JP4608971B2 - heat pump - Google Patents

Description

  The present invention relates to a heat pump used for a water heater or the like.

  In a heat pump used for a water heater or the like, in order to obtain hot water having a temperature in the range of about 70 ° C. to about 90 ° C., the degree of superheat of the refrigerant at the compressor inlet (saturation temperature and refrigerant at the pressure at the compressor inlet) The operation is performed so that the temperature of the refrigerant discharged from the compressor is higher than the temperature of the boiling water. It is common to connect two or more compressors in series with a heat pump. (For example, see Patent Document 1)

JP-A-6-2966

  The higher the degree of superheat of the refrigerant at the compressor inlet, the larger the amount of electric power consumed by the compressor to obtain the same output, and the heat pump for the hot water heater is operating less efficiently. A technique for improving the efficiency of a heat pump is desired.

The heat pump according to the present invention includes a first heat exchanger that applies heat to a refrigerant from a heat source, a first compressor that compresses the refrigerant that is heated by the first heat exchanger, and a compressor that compresses the first heat exchanger. A second compressor that compresses the refrigerant that has been discharged and maintained at a temperature equal to or higher than the temperature at which it was discharged from the first compressor, and second heat exchange that takes heat away from the refrigerant compressed by the second compressor And a return path for returning the refrigerant deprived of heat by the second heat exchanger to the first heat exchanger, and a refrigerant pipe from the first compressor to the second compressor. And a refrigerant heating means for heating the refrigerant entering the second compressor so that the temperature is higher than that of the refrigerant discharged from the first compressor.

The heat pump according to the present invention includes a first heat exchanger that applies heat to a refrigerant from a heat source, a first compressor that compresses the refrigerant that is heated by the first heat exchanger, and a compressor that compresses the first heat exchanger. A second compressor that compresses the refrigerant that has been discharged and maintained at a temperature equal to or higher than the temperature at which it was discharged from the first compressor, and second heat exchange that takes heat away from the refrigerant compressed by the second compressor And a return path for returning the refrigerant deprived of heat by the second heat exchanger to the first heat exchanger, and a refrigerant pipe from the first compressor to the second compressor. And a refrigerant heating means for heating the refrigerant entering the second compressor so that the temperature is higher than that of the refrigerant discharged from the first compressor, so that the same output is obtained as compared with the case without the refrigerant heating means. This has the effect of reducing the amount of compressor work necessary to obtain.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating the configuration of the heat pump in the first embodiment. This heat pump is a two-stage compression heat pump used as a heat source for boiling water in a water heater or the like. The refrigerant of the heat pump is carbon dioxide that has a low degree of adverse effect on the global environment. This heat pump includes a first compressor 1 on the low pressure side that compresses the refrigerant, a second compressor 2 on the high pressure side, and a refrigerant heating means that heats the refrigerant discharged from the first compressor 1 and entering the second compressor 2. 3, a radiator 4 that removes heat from the refrigerant discharged from the second compressor 2 and heats the water, a pressure reducing valve 5 that decompresses the refrigerant discharged from the heat radiator 4, and a refrigerant decompressed by the pressure reducing valve 5 It comprises an evaporator 6 that evaporates and a refrigerant pipe 7 through which refrigerant flows. The radiator 4 has a water pipe 8, and water heated in the water pipe 8 by the pump 9 flows.

The refrigerant flows and circulates in this order through the refrigerant pipe 7 between the first compressor 1, the refrigerant heating means 3, the second compressor 2, the radiator 4, the pressure reducing valve 5 and the evaporator 6. The evaporator 6 is a first heat exchanger, and the radiator 4 is a second heat exchanger. The pressure reducing valve 5 and the refrigerant pipes 7 </ b> A and 7 </ b> B on both sides thereof are return paths, and connect between the radiator 4 and the evaporator 6.
The refrigerant heating means 3 heats the refrigerant using the heat of the refrigerating machine oil discharged from the second compressor 2 and returning to the suction port of the first compressor 1 and waste heat from other heat pumps, heat storage devices, etc. Shall. The refrigeration oil is a lubricating oil for smoothing the operation of the compressor. The refrigeration oil is compressed by the compressor together with the refrigerant. The refrigeration oil discharged from the compressor may be separated and returned to the compressor inlet through a special pipe, or may flow along with the refrigerant without being separated.

