JP2009300041A - Refrigerating cycle device and pressure loss suppressing method for refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating cycle device capable of suppressing deterioration of refrigeration capacity while using an existing pipe used in the refrigerating cycle device using a conventional refrigerant when replacing the conventional refrigerant with a refrigerant with low saturated steam density such as an HFO-based refrigerant. <P>SOLUTION: In the refrigerating cycle device having a primary side refrigerant circuit sequentially connecting a compressor 1, a heat source side heat exchanger 4, and a first pressure reducing means 5, a secondary side refrigerant circuit equipped with a utilization side heat exchanger 10, and a gas side existing piping 21 and a liquid side existing piping 22 connecting the primary side refrigerant circuit and the secondary side refrigerant circuit, a pressure loss caused when a refrigerant flows through the gas side existing piping 21 is suppressed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle apparatus. More specifically, the present invention relates to a hydrofluorocarbon (hereinafter referred to as HFC) -based refrigerant, tetrafluoropropene (2,3,3,3-Tetrafluoropropene, which is a refrigerant having a lower gas density than this refrigerant. -1ene, hereinafter referred to as HFO.) When replacing with a system refrigerant or the like, the present invention relates to a technique for suppressing pressure loss while diverting existing piping equipment.

  Conventionally, in a refrigeration cycle apparatus such as an air conditioner, a compression heat pump using an HFC-based refrigerant has been used. As the HFC refrigerant, HFC-22, HFC-407C, HFC-410A and the like are often used. In these refrigeration cycle apparatuses, a refrigerant circuit in which an outdoor unit having a compressor, a heat source side heat exchanger, an accumulator, and a decompression unit and an indoor unit having a use side heat exchanger are connected by a refrigerant pipe is mainly used. It is configured.

  However, HFC refrigerants such as the HFC-22, HFC-407C, HFC-410A, etc. have a large global warming potential (GWP). Is proposed (see, for example, Patent Document 1).

JP 2006-512426 A

  This HFO refrigerant has a global warming potential (GWP) of 4, which is as small as about 1/500, for example, as compared to G4101975 of R410A, and can be said to be an excellent refrigerant from the viewpoint of global warming.

  However, the HFO refrigerant has a lower saturated vapor density of the refrigerant in the gas state than the HFC refrigerant (hereinafter, sometimes referred to as “conventional refrigerant”) that has been conventionally used in the refrigeration cycle apparatus. Therefore, in order to obtain the refrigerating capacity equivalent to that of the conventional refrigerant, it is necessary to increase the flow rate of the gaseous refrigerant in the refrigeration cycle. However, if the flow rate of the refrigerant is increased, it is assumed that the pressure loss in the pipe increases and the refrigerating capacity is likely to decrease. In particular, in a refrigeration cycle apparatus having a long connection pipe length, the refrigerant sucked into the compressor in the primary side refrigerant circuit due to pressure loss generated when the refrigerant returns from the secondary side refrigerant circuit to the primary side refrigerant circuit. The pressure of will be significantly reduced. For this reason, the refrigerant density of the refrigerant sucked into the compressor is reduced, and the amount of refrigerant circulating is also reduced, which may cause further reduction in the refrigerating capacity.

  On the other hand, in a refrigeration cycle apparatus that uses a refrigerant having a low saturated vapor density, not limited to HFC refrigerant, the refrigerant flow rate may be increased by increasing the inner diameter of the pipe to obtain a predetermined refrigeration capacity. Many. However, for example, when an extension pipe connecting an indoor unit and an outdoor unit, such as an air conditioner, is embedded in the wall surface or ceiling surface of a building, it is not easy to replace these existing pipes. Therefore, it is difficult to improve the refrigeration capacity by replacing the pipe with a thick inner diameter. Therefore, when replacing the conventional refrigerant with an HFO refrigerant, it is necessary to suppress a decrease in the refrigerating capacity while diverting the existing piping.

  The present invention has been made to solve such a problem, and in the case where the conventional refrigerant is replaced with a refrigerant having a low saturated vapor density such as an HFO refrigerant, the existing piping used in the refrigeration cycle apparatus using the conventional refrigerant. A refrigeration cycle apparatus and a pressure loss suppression method for the refrigeration cycle apparatus that can suppress a decrease in the refrigeration capacity while diverting the refrigeration capacity.

The refrigeration cycle apparatus according to the present invention is
A primary refrigerant circuit in which a compressor, a heat source side heat exchanger, and a first pressure reducing means are sequentially connected;
A secondary-side refrigerant circuit provided with a use-side heat exchanger connected to the primary-side refrigerant circuit by a connection pipe and circulating a refrigerant discharged from the compressor;
When replacing the refrigerant with a refrigerant having a low density at the same temperature from the hydrofluorocarbon-based refrigerant, the connection pipe is kept existing, and pressure loss in the pipe generated when the refrigerant flows through the connection pipe is suppressed. And a pressure suppressing means provided in the primary side refrigerant circuit.

