, when the mass flow rates of the refrigerant flowing through the other intermediate heat exchangers (41, 42) are substantially equal to those of the refrigerant flowing through the intermediate heat exchanger (43) of the highest stage, the Volumetric flow rates of the refrigerant in the other intermediate heat exchangers (41, 42) are greater than that of the refrigerant in the intermediate heat exchanger (43) of the highest stage. Even when the number of refrigerant paths in each of the other intermediate heat exchangers (41, 42) is equal to that of the intermediate heat exchanger (43) of the highest stage, the flow rates of the refrigerant flowing through the other intermediate heat exchangers (41,42) are higher than that of the refrigerant flowing through the intermediate heat exchanger (43) of the highest stage and, therefore, the pressure losses of the refrigerant in the other heat exchangers Intermediate heat (41,42) are greater than that of the intermediate heat exchanger (43) of the highest stage.

The high-stage intermediate heat exchanger (43) located in an upper part of the housing (121), where the air flow rate is high, has a high heat exchange efficiency and can be reduced in size. On the other hand, the other intermediate heat exchangers (41, 42) located in a lower part of the housing (121), where the air flow rate is low, have low heat exchange efficiencies. Therefore, to increase the amount of heat exchange, the other intermediate heat exchangers (41, 42) must be larger than in the case where these heat exchangers are located at a top.

For this reason, the size of the outdoor unit does not increase even if the size of the high-stage intermediate heat exchanger (43) and the other intermediate heat exchangers (41, 42) increases.

An increase in the size of the other intermediate heat exchangers (41, 42) increases the number of refrigerant paths in the other intermediate heat exchangers (41, 42). Therefore, in the other intermediate heat exchangers (41, 42), the flow rate of the refrigerant at each refrigerant path decreases, giving as a result a decrease in the loss of pressure of the refrigerant that passes through the refrigerant path. The flow rate of the refrigerant flowing through the other intermediate heat exchangers (41, 42) is originally high and, therefore, a decrease in the flow rate due to an increase in the number of refrigerant paths produces a relatively reduced big pressure loss.

On the other hand, a reduction in the size of the high stage intermediate heat exchanger (43) reduces the number of refrigerant paths in the high stage intermediate heat exchanger (43). Reducing the number of refrigerant paths increases the flow rate of the refrigerant in each refrigerant path, increasing the loss of pressure of the refrigerant that passes through the refrigerant path.

However, since the flow rate of the refrigerant flowing through the high-stage intermediate heat exchanger (43) is originally low, a certain degree of flow rate increase due to the reduction in the number of refrigerant paths causes a relatively small increase in pressure loss resulting from the increase in flow rate.

Therefore, by arranging the high-stage intermediate heat exchanger (43) above the other intermediate heat exchangers (41,42), the loss of refrigerant pressure in the other intermediate heat exchangers (41, 42) is It can reduce with a reduced degree of increase in the size of the outdoor unit.

In a third aspect, in the outdoor unit of the second aspect, the intermediate heat exchangers (41, 42, 43) are stacked from the bottom in order of increasing pressure of the inlet refrigerant.

In the third aspect, the intermediate heat exchangers (41, 42, 43) are stacked from the bottom in order of increasing pressure of the inlet refrigerant.

The density of the refrigerant in the intermediate heat exchanger (42), where the inlet refrigerant has a high pressure, is greater than that of the intermediate heat exchanger (41), where the inlet refrigerant has a low pressure. Therefore, when the mass flow rate of the refrigerant flowing through the low pressure intermediate heat exchanger (41) is substantially equal to that of the refrigerant flowing through the high pressure intermediate heat exchanger (42), the volumetric flow rate of the refrigerant in the intermediate heat exchanger (42) of low pressure is higher than that of the refrigerant in the intermediate heat exchanger (42) of high pressure. Even when the number of refrigerant paths in the low pressure intermediate heat exchanger (41) is equal to that of the high pressure intermediate heat exchanger (42), the flow rate of the refrigerant flowing through the intermediate heat exchanger ( 41) low pressure is greater than that of the refrigerant flowing through the high pressure intermediate heat exchanger (42) and, therefore, the loss of refrigerant pressure in the low pressure intermediate heat exchanger (41) is greater than that of the refrigerant in the high pressure intermediate heat exchanger (42).

The high pressure intermediate heat exchanger (42) located in an upper part of the housing (121), where the air flow rate is high, has a high heat exchange efficiency and can be reduced in size. On the other hand, the low pressure intermediate heat exchanger (41) located in a lower part of the housing (121), where the air flow rate is low, has a low heat exchange efficiency. Therefore, to increase the amount of heat exchange, the low pressure intermediate heat exchanger (41) must be larger than in the case where this exchanger is located at a top.

For this reason, the size of the outdoor unit does not increase even if the size of the high pressure intermediate heat exchanger (42) and the low pressure intermediate heat exchanger (41) increases.

An increase in the size of the low pressure intermediate heat exchanger (41) increases the number of refrigerant paths in the low pressure intermediate heat exchanger (41). Therefore, in the low pressure intermediate heat exchanger (41), the flow rate of the refrigerant in each refrigerant path decreases, resulting in a decrease in the pressure loss of the refrigerant passing through the refrigerant path . The flow rate of the refrigerant flowing through the low pressure intermediate heat exchanger (41) is originally high and, therefore, a decrease in the flow rate due to an increase in the number of refrigerant paths produces a relatively reduced big pressure loss.

On the other hand, a reduction in the size of the high pressure intermediate heat exchanger (42) reduces the number of refrigerant paths in the high pressure intermediate heat exchanger (42). Reducing the number of refrigerant paths increases the flow rate of the refrigerant in each refrigerant path, increasing the loss of pressure of the refrigerant that passes through the refrigerant path.

However, since the flow rate of the refrigerant flowing through the high-pressure intermediate heat exchanger (42) is originally low, a certain degree of flow rate increase due to the reduction in the number of refrigerant paths causes a relatively small increase in pressure loss resulting from the increase in flow rate.

Therefore, by arranging the high pressure intermediate heat exchanger (42) above the low pressure intermediate heat exchanger (41), the loss of refrigerant pressure in the low pressure intermediate heat exchanger (41) can be reduce with a reduced degree of increase in the size of the outdoor unit.

In a fourth aspect, in the outdoor unit of one of the first to third aspects, the intermediate heat exchanger (41, 42, 43, 161) includes a plurality of flat tubes (231) that are arranged in the upward direction and down with their side surfaces facing each other, and each of them includes a plurality of fluid passages (232) extending in the longitudinal direction of the tube, and also includes a plurality of fins (235, 235) that divide the space between adjacent flat tubes (231) in a plurality of air passages through which air flows.

In the fourth aspect, the plurality of flat tubes (231) and the plurality of fins (235, 235) are provided. The fins (235, 235) are disposed between the flat tubes (231) arranged in the upward and downward direction. In the intermediate heat exchanger (41,42, 43, 161), the air passes between the flat tubes (231) arranged in the up and down direction, and exchanges heat with the fluid flowing through the fluid passages ( 232) in the flat tubes (231).

The intermediate heat exchanger (41, 42, 43, 161) has a small loss of stacking (ventilation resistance) and, therefore, has a high velocity of the air flowing through it. In addition, flat tubes (231) increase the heat transfer area of the refrigerant and, therefore, the heat exchange efficiency of the refrigerant increases. Consequently, the coefficient of performance (COP) of the cooling system can be improved. Since the flat tubes (231) have smaller pipe diameters than those of conventional heat exchanger tubes, the flow rate in the tubes increases. Therefore, the refrigerant that passes through the fluid passage (232) has a great loss of pressure.

However, the intermediate heat exchanger (41, 42, 43, 161) located at the bottom of the housing (121, 163), where the air flow rate is low, has a low heat exchange efficiency. Therefore, to increase the amount of heat exchange, the intermediate heat exchanger (41, 42, 43, 161) is larger than in the case where the exchanger is located at an upper part. The larger intermediate heat exchanger (41, 42, 43, 161) includes a greater number of refrigerant paths (232) and, therefore, the flow rate of the refrigerant in the refrigerant paths (232) of the heat exchanger Intermediate heat (41, 42, 43, 161) decreases, thus reducing the pressure loss of the refrigerant that occurs when the refrigerant passes through the refrigerant paths (232).

Consequently, the reduction in the pipe diameter of the flat tubes (231) relatively reduces the degree of increase in the pressure loss of the refrigerant.

In a fifth aspect, in the outdoor unit of the fourth aspect, the external heat exchangers (44, 162) include a plurality of flat tubes (231) that are arranged in the upward and downward direction with their lateral surfaces facing each other , and each of them includes a plurality of fluid passages (232) that extend in the longitudinal direction of the tube, and also include a plurality of fins (235, 235) that divide the space between adjacent flat tubes (231) in a plurality of air passages through which air flows.

In the fifth aspect, the plurality of flat tubes (231) and the plurality of fins (235, 235) are provided. The fins (235, 235) are disposed between the flat tubes (231) arranged in the upward and downward direction. In the external heat exchanger (44, 162), the air passes between the flat tubes (231) arranged up and down, and exchanges heat with the fluid flowing through the fluid passages (232) in the flat tubes ( 231).

The external heat exchanger (44, 162) has a small loss of stacking and, therefore, has a high velocity of the air flowing through it. In addition, flat tubes (231) increase the heat transfer area of the refrigerant and, therefore, the heat exchange efficiency of the refrigerant increases. Consequently, the coefficient of performance (COP) of the cooling system is improved. Since the flat tubes (231) have smaller pipe diameters than those of conventional heat exchanger tubes, the flow rate in the tubes increases. Therefore, the refrigerant that passes through the fluid passages (232) has a great loss of pressure.

However, since the flow rate of the refrigerant flowing through the external heat exchangers (44, 162) is originally low, a certain degree of increase in the flow rate due to a decrease in the pipe diameters causes a Relatively small increase in pressure loss resulting from increased flow rate.

Advantages of the invention

In the first aspect, since the external heat exchanger (44, 162) is located in the upper part of the housing (121, 163), where the air flow rate is high, the efficiency of heat exchange can be increased. heat of the external heat exchanger (44, 162). In addition, as the external heat exchanger (44, 162), which has a low coolant flow rate, is located at the top of the housing (121, 163), where the air flow rate is high, the size of the external heat exchanger (44, 162) can be reduced without increasing the loss of refrigerant pressure.

On the other hand, the intermediate heat exchanger (41, 42, 43, 161) is located in the lower part of the housing (121, 163), where the air flow rate is low, to increase the number of paths of refrigerant, which ensures the prevention of increased loss of refrigerant pressure in the intermediate heat exchanger (41, 42, 43 and 161).

In the configuration described above, the external heat exchanger (44, 162), in which the loss of refrigerant pressure does not increase easily, is located at the top to reduce the size, which reduces the loss of refrigerant pressure in the intermediate heat exchanger (41, 42, 43, 161) with a small increase in the size of the outdoor unit.

In the second aspect, since the intermediate heat exchanger (43) of the highest stage is located in the upper part of the housing (121), where the air flow rate is high, the exchange efficiency can be increased of heat of the intermediate heat exchanger (43) of the highest stage. In addition, since the intermediate heat exchanger (43) of the highest stage, which has a low coolant flow rate, is located at the top of the housing (121), where the air flow rate is high, the size of the intermediate heat exchanger (43) of the highest stage can be reduced without increasing the loss of refrigerant pressure.

On the other hand, the other heat exchangers (41, 42) that have high coolant flow rates are located at the bottom of the housing (121), where the air flow rate is low, to increase the number of coolant paths, which ensures the prevention of an increase in coolant pressure loss in the other intermediate heat exchangers (41, 42).

In the configuration described above, the intermediate heat exchanger (43) of the highest stage, in which the loss of refrigerant pressure does not increase easily, is located at the top to reduce the size, which reduces the loss of coolant pressure in the other intermediate heat exchangers (41, 42) with a small increase in the outdoor unit.

In the third aspect, since the high pressure intermediate heat exchanger (42) is located in the upper part of the housing (121), where the air flow rate is high, the heat exchange efficiency can be increased of the high pressure intermediate heat exchanger (42). In addition, since the high pressure intermediate heat exchanger (42), which has a low refrigerant flow rate, is located at the top of the housing (121), where the air flow rate is high, the size The high pressure intermediate heat exchanger (42) can be reduced without increasing the loss of refrigerant pressure.

On the other hand, the low-pressure intermediate heat exchanger (41), which has a high coolant flow rate, is located at the bottom of the housing (121), where the air flow rate is low, for increase the number of coolant paths, which ensures the prevention of an increase in the loss of coolant pressure in the low-pressure intermediate heat exchanger (41).

In the configuration described above, the high pressure intermediate heat exchanger (42), in which the loss of refrigerant pressure does not increase easily, is located at the top to reduce the size, which reduces the pressure loss of the coolant in the low pressure intermediate heat exchanger (41) with a small increase in the outdoor unit.

In the fourth aspect, the plurality of flat tubes (231), in which the plurality of fluid passages (232), and the plurality of fins (235, 235) are provided, thus reducing the loss of stacking. Therefore, the flow rate of the air flowing through the air passages increases. In addition, the flat tubes (231) increase the heat transfer area of the refrigerant and, therefore, the heat exchange efficiency of the refrigerant can be increased. Consequently, the coefficient of performance (COP) of the cooling system can be improved.

In the fifth aspect the plurality of flat tubes (231) are provided, in which the plurality of fluid passages (232), and the plurality of fins (235, 235) are provided, thus reducing the loss of stacking. Therefore, the flow rate of the air flowing through the air passages increases. In addition, the flat tubes (231) increase the heat transfer area of the refrigerant and, therefore, the heat exchange efficiency of the refrigerant can be increased. Consequently, the coefficient of performance (COP) of the cooling system can be improved.

Brief description of the drawings

Figure 1 is a diagram of a pipe system illustrating the cooling operation of a refrigerant circuit according to a first embodiment.

Figure 2 is a Mollier diagram of the refrigerant circuit of the first embodiment.

Figure 3 illustrates an outdoor unit according to the first embodiment.

Figure 4 is a top view schematically illustrating the outdoor unit of the first embodiment.

Figure 5 is a cross-sectional view taken along the line V-V in Figure 4.

Figure 6 illustrates a distribution of the air flow velocity in an outer housing according to the first embodiment.

Figure 7 is a diagram of a pipe system illustrating the heating operation of the refrigerant circuit of the first embodiment.

Figure 8 is a diagram of a pipe system illustrating the cooling operation of a refrigerant circuit according to a second embodiment.

Figure 9 is a Mollier diagram of the refrigerant circuit of the second embodiment.

Figure 10 is a diagram of a pipe system illustrating the cooling operation of a refrigerant circuit according to a third embodiment.

Figure 11 is a Mollier diagram of the refrigerant circuit of the third embodiment.

Figure 12 illustrates an outdoor unit according to the third embodiment.

Figure 13 is a diagram of a pipe system illustrating the heating operation of the refrigerant circuit of the third embodiment.

Figure 14 schematically illustrates an outdoor unit according to a variation of the third embodiment. Figure 15 is an enlarged view of flat tubes and fins of a heat exchanger according to the variation of the third embodiment.

Figure 16 schematically illustrates an outdoor unit according to another embodiment.

Figure 17 is an enlarged view of flat tubes and fins of a heat exchanger according to the other embodiment.

Figures 18A and 18B schematically illustrate a configuration of an outdoor unit according to a reference example, where Figure 18A illustrates an exemplary arrangement of an outdoor heat exchange unit, and Figure 18B illustrates a flow velocity distribution of air from the outdoor heat exchange unit. Figure 19 is a cross-sectional view illustrating an outdoor heat exchange unit according to the reference example.

Figure 20 illustrates an outdoor unit according to a conventional example.

Figures 21A and 21B schematically illustrate a configuration of the outdoor unit of the conventional example, where Figure 21A illustrates an exemplary arrangement of an outdoor heat exchange unit, and Figure 21B illustrates a distribution of the air flow velocity of the outdoor heat exchange unit.

Description of realizations

Embodiments of the present invention will now be described in detail with reference to the drawings. <First realization>

-Air conditioner refrigerant circuit -As illustrated in Figure 1, an air conditioner (1) according to the first embodiment will be described. The air conditioner (1) includes a refrigerant circuit (10) in which a refrigerant flow is allowed to change reversibly, and can change between the cooling operation and the heating operation. The air conditioner (1) includes an outdoor unit (3) located outside and an indoor unit (2) located inside. The refrigerant circuit (10) of the air conditioner (1) is obtained by connecting an outdoor circuit (11) of the outdoor unit (3) and an indoor circuit (12) of the indoor unit (2) to each other through a communication pipe (13) on the gas side and a communication pipe (14) on the liquid side. The refrigerant circuit (10) is filled with carbon dioxide (hereinafter referred to as refrigerant) and is configured to perform a supercritical refrigeration cycle by multi-stage compression by circulating refrigerant through the refrigerant circuit (10).