Next, the operation will be described. FIG. 2 shows a temperature entropy diagram explaining the state change of the refrigerant. A solid line is a locus indicating the operation of the heat pump according to the present invention, and a broken line is a locus indicating the operation of the conventional heat pump. The method according to the present invention is called the present method. FIG. 3 is a diagram for explaining the position corresponding to the state of the refrigerant. In FIG. 3, symbols representing points are displayed by being surrounded by squares.
The refrigerant sucked into the first compressor 1 is a low-temperature and low-pressure gas indicated by a point A shown in FIG. By being adiabatically compressed by the first compressor 1, the refrigerant becomes an intermediate pressure gas indicated by a point B. Strictly speaking, there is slight heat conduction between the surface inside the compressor and the refrigerant. The amount of heat transmitted by this conduction is negligibly small compared to the amount of heat transferred by the heat pump.

The refrigerant is heated at a substantially constant pressure by the refrigerant heating means 3, and the temperature of the refrigerant is higher than that at the point B indicated by the point C. Then, the refrigerant is further compressed by the second compressor 2, and the refrigerant becomes a high-temperature and high-pressure gas indicated by a point D. The refrigerant at the point D is a supercritical region where the pressure is constant and the liquid does not become liquid even when the temperature is lowered.
While the water is heated by the radiator 4, the temperature of the refrigerant decreases, and the state changes from the point D to a low temperature and high pressure state indicated by a point E. Here, the positions of the points D and E are determined so as to satisfy the output of the heat pump. When the pressure is reduced by the pressure reducing valve 5, the refrigerant enters a low-temperature low-pressure gas-liquid two-phase state indicated by a point F. Then, the evaporator 6 removes heat from the outside air, the liquid refrigerant evaporates, and returns to the point A which is in the gaseous state.

On the other hand, the operation when obtaining the same output with a conventional heat pump without the refrigerant heating means 3 is as follows. In order to make the output the same, the 2nd compressor 2, the radiator 4, and the pressure-reduction valve 5 operate | move similarly to the case of this system, and the locus | trajectory of the state of a refrigerant | coolant becomes CDEF. The operations of the first compressor 1 and the evaporator 6 are different between this method and the conventional one. The first compressor 1 performs adiabatic compression so that the state of the refrigerant is changed from the point A2 to the point C. And in the evaporator 6, it heats with a constant pressure so that the state of a refrigerant | coolant may be changed from the point F to the point A2. Note that the temperature at point A2 is higher than that at point A, that is, the degree of superheat.
The reason why the temperature of the point A2 is higher than that of the point A, that is, the degree of superheat will be described. In this method, after being compressed by the first compressor 1, the refrigerant is heated from the point B to the point C by the refrigerant heating means 3, whereas in the conventional method, there is no heating by the refrigerant heating means 3. This is because the temperature of the refrigerant entering the first compressor 1 needs to be higher than that in this method in order to reach the same point C as that in this method after compression.

Generally, the coefficient of performance (COP) of a heat pump is calculated by the following formula. The higher the coefficient of performance, the more heat can be obtained with less energy. In other words, the higher the coefficient of performance, the higher the performance of the heat pump.
Coefficient of performance = amount of heat available / compressor work amount Here, the compressor work amount is an area surrounded by the locus of one cycle of the heat pump in the temperature entropy diagram. The amount of heat that can be used is determined by the positions of points D and E.

  As can be seen from FIG. 2, in the heat pump of this system, the amount of compressor work is less than that in the conventional case by the area of the portion surrounded by the hatched locus A-A2-CBA. That is, the coefficient of performance of the heat pump of this method is higher than that of the conventional heat pump. Note that the heat source in the refrigerant heating means 3 uses the waste heat from the refrigeration oil discharged from the second compressor 2 and returned to the suction port of the first compressor 1, and other heat pumps, heat storage devices, etc. There is no need to consider quantity as the denominator of the coefficient of performance.