  The present invention can suppress the pressure loss of the refrigerant that occurs when the refrigerant flows through the pipe connecting the primary side refrigerant circuit and the secondary side refrigerant circuit. For this reason, the fall of the refrigerating capacity resulting from the pressure loss of a refrigerant | coolant can be suppressed.

Embodiment 1 FIG.
FIG. 1 shows a refrigerant circuit configuration of a refrigeration cycle apparatus according to Embodiment 1 of the present invention. In the first embodiment, an example in which the refrigeration cycle apparatus is an air conditioner and a cooling operation is performed will be described. Moreover, in the figure explaining the refrigerant circuit structure demonstrated in FIG. 1 and after, the broken-line arrow shows the flow of a refrigerant | coolant.

  As shown in FIG. 1, the refrigeration cycle apparatus according to Embodiment 1 includes a primary side refrigerant circuit 200 and a secondary side refrigerant circuit 201. The primary refrigerant circuit 200 represents an outdoor unit of an air conditioner, and the secondary refrigerant circuit 201 represents an indoor unit.

The primary refrigerant circuit 200 is configured by connecting a compressor 1, a four-way valve 2, a heat source side heat exchanger 4, a refrigerant-refrigerant heat exchanger 31, an expansion valve 5, and a liquid side shut-off valve 6 in this order. The expansion valve 8 is connected to the outlet side of the refrigerant-refrigerant heat exchanger 31 via a branch part 32 by a branch pipe 34, and the outlet side pipe of the expansion valve 8 is connected to the refrigerant-refrigerant heat exchanger 31. Has been. The refrigerant-refrigerant heat exchanger 31 is connected to the accumulator 7 by a compressor introduction pipe 35. The inlet pipe of the accumulator 7 is connected to the four-way valve 2 and the refrigerant-refrigerant heat exchanger 31 via the branch part 33. The outlet pipe of the accumulator 7 is connected to the suction part of the compressor 1. A gas-side stop valve 3 is provided between the four-way valve 2 and the secondary refrigerant circuit 201.
The secondary side refrigerant circuit 201 includes the use side heat exchanger 10.

  The primary side refrigerant circuit 200 and the secondary side refrigerant circuit 201 are connected by a gas side existing pipe 21 and a liquid side existing pipe 22.

  Next, the operation of the refrigeration cycle apparatus shown in FIG. 1 will be described. The refrigerant discharged from the compressor 1 passes through the four-way valve 2, the heat source side heat exchanger 4, and the refrigerant-refrigerant heat exchanger 31, and then is divided into two at the branch portion 32. The diverted refrigerant moves to the expansion valve 8 via the branch pipe 34, is reduced in pressure and temperature by the expansion valve 8, and then proceeds to the refrigerant-refrigerant heat exchanger 31. Hereinafter, a flow in which the refrigerant that has exited the refrigerant-refrigerant heat exchanger 31 returns to the refrigerant-refrigerant heat exchanger 31 again is referred to as a bypass flow, and a flow that proceeds from the heat source side heat exchanger 4 to the expansion valve 5 is referred to as a main flow. . In the refrigerant-refrigerant heat exchanger 31, the high-temperature refrigerant that has passed through the heat source side heat exchanger 4 and the low-temperature refrigerant in the bypass flow exchange heat. Therefore, the refrigerant that has passed through the heat source side heat exchanger 4 is supercooled by the refrigerant-refrigerant heat exchanger 31.

  The refrigerant supercooled by the refrigerant-refrigerant heat exchanger 31 is depressurized by the expansion valve 5, passes through the liquid side stop valve 6 and the liquid side existing pipe 22, and then proceeds to the use side heat exchanger 10. The refrigerant exchanges heat with the use-side heat exchanger 10, passes through the gas-side existing pipe 21, and then passes through the gas-side stop valve 3, the four-way valve 2, and the accumulator 7 to the suction portion of the compressor 1. Returned.

  FIG. 2 illustrates the refrigeration cycle according to the first embodiment on a PH diagram. In FIG. 2, point 100 is the inlet of the heat source side heat exchanger 4, point 101 is the outlet of the heat source side heat exchanger 4, point 102 is the outlet of the refrigerant-refrigerant heat exchanger 31 on the branch part 32 side, and point 103 is a bypass. The outlet of the flow expansion valve 8, the point 104 is the outlet of the bypass-flow refrigerant-refrigerant heat exchanger 31, the point 105 is the outlet of the use side heat exchanger 10, and the point 106 is the state of the refrigerant in the suction portion of the compressor 1. Represents.