<External circuit>

As illustrated in Figure 1, the external circuit (11) is connected to a four-stage compressor (20), an external heat exchange unit (40), from a first to a fourth four-way valve (93, 94, 95, 96), from a first to a third subcooling heat exchanger (100, 101, 102) from a first to a fifth valve expansion (80-84), an expander (87) and a gas-liquid separator (88). The external heat exchange unit (40) includes a first to a third intermediate heat exchanger (41, 42, 43) and an external heat exchanger (44).

In this embodiment, the external heat exchanger (44) corresponds to an external heat exchanger of the present invention, and the first to third intermediate heat exchangers (41, 42, 43) are intermediate heat exchangers of the present invention. The first and second intermediate heat exchangers (41,42) are other intermediate heat exchangers of the present invention, and the third intermediate heat exchanger (43) is an intermediate heat exchanger of the highest stage of the present invention.

The external circuit (11) is also connected to four oil separators (89, 90, 91, 92), a distributor (18), a capillary tube (15), a bridge circuit (17) and check valves (CV1- CV13).

In the first embodiment, the refrigerant circuit (10) switches between the cooling operation and the heating operation by switching the four-way valves (93, 94, 95, 96) first to the fourth.

The four-stage compressor (20) includes a first to a fourth compressor (21, 22, 23, 24) and corresponds to a multi-stage compressor of the present invention. The compressors (21, 22, 23, 24) are connected to discharge pipes (25, 26, 27, 28) first to fourth by their discharge sides, while they are connected to aspiration pipes (29, 30, 31, 32) first to fourth on its suction sides. Each of the compressors (21, 22, 23, 24) compresses a gaseous refrigerant aspirated through one of the associated suction pipes (29, 30, 31, 32) to a predetermined pressure, and discharges this refrigerant from one of the discharge pipes (25, 26, 27, 28) associated.

The first four-way valve (93) has its first port connected to the first discharge pipe (25) of the first compressor (21), its second port connected to one end of a splice pipe (67), its third connected port to one end of the first intermediate heat exchanger (41), and its fourth port connected to the second suction pipe (30) of the second compressor (22). The first four-way valve (93) is switched between a first state (a state indicated by a continuous line in Figure 1), in which the first port communicates with the third port and the second port communicates with the fourth port, and a second state (a state indicated by a dashed line in Figure 1), in which the first port communicates with the fourth port and the second port communicates with the third port.

The second four-way valve (94) has its first port connected to the second discharge pipe (26) of the second compressor (22), its second port connected to a midpoint of the splice pipe (67), its third port connected to one end of the second intermediate heat exchanger (42), and its fourth port connected to the third suction pipe (31) of the third compressor (23). The second four-way valve (94) is switched between a first state (a state indicated by a continuous line in Figure 1), in which the first port communicates with the third port and the second port communicates with the fourth port, and a second state (a state indicated by a dashed line in Figure 1), in which the first port communicates with the fourth port and the second port communicates with the third port.

The third four-way valve (95) has its first port connected to the third discharge pipe (27) of the third compressor (23), its second port connected to a midpoint of the splice pipe (67), its third port connected to one end of the third intermediate heat exchanger (43), and its fourth port connected to the fourth suction pipe (32) of the fourth compressor (24). The third four-way valve (95) is switched between a first state (a state indicated by a continuous line in Figure 1), in which the first port communicates with the third port and the second port communicates with the fourth port, and a second state (a state indicated by a dashed line in Figure 1), in which the first port communicates with the fourth port and the second port communicates with the third port.

The fourth four-way valve (96) has its first port connected to the fourth discharge pipe (28) of the fourth compressor (24), its second port connected to one end of the connection pipe (66), its third connected port to one end of the external heat exchanger (44) and its fourth port connected to the communication pipe (13) on the gas side. The fourth four-way valve (96) is switched between a first state (a state indicated by a continuous line in Figure 1), in which the first port communicates with the third port and the second port communicates with the fourth port, and a second state (a state indicated by a dashed line in Figure 1), in which the first port communicates with the fourth port and the second port communicates with the third port.

The check valves (CV1, CV2, CV3) are connected to midpoints of the suction pipes (30, 31, 32) second to fourth. Each of the check valves (CV1, CV2, CV3) allows the refrigerant to flow from the first to third four-way valves (93, 94, 95) to the four-stage compressor (20), and prevents the refrigerant flow in the opposite direction.

The oil separators (89, 90, 91, 92) are connected to midpoints of the discharge pipes (25, 26, 27, 28) first to the fourth, respectively. The oil separators (89, 90, 91, 92) are used to separate the lubricating oil contained in the refrigerant flowing through the discharge pipes (25, 26, 27, 28), of the refrigerant. The oil separators (89, 90, 91, 92) are connected to oil outlet pipes (16, 16, 16, 16) through the which lubricating oil separated in the oil separators (89, 90, 91, 92) flows out of the oil separators (89, 90, 91, 92).

Specifically, the oil outlet pipe (16) of the first oil separator (89) for the first discharge pipe (25) is connected to the second suction pipe (30). The oil outlet pipe (16) of the second oil separator (90) for the second discharge pipe (26) is connected to the third suction pipe (31). The oil outlet pipe (16) of the third oil separator (91) for the third discharge pipe (27) is connected to the fourth suction pipe (32). The oil outlet pipe (16) of the fourth oil separator (92) for the fourth discharge pipe (28) is connected to the first suction pipe (29). The capillary tube (15) is connected to the midpoint of each of the oil outlet pipes (16, 16, 16, 16).

The intermediate heat exchangers (41, 42, 43) first to third and the external heat exchanger (44) are configured as fin and tube heat exchangers. An outdoor fan (122) is disposed near each of the heat exchangers (41, 42, 43, 44) so that heat exchange takes place between the outside air from the outside fan (122) and the refrigerant that flows through the heat exchanger tubes (52) of each of the heat exchangers (41, 42, 43, 44). The heat exchanger configurations (41, 42, 43, 44) will be described in detail.

One end of the first intermediate heat exchanger (41) is connected to the third port of the first four-way valve (93), one end of the second intermediate heat exchanger (42) is connected to the third port of the second four-way valve (94), one end of the third intermediate heat exchanger (43) is connected to the third port of the third four-way valve (95), and one end of the external heat exchanger (44) is connected to the third port of the fourth four-way valve (96). On the other hand, the other ends of the first to third intermediate heat exchangers (41, 42, 43) are connected to the first to third refrigerant pipes (70, 71, 72), respectively, and the other end of the heat exchanger. Outside heat (44) is connected to one end of the fourth refrigerant pipe (73).

The other end of the fourth refrigerant pipe (73) branches into two parts, of which one is connected to the bridge circuit (17) and the other is connected to a fourth outlet port (P4) of the distributor (18). The check valve (CV7) and the capillary tube (15) are located between the branch point of the fourth refrigerant pipe (73) and the fourth outlet port (P4) of the distributor. The check valve (CV7) allows the refrigerant to flow from the distributor (18) to the branch point of the fourth refrigerant pipe (73), and prevents the refrigerant from flowing in the opposite direction.

The other end of the third refrigerant pipe (72) branches into two parts, of which one is connected to a midpoint (between the check valve (CV3) and the fourth compressor (24)) of the fourth pipe suction (32) and the other is connected to a third outlet port (P3) of the distributor (18). The check valve (CV6) and the capillary tube (15) are located between the branch point of the third refrigerant pipe (72) and the third outlet port (P3) of the distributor (18). The check valve (CV6) allows the refrigerant to flow from the distributor (18) to the branch point of the third refrigerant pipe (72), and prevents the refrigerant from flowing in the opposite direction. The check valve (CV10) is located between the branch point of the third refrigerant pipe (72) and the connection point of the fourth suction pipe (32). The check valve (CV10) allows the refrigerant to flow from the branch point of the third refrigerant pipe (72) to the connection point of the fourth suction pipe (32), and prevents the refrigerant from flowing in one direction reverse.

The other end of the second refrigerant pipe (71) branches into two parts, of which one is connected to a midpoint (between the check valve (CV2) and the third compressor (23)) of the third pipe of suction (31) and the other is connected to a second outlet port (P2) of the distributor (18). The check valve (CV5) and the capillary tube (15) are located between the branch point of the second refrigerant pipe (71) and the second outlet port (P2) of the distributor (18). The check valve (CV5) allows the refrigerant to flow from the distributor (18) to the branch point of the second refrigerant pipe (71), and prevents the refrigerant from flowing in the opposite direction. The check valve (CV9) is located between the branch point of the second refrigerant pipe (71) and the connection point of the third suction pipe (31). The check valve (CV9) allows the refrigerant to flow from the branch point of the second refrigerant pipe (71) to the connection point of the third suction pipe (31), and prevents the refrigerant from flowing in one direction reverse.

The other end of the first refrigerant pipe (70) branches into two parts, of which one is connected to a midpoint (between the check valve (CV1) and the second compressor (22)) of the second pipe suction (30) and the other is connected to a first outlet port (P1) of the distributor (18). The check valve (CV4) and the capillary tube (15) are located between the branch point of the first refrigerant pipe (70) and the first outlet port (P1) of the distributor (18). The check valve (CV4) allows the refrigerant to flow from the distributor (18) to the branch point of the first refrigerant pipe (70), and prevents the refrigerant from flowing in the opposite direction. The check valve (CV8) is located between the branch point of the first refrigerant pipe (70) and the connection point of the second suction pipe (30). The check valve (CV8) allows the refrigerant to flow from the branch point of the first refrigerant pipe (70) to the connection point of the second suction pipe (30), and prevents the refrigerant from flowing in one direction reverse.

The bridge circuit (17) is a circuit in which the check valves (CV11, CV12, CV13) and a fifth expansion valve (84) are bridged. In the bridge circuit (17), one connection end located between one inlet end of the check valve (CV13) and the other end of the fifth expansion valve (84) is connected to the first outlet pipe (61) , and a connection end located between an outlet end of the check valve (CV13) and an inlet end of the check valve (CV12) is connected to the communication line (14) of the liquid side. A refrigerant line that connects the communication line (14) of the liquid side to the first internal heat exchanger (110) includes a first internal expansion valve (85) having a varying degree of opening. A refrigerant pipe connecting the communication line (14) of the liquid side to the second internal heat exchanger (111) includes a second internal expansion valve (86) having a varying degree of opening. A connection end located between an outlet end of the check valve (CV12) and an outlet end of the check valve (CV11) is connected to the inlet pipe (60). One end of the fifth expansion valve (84) is connected to the distributor (18), and the inlet end of the check valve (CV11) is connected to the fourth refrigerant pipe (73).

In the inlet pipe (60) the first subcooling heat exchanger (100), the second subcooling heat exchanger (101), the expander (87), the gas-liquid separator (88) and the third are arranged subcooling heat exchanger (102), in this order.

The first subcooling heat exchanger (100) includes a high pressure channel (100a) and a low pressure channel (100b). In the first subcooling heat exchanger (100) a heat exchange takes place between the refrigerant flowing through the high pressure channel (100a) and the refrigerant flowing through the low pressure channel (100b) to subcool the refrigerant that flows through the high pressure channel (100a).

An inlet end of the high pressure channel (100a) is connected to the inlet pipe (60), and an inlet end of the low pressure channel (100b) is connected to a first bypass pipe (62) which serves as A step for subcooling. The first bypass pipe (62) includes a second expansion valve (81) for subcooling. The second expansion valve (81) is an electronic expansion valve that has an adjustable opening degree. An outlet end of the low pressure channel (100b) is connected to one end of the injection pipe (106).

One end of the injection pipe (106) is connected to the low pressure channel (100b) of the first subcooling heat exchanger (100) and the other end of the injection pipe (106) is connected to the second refrigerant pipe (71). Specifically, the other end of the injection pipe (106) is connected to an outlet end of the check valve (CV9) in the second refrigerant pipe (71).

The second subcooling heat exchanger (101) includes a high pressure channel (101a) and a low pressure channel (101b). In the second subcooling heat exchanger (101) a heat exchange takes place between the refrigerant flowing through the high pressure channel (101a) and the refrigerant flowing through the low pressure channel (101b) to subcool the refrigerant that flows through high pressure channel (101a).

An inlet end of the high pressure channel (101a) is connected to the inlet pipe (60). One inlet end of the low pressure channel (101b) is connected to the other end of the connecting pipe (66), and one outlet end of the low pressure channel (101b) is connected to the first suction pipe (29) .

One end of the connecting pipe (66) is connected to the second port of the fourth four-way valve (96), and the other end of the connecting pipe (66) is connected to an inlet end of the low pressure channel (101b) of the second subcooling heat exchanger (101). The other end of the connection pipe (67) is connected to a midpoint of the connection pipe (66).

One end of the connection pipe (67) is connected to the second port of the first four-way valve (93), and the other end of the connection pipe (67) is connected to a midpoint of the connection pipe ( 66). A pipe that communicates with the second port of the second four-way valve (94) and the second port of the third four-way valve (95) is connected to a midpoint of the splice pipe (67).

The expander (87) includes an expander housing that has a vertically elongated cylindrical shape, and is located between the second subcooling heat exchanger (101) and the gas-liquid separator (88) on the inlet pipe (60) . An expansion mechanism is provided in the expander housing to generate energy by expanding the refrigerant. The expander (87) constitutes a so-called rotary positive displacement fluid machine. The expander (87) expands the inlet refrigerant and sends the expanded refrigerant back to the inlet pipe (60).

The inlet pipe (60) includes a bypass pipe (64) that avoids the expander (87). One end of the bypass pipe (64) is connected to an inlet end of the expander (87), and the other end of the bypass pipe (64) is connected to an outlet end of the expander (87) to avoid expander (87). The bypass pipe (64) includes a first expansion valve (80). The first expansion valve (80) is an electronic expansion valve that has an adjustable opening degree.

The gas-liquid separator (88) is an airtight container having a vertically elongated cylindrical shape. The gas-liquid separator (88) is connected to the inlet pipe (60), the first outlet pipe (61) and the second outlet pipe (65). The inlet pipe (60) is open in an upper part of the interior space of the gas-liquid separator (88). The first outlet pipe (61) is open in a lower part of the interior space of the gas-liquid separator (88). The second outlet pipe (65) is open in an upper part of the interior space of the gas-liquid separator (88). In the gas-liquid separator (88), the refrigerant from the inlet pipe (60) is separated into a saturated liquid and a saturated gas, the saturated liquid leaving the first outlet pipe (61) and the gas leaving saturated by the second outlet pipe (65).

One end of the second outlet pipe (65) is connected to the gas-liquid separator (88), and the other end of the second outlet pipe (65) is connected to a midpoint of the return pipe (68) . The second outlet pipe (65) includes a fourth expansion valve (83). The fourth expansion valve (83) is an electronic expansion valve that has an adjustable opening degree.

The third subcooling heat exchanger (102) is connected to a midpoint of the first outlet pipe (61). The third subcooling heat exchanger (102) includes a high pressure channel (102a) and a low pressure channel (102b). In the third subcooling heat exchanger (102) a heat exchange takes place between the refrigerant flowing through the high pressure channel (102a) and the refrigerant flowing through the low pressure channel (102b) to subcool the refrigerant that flows through the high pressure channel (102a).

An inlet end of the high pressure channel (102a) is connected to an outlet end of the gas liquid separator (88), and an outlet end of the high pressure channel (102a) is connected to the bridge circuit (17). An inlet end of the low pressure channel (102b) is connected to a second bypass pipe (63) that serves as a subcooling passage, and an outlet end of the low pressure channel (102b) is connected to the other end of the return pipe (68).

One end of the second bypass pipe (63) is connected to a point of the first outlet pipe (61) between the gas-liquid separator (88) and the third subcooling heat exchanger (102), and the other end of the second bypass pipe (63) is connected to an inlet end of the low pressure channel (102b) of the third subcooling heat exchanger (102). The second bypass pipe (63) includes a third expansion valve (82). The third expansion valve (82) is an electronic expansion valve that has an adjustable opening degree.

One end of the return pipe (68) is connected to the other end of the connection pipe (66), and the other end of the return pipe (68) is connected to an outlet end of the low pressure channel (102b ) of the third subcooling heat exchanger (102). The second outlet pipe (65) is connected to a point of the return pipe (68) between one end and the other end.

<Internal circuit>

In the inner circuit (12) there are arranged a pair formed by the first inner expansion valve (85) and the first inner heat exchanger (110) and a pair formed by the second inner expansion valve (86) and the second exchanger of internal heat (111), in this order from a liquid side to a gas side, and are connected in parallel. Each of the inner expansion valves (85, 86) is an electronic expansion valve that has an adjustable opening degree. Each of the interior heat exchangers (110, 111) is a fin and tube fin heat exchanger. Although they are not shown, close to the indoor heat exchangers (110, 111) are provided indoor fans to send indoor air to the indoor heat exchangers (110, 111). In each of the indoor heat exchangers (110, 111) a heat exchange takes place between the refrigerant and the indoor air.