It will be explained from another angle that the compressor work is less than that of the conventional heat pump. In FIG. 4, the pressure enthalpy figure explaining the state change of a refrigerant | coolant is shown. Similar to FIG. 2, the solid line represents the trajectory of the heat pump of the present system, and the dashed line represents the trajectory of the conventional heat pump. The meaning of the symbols representing the points is the same as in FIG.
The compressor work is the enthalpy difference at the compressor inlet and outlet. Therefore, the compressor work in this method is the sum of the enthalpy increment ΔH1 on the trajectory AB and the enthalpy increment ΔH2 on the trajectory CD. In the conventional heat pump, the enthalpy increment ΔH in the locus A2-D becomes the compressor work.

  As can be seen from FIG. 4, the compressor work required to compress the refrigerant having a low temperature and a small enthalpy to a predetermined pressure is smaller than that of the refrigerant having a high temperature and a large enthalpy. That is, the inclination of the trajectory AB in FIG. 4 is larger than the inclination of the trajectory A2-D. Therefore, ΔH1 + ΔH2 <ΔH, and the compressor work of this method is smaller.

We consider the amount of compressor work reduction by this method. The amount of reduction in compressor work is represented by a variable DH. First, the following holds from the definition of variables.
DH = ΔH−ΔH1−ΔH2 (Formula 1)
Assuming that the amount of heat given to the refrigerant by the evaporator 6 in the conventional locus A-A2 is Q1, and the amount of heat given to the refrigerant by the refrigerant heating means 3 in the locus B-C of this system is Q2, the position A to the position D in FIG. Since the amount of enthalpy required to move to is the same for any route, the following holds.
ΔH1 + Q2 + ΔH2 = Q1 + ΔH (Formula 2)
Substituting (Expression 2) into (Expression 1), the following expression is obtained.
DH = Q2-Q1 (Formula 3)
From (Equation 3), it can be seen that the difference between the amount of heat Q2 given to the refrigerant by the refrigerant heating means 3 and the amount of heat Q1 given to the refrigerant by the evaporator 6 becomes the reduction amount DH of the compressor work. That is, if the refrigerant heating means 3 gives more heat to the refrigerant than before, the compressor work can be reduced by the amount of heat more than before.

Even if some mechanical input to the heat pump is increased by adding the refrigerant heating means 3, if the amount of the increased mechanical input is smaller than the reduction amount of the compressor work expressed by (Equation 3), The efficiency of the heat pump can be improved.
From FIG. 4, it can be seen that in order to increase the reduction amount DH of the compressor work calculated by (Equation 3), the pressures at points B and C should be increased and Q2 should be increased. However, since the temperature increases when the pressure at points B and C is increased, the temperature of the heat source used by the refrigerant heating means 3 needs to be increased. The pressure at the suction port of the first compressor 1, the pressure at the discharge port of the first compressor 1, that is, the pressure at the suction port of the second compressor 2, and the pressure at the discharge port of the second compressor 2 are Determine comprehensively considering various factors.

In the first embodiment, the case where two compressors are connected in series has been described. However, the present invention can also be applied to a case where three or more compressors are connected in series. The effect that the heat work of the compressor of the heat pump can be reduced compared to the case where the refrigerant heating means is not arranged between the compressors, wherever the refrigerant heating means is arranged between the compressors connected in series. There is.
Even when there are three or more compressors, in order to increase the reduction amount DH of the compressor work, it is effective to heat the refrigerant entering the compressor with the highest pressure at the most downstream side as viewed from the refrigerant flow. is there. When the temperature of the heat source that can be used by the refrigerant heating means 3 is limited, the refrigerant is heated at a plurality of locations so that the amount of heat given to the refrigerant is as large as possible.
If the heat pump has at least two compressors connected in series, there may be a compressor connected in parallel.

In the first embodiment, the heat pump using carbon dioxide as a refrigerant has been described, but the refrigerant may be other than carbon dioxide. Moreover, although demonstrated in the case of utilizing with a hot water heater, you may make it utilize with a thermal storage apparatus etc.
The above also applies to other embodiments.

Embodiment 2. FIG.
FIG. 5 is a diagram illustrating the configuration of the heat pump in the second embodiment. The second embodiment is a modification of the first embodiment so as to have a specific configuration as the refrigerant heating means 3 that uses the heat of the refrigerating machine oil discharged from the second compressor 2. The amount of refrigeration oil is about 10% of the amount of refrigerant in the compressor.