  In FIG. 2, the refrigerant that has exited the heat source side heat exchanger 4 exchanges heat with the refrigerant-refrigerant heat exchanger 31. That is, in the refrigerant-refrigerant heat exchanger 31, the main flow dissipates heat between the points 101 and 102, and the bypass flow absorbs heat between the points 103 and 104. At this time, the refrigerant in the bypass flow absorbs the heat in the main flow by heat exchange and then merges with the refrigerant on the suction side of the compressor 1, so there is little waste of heat.

  On the other hand, since the bypass flow is divided at the outlet of the refrigerant-refrigerant heat exchanger 31, the flow rate of the refrigerant flowing into the use-side heat exchanger 10 decreases. However, since the main-stream refrigerant is in a supercooled state (point 102), the amount of heat exchange in the use side heat exchanger 10 hardly changes even if the flow rate is reduced. In particular, in a refrigeration cycle apparatus in which the gas-side existing pipe 21 is laid for a long time, when the refrigerant flow rate in the gas-side existing pipe 21 decreases, the pressure loss also decreases accordingly. Compared to this, improvement in refrigeration capacity can be expected.

  As described above, according to the first embodiment, the refrigerant in the main flow is supercooled by the refrigerant-refrigerant heat exchanger 31 and then heat is exchanged by the use-side heat exchanger 10, so that the conventional refrigeration cycle apparatus The refrigeration effect can be increased as compared with. Further, since the bypass-flow refrigerant absorbed by the refrigerant-refrigerant heat exchanger 31 is caused to flow into the compressor 1, waste of heat can be reduced. Furthermore, since a circulation flow rate of the refrigerant passing through the use side heat exchanger 10 is reduced by allowing a part of the refrigerant to flow into the compressor 1 as a bypass flow, the pipe when the refrigerant passes through the existing gas side pipe 21. The pressure loss inside can be reduced. Therefore, the above-described series of effects can suppress a decrease in refrigeration capacity. In particular, in an HFO refrigerant having a small saturated vapor density and a large pressure loss in the pipe, the application of the first embodiment can greatly contribute to the suppression of the refrigerating capacity. For this reason, even when it replaces with a refrigerant | coolant with a small saturated vapor density, the refrigerating-cycle apparatus which can suppress the fall of refrigerating capacity can be obtained, diverting existing piping equipment.

  In the above description and FIG. 2, the heat exchange in the refrigerant-refrigerant heat exchanger 31 is performed between the bypass-flow refrigerant that has passed through the expansion valve 8 and the main-flow refrigerant before branching at the branch portion 32. The example in the case of performing in was demonstrated. However, the connection form of the pipe through which the main-flow refrigerant that exchanges heat with the refrigerant-refrigerant heat exchanger 31 flows is not limited to this. For example, a configuration may be adopted in which the main-flow refrigerant after branching at the branch portion 32 performs heat exchange with the refrigerant-refrigerant heat exchanger 31. The same applies to the following embodiments.

  In addition, the refrigeration cycle apparatus according to Embodiment 1 is also suitable for reusing the use side heat exchanger 10. In a large-scale air conditioner such as a commercial air conditioner, the use-side heat exchanger 10 is usually divided into a plurality of paths, and the outlet temperature of the path differs for each path. For this reason, when trying to change the refrigerant to be used, the outlet temperature of multiple passes is different, so air below the dew point temperature and air above the dew point temperature will coexist, causing phenomena such as condensation There is.

  In the refrigeration cycle apparatus according to the first embodiment, the refrigerant state is controlled by the expansion valve 5 and the expansion valve 8. Therefore, the expansion valve 5 is loosened and the expansion valve 8 is controlled to be squeezed to make the outlet side refrigerant of the use side heat exchanger 10 wet, and the refrigerant that has passed through the refrigerant-refrigerant heat exchanger 31 as a bypass flow is overheated. It can be gas. By doing in this way, the state of the exit refrigerant | coolant of the utilization side heat exchanger 10 can be controlled, without changing the state of the suction part of the accumulator 7 or the compressor 1 so much.

  FIG. 3 shows the control state as described above on the PH diagram. In FIG. 3, points 110 to 116 correspond to points 100 to 106 in FIG.

  When the state of FIG. 3 is compared with the state of FIG. 2, the enthalpy of the point 115 indicating the outlet of the use side heat exchanger 10 is lowered, and the point 114 indicating the outlet of the bypass-flow refrigerant-refrigerant heat exchanger 31 is the superheated gas. It has become. However, when the point 116 indicating the suction portion of the compressor 1 is viewed, there is almost no change from the corresponding point 106 in FIG. 2, and it is possible to store almost the same amount of surplus refrigerant in the accumulator.

  Therefore, with the refrigerant circuit configuration of the first embodiment, the state of the outlet refrigerant of the use side heat exchanger 10 is optimally controlled even in the use side heat exchanger 10 divided into a plurality of passes as described above. And the reuse of the use side heat exchanger 10 can be performed appropriately.