<Outdoor unit configuration>

As illustrated in Figures 3-5, the outdoor unit (3) includes an outer housing (121) that is a housing of the present invention. The outer housing (121) is in the form of a rectangular box elongated vertically, and has an air inlet (123) in a lower part of the front surface and an air outlet (124) in an upper surface thereof. The air inlet (123) is a suction port of the present invention. The outer heat exchanger (44), the first intermediate heat exchanger (41), the second intermediate heat exchanger (42) and the third intermediate heat exchanger (43), which constitute the outdoor heat exchange unit (40), and the outdoor fan (122). Each of the heat exchangers (41, 42, 43, 44) has approximately a U-shape seen in plan, and is located along the air inlet (123).

The external fan (122) is a fan for sending air taken in the outer casing (121) to the heat exchangers (41, 42, 43, 44), and consists of a so-called siroco fan. The outdoor fan (122) is located above the heat exchangers (41, 42, 43, 44) in the outer housing (121). The outdoor fan (122) causes the air sucked through the air inlet (123) to pass through the heat exchangers (41, 42, 43, 44) and then flow outwards through the air outlet air (124).

As illustrated in Figure 5, the first intermediate heat exchanger (41), the second intermediate heat exchanger (42), the third intermediate heat exchanger (43) and the heat exchanger are stacked in the outer casing (121). outside heat (44), in this order from the bottom up. The first intermediate heat exchanger (41) and the second intermediate heat exchanger (42) can be replaced with each other in the up and down direction.

The first intermediate heat exchanger (41) is a so-called fin and tube fin heat exchanger. The first intermediate heat exchanger (41) includes a plurality of groups (50) of heat exchanger tubes, each of which includes a plurality of heat exchanger tubes (52) and a plurality of U-shaped tubes , and also includes heat transfer fins (51).

As groups (50) of heat exchanger tubes, seven groups (50) of heat exchanger tubes are aligned in the upward and downward direction. A plurality (six in Figure 5) of heat exchanger tubes (52) is arranged in each of the groups (50) of heat exchanger tubes such that three rows of heat exchanger tubes (52) , each along an air flow direction, are arranged side by side and each of the three rows includes two heat exchanger tubes (52) aligned in the upward and downward direction. In addition, a first bank (53) of tubes is arranged on the left in Figure 5 (i.e., the windward side), a second bank (54) of tubes is arranged in the center in Figure 5, and a third Bank (55) of tubes is arranged on the right in Figure 5 (ie the leeward side). That is, in each of the groups (50) of heat exchanger tubes, the heat exchanger tubes (52) are arranged in two stages in each row.

In each of the groups (50) of heat exchanger tubes, between the heat exchanger tubes (52), the ends of the heat exchanger tubes (52) on one side, except one end (a first end ) of the heat exchanger tubes (52) of the upper stage of the first bank (53) of tubes and one end (a second end) of the heat exchanger tubes (52) of the lower stage of the third bank (55 ) of tubes, are connected to each other with the U-shaped tubes, thus forming a refrigerant path in which one end is the first end and the other end is the second end. The first end of the first tube bank (53) of each of the groups (50) of heat exchanger tubes is connected to the first refrigerant pipe (70) of the refrigerant circuit (10) through manifolds. The second end of the third bank (55) of tubes of each of the groups (50) of heat exchanger tubes communicates with the third port of the first four-way valve (93).

As illustrated in Figure 5, each of the heat transfer fins (51) is in the form of an approximately rectangular thin plate. The heat transfer fins (51) are arranged at predetermined intervals along the direction in which the groups (50) of heat exchanger tubes extend. Each of the heat transfer fins (51) has three rows of through holes through which the heat exchanger tubes (52) penetrate. In this way, the heat transfer fins (51) are arranged around the heat exchanger tubes (52), and therefore, the heat transfer area increases, thereby promoting heat transmission.

The second intermediate heat exchanger (42) is a so-called fin and tube fin heat exchanger. The second intermediate heat exchanger (42) includes a plurality of groups (50) of heat exchanger tubes, each of which includes a plurality of heat exchanger tubes (52) and a plurality of U-shaped tubes , and also includes heat transfer fins (51).

As groups (50) of heat exchanger tubes, seven groups (50) of heat exchanger tubes are aligned in the upward and downward direction. A plurality (six in Figure 5) of heat exchanger tubes (52) is arranged in each of the groups (50) of heat exchanger tubes such that three rows of heat exchanger tubes (52) , each along an air flow direction, are arranged side by side and each of the three rows includes two heat exchanger tubes (52) aligned in the upward and downward direction. In addition, a first bank (53) of tubes is arranged on the left in Figure 5 (i.e., the windward side), a second bank (54) of tubes is arranged in the center in Figure 5, and a third Bank (55) of tubes is arranged on the right in Figure 5 (ie the leeward side). That is, in each of the groups (50) of heat exchanger tubes, the heat exchanger tubes (52) are arranged in two stages in each row.

In each of the groups (50) of heat exchanger tubes, between the heat exchanger tubes (52), the ends of the heat exchanger tubes (52) on one side, except one end (a first end ) of the heat exchanger tubes (52) of the upper stage of the first bank (53) of tubes and one end (a second end) of the heat exchanger tubes (52) of the lower stage of the third bank (55 ) of tubes, are connected to each other with the U-shaped tubes, thus forming a refrigerant path in which one end is the first end and the other end is the second end. The first end of the first tube bank (53) of each of the groups (50) of heat exchanger tubes is connected to the second refrigerant pipe (71) of the refrigerant circuit (10) through manifolds. The second end of the third bank (55) of tubes of each of the groups (50) of heat exchanger tubes communicates with the third port of the second four-way valve (94).

As illustrated in Figure 5, each of the heat transfer fins (51) is in the form of an approximately rectangular thin plate. The heat transfer fins (51) are arranged at predetermined intervals along the direction in which the groups (50) of heat exchanger tubes extend. Each of the heat transfer fins (51) has three rows of through holes through which the heat exchanger tubes (52) penetrate. In this way, the heat transfer fins (51) are arranged around the heat exchanger tubes (52), and therefore, the heat transfer area increases, thereby promoting heat transmission.

The third intermediate heat exchanger (43) is a so-called fin and tube fin heat exchanger. The third intermediate heat exchanger (43) includes a plurality of groups (50) of heat exchanger tubes, each of which includes a plurality of heat exchanger tubes (52) and a plurality of U-shaped tubes , and also includes heat transfer fins (51).

As groups (50) of heat exchanger tubes, six groups (50) of heat exchanger tubes are aligned in the upward and downward direction. A plurality (six in Figure 5) of heat exchanger tubes (52) is arranged in each of the groups (50) of heat exchanger tubes such that three rows of heat exchanger tubes (52) , each along an air flow direction, are arranged side by side and each of the three rows includes two heat exchanger tubes (52) aligned in the upward and downward direction. In addition, a first bank (53) of tubes is arranged on the left in Figure 5 (i.e., the windward side), a second bank (54) of tubes is arranged in the center in Figure 5, and a third Bank (55) of tubes is arranged on the right in Figure 5 (ie the leeward side). That is, in each of the groups (50) of heat exchanger tubes, the heat exchanger tubes (52) are arranged in two stages in each row.

In each of the groups (50) of heat exchanger tubes, between the heat exchanger tubes (52), the ends of the heat exchanger tubes (52) on one side, except one end (a first end ) of the heat exchanger tubes (52) of the upper stage of the first bank (53) of tubes and one end (a second end) of the heat exchanger tubes (52) of the lower stage of the third bank (55 ) of tubes, are connected to each other with the U-shaped tubes, thus forming a refrigerant path in which one end is the first end and the other end is the second end. The first end of the first tube bank (53) of each of the groups (50) of heat exchanger tubes is connected to the third refrigerant pipe (72) of the refrigerant circuit (10) through manifolds. The second end of the third bank (55) of tubes of each of the groups (50) of heat exchanger tubes communicates with the third port of the third four-way valve (95).

As illustrated in Figure 5, each of the heat transfer fins (51) is in the form of an approximately rectangular thin plate. The heat transfer fins (51) are arranged at predetermined intervals along the direction in which the groups (50) of heat exchanger tubes extend. Each of the heat transfer fins (51) has three rows of through holes through which the heat exchanger tubes (52) penetrate. In this way, the heat transfer fins (51) are arranged around the heat exchanger tubes (52), and therefore, the heat transfer area increases, thereby promoting heat transmission.

The external heat exchanger (44) is a so-called fin and tube fin heat exchanger. The external heat exchanger (44) includes a plurality of groups (50) of heat exchanger tubes, each of which includes a plurality of heat exchanger tubes (52) and a plurality of U-shaped tubes, and also includes heat transfer fins (51).

As groups (50) of heat exchanger tubes, eight groups (50) of heat exchanger tubes are aligned in the upward and downward direction. A plurality (six in Figure 5) of heat exchanger tubes (52) is arranged in each of the groups (50) of heat exchanger tubes such that three rows of heat exchanger tubes (52) , each along an air flow direction, are arranged side by side and each of the three rows includes two heat exchanger tubes (52) aligned in the upward and downward direction. In addition, a first bank (53) of tubes is arranged on the left in Figure 5 (i.e., the windward side), a second bank (54) of tubes is arranged in the center in Figure 5, and a third Bank (55) of tubes is arranged on the right in Figure 5 (ie the leeward side). That is, in each of the groups (50) of heat exchanger tubes, the heat exchanger tubes (52) are arranged in two stages in each row.

In each of the groups (50) of heat exchanger tubes, between the heat exchanger tubes (52), the ends of the heat exchanger tubes (52) on one side, except one end (a first end ) of the heat exchanger tubes (52) of the upper stage of the first bank (53) of tubes and one end (a second end) of the heat exchanger tubes (52) of the lower stage of the third bank (55 ) of tubes, are connected to each other with the U-shaped tubes, thus forming a refrigerant path in which one end is the first end and the other end is the second end. The first end of the first tube bank (53) of each of the groups (50) of heat exchanger tubes is connected to the fourth refrigerant pipe (74) of the refrigerant circuit (10) through manifolds. The second end of the third bank (55) of tubes of each of the groups (50) of heat exchanger tubes communicates with the third port of the fourth four-way valve (96).

As illustrated in Figure 5, each of the heat transfer fins (51) is in the form of an approximately rectangular thin plate. The heat transfer fins (51) are arranged at predetermined intervals along the direction in which the groups (50) of heat exchanger tubes extend. Each of the heat transfer fins (51) has three rows of through holes through which the heat exchanger tubes (52) penetrate. In this way, the heat transfer fins (51) are arranged around the heat exchanger tubes (52), and therefore, the heat transfer area increases, thereby promoting heat transmission.

-Operation-

Next, the operation of the air conditioner (1) will be described. In the air conditioner (1) a switching between the four-way valves (93, 94, 95, 96) is carried out first to fourth to change the operation of the refrigerant circuit (10) between the cooling operation and the heating operation Reference numbers 1-26 in Figures 1 and 2 represent refrigerant pressure states.

-Cooling operation-

The cooling operation of the air conditioner (1) will be described with reference to Figures 1 and 2. In Figure 1, a refrigerant flow in this cooling operation is represented by continuous line arrows. In the cooling operation, the external heat exchanger (44) functions as a heat sink, and the internal heat exchangers (110, 111) function as evaporators, thus performing a four-stage supercritical compression refrigeration cycle. Intermediate heat exchangers (41, 42, 43) first to third function as chillers that cool the high-pressure refrigerant discharged from the compressors (21, 22, 23).

In the cooling operation, all four-way valves (93, 94, 95, 96) are adjusted in the first states and the four-stage compressor (20) is operated. When the four-stage compressor (20) is operated, the refrigerant is compressed in the compressors (21,22, 23, 24). The compressed refrigerant in the first compressor (21) is discharged to the first discharge pipe (25) (see "2" in Figures 1 and 2). In this state, the first oil separator (89) of the first discharge pipe (25) separates the lubricating oil from the gaseous refrigerant flowing through the first discharge pipe (25). The separated lubricating oil is sent from the oil outlet pipe (16) to the second suction pipe (30). The refrigerant flowing through the first discharge line (25) passes through the first four-way valve (93) and flows into the first intermediate heat exchanger (41). In the first intermediate heat exchanger (41), the refrigerant dissipates heat to the outside air to cool. The refrigerant cooled in the first intermediate heat exchanger (41) flows into the first refrigerant pipe (70). The refrigerant flowing through the first refrigerant pipe (70) passes through the check valve (CV8), flows into the second suction pipe (30) and is sucked into the second compressor (22) (see "3" in Figures 1 and 2).

The compressed refrigerant in the second compressor (22) is discharged to the second discharge pipe (26) (see "4" in Figures 1 and 2). In this state, the second oil separator (90) of the second discharge pipe (26) separates the lubricating oil from the gaseous refrigerant flowing through the second discharge pipe (26). The separated lubricating oil is sent from the oil outlet pipe (16) to the second suction pipe (30). The refrigerant that flows through the second discharge pipe (26) passes through the second four-way valve (94) and flows into the second intermediate heat exchanger (42). In the second intermediate heat exchanger (42), the refrigerant dissipates heat to the outside air to cool. The refrigerant cooled in the second intermediate heat exchanger (42) flows into the second refrigerant pipe (71) (see "5" in Figures 1 and 2). The refrigerant that flows through the second refrigerant pipe (71) passes through the check valve (CV9), is combined with the refrigerant that flows through the injection pipe (106), flows into the third suction pipe (31) and is sucked into the third compressor (23) (see "6" in Figures 1 and 2).

The compressed refrigerant in the third compressor (23) is discharged to the third discharge pipe (27) (see "7" in Figures 1 and 2). In this state, the third oil separator (91) of the third discharge pipe (27) separates the lubricating oil from the gaseous refrigerant flowing through the third discharge pipe (27). The separated lubricating oil is sent from the oil outlet pipe (16) to the fourth suction pipe (32). The refrigerant that flows through the third discharge pipe (27) passes through the third four-way valve (95) and flows into the third intermediate heat exchanger (43). In the third intermediate heat exchanger (43), the refrigerant dissipates heat to the outside air to cool. The refrigerant cooled in the third intermediate heat exchanger (43) flows into the third refrigerant pipe (72). The refrigerant flowing through the third refrigerant pipe (72) passes through the check valve (CV10), flows into the fourth suction pipe (32) and is sucked into the fourth compressor (24) (see "8" in Figures 1 and 2).

The compressed refrigerant in the fourth compressor (24) is discharged to the fourth discharge pipe (28) (see "9" in Figures 1 and 2). The compression and cooling operations described above are performed alternately so that the compression strokes of the four-stage compressor (20) are close to those of isothermal compression in order to reduce the compression power required for the four-stage compressor (20). At this time, the fourth oil separator (92) of the fourth discharge pipe (28) separates the lubricating oil from the gaseous refrigerant flowing through the fourth discharge pipe (28). The separated lubricating oil is sent from the oil outlet pipe (16) to the first suction pipe (29). The refrigerant that flows through the fourth discharge pipe (28) passes through the fourth four-way valve (96) and flows into the exterior heat exchanger (44). In the outdoor heat exchanger (44), the refrigerant dissipates heat to the outside air to cool. The refrigerant cooled in the external heat exchanger (44) flows into the fourth refrigerant pipe (73). The refrigerant that flows through the fourth refrigerant pipe (73) passes through the check valve (CV11) and flows into the inlet pipe (60).

Part of the refrigerant that flows through the inlet pipe (60) flows into the first bypass pipe (62). The pressure of the refrigerant flowing through the first bypass pipe (62) (see "10" in Figures 1 and 2) is reduced in the second expansion valve (81). The refrigerant whose pressure has been reduced in the second expansion valve (81) (see "11" in Figures 1 and 2) flows into the low pressure channel (100b) of the first subcooling heat exchanger (100). On the other hand, the other part of the refrigerant flowing through the inlet pipe (60) flows into the high pressure channel (100a) of the first subcooling heat exchanger (100) (see "10" in Figures 1 and 2). In the first subcooling heat exchanger (100) a heat exchange takes place between the refrigerant flowing through the high pressure channel (100a) and the refrigerant flowing through the low pressure channel (100b) to subcool the refrigerant that flows through the high pressure channel (100a).

The refrigerant that has left the high pressure channel (100a) of the first subcooling heat exchanger (100) flows again through the inlet pipe (60) (see "13" in Figures 1 and 2), and flows to the inside the high pressure channel (101a) of the second subcooling heat exchanger (101). On the other hand, the refrigerant that has left the low pressure channel (100b) of the first subcooling heat exchanger (100) (see "12" in Figures 1 and 2) flows into the injection pipe (106) . The refrigerant flowing through the injection pipe (106) flows into the second refrigerant pipe (71) and is combined with the refrigerant flowing through the second refrigerant pipe (71) (see "6" in Figures 1 and 2). That is, the refrigerant that has entered the injection pipe (106) is injected towards the suction side of the third compressor (23).

In the second subcooling heat exchanger (101) a heat exchange takes place between the refrigerant flowing through the high pressure channel (101a) and the refrigerant flowing through the low pressure channel (101b) to subcool the refrigerant that flows through the high pressure channel (101a).