Only differences from Embodiment 1 in FIG. 1 will be described. A refrigerating machine oil pipe 13 connecting the oil separator 10, the refrigerant heating heat exchanger 11 and the second pressure reducing valve 12, and the refrigerant pipe 7 on the suction side of the first compressor 1 is added. The refrigerant heating means 3 in FIG. 1 is not present in FIG.
The oil separator 10 is between the second compressor 2 and the radiator 4 and separates refrigeration oil from the refrigerant. The high-temperature and high-pressure refrigerating machine oil separated by the oil separator 10 is sent to the refrigerant heating heat exchanger 11 through the refrigerating machine oil pipe 13. In the refrigerant heating heat exchanger 11, the refrigerant discharged from the first compressor 1 and entering the second compressor 2 is heated by high-temperature and high-pressure refrigeration oil. The second pressure reducing valve 12 depressurizes the refrigeration oil from the refrigerant heating heat exchanger 11. A refrigerator oil pipe 13 from the second pressure reducing valve 12 is connected to the refrigerant pipe 7 on the suction side of the first compressor 1.
A heat pump having a configuration similar to that of the second embodiment but not including only the heat exchanger 11 for heating the refrigerant has conventionally existed. The feature of the second embodiment is that a heat exchanger 11 for heating the refrigerant is added. In the second embodiment, the refrigerant heating heat exchanger 11 is a refrigerant heating means.

Next, the operation will be described. Even in the second embodiment, the state change of the refrigerant is the same as in the first embodiment. Here, the state change of B-C means that the refrigerant is heated by the heat of the refrigerating machine oil in the refrigerant heating heat exchanger 11.
The high-temperature and high-pressure refrigerating machine oil separated by the oil separator 10 heats the refrigerant (including refrigerating machine oil) discharged from the first compressor 1 by the refrigerant heating heat exchanger 11, and the temperature decreases. The refrigerating machine oil whose temperature has been lowered in the refrigerant heating heat exchanger 11 is decompressed by the second pressure reducing valve 12 and mixed with the refrigerant on the suction side of the first compressor 1.

Conventionally, the high-temperature and high-pressure refrigerating machine oil separated by the oil separator 10 is directly returned to the suction port of the first compressor 1 without being used for refrigerant heating on the way. In contrast, the heat of the high-temperature and high-pressure refrigerating machine oil is used in the refrigerant heating heat exchanger 11 to heat the refrigerant discharged from the first compressor 1 and entering the second compressor 2. This is the point of the configuration in the second embodiment.
Also in the second embodiment, the compressor work in the compressor can be reduced. Note that the amount of heat of the refrigerating machine oil used in the refrigerant heating heat exchanger 11 has not been used effectively conventionally, and even with such a configuration, the mechanical input to the heat pump does not increase.

Embodiment 3 FIG.
FIG. 6 is a diagram illustrating the configuration of the heat pump in the third embodiment. The third embodiment is a heat pump in which there is also a bypass that returns a part of the refrigerant exiting from the radiator 4 to the suction port of the second compressor 2, and the refrigerant that returns to the suction port of the second compressor 2 is made of refrigeration oil. It is designed to be heated.

The heat pump in the third embodiment is similar to the second embodiment in the first compressor 1, the second compressor 2, the radiator 4, the pressure reducing valve 5, the evaporator 6, the oil separator 10, and the second pressure reducing valve. 12 and a refrigerant pipe 7 and a refrigerator oil pipe 13 connecting them. There are also a water pipe 8 and a pump 9 connected to the radiator 4. In addition to these, the third pressure reducing valve 14 and the bypass refrigerant pipe 7C, which are bypass paths for returning the refrigerant to the suction port of the second compressor 2 from the middle of the refrigerant pipe 7A between the radiator 4 and the pressure reducing valve 5, The heat exchanger 15 for supercooling that moves the heat of the refrigerant flowing through the refrigerant pipe 7A to the refrigerant flowing through the bypass refrigerant pipe 7C, and the bypass refrigerant pipe 7C with the heat of the high-temperature and high-pressure refrigeration oil separated by the oil separator 10 There is a refrigerant heating heat exchanger 11 that heats the flowing refrigerant.
Here, the refrigerant pipe 7 connecting the discharge port of the first compressor 1 and the suction port of the second compressor 2 is divided at the junction point with the bypass refrigerant pipe 7C, and the first compressor 1 side is refrigerant. A pipe 7D is used, and the second compressor 2 side is a refrigerant pipe 7E.