Embodiment 2. FIG.
FIG. 4 shows the refrigerant circuit configuration of the refrigeration cycle apparatus according to Embodiment 2 of the present invention. The same components as those in the first embodiment are given the same reference numerals. The second embodiment is different from the first embodiment in that the liquid receiver 9 is provided and the accumulator 7 and the refrigerant-refrigerant heat exchanger 31 are not provided.

As shown in FIG. 4, the refrigeration cycle apparatus according to Embodiment 2 includes a primary side refrigerant circuit 200 and a secondary side refrigerant circuit 201.
The primary refrigerant circuit 200 includes a compressor 1, a four-way valve 2, a heat source side heat exchanger 4, an expansion valve 8, a liquid receiver 9, an expansion valve 5, and a liquid side shut-off valve 6 connected in order. . The expansion valve 8 is provided to reduce the pressure of the refrigerant and protect the pressure vessel of the liquid receiver 9. Further, a gas-side stop valve 3 is provided between the four-way valve 2 and the secondary-side refrigerant circuit 201.
The secondary side refrigerant circuit 201 includes the use side heat exchanger 10.
The primary side refrigerant circuit 200 and the secondary side refrigerant circuit 201 are connected by a gas side existing pipe 21 and a liquid side existing pipe 22.

  Next, the operation of the refrigeration cycle apparatus shown in FIG. 4 will be described. The refrigerant discharged from the compressor 1 passes through the four-way valve 2 and the heat source side heat exchanger 4 and is reduced in temperature and pressure by the expansion valve 8. The refrigerant is decompressed by the expansion valve 5 via the liquid receiver 9, passes through the liquid side stop valve 6 and the liquid side existing pipe 22, and then proceeds to the use side heat exchanger 10. Subsequently, the refrigerant exchanges heat with the use side heat exchanger 10, passes through the gas side existing pipe 21, and then returns to the suction portion of the compressor 1 through the gas side stop valve 3 and the four-way valve 2. .

  Here, in order to explain the advantages of the refrigeration cycle apparatus according to Embodiment 2, a general refrigeration cycle apparatus will be described as a comparison target. FIG. 10 shows a refrigerant circuit configuration of a general refrigeration cycle apparatus, and the same components as those in FIG. 4 are denoted by the same reference numerals. According to FIG. 10, the accumulator 7 is provided on the suction side of the compressor 1, and the refrigerant liquid is stored in the accumulator 7. In this case, the refrigerant at the outlet of the use side heat exchanger 10 is in substantially the same state as the refrigerant at the inlet of the accumulator 7. Therefore, if the outlet refrigerant of the use side heat exchanger 10 becomes superheated gas, the refrigerant at the inlet of the accumulator 7 also becomes superheated gas. In this case, the accumulator 7 is filled with only the vapor refrigerant, and the liquid refrigerant cannot be stored. In order to avoid such a situation, in the conventional general refrigeration cycle apparatus, when surplus refrigerant is generated, the outlet refrigerant of the use-side heat exchanger 10 is controlled to become a gas-liquid two-phase refrigerant, and the accumulator 7 It is not filled with vapor refrigerant alone.

  According to the refrigeration cycle apparatus according to Embodiment 2, the accumulator 7 is not provided on the suction side of the compressor 1, and the liquid receiver 9 is provided between the heat source side heat exchanger 4 and the use side heat exchanger 10. The surplus refrigerant is stored in the liquid receiver 9. Therefore, it is not always necessary to control the outlet refrigerant of the use side heat exchanger 10 to be a gas-liquid two-phase refrigerant. That is, mainly by controlling the expansion valve 5 to adjust the amount of liquid refrigerant stored in the liquid receiver 9, the outlet refrigerant of the use side heat exchanger 10 can be easily made into superheated gas. Therefore, the liquid refrigerant can be prevented from flowing into the compressor 1 without providing an accumulator.

Next, pressure loss in the refrigeration cycle apparatus according to Embodiment 2 will be described. When the refrigerant circulation amount in the pipe is the same, the pressure loss is lower in the case of superheated gas when the state of the refrigerant is a gas-liquid mixed flow and in the case of superheated gas.
Assuming that the multiplication factor for the pressure loss of the single-phase gas is φg ² , φg is expressed by the following equation (1) by the parameter Xtt used in the Lockhart-Martinelli calculation method, and Xtt is expressed by equation (2): It is.
φg = 1 + 2Xtt ^0.5 + Xtt (1)
Xtt = F (fl / fg) × G (ρg / ρl) × H ((1-x) / x) (2)
Here, f is a friction coefficient, ρ is a density, x is a dryness, g is a gas, l is a liquid, F, G, and H are exponential functions.
Generally, the pressure loss becomes maximum when the dryness x is about 0.7. For example, in the refrigerant circuit including the accumulator 7 as shown in FIG. 10, the dryness x is 0.9 to 1.0, and in this case, an increase in pressure loss of several% to 20% is expected.