The refrigerant that has left the high pressure channel (101a) of the second subcooling heat exchanger (101) flows back into the inlet pipe (60) (see "14" in Figures 1 and 2), and part of this refrigerant flows into the expander (87). The expander (87) expands the inlet refrigerant (see "14" to "16" in Figures 1 and 2), and sends the expanded refrigerant back to the inlet pipe (60). On the other hand, the other part of the refrigerant that has left the high pressure channel (101a) of the second subcooling heat exchanger (101) branches into the bypass line (64). The refrigerant flowing through the bypass pipe (64) is subjected to a pressure reduction in the first expansion valve (80) (see "15" in Figures 1 and 2) and returns to the inlet pipe (60) . The refrigerant that has left the expander (87) and the refrigerant that has left the bypass pipe (64) combine with each other in the inlet pipe (60) (see "17" in Figures 1 and 2) and flow towards the gas-liquid separator (88). The gas-liquid separator (88) separates the inlet refrigerant into gaseous refrigerant (see "22" in Figures 1 and 2) and liquid refrigerant (see "18" in Figures 1 and 2).

The liquid refrigerant (see "18" in Figures 1 and 2) that has left the gas-liquid separator (88) flows through the first outlet pipe (61), and part of this refrigerant flows into the second pipe bypass (63). The pressure of the refrigerant flowing through the second bypass pipe (63) is reduced in the third expansion valve (82). The refrigerant whose pressure has been reduced in the third expansion valve (82) (see "19" in Figures 1 and 2) flows into the low pressure channel (102b) of the third subcooling heat exchanger (102). On the other hand, the other part of the refrigerant flowing through the outlet tube (61) flows into the high pressure channel (102a) of the third subcooling heat exchanger (102).

In the third subcooling heat exchanger (102) a heat exchange takes place between the refrigerant flowing through the high pressure channel (102a) and the refrigerant flowing through the low pressure channel (102b) to subcool the liquid refrigerant flowing through the high pressure channel (102a).

The liquid refrigerant that has left the high pressure channel (102a) of the third subcooling heat exchanger (102) (see "20" in Figures 1 and 2) flows again through the first outlet pipe (61), passes through the check valve (CV13) of the bridge circuit (17), and flows into the communication line (14) of the liquid side. On the other hand, the refrigerant that has left the low pressure channel (102b) of the third subcooling heat exchanger (102) flows through the return line (68). The refrigerant flowing through the return line (68) (see "24" in Figures 1 and 2) is combined with the gaseous refrigerant that has left the second outlet pipe (65) (see "23" in the Figures 1 and 2) at a midpoint of it, and still flowing. The refrigerant that has left the return line (68) is combined with the refrigerant that has left the connection pipe (66). The combined refrigerant (see "26" in Figures 1 and 2) flows into the low pressure channel (101b) of the second subcooling heat exchanger (101).

Part of the liquid refrigerant flowing through the communication line (14) on the liquid side branches and undergoes a pressure reduction in the first inner expansion valve (85). The reduced pressure refrigerant (see "21a" in Figures 1 and 2) flows into the first interior heat exchanger (110). In the first indoor heat exchanger (110), the liquid refrigerant absorbs heat from the indoor air and evaporates. The evaporated gaseous refrigerant (see "25a" in Figures 1 and 2) flows into the communication line (13) on the gas side.

The pressure of the other part of the liquid refrigerant flowing through the communication line (14) of the liquid side is reduced in the second inner expansion valve (86). The refrigerant under reduced pressure (see "21b" in Figures 1 and 2) flows into the second interior heat exchanger (111). In the second indoor heat exchanger (111), the liquid refrigerant absorbs heat from the indoor air and evaporates. The evaporated gaseous refrigerant (see "25b" in Figures 1 and 2) flows into the communication line (13) on the gas side.

The refrigerant that has left the first internal heat exchanger (110) and the refrigerant that has left the second internal heat exchanger (111) are combined with each other in the communication line (13) on the gas side. The refrigerant that flows through the communication line (13) on the gas side passes through the fourth four-way valve (96) and flows into the connecting pipe (66). Part of the refrigerant flowing through the connecting pipe (66) branches from the junction pipe (67) into parts that flow into the first to third four-way valves (92, 93, 94).

The refrigerant that has passed through the second port of the first four-way valve (93) flows into the second suction pipe (30). The refrigerant that flows through the second suction pipe (30) passes through the check valve (CV1) and is combined with the refrigerant that flows through the first refrigerant pipe (70), to be sucked into the second compressor (22). The refrigerant that has passed through the second port of the second four-way valve (94) flows into the third suction pipe (31). The refrigerant that flows through the third suction pipe (31) passes through the check valve (CV2) and is combined with the refrigerant that flows through the second refrigerant pipe (71), to be sucked into the third compressor (2. 3). The refrigerant that has passed through the second port of the third four-way valve (95) flows into the fourth suction pipe (32). The refrigerant that flows through the fourth suction pipe (32) passes through the check valve (CV3) and is combined with the refrigerant that flows through the third refrigerant pipe (72), to be sucked into the fourth compressor (24).

The other part of the refrigerant flowing through the connecting pipe (66) is combined with the refrigerant flowing through the return pipe (68). The combined refrigerant (see "26" in Figures 1 and 2) passes through the low pressure channel (101b) of the second subcooling heat exchanger (101) and flows into the first suction pipe (29). The refrigerant flowing through the first suction pipe (29) (see "1" in Figures 1 and 2) is compressed again in the first compressor (21) of the four-stage compressor (20).

-Heating operation-

Next, the heating operation of the air conditioner (1) will be described with reference to Figure 7. In Figure 7, a refrigerant flow in this heating operation is represented by dashed arrows. In the heating operation, the internal heat exchangers (110, 111) function as heat sinks, and the first to third intermediate heat exchangers (41, 42, 43) and the external heat exchanger (44) function as evaporators , thus performing a supercritical four-stage compression refrigeration cycle.

In the heating operation, all four-way valves (93, 94, 95, 96) are adjusted in the second states and the four-stage compressor (20) is operated. When the four-stage compressor (20) is operated, the refrigerant is compressed in the compressors (21,22, 23, 24). The compressed refrigerant in the first compressor (21) is discharged to the first discharge pipe (25). The refrigerant flowing through the first discharge pipe (25) passes through the first four-way valve (93) and is sucked into the second compressor (22). The additional compressed refrigerant in the second compressor (22) passes through the second four-way valve (94) and is sucked into the third compressor (23). The additional compressed refrigerant in the third compressor (23) passes through the third four-way valve (95) and is sucked into the fourth compressor (24). The refrigerant is compressed further into the fourth compressor (24). Thus, unlike the cooling operation, four-stage compression is performed without cooling in the heating operation. In this heating operation, the temperature of the refrigerant discharged from the four-stage compressor (20) does not decrease, unlike the case in which the four-stage compression is carried out with cooling. As a result, the heating operation shows a greater heating capacity than in the case of four-stage compression with cooling.

The refrigerant discharged from the fourth compressor (24) passes through the fourth four-way valve (96) and is sent to the first and second interior heat exchangers (110, 111). In the first and second indoor heat exchangers (110, 111), the refrigerant dissipates heat to the outside air to cool. The refrigerant cooled in the interior heat exchangers (110, 111) is subjected to a pressure reduction in the first and second inner expansion valves (85, 86) and then sent to the bridge circuit (17). This refrigerant passes through the check valve (CV12) and flows into the inlet pipe (60).

Part of the refrigerant that flows through the inlet pipe (60) flows into the first bypass pipe (62). The pressure of the refrigerant flowing through the first bypass pipe (62) is reduced in the second expansion valve (81). The refrigerant whose pressure has been reduced in the second expansion valve (81) flows into the low pressure channel (100b) of the first subcooling heat exchanger (100). On the other hand, the other part of the refrigerant flowing through the inlet pipe (60) flows into the high pressure channel (100a) of the first subcooling heat exchanger (100). In the first subcooling heat exchanger (100) a heat exchange takes place between the refrigerant flowing through the high pressure channel (100a) and the refrigerant flowing through the low pressure channel (100b) to subcool the refrigerant that flows through the high pressure channel (100a).

The refrigerant that has left the high pressure channel (100a) of the first subcooling heat exchanger (100) flows again through the first outlet pipe (61), and flows into the high pressure channel (101a) of the second subcooling heat exchanger (101). On the other hand, the refrigerant that has left the low pressure channel (100b) of the first subcooling heat exchanger (100) flows into the injection pipe (106). The refrigerant flowing through the injection pipe (106) flows into the second refrigerant pipe (71) and is combined with the refrigerant in the second refrigerant pipe (71). That is, the refrigerant that has flowed into the injection pipe (106) is injected into a suction side of the third compressor (23).

In the second subcooling heat exchanger (101) a heat exchange takes place between the refrigerant flowing through the high pressure channel (101a) and the refrigerant flowing through the low pressure channel (101b) to subcool the refrigerant that flows through the high pressure channel (101a).

The refrigerant that has left the high pressure channel (101a) of the second subcooling heat exchanger (101) flows again through the first outlet pipe (61), and part of this refrigerant flows into the expander (87). The expander (87) expands the inlet refrigerant, and sends the expanded refrigerant back to the inlet pipe (60). On the other hand, the other part of the refrigerant that has left the high pressure channel (101a) of the second subcooling heat exchanger (101) branches into the bypass line (64). The refrigerant flowing through the bypass pipe (64) is subjected to a pressure reduction in the first expansion valve (80) and returns to the inlet pipe (60). The refrigerant that has left the expander (87) and the refrigerant that has left the bypass pipe (64) combine with each other in the inlet pipe (60) and flow into the gas-liquid separator (88). The gas-liquid separator (88) separates the inlet refrigerant into gaseous refrigerant and liquid refrigerant.

The liquid refrigerant that has left the gas-liquid separator (88) flows through the first outlet pipe (61), and part of this refrigerant flows into the second bypass pipe (63). The pressure of the refrigerant flowing through the second bypass pipe (63) is reduced in the third expansion valve (82). The refrigerant whose pressure has been reduced in the third expansion valve (82) flows into the low pressure channel (102b) of the third subcooling heat exchanger (102). On the other hand, the other part of the refrigerant flowing through the inlet pipe (60) flows into the high pressure channel (102a) of the third subcooling heat exchanger (102).

In the third subcooling heat exchanger (102) a heat exchange takes place between the refrigerant flowing through the high pressure channel (102a) and the refrigerant flowing through the low pressure channel (102b) to subcool the liquid refrigerant flowing through the high pressure channel (102a).

The liquid refrigerant that has left the high pressure channel (102a) of the third subcooling heat exchanger (102) flows again through the first outlet pipe (61), is subjected to a pressure reduction in the fifth expansion valve (84) of the bridge circuit (17), and then sent to the distributor (18). The refrigerant distributed in the distributor (18) passes through the capillary tube (15) and the check valves (CV4, CV5, CV6, CV7) to flow into the intermediate heat exchangers (41, 42, 43) first to third and the external heat exchanger (44). In the first to third intermediate heat exchangers (41, 42, 43) and the external heat exchanger (44), the liquid refrigerant absorbs heat from the outside air and evaporates. The refrigerant that has left the first intermediate heat exchanger (41) passes through the first four-way valve (93) and flows into the junction pipe (67). The refrigerant that has left the second intermediate heat exchanger (42) passes through the second four-way valve (94) and flows into the junction pipe (67). The refrigerant that has left the third intermediate heat exchanger (43) passes through the third four-way valve (95) and flows into the junction pipe (67). The refrigerant that has left the intermediate heat exchangers (41,42, 43) first to third passes through the junction pipe (67) and flows into the connecting pipe (66).

The refrigerant that has left the external heat exchanger (44) passes through the fourth four-way valve (96), flows into the connecting pipe (66) and is combined with the refrigerant that has left the exchangers of intermediate heat (41,42, 43) first to third. The combined refrigerant flows through the connecting pipe (66) and is combined with the refrigerant flowing through the return pipe (68). The combined refrigerant inside the first suction pipe (29). The refrigerant flowing through the first suction pipe (29) is compressed again into the first compressor (21) of the four-stage compressor (20).

-External unit

The outdoor unit will be described below. As illustrated in Figure 3, the air introduced into the outer casing (121) from the air inlet (123) is subjected to heat exchange in the intermediate heat exchangers (41, 42, 43) first to third and the External heat exchanger (44), flows to the upper space in the outer shell (121), and is expelled through the air outlet (124).

As illustrated in Figure 6, the outdoor unit (3) is of a so-called upward blow type, in which air is drawn through the air inlet (123) on the side surface and blown towards up from the air outlet (124). Therefore, the speed of the air flow is greater in an upper part of the air inlet (123) than in a lower part of the air inlet (123). As illustrated in Figure 2, the pressure of the refrigerant flowing through the intermediate heat exchangers (41,42, 43) first to third is lower than that of the refrigerant flowing through the external heat exchanger (44) and , therefore, the densities of the refrigerant flowing through the intermediate heat exchangers (41, 42, 43) first to third are lower than those of the refrigerant flowing through the external heat exchanger (44). In view of this, when the mass flow rates of the refrigerant flowing through the intermediate heat exchangers (41, 42, 43) first to third are substantially equal to those of the refrigerant flowing through the external heat exchanger (44), the volumetric flow rates of the refrigerant in the intermediate heat exchangers (41, 42, 43) first to third are higher than those of the refrigerant in the external heat exchanger (44). Even when the number of refrigerant paths in each of the first to third intermediate heat exchangers (41, 42, 43) is equal to that of the external heat exchanger (44), the flow rates of the refrigerant flowing through the exchangers First to third intermediate heat exchanges (41, 42, 43) are higher than those of the refrigerant flowing through the external heat exchanger (44) and, therefore, the pressure losses of the refrigerant in the intermediate heat exchangers ( 41, 42, 43) first to third are larger than in the external heat exchanger (44).

The external heat exchanger (44) located in an upper part of the outer casing (121), where the air flow rate is high, has a high heat exchange efficiency and can be reduced in size. On the other hand, the first to third intermediate heat exchangers (41,42, 43) located in a lower part of the outer casing (121), where the air flow rate is low, have low heat exchange efficiencies. Therefore, to increase the amount of heat exchange, the intermediate heat exchangers (41, 42, 43) first to third must be larger than in the case where these heat exchangers are located at a top.

For this reason, the size of the outdoor heat exchange unit (40) does not increase even if the size of the outdoor heat exchanger (44) and the intermediate heat exchangers (41, 42, 43) first to third increases.

An increase in the size of the intermediate heat exchangers (41,42, 43) first to third increases the number of refrigerant paths in each of the intermediate heat exchangers (41, 42, 43) first to third. Therefore, in the intermediate heat exchangers (41, 42, 43) first to third, the flow rate of the refrigerant decreases on each refrigerant path, resulting in a decrease in the loss of pressure of the refrigerant that passes to through the refrigerant path. The flow rates of the refrigerant flowing through the intermediate heat exchangers (41, 42, 43) first to third are originally high and, therefore, a decrease in the flow rate due to an increase in the number of refrigerant paths produces a relatively large reduction in pressure loss.

On the other hand, a reduction in the size of the external heat exchanger (44) reduces the number of refrigerant paths in the external heat exchanger (44). Reducing the number of refrigerant paths increases the flow rate of the refrigerant in each refrigerant path, increasing the loss of pressure of the refrigerant that passes through the refrigerant path.

However, since the flow rate of the refrigerant flowing through the external heat exchanger (44) is originally low, a certain degree of flow rate increase due to the reduction in the number of refrigerant paths causes a relatively increased small pressure loss resulting from increased flow rate.

Therefore, by arranging the external heat exchanger (44) above the intermediate heat exchangers (41, 42, 43) first to third, the pressure losses of the refrigerant in the intermediate heat exchangers (41, 42) can be reduced , 43) first to third with a reduced degree of increase in the size of the outdoor heat exchange unit (40).

Since the pressure of the refrigerant flowing through the third intermediate heat exchanger (43) is greater than that of the refrigerant flowing through the first and second intermediate heat exchangers (41, 42) as illustrated in Figure 2, the Densities of the coolant flowing through the first and second intermediate heat exchangers (41,42) are lower than those of the coolant flowing through the third intermediate heat exchanger (43). Therefore, when the mass flow rates of the refrigerant flowing through the first and second intermediate heat exchangers (41,42) are substantially equal to those of the refrigerant flowing through the third intermediate heat exchanger (43), the volumetric flow rates of the refrigerant in the first and second intermediate heat exchangers (41, 42) are higher than those of the refrigerant in the third intermediate heat exchanger (43). Even when the number of refrigerant paths in the first and second intermediate heat exchangers (41, 42) is substantially equal to that of the third intermediate heat exchanger (43), the pressure losses of the refrigerant in the intermediate heat exchangers (41, 42) first and second are larger than that of the refrigerant in the third intermediate heat exchanger (43), since the flow rates of the refrigerant in the first and second intermediate heat exchangers (41, 42) are greater than that of the third intermediate heat exchanger (43).