  The refrigerant circulates in a double loop. One loop is a loop that passes through the first compressor 1, the second compressor 2, the oil separator 10, the radiator 4, the supercooling heat exchanger 15, the pressure reducing valve 5, and the evaporator 6. The other loop is a loop that passes through the second compressor 2, the oil separator 10, the radiator 4, the supercooling heat exchanger 15, the third pressure reducing valve 14, and the bypass refrigerant pipe 7C. The amount of refrigerant passing through the bypass refrigerant pipe 7C is about 5 to 10% of the whole.

Next, the operation will be described. FIG. 7 shows a temperature entropy diagram for explaining the state change of the refrigerant in the heat pump of the third embodiment. FIG. 7 (a) shows the locus of the refrigerant passing through the evaporator 6, and FIG. 7 (b) shows the locus of the refrigerant passing through the bypass refrigerant pipe 7C. The solid line is the locus of the heat pump of this system, and the broken line is the locus of the conventional heat pump that does not have the refrigerant heating heat exchanger 11. FIG. 8 is a view for explaining the position corresponding to the state of the refrigerant in the configuration of the heat pump in the third embodiment.
The refrigerant passing through the evaporator 6 passes through the trajectory A-B-C-D-E, similar to the case of the first embodiment, after being sucked into the first compressor 1 and exiting the radiator 4. For points that are not on the corner of the locus, such as point E, the positions of the points are indicated by black circles.
In the second embodiment, the refrigerant is heated by the refrigerant heating heat exchanger 11, so that the BC change occurs, whereas the BC change in the third embodiment is as follows: This means that the refrigerant is mixed with the refrigerant from the bypass refrigerant pipe 7C.
The refrigerant leaving the radiator 4 is further deprived of heat by the supercooling heat exchanger 15 and moves to a state where the temperature is lower than the point E indicated by the point E2. When the pressure is reduced by the pressure reducing valve 5, the state of the refrigerant moves to the point F2, which is a low-temperature low-pressure gas-liquid two-phase state. In the evaporator 6, the liquid refrigerant evaporates by taking heat from the outside air and returns to the gaseous state indicated by the point A.

  The refrigerant passing through the bypass refrigerant pipe 7C passes through the same path C-D-E-E2 as the refrigerant passing through the evaporator 6 until it is drawn into the second compressor 2 and exits the supercooling heat exchanger 15. . Upon exiting the supercooling heat exchanger 15, the pressure is reduced by the third pressure reducing valve 14, and the refrigerant is in a state indicated by a point G that is a gas at an intermediate pressure. The supercooling heat exchanger 15 is heated by the refrigerant coming out of the radiator 4 and becomes a state indicated by a point H where the temperature is slightly increased. Then, the refrigerant is heated by the high-temperature and high-pressure refrigerating machine oil discharged from the second compressor 2 in the refrigerant heating heat exchanger 11, and the state of the refrigerant changes to a state indicated by a high-temperature point J at an intermediate pressure. The refrigerant is mixed with the refrigerant discharged from the first compressor 1 on the suction side of the second compressor 2, and the temperature of the refrigerant is changed to a state indicated by a point C.

The operation in the case of obtaining the same output as that of the present system with a conventional heat pump that does not have the heat exchanger 11 for heating the refrigerant is as follows. Since the output is the same as that in the present method, the locus of the state change of the refrigerant from the time when it is sucked into the second compressor 2 through the refrigerant pipe 7A to the subcooling heat exchanger 15 is the same as that in the present method. C-D-E-E2.
Even in the conventional heat pump, the state of the refrigerant passing through the bypass refrigerant pipe 7 </ b> C changes by the same locus E <b> 2 -G-H until it exits the supercooling heat exchanger 15 through the pressure reducing valve 5. Before being sucked into the second compressor 2, it is mixed with the refrigerant discharged from the first compressor 1, the temperature rises, and the state changes from the point H to the point C.