  In the second embodiment, since the liquid receiver 9 is provided between the heat source side heat exchanger 4 and the use side heat exchanger 10, it is used by controlling the opening degree of the expansion valve 5 as described above. The outlet refrigerant of the side heat exchanger 10 can be superheated gas. Therefore, it is possible to reduce the pressure loss in the gas-side existing pipe 21 as compared with a general refrigeration cycle apparatus including the accumulator 7 on the suction side of the compressor 1. In particular, when an HFO refrigerant having a large pressure loss in the piping is used, the refrigerant at the outlet of the use side heat exchanger 10 is superheated to reduce the pressure loss, thereby greatly contributing to the improvement of the refrigerating capacity. it can. For this reason, even when it replaces with a refrigerant | coolant with a small saturated vapor density, the refrigerating-cycle apparatus which can suppress the fall of refrigerating capacity can be obtained, diverting existing piping equipment.

Embodiment 3 FIG.
FIG. 5 shows the refrigerant circuit configuration of the refrigeration cycle apparatus according to Embodiment 3 of the present invention. The same components as those in the first embodiment are given the same reference numerals. The third embodiment has the same configuration as that of the first embodiment, but the expansion valve 45 and the liquid receiver 9 are provided between the branch portion 32 and the expansion valve 5 in the main flow. And the point which is not providing the accumulator 7 is different. In the third embodiment, these differences will be mainly described.

  In FIG. 5, an expansion valve 45 and a liquid receiver 9 are connected between the branch portion 32 and the expansion valve 5 in the main flow. The expansion valve 45 is provided to reduce the pressure of the refrigerant and protect the pressure vessel of the liquid receiver 9.

  Next, the operation of the refrigeration cycle apparatus shown in FIG. 5 will be described. The refrigerant discharged from the compressor 1 passes through the four-way valve 2, the heat source side heat exchanger 4, and the refrigerant-refrigerant heat exchanger 31, and then is divided into two at the branch portion 32. The branched bypass flow moves to the expansion valve 8 via the branch pipe 34, and is lowered to a low pressure and a low temperature by the expansion valve 8, and then proceeds to the refrigerant-refrigerant heat exchanger 31. In the refrigerant-refrigerant heat exchanger 31, the high-temperature refrigerant that has passed through the heat source side heat exchanger 4 and the low-temperature refrigerant in the bypass flow exchange heat.

  The main-flow refrigerant is reduced in pressure and temperature by the expansion valve 45 via the branch portion 32 and proceeds to the liquid receiver 9. Then, after leaving the liquid receiver 9, the pressure is reduced by the expansion valve 5, and after passing through the liquid side stop valve 6 and the liquid side existing pipe 22, the process proceeds to the use side heat exchanger 10. The refrigerant exchanges heat with the use-side heat exchanger 10, passes through the gas-side existing pipe 21, and then returns to the suction portion of the compressor 1 through the gas-side stop valve 3 and the four-way valve 2.

As described above, according to the third embodiment, the refrigerant in the main flow is supercooled by the refrigerant-refrigerant heat exchanger 31 and then heat is exchanged by the use-side heat exchanger 10. Similarly to 1, it is possible to suppress a decrease in the refrigerating capacity due to pressure loss in the pipe.
In addition, since the liquid receiver 9 is provided between the heat source side heat exchanger 4 and the use side heat exchanger 10, the outlet refrigerant of the use side heat exchanger 10 is superheated by controlling the opening degree of the expansion valve 5. Gas can be used, and pressure loss in the gas-side existing pipe 21 can be reduced. Therefore, it is possible to suppress a decrease in refrigeration capacity due to pressure loss. For this reason, even when it replaces with a refrigerant | coolant with a small saturated vapor density, the refrigerating-cycle apparatus which can suppress the fall of refrigerating capacity can be obtained, diverting existing piping equipment.

Embodiment 4 FIG.
FIG. 6 shows a refrigerant circuit configuration of a refrigeration cycle apparatus according to Embodiment 4 of the present invention. The same components as those in the third embodiment are denoted by the same reference numerals. Although the fourth embodiment has the same configuration as that of the third embodiment, an injection pipe 36 for injecting refrigerant into the compressor 1 is provided on the outlet side of the bypass-flow refrigerant-refrigerant heat exchanger 31. The provided points are different. In the fourth embodiment, this difference will be mainly described.

  In FIG. 6, an injection pipe 36 is connected to the outlet side of the bypass-flow refrigerant-refrigerant heat exchanger 31. The injection pipe 36 is a pipe provided for injecting the refrigerant that has passed through the refrigerant-refrigerant heat exchanger 31 in the middle of the compression process of the compressor 1.