Since the third intermediate heat exchanger (43) located in an upper part of the outer casing (121), where the air flow rate is high, has a high heat exchange efficiency, the size of the third heat exchanger Intermediate (43) can be reduced. On the other hand, the first and second intermediate heat exchangers (41, 42) located in a lower part of the outer casing (121), where the air flow rate is low, have low heat exchange efficiencies. Therefore, to increase the amount of heat exchange, the first and second intermediate heat exchangers (41,42, 43) must be larger than in the case where these heat exchangers are located at an upper part.

For this reason, the size of the outdoor heat exchange unit (40) does not increase even if the size of the third intermediate heat exchanger (43) and the first and second intermediate heat exchangers (41, 42) increases.

An increase in the size of the first and second intermediate heat exchangers (41.42) increases the number of refrigerant paths in the first and second intermediate heat exchangers (41.42). Therefore, in the first and second intermediate heat exchangers (41, 42), the flow rate of the refrigerant in each refrigerant path decreases, resulting in a decrease in the loss of pressure of the refrigerant passing through the path of refrigerant The flow rates of the refrigerant flowing through the first and second intermediate heat exchangers (41, 42) are originally high and, therefore, a decrease in the flow rate due to an increase in the number of refrigerant paths produces a relatively large reduction in pressure loss.

On the other hand, a reduction in the size of the third intermediate heat exchanger (43) reduces the number of refrigerant paths in the third intermediate heat exchanger (43). Reducing the number of coolant paths increases the coolant flow rate on each coolant path, increasing the loss of coolant pressure that passes through the coolant paths.

However, since the flow rate of the refrigerant flowing through the third intermediate heat exchanger (43) is originally low, a certain degree of flow rate increase due to the reduction in the number of refrigerant paths causes an increase relatively small pressure loss resulting from increased flow rate.

Therefore, arranging the third intermediate heat exchanger (43) above the first and second intermediate heat exchangers (41, 42) can reduce the pressure losses of the refrigerant in the intermediate heat exchangers (41,42) first and second with a reduced degree of increase in the size of the outdoor heat exchange unit (40).

As illustrated in Figure 2, the density of the refrigerant in the second intermediate heat exchanger (42), in which the inlet refrigerant has a high pressure, is greater than that of the first intermediate heat exchanger (41), in which the inlet refrigerant has a low pressure. Therefore, when the mass flow rate of the refrigerant flowing through the first intermediate heat exchanger (41) is substantially equal to that of the refrigerant flowing through the second intermediate heat exchanger (42), the volumetric flow rate of the refrigerant in the first exchanger Intermediate heat (41) is higher than that of the refrigerant in the second intermediate heat exchanger (42). Even when the number of refrigerant paths in the first intermediate heat exchanger (41) is substantially equal to that of the second intermediate heat exchanger (42), the loss of refrigerant pressure in the first intermediate heat exchanger (41) is greater than that of the refrigerant in the second intermediate heat exchanger (42), since the flow rate of the refrigerant in the first intermediate heat exchanger (41) is higher than in the second intermediate heat exchanger (42). The first intermediate heat exchanger (41) is located in a lower part of the outer casing (121), where the air flow rate is low, does not have a high heat exchange efficiency and, therefore, does not decrease of size. Since the number of refrigerant paths in the first intermediate heat exchanger (41) does not decrease, the loss of refrigerant pressure does not increase. The above reasons allow reducing the increase in pressure loss of the refrigerant in the first intermediate heat exchanger (41).

-Advantages of the first embodiment-

In the first embodiment, since the outer heat exchanger (44) is located in an upper part of the outer housing (121), where the air flow rate is high, the heat exchange efficiency of the exchanger can be increased of external heat (44). Furthermore, as the external heat exchanger (44), which has a low refrigerant flow rate, is located in an upper part of the outer casing (121), where the air flow rate is high, the size of the external heat exchanger (44) can be reduced without increasing the loss of refrigerant pressure.

On the other hand, the first to third intermediate heat exchangers (41, 42, 43) are located in a lower part of the outer casing (121), where the air flow rate is low, to increase the number of air travel coolant, which ensures the prevention of increased coolant pressure loss in intermediate heat exchangers (41, 42, 43) first to third.

In the configuration described above, the external heat exchangers (44, 162), in which the pressure loss of the refrigerant does not increase easily, are located in the upper parts to reduce the size, which reduces the pressure losses of the refrigerant in the intermediate heat exchangers (41, 42, 43) first to third with a small increase in the external heat exchange unit (40).

In addition, since the third intermediate heat exchanger (43) is located in an upper part of the outer casing (121), where the air flow rate is high, the heat exchange efficiency of the third intermediate heat exchanger ( 43) can be increased. In addition, as the third intermediate heat exchanger (43), which has a low refrigerant flow rate, is located in an upper part of the outer casing (121), where the air flow rate is high, the size of the Third intermediate heat exchanger (43) can be reduced without increasing the loss of refrigerant pressure.

On the other hand, the first and second intermediate heat exchangers (41, 42), which have high coolant flow rates, are located in a lower part of the outer casing (121), where the air flow rate is low , to increase the number of coolant paths, thus ensuring the prevention of an increase in coolant pressure loss in the first and second intermediate heat exchangers (41,42).

In the configuration described above, the third intermediate heat exchanger (43), in which the loss of refrigerant pressure does not increase easily, is located at the top to reduce the size, which reduces the loss of refrigerant pressure by the other intermediate heat exchangers (41, 42) with a reduced size increase in the outdoor heat exchange unit (40).

In addition, the first intermediate heat exchanger (41), which has a high refrigerant flow rate, is located in a lower part of the outer casing (121), where the air flow rate is low, to increase the number of coolant paths, which ensures the prevention of an increase in coolant pressure loss in the first intermediate heat exchanger (41). This configuration can reduce the increase in refrigerant pressure loss in the first intermediate heat exchanger (41).

<Second embodiment>

Next, a second embodiment according to the present invention will be described. As illustrated in Figure 8, the air conditioner (1) according to this second embodiment has a configuration of a refrigerant circuit different from that of the air conditioner (1) of the first embodiment. In the second embodiment, only the part of the configuration different from that of the first embodiment is described, and similar reference characters are used to designate identical or equivalent elements.

Specifically, the refrigerant circuit (10) of the second embodiment includes three subcooling heat exchangers: a first subcooling heat exchanger (103), a first subcooling heat exchanger (104) and a first c subcooling heat exchanger (105).

-Configuration of the circuit-

The first subcooling heat exchanger (103) includes a high pressure channel (103a) and a low pressure channel (103b). In the first subcooling heat exchanger (103) a heat exchange takes place between the high pressure channel (103a) and the low pressure channel (103b) to subcool the refrigerant flowing through the high pressure channel ( 103a).

An inlet end of the high pressure channel (103a) is connected to an inlet pipe (60), and an inlet end of the low pressure channel (103b) is connected to a first-to bypass pipe (62a) It serves as a step for subcooling. The first bypass pipe (62a) includes a second expansion valve (81a) for subcooling. The second expansion valve (81a) is an electronic expansion valve that has an adjustable opening degree. An outlet end of the low pressure channel (103b) is connected to an end of a first injection pipe (107).

One end of the first injection pipe (107) is connected to the low pressure channel (103b) of the first subcooling heat exchanger (103), and the other end of the first injection pipe (107) is connected to a third refrigerant pipe (72). The other end of the first injection pipe (107) is connected to an outlet end of a check valve (CV10) in the third refrigerant pipe (72). The first subcooling heat exchanger (103) and the second expansion valve (81a) constitute a so-called economizer circuit.

The first sub-cooling heat exchanger (104) includes a high pressure channel (104a) and a low pressure channel (104b). In the first subcooling heat exchanger (104) a heat exchange takes place between the refrigerant flowing through the high pressure channel (104a) and the refrigerant flowing through the low pressure channel (104b) to subcool the refrigerant flowing through the high pressure channel (104a).

An inlet end of the high pressure channel (104a) is connected to the inlet pipe (60), and an inlet end of the low pressure channel (104b) is connected to a first-b bypass pipe (62b) that It serves as a step for subcooling. The first-b bypass pipe (62b) includes a second-b expansion valve (81b) for subcooling. The second-b expansion valve (81b) is an electronic expansion valve that has an adjustable opening degree. An outlet end of the low pressure channel (104b) is connected to an end of a second injection pipe (108).

One end of the second injection pipe (108) is connected to the low pressure channel (104b) of the first subcooling heat exchanger (104), and the other end of the second injection pipe (108) is connected to the second refrigerant pipe (71). The other end of the second injection pipe (108) is connected to an outlet end of a check valve (CV9) in the second refrigerant pipe (71). The first-b subcooling heat exchanger (104) and the second-b expansion valve (81b) constitute a so-called economizer circuit.

The first subcooling heat exchanger (105) includes a high pressure channel (105a) and a low pressure channel (105b). In the first subcooling heat exchanger (105) a heat exchange takes place between the refrigerant flowing through the high pressure channel (105a) and the refrigerant flowing through the low pressure channel (105b) to subcool the refrigerant flowing through the high pressure channel (105a).

An inlet end of the high pressure channel (105a) is connected to the inlet pipe (60), and an inlet end of the low pressure channel (105b) is connected to a first-c bypass pipe (62c) that It serves as a step for subcooling. The first-c bypass pipe (62c) includes a second-c expansion valve (81c) for subcooling. The second-c expansion valve (81c) is an electronic expansion valve that has an adjustable opening degree. An outlet end of the low pressure channel (105b) is connected to an end of a third injection pipe (109).

One end of the third injection pipe (109) is connected to the low pressure channel (105b) of the first subcooling heat exchanger (105), and the other end of the third injection pipe (109) is connected to the first refrigerant tube (70). The other end of the third injection pipe (109) is connected to an outlet end of a check valve (CV8) in the first refrigerant pipe (70). The first-c subcooling heat exchanger (105) and the second-c expansion valve (81c) constitute a so-called economizer circuit.

-Operation of the circuit-

Next, operations of the subcooling heat exchangers (103, 104, 105) and the expansion valves (81a, 81b, 81c) will be described with reference to Figures 8 and 9. The description of part of the operations also described in The first embodiment will not be repeated.

The compressed refrigerant in a fourth compressor (24) of a four-stage compressor (20) is discharged to a fourth discharge pipe (28). Compression and cooling operations are performed alternately on the four-stage compressor (20) and the intermediate heat exchangers (41, 42, 43) first to third so that the compression strokes of the four-stage compressor (20) approach to those of isothermal compression in order to reduce the compression power necessary for the four-stage compressor (20).

The refrigerant that flows through the fourth discharge pipe (28) passes through a fourth four-way valve (96) and flows into an external heat exchanger (44). In the outdoor heat exchanger (44), the refrigerant dissipates heat to the outside air to cool. The refrigerant cooled in the external heat exchanger (44) flows into a fourth refrigerant pipe (73). The refrigerant flowing through the fourth refrigerant pipe (73) passes through a check valve (CV11) and flows into the inlet pipe (60).

Part of the refrigerant that flows through the inlet pipe (60) flows into the first bypass pipe (62a). The pressure of the refrigerant flowing through the first bypass pipe (62a) (see "27" in Figures 8 and 9) is reduced in the second expansion valve (81a). The refrigerant whose pressure has been reduced in the second expansion valve to (81a) (see "28" in Figures 8 and 9) flows into the low pressure channel (103b) of the first heat exchanger subcooling (103). On the other hand, the other part of the refrigerant flowing through the inlet pipe (60) flows into the high pressure channel (103a) of the first subcooling heat exchanger (103) (see "27" in the Figures 8 and 9). In the first subcooling heat exchanger (103) a heat exchange takes place between the refrigerant flowing through the high pressure channel (103a) and the refrigerant flowing through the low pressure channel (103b) to subcool the refrigerant flowing through the high pressure channel (103a).

The refrigerant that has left the high pressure channel (103a) of the first subcooling heat exchanger (103) flows again through the inlet pipe (60) (see "31" in Figures 8 and 9), and flows into the high pressure channel (104a) of the first sub-cooling heat exchanger (104). On the other hand, the refrigerant that has left the low pressure channel (103b) of the first subcooling heat exchanger (103) (see "29" in Figures 8 and 9) flows into the first injection pipe (107). The refrigerant flowing through the first injection pipe (107) flows into the third refrigerant pipe (72) and is combined with the refrigerant (see "30" in Figures 8 and 9) in the third refrigerant pipe ( 72) to become a combined refrigerant (see "8" in Figures 8 and 9). That is, the refrigerant that has entered the first injection pipe (107) is injected towards the suction side of a fourth compressor (24).

Then, part of the refrigerant that has left the first subcooling heat exchanger (103) and flows through the inlet pipe (60) flows into the first-b bypass pipe (62b). The pressure of the refrigerant flowing through the first-b bypass pipe (62b) (see "31" in Figures 8 and 9) is reduced in the second-b expansion valve (81b). The refrigerant whose pressure has been reduced in the second-b expansion valve (81b) (see "32" in Figures 8 and 9) flows into the low-pressure channel (104b) of the first sub-subcooling heat exchanger (104). On the other hand, the other part of the refrigerant flowing through the inlet pipe (60) flows into the high pressure channel (104a) of the first subcooling heat exchanger (104) (see "31" in the Figures 8 and 9). In the first subcooling heat exchanger (104) a heat exchange takes place between the refrigerant flowing through the high pressure channel (104a) and the refrigerant flowing through the low pressure channel (104b) to subcool the refrigerant flowing through the high pressure channel (104a).

The refrigerant that has left the high pressure channel (104a) of the first subcooling heat exchanger (104) flows again through the inlet pipe (60) (see "34" in Figures 8 and 9) and flows inside the high pressure channel (105a) of the first-c subcooling heat exchanger (105). On the other hand, the refrigerant that has left the low pressure channel (104b) of the first subcooling heat exchanger (104) (see "33" in Figures 8 and 9) flows into the second injection pipe (108). The refrigerant flowing through the second injection pipe (108) flows into the second refrigerant pipe (71), and is combined with the refrigerant (see "5" in Figures 8 and 9) in the second refrigerant pipe (71) to become a combined refrigerant (see "6" in Figures 8 and 9). That is, the refrigerant that has entered the second injection pipe (108) is injected towards the suction side of a third compressor (23).

Part of the refrigerant that has left the first subcooling heat exchanger (104) and flowing through the inlet pipe (60) flows into the first-c bypass pipe (62c). The pressure of the refrigerant flowing through the first-c bypass pipe (62c) (see "34" in Figures 8 and 9) is reduced in the second-c expansion valve (81c). The refrigerant whose pressure has been reduced in the second-c expansion valve (81c) (see "35" in Figures 8 and 9) flows into the low pressure channel (105b) of the first-c subcooling heat exchanger (105). On the other hand, the other part of the refrigerant flowing through the inlet pipe (60) flows into the high pressure channel (105a) of the first subcooling heat exchanger (105) (see "34" in the Figures 8 and 9). In the first subcooling heat exchanger (105) a heat exchange takes place between the refrigerant flowing through the high pressure channel (105a) and the refrigerant flowing through the low pressure channel (105b) to subcool the refrigerant flowing through the high pressure channel (105a).

The refrigerant that has left the high pressure channel (105a) of the first subcooling heat exchanger (105) flows again through the inlet pipe (60) (see "38" in Figures 8 and 9), and flows into the high pressure channel (101a) of the second subcooling heat exchanger (101). On the other hand, the refrigerant that has left the low pressure channel (105b) of the first subcooling heat exchanger (105) (see "36" in Figures 8 and 9) flows into the first injection pipe (107). The refrigerant that flows through the first injection pipe (107) flows into the first refrigerant pipe (70) and is combined with the refrigerant (see "37" in Figures 8 and 9) that flows through the first water pipe. refrigerant (70) to become combined refrigerant (see "3" in Figures 8 and 9). That is, the refrigerant that has entered the third injection pipe (109) is injected towards the suction side of a second compressor (22). The other configurations, operations and advantages are similar to those of the first embodiment.

<Third embodiment>

A third embodiment according to the present invention will be described below. As illustrated in Figure 10, an air conditioner (140) according to the third embodiment has a configuration of a refrigerant circuit different from that of the air conditioner (1) of the first embodiment. In the third embodiment only the part of the configuration different from that of the first embodiment is described.

Specifically, the air conditioner 140 of the third embodiment will now be described. The air conditioner (140) includes a refrigerant circuit (143) in which the refrigerant flow is allowed to change reversibly, and can change between the cooling operation and the heating operation. The air conditioner (140) includes an outdoor unit (142) located outside and an indoor unit (141) located inside. The refrigerant circuit (143) of the air conditioner (140) is obtained by connecting an outdoor circuit (144) of the outdoor unit (142) and an indoor circuit (145) of the indoor unit (141) to each other through a communication pipe (146) and a communication pipe (147) of the liquid side. The refrigerant circuit (143) is filled with carbon dioxide (hereinafter referred to as refrigerant) and configured to perform a supercritical refrigeration cycle by multi-stage compression by circulating refrigerant in the refrigerant circuit (143).

<External circuit>

As illustrated in Figure 10, the external circuit (144) is connected to a two-stage compressor (150), an external heat exchange unit (160), first and second four-way valves (175, 176), first and second subcooling heat exchangers (191), 192), first to fifth expansion valves (201-205), an expander (193) and a gas-liquid separator (194). The external heat exchange unit (160) includes an intermediate heat exchanger (161) and an external heat exchanger (162).