The state of the refrigerant passing through the evaporator 6 changes from the point E2 to the point F2 in the pressure reducing valve 5 as in the present method. The evaporator 6 is heated to a point A3 where the temperature, that is, the degree of superheat, is higher than the point A in this method. The reason for heating to A3 having a high degree of superheat is that after compression in the first compressor 1, the refrigerant is mixed with a refrigerant having a temperature lower than the point J in this method, which is the point H from the bypass pipe 7C, and the same point C as in this method This is because it is necessary to be in the state indicated by.
Before compression, the state of the refrigerant indicated by the point A3 is compressed by the first compressor 1 and moves to a point C2 having a higher temperature and higher entropy than the point C that is the suction port of the second compressor 2. And it mixes with the refrigerant | coolant of the low temperature low entropy of the state shown by the point H from the bypass refrigerant | coolant piping 7C, and will be in the state shown by the point C.

  Compared with the conventional heat pump, the refrigerant passing through the evaporator 6 of this system has a smaller amount of compressor work by the area surrounded by the locus A-A3-C2-CBA. In the refrigerant passing through the bypass refrigerant pipe 7C of this method, the area surrounded by the locus H-C-J-H is zero, so the compressor work does not change. Thus, this Embodiment 3 also has an effect that the compressor work amount can be reduced and the coefficient of performance of the heat pump can be improved.

In the third embodiment, only the refrigerant flowing through the bypass refrigerant pipe 7C is heated by the refrigerant heating heat exchanger 11, but flows through at least one of the bypass refrigerant pipe 7C, the refrigerant pipe 7D, and the refrigerant pipe 7E. The refrigerant may be heated. As long as the refrigerant entering the second compressor 2 is heated to a temperature higher than that of the refrigerant discharged from the first compressor 1, the refrigerant heating heat exchanger 11 may be any type. Since the refrigerant flowing through the bypass refrigerant pipe 7C has the lowest temperature before heating, the heat exchange with the refrigerant flowing through the bypass refrigerant pipe 7C can give more heat to the refrigerant, and the compressor work load The amount of reduction can be increased.
As described in the case of having two compressors, the refrigerant sucked from the intermediate pressure suction port is heated by the refrigerant in one intermediate pressure injection compressor having an intermediate pressure suction port capable of sucking an intermediate pressure fluid. The same effect can be obtained even when heating is performed with the industrial heat exchanger 11.

Embodiment 4 FIG.
FIG. 9 is a diagram illustrating the configuration of the heat pump in the fourth embodiment. The fourth embodiment is a heat pump in which a part of the refrigerant coming out of the radiator 4 and high-temperature and high-pressure refrigerating machine oil are sucked from an intermediate pressure suction port of the intermediate pressure injection compressor.
Also in this fourth embodiment, similar to the third embodiment, the radiator 4, the pressure reducing valve 5, the evaporator 6, the oil separator 10, the second pressure reducing valve 12, the third pressure reducing valve 14, and the supercooling heat exchanger. 15 and refrigerant pipes 7 such as a refrigerant pipe 7A, a refrigerant pipe 7B, and a bypass refrigerant pipe 7C between them. There are also a water pipe 8 and a pump 9 connected to the radiator 4.

There is one intermediate pressure injection compressor 16 instead of two compressors. The refrigerating machine oil pipe 13 returns the refrigerating machine oil not to the low pressure suction port 16A that is the low pressure suction port of the intermediate pressure injection compressor 16 but to the intermediate pressure suction port 16B that is the suction port of the intermediate pressure. There is no heat exchanger 11 for heating the refrigerant, and the pipe connection point 13A where the refrigerating machine oil pipe 13 and the bypass refrigerant pipe 7C from the second pressure reducing valve 12 are in front of the intermediate pressure inlet 16B of the intermediate pressure injection compressor 16 is provided. Connected with.
Connecting the refrigerating machine oil pipe 13 to the bypass refrigerant pipe 7C at the pipe connection point 13A is the refrigerant heating means in the fourth embodiment.

Next, the operation will be described. The radiator 4, the pressure reducing valve 5, the evaporator 6, the oil separator 10, the second pressure reducing valve 12, the third pressure reducing valve 14 and the supercooling heat exchanger 15 operate in the same manner as in the third embodiment. The intermediate-pressure injection compressor 16 sucks low-temperature and low-pressure refrigerant from the low-pressure suction port 16A, and sucks refrigerant from the bypass refrigerant pipe 7C mixed with high-temperature refrigeration oil from the intermediate-pressure suction port 16B. Refrigerant sucked from the intermediate-pressure suction inlet 16B is higher than the refrigerant that will be drawn from the low pressure inlet 16A.