  Next, the operation of the refrigeration cycle apparatus shown in FIG. 6 will be described. The refrigerant discharged from the compressor 1 passes through the four-way valve 2, the heat source side heat exchanger 4, and the refrigerant-refrigerant heat exchanger 31, and then is divided into two at the branch portion 32. The branched bypass flow moves to the expansion valve 8 via the branch pipe 34, and is lowered to a low pressure and a low temperature by the expansion valve 8, and then proceeds to the refrigerant-refrigerant heat exchanger 31. In the refrigerant-refrigerant heat exchanger 31, the high-temperature refrigerant that has passed through the heat source side heat exchanger 4 and the low-temperature refrigerant in the bypass flow exchange heat. Further, the bypass-flow refrigerant heat-exchanged by the refrigerant-refrigerant heat exchanger 31 is guided by the injection pipe 36 and injected during the compression process of the compressor 1.

  The main-flow refrigerant is reduced in pressure and temperature by the expansion valve 45 via the branch portion 32 and proceeds to the liquid receiver 9. Then, after leaving the liquid receiver 9, the pressure is reduced by the expansion valve 5, and after passing through the liquid side stop valve 6 and the liquid side existing pipe 22, the process proceeds to the use side heat exchanger 10. The refrigerant exchanges heat with the use-side heat exchanger 10, passes through the gas-side existing pipe 21, and then returns to the suction portion of the compressor 1 through the gas-side stop valve 3 and the four-way valve 2.

  As described above, according to the fourth embodiment, the refrigerant in the main flow is supercooled by the refrigerant-refrigerant heat exchanger 31, and then the heat exchange is performed by the use side heat exchanger 10. Similarly to 1, it is possible to suppress a decrease in the refrigerating capacity due to the loss of the pressure in the pipe.

  In addition, since the bypass-flow refrigerant heat-exchanged by the refrigerant-refrigerant heat exchanger 31 is injected into the compressor 1 by the injection pipe 36 during the compression process, the initial process portion of the compressor 1 is omitted. Can be compressed. Therefore, the compressor 1 can be operated with less power than when the refrigerant is introduced into the suction portion of the compressor 1. At this time, it is desirable to control the refrigerant flow rate of the bypass flow according to the discharge temperature of the compressor 1.

  In addition, since the liquid receiver 9 is provided between the heat source side heat exchanger 4 and the use side heat exchanger 10, the outlet refrigerant of the use side heat exchanger 10 is superheated by controlling the opening degree of the expansion valve 5. As in the third embodiment, it is possible to suppress a decrease in the refrigerating capacity due to pressure loss. For this reason, even when it replaces with a refrigerant | coolant with a small saturated vapor density, the refrigerating-cycle apparatus which can suppress the fall of refrigerating capacity can be obtained, diverting existing piping equipment.

Embodiment 5 FIG.
FIG. 7 shows a refrigerant circuit configuration of an air conditioner according to Embodiment 5 of the present invention. The same components as those in the first embodiment are given the same reference numerals. Since the fifth embodiment is characterized in that an oil separator 46 and a capillary 47 are provided, these points will be mainly described.

  In FIG. 7, the primary refrigerant circuit 200 is configured by sequentially connecting a compressor 1, an oil separator 46, a four-way valve 2, a heat source side heat exchanger 4, an expansion valve 5, and a liquid side shut-off valve 6. . Further, in this refrigeration cycle apparatus, refrigeration oil having an oil viscosity of about 32 cst is enclosed as oil for lubricating the sliding portion of the compressor 1. The oil separator 46 is a device for separating and storing refrigeration oil. An accumulator 7 is connected to the suction side of the compressor 1. A capillary 47 is connected to a position where the inlet pipe of the accumulator 7 and the oil side pipe of the oil separator 46 are connected.

  Next, the operation of the refrigeration cycle apparatus shown in FIG. 7 will be described. The refrigerant discharged from the compressor 1 is separated into refrigerant and refrigerating machine oil by the oil separator 46. Then, the refrigerant flows into the use side heat exchanger 10 via the four-way valve 2, the heat source side heat exchanger 4, the expansion valve 5, and the liquid side closing valve 6. On the other hand, the refrigerating machine oil separated by the oil separator 46 is decompressed by the capillary 47, flows into the accumulator 7, and is further returned to the suction portion of the compressor 1.

  Usually, in a refrigerant circuit that does not use an oil separator, about 0.2 to several percent of refrigerating machine oil is taken out from the compressor together with the refrigerant and circulated. As the refrigerating machine oil circulates, pressure loss in the piping increases mainly when the refrigerant is in a gas state. In the refrigerant circuit according to the fifth embodiment, since the oil separator 46 is provided, the circulation rate of the refrigerating machine oil circulating through the gas-side existing pipe 21 can be reduced. As a result, the pressure loss of the refrigerant can be suppressed, and a great effect for suppressing the pressure loss can be obtained particularly in the cooling operation in which the performance deterioration due to the circulation of the refrigerating machine oil is large. The oil separation efficiency of the oil separator 46 is desirably 90% or more. In this way, for example, in a refrigerant circuit with an oil circulation rate of 2%, when an oil separator 46 with an oil separation efficiency of 90% is used, the oil circulation rate can be reduced to about 0.2%. . Therefore, if it calculates with the refrigerant | coolant circulation amount used with a normal air conditioner, about 20 to 50% of pressure loss can be suppressed. For this reason, even when it replaces with a refrigerant | coolant with a small saturated vapor density, the refrigerating-cycle apparatus which can suppress the fall of refrigerating capacity can be obtained, diverting existing piping equipment.