The external circuit (144) is also connected to two oil separators (174, 174), a distributor (173), a capillary tube (170), a bridge circuit (172) and check valves (CV1-CV7).

In the third embodiment, the refrigerant circuit (143) switches between the cooling operation and the heating operation by switching the first and second four-way valves (175, 176).

The two-stage compressor (150) includes the first and second compressors (151, 152) and consists of a multi-stage compressor of the present invention. The first and second compressors (151, 152) are connected to the first and second discharge pipes (153, 154) by their discharge sides, while they are connected to the first and second suction pipes (155, 156) by their suction sides. Each of the compressors (151, 152) compresses the low pressure gaseous refrigerant sucked through one of the associated suction pipes (155, 156) to convert it into a high pressure gaseous refrigerant, which is then discharged from the download (153, 154).

The first four-way valve (175) has its first port connected to the first discharge pipe (153) of the first compressor (151), its second port connected to one end of the splice pipe (187), its third connected port to one end of the intermediate heat exchanger (161), and its fourth port connected to the second suction pipe (156) of the second compressor (152). The first four-way valve (175) is switched between a first state (a state indicated by a continuous line in Figure 10), in which the first port communicates with the third port and the second port communicates with the fourth port, and a second state (a state indicated by a dashed line in Figure 10), in which the first port communicates with the fourth port and the second port communicates with the third port.

The second four-way valve (176) has its first port connected to the second discharge pipe (154) of the second compressor (152), its second port connected to one end of the connection pipe (186), its third connected port to one end of the external heat exchanger (162), and its fourth port connected to the communication pipe (146) on the gas side. The first four-way valve (175) is switched between a first state (a state indicated by a continuous line in Figure 10), in which the first port communicates with the third port and the second port communicates with the fourth port, and a second state (a state indicated by a dashed line in Figure 10), in which the first port communicates with the fourth port and the second port communicates with the third port.

The check valve (CV1) is connected to a midpoint of the second suction pipe (156). The check valve (CV1) allows the refrigerant to flow from the first four-way valve (175) to the two-stage compressor (150), and prevents the refrigerant from flowing in the reverse direction.

The oil separators (174, 174) are connected to midpoints of the first and second discharge pipes (153, 154), respectively. The oil separators (174, 174) separate the lubricating oil contained in the high pressure gaseous refrigerant flowing through the discharge pipes (153, 154) of the high pressure gaseous refrigerant. The oil separators (174, 174) are connected to the oil outlet pipe (171, 171) through which the lubricating oil separated in the oil separators (174, 174) flows out of the oil separators (174, 174).

Specifically, the oil outlet pipe (171) of the oil separator (174) for the first discharge pipe (153) is connected to the second suction pipe (156). The oil outlet pipe (171) of the oil separator (174) for the second discharge pipe (154) is connected to the first suction pipe (155). The capillary tubes (170, 170) are connected to midpoints of the oil outlet pipes (171, 171), respectively.

The intermediate heat exchanger (161) and the external heat exchanger (162) are configured as fin and tube heat exchangers. The intermediate heat exchanger (161) corresponds in this embodiment to an intermediate heat exchanger of the present invention, and the external heat exchanger (162) corresponds in this embodiment to an external heat exchanger of the present invention. An outdoor fan (122) is arranged near each of the heat exchangers (161, 162) such that a heat exchange is performed between the outside air from the outside fan (122) and the refrigerant flowing through the heat exchanger tubes of heat exchangers (161, 162).

One end of the intermediate heat exchanger (161) is connected to the third port of the first four-way valve (175), and one end of the external heat exchanger (162) is connected to the third port of the second four-way valve ( 176). On the other hand, the other end of the intermediate heat exchanger (161) is connected to the first refrigerant pipe (181), and the other end of the external heat exchanger (162) is connected to the second refrigerant pipe (182) .

The other end of the second refrigerant pipe (182) branches into two parts, of which one is connected to the bridge circuit (172) and the other is connected to a second outlet port (P2) of the distributor (173). The check valve (CV3) and the capillary tube (170) are located between the branch point of the second refrigerant pipe (182) and the second outlet port (P2) of the distributor (173). The check valve (CV3) allows the refrigerant to flow from the distributor (173) to the branch point of the second refrigerant pipe (182), and prevents the refrigerant from flowing in the opposite direction.

The other end of the first refrigerant pipe (181) branches into two parts, of which one is connected to a midpoint (between the check valve (CV1) and the second compressor (152)) of the second pipe of suction (156) and the other is connected to a first outlet port (P1) of the distributor (173). The check valve (CV2) and the capillary tube (170) are located between the branch point of the first refrigerant pipe (181) and the first outlet port (P1) of the distributor (173). The check valve (CV2) allows the refrigerant to flow from the distributor (173) to the branch point of the first refrigerant pipe (181), and prevents the refrigerant from flowing in the opposite direction. The check valve (CV4) is located between the branch point of the first refrigerant pipe (181) and the connection point of the second suction pipe (156). The check valve (CV4) allows the refrigerant to flow from the branch point of the first refrigerant pipe (181) to the connection point of the second suction pipe (156), and prevents the refrigerant from flowing in one direction reverse.

The bridge circuit (172) is a circuit in which the check valves (CV5, CV6, CV7) and a fifth expansion valve (205) are bridged. In the bridge circuit (172), one connection end between one inlet end of the check valve (CV7) and the other end of the fifth expansion valve (205) is connected to the first outlet pipe (180), and a connection end located between the outlet end of the check valve (CV7) and an inlet end of the check valve (CV6) is connected to the communication line (147) of the liquid side. A refrigerant pipe connecting the communication line (147) of the liquid side and the first inner heat exchanger (211) includes a first inner expansion valve (206) having a varying degree of opening. A refrigerant pipe connecting the communication line (147) of the liquid side and the second internal heat exchanger (212) includes a second internal expansion valve (207) having a varying degree of opening. A connection end located between an outlet end of the check valve (CV6) and an outlet end of the check valve (CV5) is connected to the inlet pipe (179). One end of the fifth expansion valve (205) is connected to the distributor (173), and one inlet end of the check valve (CV5) is connected to the second refrigerant pipe (182).

In the inlet pipe (179) the first subcooling heat exchanger (191), the expander (193), the gas-liquid separator (194) and the second subcooling heat exchanger (192) are arranged in this order.

The first subcooling heat exchanger (191) includes a high pressure channel (191a) and a low pressure channel (191b). In the first subcooling heat exchanger (191) a heat exchange takes place between the refrigerant flowing through the high pressure channel (191a) and the refrigerant flowing through the low pressure channel (191b) to subcool the refrigerant that flows through the high pressure channel (191a).

An inlet end of the high pressure channel (191a) is connected to the inlet pipe (179), and an inlet end of the low pressure channel (191b) is connected to the first bypass pipe (177) which serves as A step for subcooling. The first bypass pipe (177) includes a second expansion valve (202) for subcooling. The second expansion valve (202) is an electronic expansion valve that has an adjustable opening degree. An outlet end of the low pressure channel (191b) is connected to one end of the injection pipe (188).

One end of the injection pipe (188) is connected to the low pressure channel (191b) of the first subcooling heat exchanger (191), and the other end of the injection pipe (188) is connected to the first pipe of refrigerant (181). The other end of the injection pipe (188) is connected to an outlet end of the check valve (CV4) in the first refrigerant pipe (181).

The expander (193) includes an expander housing that has a vertically elongated cylindrical shape, and is located between the first subcooling heat exchanger (191) and the gas-liquid separator (194) on the inlet pipe (179) . An expansion mechanism is provided in the expander housing to generate energy by expanding the refrigerant. The expander (193) constitutes a so-called rotary positive displacement fluid machine. The expander (193) expands the inlet refrigerant and sends the expanded refrigerant back to the inlet pipe (179).

The inlet pipe (179) includes a bypass pipe (183) that avoids the expander (193). One end of the bypass pipe (183) is connected to an inlet end of the expander (193), and the other end of the bypass pipe (183) is connected to an outlet end of the expander (193) to avoid expander (193). The bypass pipe (183) includes a first expansion valve (201). The first expansion valve (201) is an electronic expansion valve that has an adjustable opening degree.

The gas-liquid separator (194) is an airtight container that has a vertically elongated cylindrical shape. The gas-liquid separator (194) is connected to the inlet pipe (179), the first outlet pipe (180) and the second outlet pipe (184). The inlet pipe (179) is open in an upper part of the interior space of the gas-liquid separator (194). The first outlet pipe (180) is open in a lower part of the interior space of the gas-liquid separator (194). The second outlet pipe (184) is open in an upper part of the interior space of the gas-liquid separator (194). In the gas-liquid separator (194), the refrigerant from the inlet pipe (179) is separated into a saturated liquid and a saturated gas, the saturated liquid leaving the first outlet pipe (180) and the gas leaving saturated by the second outlet pipe (184).

One end of the second outlet pipe (184) is connected to the gas-liquid separator (194), and the other end of the second outlet pipe (184) is connected to a midpoint of the second bypass pipe (178 ). The second outlet pipe (184) includes a fourth expansion valve (204). The fourth expansion valve (204) is an electronic expansion valve that has an adjustable opening degree.

The second subcooling heat exchanger (192) is connected to a midpoint of the first outlet pipe (180). The second subcooling heat exchanger (192) includes a high pressure channel (192a) and a low pressure channel (192b). In the second subcooling heat exchanger (192) a heat exchange takes place between the refrigerant flowing through the high pressure channel (192a) and the refrigerant flowing through the low pressure channel (192b) to subcool the refrigerant that flows through the high pressure channel (192a).

An inlet end of the high pressure channel (192a) is connected to an outlet end of the gas liquid separator (194), and an outlet end of the high pressure channel (192a) is connected to the bridge circuit (172). An inlet end of the low pressure channel (192b) is connected to the second bypass pipe (178) that serves as a subcooling passage, and an outlet end of the low pressure channel (192b) is connected to the other end of the return pipe (185).

One end of the second bypass pipe (178) is connected to a midpoint of the first outlet pipe (180) between the gas-liquid separator (194) and the second subcooling heat exchanger (192), and the Another end of the second bypass pipe (178) is connected to an inlet end of the low pressure channel (192b) of the second subcooling heat exchanger (192), where the second outlet pipe (184) is connected between a extreme and the other extreme. The second bypass pipe (178) includes a third expansion valve (203). The third expansion valve (203) is an electronic expansion valve that has an adjustable opening degree.

One end of the return pipe (185) is connected to the other end of the connection pipe (186), and the other end of the return pipe (185) is connected to an outlet end of the low pressure channel (192b ) of the second subcooling heat exchanger (192).

One end of the connection pipe (186) is connected to the second port of the second four-way valve (176), and the other end of the connection pipe (186) is connected to one end of the return pipe (185 ) and the other end of the first suction pipe (155), where the other end of the splice pipe (187) is connected to a midpoint of the connecting pipe (186) between the second port and the connection point which connects the end of the return pipe (185) and the other end of the first suction pipe (155).

One end of the connection pipe (187) is connected to the second port of the first four-way valve (175), and the other end of the connection pipe (187) is connected to a midpoint of the connection pipe ( 186).

<Internal circuit>

In the inner circuit (145) there are arranged a pair formed by the first inner expansion valve (206) and the first inner heat exchanger (211) and a pair formed by the second inner expansion valve (207) and the second exchanger of internal heat (212), in this order from a liquid side to a gas side, and are connected in parallel. Each of the inner expansion valves (206, 207) is an electronic expansion valve that has an adjustable opening degree. Each of the interior heat exchangers (211, 212) is a fin and tube fin heat exchanger. Although not shown, close to the indoor heat exchangers (211, 212) are provided indoor fans to send indoor air to the indoor heat exchangers (211, 212). In each of the indoor heat exchangers (211,212) a heat exchange takes place between the refrigerant and the indoor air.

<Outdoor unit configuration>

As illustrated in Figure 12, the outdoor unit (142) includes an outer housing (163). The outer housing (163) is in the form of a rectangular box elongated vertically, and has an air inlet (164) in a lower part of the front surface and an air outlet (165) in an upper surface thereof. The outer heat exchange unit (160) and the outer fan (166) are arranged in the outer housing (163).

The external fan (166) is a fan for sending air taken in the outer housing (163) to the heat exchangers (161, 162), and consists of a so-called siroco fan. The outdoor fan (166) is located above the heat exchangers (161, 162) in the outer housing (163). The outside fan (166) causes the air sucked through the air inlet (164) to pass through the heat exchangers (161, 162) and then flow outward through the air outlet (165) .

As illustrated in Figure 12, in the outer housing (163), the external heat exchange unit (160) is oriented such that the intermediate heat exchanger (161) and the external heat exchanger (162) are stacked in this order from the bottom. That is, the external heat exchanger (162) is located above the intermediate heat exchanger (161).

Each of the heat exchangers (161, 162) is a so-called fin and tube fin heat exchanger. Each of the heat exchangers (161, 162) includes a plurality of groups of heat exchanger tubes, each of which includes a plurality of heat exchanger tubes and a plurality of U-shaped tubes, and also It includes a heat transfer fin.

The groups of heat exchanger tubes are aligned in the upward and downward direction. A plurality of heat exchanger tubes is arranged in each of the heat exchanger tube groups such that three rows of heat exchanger tubes, each along an air flow direction, are arranged side by side and each of the three rows includes two heat exchanger tubes aligned in the up and down direction. In addition, a first tube bank is arranged on the windward side, a second tube bank is arranged in the center, and a third tube bank is arranged on the leeward side. That is, in each of the heat exchanger tube groups, the heat exchanger tubes are arranged in two stages in each row.

-Operation-

Next, the operation of the air conditioner (140) will be described. In the air conditioner (140), the refrigerant circuit (143) switches between the cooling operation and the heating operation by switching the first and second four-way valves (175, 176). Reference numbers 1-18 in Figures 10 and 11 represent refrigerant pressure states.

-Cooling operation-

The cooling operation of the air conditioner (140) will be described with reference to Figure 10. In Figure 10, a refrigerant flow in this cooling operation is represented by continuous line arrows. In the cooling operation, the external heat exchanger (162) functions as a heat sink, and the internal heat exchangers (211,212) function as evaporators, thus performing a two-stage supercritical compression refrigeration cycle. The intermediate heat exchanger (161) functions as a cooler that cools the high pressure refrigerant discharged from the first compressor (151).

In the cooling operation, all four-way valves (175, 176) are adjusted in the first states and the two-stage compressor (150) is operated. When the two-stage compressor (150) is operated, the refrigerant is compressed in the compressors (161, 162). The compressed refrigerant in the first compressor (151) is discharged to the first discharge pipe (153) (see "2" in Figures 10 and 11). In this state, the oil separator (174) of the first discharge pipe (153) separates the lubricating oil from the gaseous refrigerant flowing through the first discharge pipe (153). The separated lubricating oil is sent from the oil outlet pipe (171) to the second suction pipe (156). The refrigerant that flows through the first discharge pipe (153) passes through the first four-way valve (175) and flows into the intermediate heat exchanger (161). In the intermediate heat exchanger (161), the refrigerant dissipates heat to the outside air to cool. The refrigerant cooled in the intermediate heat exchanger (161) flows into the first refrigerant pipe (181). The refrigerant flowing through the first refrigerant pipe (181) (see "3" in Figures 10 and 11) passes through the check valve (CV4) and is combined with the refrigerant flowing through the injection pipe ( 188). The combined refrigerant flows into the second suction pipe (156) and is sucked into the second compressor (152) (see "4" in Figures 10 and 11).

The compressed refrigerant in the second compressor (152) (see "5" in Figures 10 and 11) is discharged into the second discharge pipe (154). The compression and cooling operations described above are alternately performed so that the compression strokes of the two-stage compressor (150) are close to those of isothermal compression in order to reduce the compression power necessary for the two-stage compressor ( 150). At this time, the oil separator (174) of the second discharge pipe (154) separates the oil gaseous refrigerant lubricant flowing through the second discharge pipe (154). The separated lubricating oil is sent from the oil outlet pipe (171) to the first suction pipe (155). The refrigerant that flows through the second discharge pipe (154) passes through the second four-way valve (176) and flows into the exterior heat exchanger (162). In the outdoor heat exchanger (162), the refrigerant dissipates heat to the outside air to cool. The refrigerant cooled in the external heat exchanger (162) flows into the second refrigerant pipe (182). The refrigerant flowing through the second refrigerant pipe (182) passes through the check valve (CV5) and flows into the inlet pipe (179).

Part of the refrigerant flowing through the inlet pipe (179) (see "6" in Figures 10 and 11) flows into the first bypass pipe (177). The pressure of the refrigerant flowing through the first bypass pipe (177) is reduced in the second expansion valve (202). The refrigerant whose pressure has been reduced in the second expansion valve (202) (see "7" in Figures 10 and 11) flows into the low pressure channel (191b) of the first subcooling heat exchanger (191). On the other hand, the other part of the refrigerant flowing through the inlet pipe (179) flows into the high pressure channel (191a) of the first subcooling heat exchanger (191) (see "6" in Figures 10 and eleven). In the first subcooling heat exchanger (191) a heat exchange takes place between the refrigerant flowing through the high pressure channel (191a) and the refrigerant flowing through the low pressure channel (191b) to subcool the refrigerant that flows through the high pressure channel (191a).