  The refrigerating machine oil sucked from the intermediate pressure suction port 16B travels along the inner surface of the intermediate pressure injection compressor 16 and moves to the low pressure suction port 16A. For this reason, even if the refrigerating machine oil is injected from the intermediate pressure suction port 16B, a situation where the refrigerating machine oil is insufficient between the low pressure suction port 16A and the intermediate pressure suction port 16B and the lubrication becomes insufficient does not occur.

A temperature entropy diagram for explaining the state change of the refrigerant in the heat pump of the fourth embodiment is the same as that of the third embodiment shown in FIG. However, the point B means the state of the refrigerant before being mixed with the refrigerant from the intermediate pressure inlet 16B of the intermediate pressure injection compressor 16, and the point C means the state after being mixed.
The fourth embodiment also has the effect of reducing the compressor work and improving the coefficient of performance of the heat pump. Thus, the temperature of the refrigerant entering the higher pressure side than the intermediate pressure inlet 16B of the intermediate pressure injection compressor 16 becomes higher than the temperature of the refrigerant compressed by the intermediate pressure injection compressor 16 at the intermediate pressure inlet 16B. As long as it can be heated in this way, any refrigerant heating means may be used.

  As described in the case of the intermediate pressure injection compressor, even in a heat pump in which two compressors are connected in series and the refrigerant from the bypass refrigerant pipe 7C is mixed and sucked into the latter stage compressor, high-temperature and high-pressure refrigerating machine oil is used. Mixing with the refrigerant from the bypass refrigerant pipe 7C can be applied, and the same effect can be obtained. Further, even with a two-stage compression heat pump that does not have the bypass refrigerant pipe 7 </ b> C, the high-temperature and high-pressure refrigerating machine oil discharged from the second compressor 2 may be returned to the suction port of the second compressor 2.

Embodiment 5 FIG.
FIG. 10 illustrates a configuration of the heat pump in the fifth embodiment. In the fifth embodiment, only the refrigerating machine oil is injected into the intermediate pressure inlet 16B of the intermediate pressure injection compressor 16.
The fifth embodiment also includes the radiator 4, the pressure reducing valve 5, the evaporator 6, the second pressure reducing valve 12, and the refrigerant pipe 7 between them, as in the second embodiment. There are also a water pipe 8 and a pump 9 connected to the radiator 4.

The intermediate pressure injection compressor 16 in the fifth embodiment has a high pressure hermetic structure. There are an electric motor 16D and a compression mechanism 16E in the sealed container 16C. Here, the compression mechanism means that the power source (electric motor) is removed from the compressor. The airtight container 16C is filled with a high-pressure and high-temperature gaseous refrigerant, and refrigerating machine oil is accumulated in the lower part of the airtight container 16C.
A refrigerant pipe 7 from the evaporator 6 is connected to the low pressure suction port 16A. A refrigerator oil pipe 13 from the second pressure reducing valve 12 is connected to the intermediate pressure suction port 16B. A discharge port 16F that discharges the refrigerant compressed by the compression mechanism 16E of the intermediate pressure injection compressor 16 is inside the sealed container 16C. The refrigerator oil piping 13 is also connected between the bottom of the hermetic container 16 </ b> C and the second pressure reducing valve 12. A refrigerant pipe 7 to the radiator 4 is provided on the upper surface of the sealed container 16C.
The refrigerating machine oil pipe 13 connected to the intermediate pressure suction port 16B is the refrigerant heating means in the fifth embodiment.