  Further, the oil viscosity of the refrigeration oil affects the pressure loss in the pipe. In a normal air conditioner, a refrigerating machine oil having a viscosity of about 32 to 68 cst is used. In the refrigeration cycle apparatus according to the fifth embodiment, since the low viscosity refrigerating machine oil having a viscosity of about 32 cst is used, the influence on the pressure loss can be reduced as compared with a normal air conditioner. In the present invention, the refrigerating machine oil having a viscosity of about 32 cst is referred to as “a refrigerating machine oil having a low oil viscosity”.

  Note that the oil separator 46 and the capillary 47 described in the fifth embodiment can be applied to the refrigeration cycle apparatuses of the first to fourth embodiments. In the case of a circuit configuration that does not have an accumulator as in the second to fourth embodiments, the outlet side of the capillary 47 is joined to the outlet side pipe of the four-way valve 2 and connected to the suction portion of the compressor 1.

Embodiment 6 FIG.
In the sixth embodiment, an example in which the inside of a pipe is washed to suppress pressure loss in the pipe when the refrigerant is changed while using existing pipe equipment will be described. In the sixth embodiment, an air conditioner including an indoor unit and an outdoor unit will be described as an example.

  FIG. 8 is a work flow when changing the refrigerant according to the sixth embodiment. Hereinafter, each step will be described.

When changing the refrigerant, first, it is confirmed whether or not the outdoor unit can be operated (S61). If the outdoor unit can be operated, the process proceeds to step S62, and if it cannot be operated, the process proceeds to step S63.
When the outdoor unit is operable, it is confirmed whether or not the new refrigerant is an HFO refrigerant (S62). If the new refrigerant is an HFO refrigerant, the process proceeds to step S63, and if not, the process proceeds to step S68.

When the outdoor unit cannot be operated, or when the new refrigerant is an HFO refrigerant, the enclosed refrigerant is collected using the refrigerant collecting machine (S63). After collecting the refrigerant, the outdoor unit and the indoor unit used when the old refrigerant is used are removed. When the outdoor unit and the indoor unit are removed, existing piping equipment is left in the building or the like. And the indoor unit side connection part of these piping facilities is connected using a bypass pipe. (S64).
Then, the inside of the pipe is cleaned using an inner surface cleaning device 50 described later (S65).
After the pipe cleaning, the cleaning refrigerant used for cleaning is recovered using a refrigerant recovery machine (S66).
After the cleaning refrigerant is collected, the pipe cleaning machine and the bypass pipe are removed from the pipe, and an outdoor unit and an indoor unit for new refrigerant are attached (S67).
Then, vacuuming is performed to remove air and moisture in the existing piping (S71), and the ball valve of the outdoor unit is opened to fill the refrigerant (S72).

Next, a refrigerant replacement operation when the new refrigerant is not an HFO refrigerant (S62) will be described.
If the new refrigerant is not an HFO refrigerant, forced cooling operation of the outdoor unit is performed (S68). Thereby, the refrigerating machine oil remaining in the existing piping equipment to be diverted can be managed below a predetermined level.
Then, the outdoor unit is pumped down to collect the refrigerant (S69).
After the refrigerant is recovered, the old refrigerant outdoor unit and the indoor unit are removed and replaced with the new refrigerant outdoor unit and the indoor unit (S70). Thereafter, the process proceeds to step S71 described above.

  Conventionally, when changing the refrigerant while using existing piping equipment, it is determined in step S61 in FIG. 8 whether or not the outdoor unit operation is possible. If the outdoor unit operation is possible, steps S68 to S70 are performed. The operation (hereinafter referred to as “refrigerant recovery operation of the outdoor unit”) was performed, and when the outdoor unit operation was not possible, the operation of steps S63 to S67 (hereinafter referred to as “pipe cleaning”) was performed. That is, the pipe cleaning (steps S63 to S67) is performed only when the outdoor unit cannot be operated.

  However, it may be difficult to sufficiently recover the refrigeration oil and the like adhering to the surface of the pipe only by performing the refrigerant recovery operation of the outdoor unit. If refrigeration oil or the like adheres to the surface of the pipe, the pressure loss tends to increase by several percent compared to when a new pipe is used due to the influence of these impurities and the like. In the case of using a conventional HFC refrigerant, even if the pressure loss is somewhat increased, there has been no practical problem. However, when an HFO refrigerant is used, the pressure loss is larger than that of a conventional refrigerant, so it is difficult to ignore the influence of the pressure loss due to impurities on the pipe surface.