The refrigerant that has left the high pressure channel (191a) of the first subcooling heat exchanger (191) flows again through the inlet pipe (179), and the refrigerant that has left the low pressure channel (100b) of the First subcooling heat exchanger (191) flows into the injection pipe (188). The refrigerant flowing through the injection pipe (188) (see "8" in Figures 10 and 11) flows into the first refrigerant pipe (181) and is combined with the refrigerant in the first refrigerant pipe (181) ) (see "4" in Figures 10 and 11). That is, the refrigerant that has entered the injection pipe (188) is injected towards the suction side of the second compressor (152).

The refrigerant that has left the high pressure channel (191a) of the first subcooling heat exchanger (191) flows again through the inlet pipe (179) (see "9" in Figures 1 and 2), and part of This refrigerant flows into the expander (193). The expander (193) expands the inlet refrigerant (see "9" to "11" in Figures 10 and 11), and sends the expanded refrigerant back to the inlet pipe (179). On the other hand, the other part of the refrigerant that has left the high pressure channel (191a) of the first subcooling heat exchanger (191) branches into the bypass line (183). The refrigerant flowing through the bypass line (183) undergoes a pressure reduction in the first expansion valve (201) (see "9" to "10" in Figures 10 and 11) and returns to the line entry (179). The refrigerant that has left the expander (193) and the refrigerant that has left the bypass pipe (183) combine with each other in the inlet pipe (179) (see "12" in Figures 10 and 11) and flow inside the gas-liquid separator (194). The gas-liquid separator (194) separates the inlet refrigerant into gaseous refrigerant (see "15" in Figures 10 and 11) and liquid refrigerant (see "13" in Figures 10 and 11).

The liquid refrigerant (see "13" in Figures 10 and 11) that has left the gas-liquid separator (194) flows through the inlet pipe (179), and part of this refrigerant flows into the second pipe bypass (178). On the other hand, the other part of the refrigerant flowing through the inlet pipe (179) flows into the high pressure channel (192a) of the second subcooling heat exchanger (192).

The refrigerant (see "15" in Figures 10 and 11) that has left the gas-liquid separator (194) flows through the second outlet pipe (184), undergoes a pressure reduction in the fourth expansion valve (204) (see "18" in Figures 10 and 11), and flows into the second bypass pipe (178). The pressure of the refrigerant flowing through the second bypass pipe (178) is reduced in the third expansion valve (203). The reduced pressure refrigerant (see "17" in Figures 10 and 11) in the third expansion valve (203) is combined with the refrigerant flowing through the second outlet pipe (184).

The combined refrigerant flows into the low pressure channel (192b) of the second subcooling heat exchanger (192). In the second subcooling heat exchanger (192) a heat exchange takes place between the refrigerant flowing through the high pressure channel (192a) and the refrigerant flowing through the low pressure channel (192b) to subcool the liquid refrigerant flowing through the high pressure channel (192a).

The liquid refrigerant that has left the high pressure channel (192a) of the second subcooling heat exchanger (192) (see "14" in Figures 10 and 11) flows again through the first outlet pipe (180), passes through the check valve (CV7) of the bridge circuit (172) and flows into the communication line (147) of the liquid side. On the other hand, the refrigerant that has left the low pressure channel (192b) of the second subcooling heat exchanger (192) flows through the return line (185). The refrigerant that has left the return line (185) is combined with the refrigerant that has left the connection pipe (186). The combined refrigerant flows into the suction side of the first compressor (151).

Part of the liquid refrigerant flowing through the communication line (147) on the liquid side branches and undergoes a pressure reduction in the first inner expansion valve (206). The reduced pressure refrigerant (see "16a" in Figures 10 and 11) flows into the first interior heat exchanger (211). In the first indoor heat exchanger (211), the liquid refrigerant absorbs heat from the indoor air and evaporates. The evaporated gaseous refrigerant flows into the communication line (146) on the gas side.

The pressure of the other part of the liquid refrigerant flowing through the communication line (147) of the liquid side is reduced in the second inner expansion valve (207). The reduced pressure refrigerant (see "16b" in Figures 10 and 11) flows into the second interior heat exchanger (212). In the second indoor heat exchanger (212), the liquid refrigerant absorbs heat from the indoor air and evaporates. The evaporated gaseous refrigerant flows into the communication line (146) on the gas side.

The refrigerant that has left the first indoor heat exchanger (211) and the refrigerant that has left the second indoor heat exchanger (212) are combined with each other in the communication line (146) on the gas side. The refrigerant that flows through the communication line (146) on the gas side passes through the second four-way valve (176) and flows into the connecting pipe (186). The refrigerant that flows through the connection pipe (186) is combined with the refrigerant that flows through the return pipe (185) and is sucked into the first suction pipe (155). The refrigerant flowing through the first suction pipe (155) (see "1" in Figures 10 and 11) is compressed again in the first compressor (151) of the two-stage compressor (150).

-Heating operation-

The heating operation of the air conditioner (140) will now be described with reference to Figure 13. In Figure 13, a flow of refrigerant in this heating operation is represented by dashed arrows. In the heating operation, the internal heat exchangers (211, 212) function as heat sinks, and the intermediate heat exchanger (161) and the external heat exchanger (162) function as evaporators, thus performing a refrigeration cycle Supercritical two-stage compression.

In the heating operation, all four-way valves (175, 176) are adjusted in the second states and the two-stage compressor (150) is operated. When the two-stage compressor (150) is operated, the refrigerant is compressed in the compressors (151, 152). The compressed refrigerant in the first compressor (151) is discharged to the first discharge pipe (153). The oil separator (174) of the first discharge pipe (153) separates the lubricating oil from the gaseous refrigerant flowing through the first discharge pipe (153). The separated lubricating oil is sent from the oil outlet pipe (171) to the second suction pipe (156). The refrigerant flowing through the first discharge pipe (153) passes through the first four-way valve (175) and is sucked into the second compressor (152). The refrigerant is compressed further into the second compressor (152). Thus, unlike the cooling operation, the two-stage compression is performed without cooling in the heating operation. In this heating operation, the temperature of the refrigerant discharged from the two-stage compressor (150) does not decrease, unlike the case in which the two-stage compression is carried out with cooling. As a result, the heating operation shows a greater heating capacity than in the case of two-stage compression with cooling.

The refrigerant discharged from the second compressor (152) passes through the second four-way valve (176) and is sent to the first and second indoor heat exchangers (211, 212). In the first and second indoor heat exchangers (211, 212), the refrigerant dissipates heat to the outside air to cool. The refrigerant cooled in the indoor heat exchangers (211, 212) is subjected to a pressure reduction in the first and second inner expansion valves (206, 207) and then sent to the bridge circuit (172). This refrigerant passes through the check valve (CV6) and flows into the inlet pipe (179).

Part of the refrigerant that flows through the inlet pipe (179) flows into the first bypass pipe (177). The pressure of the refrigerant flowing through the first bypass pipe (177) is reduced in the second expansion valve (202). The refrigerant whose pressure has been reduced in the second expansion valve (202) flows into the low pressure channel (191b) of the first subcooling heat exchanger (191). On the other hand, the other part of the refrigerant flowing through the inlet pipe (179) flows into the high pressure channel (191a) of the first subcooling heat exchanger (191). In the first subcooling heat exchanger (191) a heat exchange takes place between the refrigerant flowing through the high pressure channel (191a) and the refrigerant flowing through the low pressure channel (191b) to subcool the refrigerant that flows through the high pressure channel (191a).

The refrigerant that has left the high pressure channel (191a) of the first subcooling heat exchanger (191) flows again through the inlet pipe (179), and the refrigerant that has left the low pressure channel (191b) of the First subcooling heat exchanger (191) flows into the injection pipe (188). The refrigerant flowing through the injection pipe (188) flows into the first refrigerant pipe (181) and is combined with the refrigerant in the first refrigerant pipe (181). That is, the refrigerant that has entered the injection pipe (188) is injected towards the suction side of the second compressor (152).

The refrigerant that has left the high pressure channel (191a) of the first subcooling heat exchanger (191) flows again through the inlet pipe (179), and part of the refrigerant flows into the expander (193). The expander (193) expands the inlet refrigerant and sends the expanded refrigerant back to the inlet pipe (179). On the other hand, the other part of the refrigerant that has left the high pressure channel (191a) of the first Subcooling heat exchanger (191) branches into the bypass pipe (183). The refrigerant flowing through the bypass pipe (183) is subjected to a pressure reduction in the first expansion valve (201) and returns to the inlet pipe (179). The refrigerant that has left the expander (193) and the refrigerant that has left the bypass pipe (183) are combined with each other in the inlet pipe (179) and flow into the gas liquid separator (194). The gas-liquid separator (194) separates the inlet refrigerant into gaseous refrigerant and liquid refrigerant.

The liquid refrigerant that has left the gas-liquid separator (194) flows through the first outlet pipe (180), and part of this refrigerant flows into the second bypass pipe (178). On the other hand, the other part of the refrigerant flowing through the inlet pipe (179) flows into the high pressure channel (192a) of the second subcooling heat exchanger (192).

The gaseous refrigerant that has left the gas-liquid separator (194) flows through the second outlet pipe (184), undergoes a pressure reduction in the fourth expansion valve (204) and flows into the second pipe bypass (178). The pressure of the refrigerant flowing through the second bypass pipe (178) is reduced in the third expansion valve (203). The refrigerant whose pressure has been reduced in the third expansion valve (203) is combined with the refrigerant in the second outlet pipe (184).

The combined refrigerant flows into the low pressure channel (192b) of the second subcooling heat exchanger (192). In the second subcooling heat exchanger (192) a heat exchange takes place between the refrigerant flowing through the high pressure channel (192a) and the refrigerant flowing through the low pressure channel (192b) to subcool the liquid refrigerant flowing through the high pressure channel (192a).

The liquid refrigerant that has left the high pressure channel (192a) of the second subcooling heat exchanger (192) flows again through the first outlet pipe (180), is subjected to a pressure reduction in the fifth expansion valve (205) of the bridge circuit (172), and then sent to the distributor (173). The refrigerant distributed in the distributor (173) passes through the capillary tube (170) and the check valves (CV2, CV3) and flows into the intermediate heat exchanger (161) and the external heat exchanger (162). In the intermediate heat exchanger (161) the external heat exchanger (162), the liquid refrigerant absorbs heat from the outside air and evaporates. The refrigerant that has left the intermediate heat exchanger (161) passes through the first four-way valve (175), flows into the junction pipe (187) and then flows into the connecting pipe (186) ).

The refrigerant that has left the external heat exchanger (162) passes through the second four-way valve (176), flows into the connecting pipe (186) and is combined with the refrigerant that has left the heat exchanger. intermediate heat (161). The combined refrigerant flows through the connecting pipe (186) and is combined with the refrigerant flowing through the return pipe (185). The combined refrigerant flows into the first suction pipe (155). The refrigerant flowing through the first suction pipe (155) is compressed again into the first compressor (151) of the two-stage compressor (150).

-External unit-

As illustrated in Figure 12, the air taken in the outer casing (163) from the air inlet (164) is subjected to heat exchange in the intermediate heat exchanger (161) and the external heat exchanger (162) , flows into the upper space of the outer shell (163), and is ejected through the air outlet (124).

The outdoor unit (3) is of a so-called upward blow type, in which air is drawn through the air inlet (164) on the side surface and blown up from the air outlet (124 ). Therefore, the air flow rate is higher in an upper part of the air inlet (164) than in a lower part of the air inlet (164). As illustrated in Figure 11, the pressure of the refrigerant flowing through the intermediate heat exchanger (161) is lower than that of the refrigerant flowing through the external heat exchanger (162) and, therefore, the density of the refrigerant that flows through the intermediate heat exchanger (161) is smaller than that of the refrigerant that flows through the external heat exchanger (162). In view of this, when the mass flow rate of the refrigerant flowing through the intermediate heat exchanger (161) is substantially equal to that of the refrigerant flowing through the external heat exchanger (162), the volumetric flow rate of the refrigerant in the heat exchanger Intermediate (161) is higher than that of the refrigerant flowing through the external heat exchanger (162). Even when the number of refrigerant paths in the intermediate heat exchanger (161) is equal to that of the external heat exchanger (162), the flow rate of the refrigerant flowing through the intermediate heat exchanger (161) is higher than that of the refrigerant flowing through the external heat exchanger (162) and, therefore, the loss of refrigerant pressure in the intermediate heat exchanger (161) is greater than in the external heat exchanger (162).

The external heat exchanger (162) located in an upper part of the outer casing (163), where the air flow rate is high, has a high heat exchange efficiency and can be reduced in size. On the other hand, the intermediate heat exchanger (161) located in a lower part of the outer casing (163), where the air flow rate is low, has a low heat exchange efficiency. Therefore, to increase the amount of heat exchange, the intermediate heat exchanger (161) must be larger than in the case where this exchanger is located in an upper part.

For this reason, the size of the outdoor heat exchange unit (160) does not increase even if the size of the outdoor heat exchanger (162) and the intermediate heat exchanger (161) increases.

An increase in the size of the intermediate heat exchanger (161) increases the number of refrigerant paths in the intermediate heat exchanger (161). Therefore, in the intermediate heat exchanger (161), the refrigerant flow rate in each refrigerant path decreases, resulting in a decrease in the loss of refrigerant pressure that passes through the refrigerant path. The flow rate of the refrigerant flowing through the intermediate heat exchanger (161) is originally high and, therefore, a decrease in the flow rate due to an increase in the number of refrigerant paths produces a relatively large reduction in the loss of pressure

On the other hand, reducing the size of the external heat exchanger (162) reduces the number of refrigerant paths in the external heat exchanger (162). Reducing the number of refrigerant paths increases the flow rate of the refrigerant in each refrigerant path, increasing the loss of pressure of the refrigerant that passes through the refrigerant path.

However, since the flow rate of the refrigerant flowing through the external heat exchanger (162) is originally low, a certain degree of flow rate increase due to the reduction in the number of refrigerant paths causes a relatively increased small pressure loss resulting from increased flow rate.

Therefore, by arranging the external heat exchanger (162) above the intermediate heat exchanger (161) the pressure losses of the refrigerant in the intermediate heat exchanger (161) can be reduced with a reduced degree of increase in the size of the outdoor heat exchange unit (160).

-Advantages of third embodiment-

In the third embodiment, since the outer heat exchanger (162) is located in an upper part of the outer housing (163), where the air flow rate is high, the heat exchange efficiency of the exchanger can be increased of external heat (162). In addition, since the external heat exchanger (162), which has a low coolant flow rate, is located in an upper part of the outer casing (163), where the air flow rate is high, the size of the exchanger External heat (162) can be reduced without increasing the loss of refrigerant pressure.

On the other hand, the intermediate heat exchanger (161) is located in a lower part of the outer casing (163), where the air flow rate is low, to increase the number of coolant paths, which ensures prevention of an increase in the pressure loss of the refrigerant in the intermediate heat exchanger (161).

In the configuration described above, the external heat exchanger (162), in which the loss of refrigerant pressure does not increase easily, is located at the top to reduce the size, which reduces the loss of refrigerant pressure in the intermediate heat exchanger (161) with a reduced size increase in the outdoor heat exchange unit (160). The other configurations, operations and advantages are similar to those of the first and second embodiments.

-Variation of the third embodiment-

A variation of the third embodiment of the present invention will now be described with reference to the drawings. An air conditioner according to this variation has a different heat exchanger configuration than that of the air conditioner (140) of the third embodiment. In this variation only the part of the configuration different from that of the third embodiment is described.

Specifically, as illustrated in Figures 14 and 15, the outdoor unit (142) includes the outer housing (163). The outer shell (163) is in the form of a rectangular box elongated vertically, and has the air inlet (164) in a lower part of the front surface and the air outlet (165) in an upper surface thereof. The outer heat exchange unit (160) and the outer fan (166) are arranged in the outer housing (163). The external heat exchange unit (160) includes the external heat exchanger (162) and the intermediate heat exchanger (161).

The external fan (166) is a fan for sending air taken in the outer housing (163) to the heat exchangers (161, 162), and consists of a so-called siroco fan. The outdoor fan (166) is located above the heat exchangers (161, 162) in the outer housing (163). The outside fan (166) causes the air sucked through the air inlet (164) to pass through the heat exchangers (161, 162) and then flow out through the air outlet (165).

As illustrated in Figure 14, the intermediate heat exchanger (161) and the external heat exchanger (162) are stacked in the outer casing (163), in this order from the bottom.