  Next, the operation will be described. The radiator 4, the pressure reducing valve 5, and the evaporator 6 operate in the same manner as in the second embodiment. The intermediate pressure injection compressor 16 compresses the refrigerant sucked from the low pressure suction port 16A. Since high-temperature refrigerating machine oil is sucked from the intermediate pressure suction port 16B, the refrigerant has a higher temperature than when it is only compressed. High-temperature and high-pressure refrigerant and refrigerating machine oil are discharged from the discharge port 16F of the intermediate pressure injection compressor 16 into the sealed container 16C. The liquid refrigeration oil falls downward inside the sealed container 16C and is separated from the refrigerant. Refrigerating machine oil accumulates at the bottom of the sealed container 16C. The refrigerant is sent to the radiator 4 through the refrigerant pipe 7 connected to the upper surface of the sealed container 16C. Since some of the refrigerating machine oil is floating inside the sealed container 16C, some of the refrigerating machine oil is included in the refrigerant flowing out of the refrigerant pipe 7. In this manner, the refrigerating machine oil can be separated from the refrigerant by the sealed container 16C, the refrigerant pipe 7, and the refrigerating machine oil pipe 13.

  The refrigerating machine oil accumulated in the lower portion of the sealed container 16C is sucked into the refrigerating machine oil pipe 13 because the pressure on the opposite side of the second pressure reducing valve 12 is reduced. The refrigerating machine oil decompressed by the second pressure reducing valve 12 is substantially equal to the refrigerant pressure at the intermediate pressure inlet 16B of the intermediate pressure injection compressor 16. The refrigerating machine oil is sucked into the intermediate pressure inlet 16B of the intermediate pressure injection compressor 16.

  A temperature entropy diagram for explaining the state change of the refrigerant in the heat pump of the fifth embodiment is FIG. 2 similar to that of the first embodiment. This Embodiment 5 also has an effect that the compressor work amount can be reduced and the coefficient of performance of the heat pump can be improved.

  Separating the refrigerating machine oil without using the oil separator 10 by using the arrangement of the hermetic container and piping of the compressor can be applied to other embodiments.

It is a figure explaining the structure of the heat pump in Embodiment 1 of this invention. It is a temperature entropy figure explaining the state change of the refrigerant | coolant in Embodiment 1 of this invention. It is a figure explaining the position corresponding to the state of the refrigerant in Embodiment 1 of this invention. It is a pressure enthalpy figure explaining the state change of the refrigerant in Embodiment 1 of this invention. It is a figure explaining the structure of the heat pump in Embodiment 2 of this invention. It is a figure explaining the structure of the heat pump in Embodiment 3 of this invention. It is a temperature entropy figure explaining the state change of the refrigerant | coolant in Embodiment 3 of this invention. It is a figure explaining the position corresponding to the state of the refrigerant in Embodiment 3 of this invention. It is a figure explaining the structure of the heat pump in Embodiment 4 of this invention. It is a figure explaining the structure of the heat pump in Embodiment 5 of this invention.

Explanation of symbols

1: 1st compressor 2: 2nd compressor 3: Refrigerant heating means 4: Radiator (2nd heat exchanger)
5: Pressure reducing valve (return path)
6: Evaporator (first heat exchanger)
7: Refrigerant piping 7A: Refrigerant piping (return path)
7B: Refrigerant piping (return path)
7C: Bypass refrigerant pipe 7D: Refrigerant pipe 7E: Refrigerant pipe 8: Water pipe 9: Pump 10: Oil separator 11: Heat exchanger for refrigerant heating (refrigerant heating means)
12: Second pressure reducing valve 13: Refrigerating machine oil piping (refrigerant heating means)
13A: Piping connection location (refrigerant heating means)
14: Third pressure reducing valve 15: Supercooling heat exchanger 16: Intermediate pressure injection compressor 16A: Low pressure inlet 16B: Intermediate pressure inlet 16C: Sealed container 16D: Electric motor 16E: Compression mechanism 16F: Discharge port

Claims (2)

A first heat exchanger that applies heat to the refrigerant by a heat source;
A first compressor that compresses the refrigerant that is heated by the first heat exchanger;
A second compressor that compresses the refrigerant compressed by the first compressor and maintained at a temperature equal to or higher than the temperature at which the refrigerant was discharged from the first compressor;
A second heat exchanger that takes heat away from the refrigerant compressed by the second compressor;
A return path for returning the refrigerant deprived of heat by the second heat exchanger to the first heat exchanger;
Refrigerant heating means that is provided in a refrigerant pipe from the first compressor toward the second compressor and that heats the refrigerant entering the second compressor so that the temperature is higher than the refrigerant discharged from the first compressor. And a heat pump. The heat pump according to claim 1, wherein the refrigerant heating unit uses heat of lubricating oil discharged from the second compressor.

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