-Configuration of the heat exchanger-

As illustrated in Figures 14 and 15, each of the heat exchangers (161, 162) of this variation includes a first concentrate collecting pipe (240), a second concentrate collecting pipe (250), a large amount of flat tubes (231) and a large number of fins (235). The first concentrate collecting pipe (240), the second concentrate collecting pipe (250), the flat tubes (231) and the fins (235) are made of an aluminum alloy and welded together.

The first concentrate collecting pipe (240) and the second concentrate collecting pipe (250) consist of thin hollow tubes. In each of the heat exchangers (161, 162), the first concentrate collecting pipe (240) is located at one end of the flat tubes (231) and the second concentrate collecting pipe (250) is located at the other end of flat tubes (231). That is, both the first concentrate collecting pipe (240) and the second concentrate collecting pipe (250) extend in the upward and downward direction such that their axis extends vertically.

The first concentrate collecting pipe (240) has its upper and lower ends closed, and has its lower end connected to a first connecting pipe (240b). The first connection pipe (240b) communicates with a liquid side of the refrigerant circuit (143). That is, the first concentrate collecting pipe (240) constitutes a liquid side manifold through which the liquid containing refrigerant flows (liquid single-phase refrigerant or gas-liquid two-phase refrigerant). The second concentrate collecting pipe (250) has its upper and lower ends closed, and a second connecting pipe (250b) is connected to an upper part of the second concentrate collecting pipe (250). The second connection pipe (250b) is connected to a gas side of the refrigerant circuit (143). That is, the second concentrate collecting pipe (250) constitutes a gas side manifold through which a gaseous refrigerant flows.

Each of the heat exchangers (161, 162) of this variation includes a plurality of flat tubes (231). Each of the flat tubes (231) is a heat exchanger tube whose cross-sectional shape perpendicular to the axis thereof is a flat ellipse or a rectangle. In each of the heat exchangers (161, 162), the flat tubes (231) extend in transverse direction with their flat side surfaces facing each other. The flat tubes (231) are arranged side by side at predetermined intervals in the up and down direction. One end of each of the flat tubes (231) is located in the first concentrate collecting pipe (240), and the other end thereof is located in the second concentrate collecting pipe (250).

As illustrated in Figure 15, each of the flat tubes (231) includes a plurality of coolant paths (232). Coolant paths (232) are steps that extend in the direction in which the flat tubes (231) extend. In each of the flat tubes (231), the refrigerant paths (232) are arranged in a row along a transverse direction perpendicular to the direction in which the flat tubes (231) extend. Each of the coolant paths (232) of the flat tubes (231) has one end in communication with the interior space of the first concentrate collecting pipe (240) and the other end in communication with the interior space of the second pipe concentrate collector (250). The refrigerant paths (232) constitute fluid passages of the present invention.

Each of the fins (235) is a corrugated fin that bends up and down and is located between the flat tubes (231) adjacent to each other in the up and down direction. Each of the fins (235) includes a plurality of heat transfer parts (236) arranged in the direction in which the flat tubes (231) extend. Each of the heat transfer parts (236) has a plate shape that extends from one of the flat tubes (231) adjacent to the other. The heat transmission parts (236) include a plurality of lattices (237) that bend outwardly from the heat transmission parts (236). The lattices (237) extend in the up and down direction so that they are substantially parallel to the leading edges (i.e., the windward ends) of the heat transfer parts (236). In the heat transfer parts (236), the lattices (237) are arranged side by side from the windward side to the leeward side.

The leeward ends of the heat transfer parts (236) are attached to the protruding plate portions (238), which protrude further to leeward. Each of the protruding plate parts (238) is in the form of a trapezoidal plate that protrudes from the heat transfer parts (236) in the up and down direction. In each of the heat exchangers (161, 162), the protruding plate portions (238, 238) adjacent in the upward and downward direction overlap each other in the thickness direction, and are substantially in contact with each other. .

The amount of flat tubes (231) and fins (235, 235) is two or more in each case. The fins (235, 235) are disposed between the flat tubes (231) arranged in the upward and downward direction. In the intermediate heat exchangers (41, 42, 43, 161), the air passes between the flat tubes (231) arranged in the direction up and down, and exchanges heat with the fluid flowing through the fluid passages (232) in the flat tubes (231).

The intermediate heat exchanger (161) has a small loss of stacking (ventilation resistance) and, therefore, has a high velocity of the air flowing inside it. In addition, flat tubes (231) increase the heat transfer area of the refrigerant and, therefore, the heat exchange efficiency of the refrigerant increases. Consequently, the coefficient of performance (COP) of the cooling system is improved. Since the flat tubes (231) have smaller pipe diameters than conventional heat exchanger tubes, the flow rate in the tubes increases. Therefore, the refrigerant that passes through the refrigerant paths (232) has a great loss of pressure.

However, in the intermediate heat exchanger (161) located in the lower part of the outer casing (163), where the air flow rate is low, it has a low heat exchange efficiency. Therefore, to increase the amount of heat exchange, the intermediate heat exchanger (161) must be larger than in the case where this exchanger is located at an upper part. The larger intermediate heat exchanger (161) includes a larger number of refrigerant paths (232) and, therefore, the flow rate of the refrigerant in the refrigerant paths (232) of the intermediate heat exchanger (161) decreases , which reduces the loss of refrigerant pressure that occurs when the refrigerant passes through the refrigerant paths (232). Consequently, the reduction in the pipe diameter of the flat tubes (231) relatively reduces the degree of increase in the loss of refrigerant pressure.

The external heat exchanger (162) has a small loss of stacking and, therefore, has a high velocity of the air flowing inside it. In addition, flat tubes (231) increase the heat transfer area of the refrigerant and, therefore, the heat exchange efficiency of the refrigerant increases. Consequently, the coefficient of performance (COP) of the cooling system is improved. Since the flat tubes (231) have smaller pipe diameters than those of conventional heat exchanger tubes, the flow rate in the tubes increases. Therefore, the refrigerant that passes through the refrigerant paths (232) has a great loss of pressure.

However, since the flow rate of the refrigerant flowing through the external heat exchanger (162) is originally low, even when the flow rate increases to some extent due to a reduction in the pipe diameter of the flat tubes (231 ), the magnitude of the increase in pressure loss due to this increase is relatively small.

In this variation, since the intermediate heat exchanger (161) and the external heat exchanger (162) include the flat tubes (231), which include in each case the refrigerant paths (232) and the fins (235, 235 ), the loss of stacking (ventilation resistance) can be reduced. As a result, the speed of the air flowing through the air passages increases. In addition, flat tubes (231) increase the heat transfer area of the refrigerant, which increases the heat exchange efficiency of the refrigerant. As a result, the coefficient of performance (COP) of the air conditioner can be improved. The other configurations, operations and advantages are similar to those of the third embodiment.

<Reference example>

A reference example will be described below. As illustrated in Figures 18 and 19, in this reference example, the distribution of the air flow rate in the indoor unit is uniform in the up and down direction.

An external heat exchange unit (40) of this reference example is configured such that an external heat exchanger (44), a first intermediate heat exchanger (41), a second intermediate heat exchanger (42) and A third intermediate heat exchanger (43) is stacked in this order from the bottom. The first intermediate heat exchanger (41) and the second intermediate heat exchanger (42) can be replaced with each other in the up and down direction.

The size of the heat exchanger increases in this order: external heat exchanger (44), third intermediate heat exchanger (43), first intermediate heat exchanger (41) and second intermediate heat exchanger (42).

The heat exchangers (41, 42, 43, 44) are so-called fin heat exchangers and cross-fin type tubes. Each of the heat exchangers (41, 42, 43, 44) includes a plurality of groups (50) of heat exchanger tubes, each of which includes a plurality of heat exchanger tubes (52) and a plurality of U-shaped tubes, and also includes heat transfer fins (51).

The groups (50) of heat exchanger tubes are aligned up and down. In each of the groups (50) of heat exchanger tubes, a plurality of heat exchanger tubes (52) are arranged such that three rows of heat exchanger tubes (52), each along of an air flow direction, they are arranged side by side and each of the three rows includes two heat exchanger tubes (52) aligned in the up and down direction. In addition, a first bank (53) of tubes is arranged on the left in Figure 19 (i.e., the windward side), a second bank (54) of tubes is arranged in the center in Figure 19, and a third bank (55) of tubes is arranged on the right in Figure 19 (that is, the leeward side). That is, in each of the groups (50) of heat exchanger tubes, the heat exchanger tubes (52) are arranged in two stages in each row.

<Other realizations>

The present invention may have the following configurations with respect to the first and second embodiments.

In the first and second embodiments, the four-stage compressor (20) is used. However, the present invention is not limited to this configuration, and two two-stage compressors can be provided.

In the first to fourth embodiments, the two-stage supercritical compression refrigeration cycle and the four-stage supercritical compression refrigeration cycle are used. However, the present invention is not limited to this, and is applicable to a supercritical refrigeration cycle of a three-stage compressor or a refrigeration cycle of another type of multi-stage compressor, for example.

In the first and second embodiments, the heat exchanger is the fin and tube heat exchanger. However, the present invention is not limited to this type.

Specifically, as illustrated in 16, the outdoor unit (3) may include the outer housing (121). The outer shell (121) is in the form of a vertical rectangular box, and has an air inlet (123) in a lower part of the front surface and an air outlet (124) in an upper surface thereof. The outdoor heat exchange unit (40) and the outdoor fan (122) are located in the outer housing (121). The external heat exchange unit (40) includes the external heat exchanger (44), the first intermediate heat exchanger (41), the second intermediate heat exchanger (42) and the third intermediate heat exchanger (43).

As illustrated in Figure 16, the first intermediate heat exchanger (41), the second intermediate heat exchanger (42), the third intermediate heat exchanger (43) and the heat exchanger are stacked in the outer casing (121). outside heat (162), in this order from the bottom. That is, the external heat exchanger (162) is located above the intermediate heat exchangers (41, 42, 43) first to third. In this configuration, the first intermediate heat exchanger (41) and the second intermediate heat exchanger (42) can be replaced with each other in the up and down direction.

-Configuration of the heat exchanger-

As illustrated in Figures 16 and 17, each of the heat exchangers (41, 42, 43, 44) of this embodiment includes a first concentrate collecting pipe (240), a second concentrate collecting pipe (250), a large number of flat tubes (231), and a large number of fins (235). The first concentrate collecting pipe (240), the second concentrate collecting pipe (250), the flat tubes (231) and the fins (235) are made of an aluminum alloy and welded together.

The first concentrate collecting pipe (240) and the second concentrate collecting pipe (250) consist of thin hollow tubes. In each of the heat exchangers (41,42, 43, 44), the first concentrate collecting pipe (240) is located at one end of the flat tubes (231) and the second concentrate collecting pipe (250) is located at the other end of the flat tubes (231). That is, both the first concentrate collecting pipe (240) and the second concentrate collecting pipe (250) extend in the upward and downward direction such that their axis extends vertically.

The first concentrate collecting pipe (240) has its upper and lower ends closed, and its lower end is connected to a first connecting pipe (240b). The first connecting pipe (240b) communicates with a liquid side of the refrigerant circuit (10). That is, the first concentrate collecting pipe (240) constitutes a liquid side manifold through which the liquid containing refrigerant flows (liquid single-phase refrigerant or gas-liquid two-phase refrigerant). The second concentrate collecting pipe (250) has its upper and lower ends closed, and a second connecting pipe (250b) is connected to an upper part of the second concentrate collecting pipe (250). The second connection pipe (250b) is connected to a gas side of the refrigerant circuit (10). That is, the second concentrate collecting pipe (250) constitutes a gas side manifold through which a gaseous refrigerant flows.

Each of the heat exchangers (41, 42, 43, 44) of this embodiment includes a plurality of flat tubes (231). Each of the flat tubes (231) is a heat exchanger tube whose cross-sectional shape perpendicular to the axis thereof is a flat ellipse or a rectangle. In each of the heat exchangers (41, 42, 43, 44), the flat tubes (231) extend in transverse direction with their flat side surfaces facing each other. The flat tubes (231) are arranged side by side at predetermined intervals in the up and down direction. One end of each of the flat tubes (231) is located in the first concentrate collecting pipe (240), and the other end is located in the second concentrate collecting pipe (250).

As illustrated in Figure 17, each of the flat tubes (231) includes a plurality of coolant paths (232). The coolant paths (232) are fluid passages of the present invention that extend in the direction in which the flat tubes (231) extend. In each of the flat tubes (231), the refrigerant paths (232) are arranged in a row along a transverse direction perpendicular to the direction in which the flat tubes (231) extend. Each of the coolant paths (232) of the flat tubes (231) has one end in communication with the interior space of the first concentrate collecting pipe (240) and the other end in communication with the interior space of the second collecting pipe of concentrate (250).

Each of the fins (235) is a corrugated fin that bends up and down and is located between the flat tubes (231) adjacent to each other in the up and down direction. Each of the fins (235) includes a plurality of heat transfer parts (236) arranged in the direction in which the flat tubes (231) extend. Each of the heat transfer parts (236) has a plate shape that extends from one of the flat tubes (231) adjacent to the other. The heat transmission parts (236) include a plurality of lattices (237) that bend outwardly from the heat transmission parts (236). The lattices (237) extend in the up and down direction so that they are substantially parallel to the leading edges (i.e., the windward ends) of the heat transfer parts (236). In the heat transfer parts (236), the lattices (237) are arranged side by side from the windward side to the leeward side.

The leeward ends of the heat transfer parts (236) are attached to the protruding plate portions (238), which protrude further to leeward. Each of the protruding plate parts (238) is in the form of a trapezoidal plate that protrudes from the heat transfer parts (236) in the up and down direction. In each of the heat exchangers (41, 42, 43, 44), the protruding plate portions (238, 238) adjacent in the upward and downward direction overlap each other in the thickness direction, and are substantially in contact with each other. The other configurations, operations and advantages are similar to those of the variation of the third embodiment.

The above embodiments are simply examples of a preferred nature, and are not intended to limit the scope, applications and use of the invention.

Industrial applicability

As described above, the present invention is useful for a refrigeration system that performs a multi-stage compression refrigeration cycle.

Description of the reference characters

21 First compressor

22 Second compressor

23 Third compressor

24 Fourth compressor

41 First intermediate heat exchanger

42 Second intermediate heat exchanger

43 Third intermediate heat exchanger

44 External heat exchanger

121 outer shell

123 Air inlet

151 First compressor

152 Second compressor

161 External heat exchanger

162 Intermediate heat exchanger

163 outer shell

164 Air inlet

231 Flat tube

232 Coolant path 235 Fin

Claims (5)

1. An outdoor unit of a cooling system, the outdoor unit comprising: a multi-stage compressor (20, 150) that includes a plurality of compression mechanisms (21-24, 151, 152) connected in series, in which the refrigerant discharged from one of the compression mechanisms (21, 22, 23 , 151) low stage is aspirated and compressed in one of the high stage compression mechanisms (22, 23, 24, 152); an intermediate heat exchanger (41, 42, 43, 161) located between two of the adjacent compression mechanisms (21, 22, 23, 24, 151, 152) and configured to cause the refrigerant to flow from the compression mechanism ( 21, 22, 23, 151) of low stage to the compression mechanism (22, 23, 24, 152) of high stage to exchange heat with outside air to be cooled; an external heat exchanger (44, 162) configured to cause the refrigerant discharged from the compression mechanism (24, 152) of the highest stage to exchange heat with outside air; Y a housing (121, 163) having a lateral surface on which an air intake port (123, 164) and an upper surface on which an air outlet (124, 165) is provided, and housing is provided the compression mechanisms (21-24, 151, 152), the intermediate heat exchanger (41, 42, 43, 161) and the external heat exchanger (44, 162), where the intermediate heat exchanger (41, 42, 43, 161) and the external heat exchanger (44, 162) are arranged along the suction port (123, 164) of the housing (121, 163), and the External heat exchanger (44, 162) is located above all intermediate heat exchangers (41, 42, 43, 161). 2. The outdoor unit of claim 1, wherein The multi-stage compressor (20) includes three or more compression mechanisms (21-24), the intermediate heat exchanger comprises a plurality of intermediate heat exchangers (41,42, 43), and The intermediate heat exchanger (43) of the highest stage is located above the other intermediate heat exchangers (41, 42) and below the external heat exchanger (44). 3. The outdoor unit of claim 2, wherein The intermediate heat exchangers (41, 42, 43) are stacked from the bottom in the order of increasing pressure of the inlet refrigerant. 4. The outdoor unit of claim 1, wherein The intermediate heat exchanger (41, 42, 43, 161) includes a plurality of flat tubes (231) that are arranged in the upward and downward direction with their side surfaces facing each other and each of which includes a plurality of fluid passages (232) extending in the longitudinal direction of the tube, and also includes a plurality of fins (235, 235) that divide the space between adjacent flat tubes (231) into a plurality of air passages by the Air is flowing 5. The outdoor unit of claim 4, wherein the outer heat exchangers (44, 162) include a plurality of flat tubes (231) that are arranged in the upward and downward direction with their side surfaces facing each other, and each of which includes a plurality of passages of fluid (232) extending in the longitudinal direction of the tube, and also include a plurality of fins (235, 235) that divide the space between adjacent flat tubes (231) into a plurality of air passages through which the air.