A more specific description will be given using R410A as an example of an HFC refrigerant and HFO-1234 as an example of an HFO refrigerant.
The saturated vapor density of R410A at a temperature of 25 ° C. is 66 kg / m ³ , whereas HFO-1234 is 32 kg / m ³ . That is, the saturated vapor density of HFO-1234 is about 48% of R410A. When a vapor refrigerant having a certain mass flow is flowing in the refrigerant pipe, the refrigerant flow rate is inversely proportional to the vapor density. Therefore, the steam flow rate of HFO-1234 is 2.08 times (= 1 / 0.48) of R410A. Furthermore, since the pipe friction loss is proportional to the 1.75th power of the refrigerant flow rate, the refrigerant pressure loss of the HFO-1234 steam pipe is 3.6 times (= 2.08 ^1.75 ) of R410A.

  In general, the pressure loss in the gas side connection pipe mainly depends on the pipe length. In the case of the R410A refrigerant, there is a pressure loss of about 0.01 to 0.1 MPa in the cooling operation. Assuming that the pressure loss is 0.1 MPa, and assuming that the pressure loss when foreign matter adheres to the inner surface of the pipe increases by 10%, the pressure loss that was 0.1 MPa becomes 0.11 MPa. The change in the refrigerating capacity at this time is almost proportional to the change in the specific gravity of the suction refrigerant. Therefore, when the refrigerant suction temperature is about 0 to 10 ° C. as used for normal air conditioning, the change in the refrigerating capacity is about 1%.

  However, when HFO-1234 is used, the refrigerant pressure loss is about 3.6 times that of R410 as described above. Therefore, the pressure loss of 0.1 MPa with the R410A refrigerant becomes 0.36 MPa with the HFO-1234 refrigerant. If the pressure loss increases by 10% due to the influence of foreign matter on the inner surface of the pipe at this time, the pressure loss becomes 0.396 MPa. Similarly, the change in refrigeration capacity is about 4%, and its influence is large. As the amount of deposits on the pipe surface increases, the degree of influence increases. Therefore, when an HFO refrigerant is used, it is necessary to resist pressure loss due to deposits in the pipe. Therefore, when using the HFO refrigerant as the working refrigerant, it is desirable to clean the piping even if the outdoor unit can be operated.

  In the sixth embodiment, as shown in FIG. 8, pipe cleaning is performed not only when the outdoor unit operation is impossible, but also when an HFO refrigerant is used as a new refrigerant (steps S63 to S67). . For this reason, the influence of the pressure loss by using a HFO type | system | group refrigerant | coolant can be minimized.

  FIG. 9 is a schematic diagram of a main part of the inner surface cleaning apparatus 50 according to the sixth embodiment. FIG. 9 shows a view in which the inner surface cleaning device 50 cleans the inside of the existing pipe 53. A rotating object 51 having an acute end face is rotatably provided at the tip of the inner surface cleaning device 50. The rotating object 51 is rotated by a driving force of a fluid such as a cleaning refrigerant or nitrogen gas. The diameter of the rotating object 51 is preferably about 0.05 to 0.1 mm shorter than the inner diameter of the pipe. A bendable variable fixing portion 52 is provided in front of the rotating object 51. Since the variable fixing portion 52 can be bent, the variable fixing portion 52 can also move in the bent pipe.

  In the inner surface cleaning device 50 configured as described above, when cleaning the inside of the pipe, the inner surface cleaning device 50 is inserted into the pipe 53. Then, the rotating object 51 advances while rotating by the driving force of the fluid, and if there are adhering substances adhering unevenly in the pipe, these are deleted. Thus, the pressure loss resulting from the rough inner surface in the piping can be suppressed by reliably removing the physical deposits on the inner surface of the piping.

  In the sixth embodiment, the example in which the inner surface cleaning device 50 is used when performing pipe cleaning in step S65 of FIG. 8 has been described, but the cleaning device is not limited to this. Other cleaning devices that can clean the inside of the pipe can also be used.

  Further, the sixth embodiment can be applied to the refrigeration cycle apparatuses described in the first to fifth embodiments, and the effect of suppressing the pressure loss can be further improved by using the sixth embodiment together.

  In the above description, an example in which the refrigeration cycle apparatus is an air conditioner and performs a cooling operation has been described, but the same effect can be obtained even when applied to a heating operation. Moreover, it can be applied not only to the refrigeration cycle apparatus but also to other refrigeration cycle apparatuses such as a heat pump water heater.

It is a refrigerant circuit figure of the refrigerating cycle device concerning Embodiment 1 of the present invention. It is a PH diagram of the refrigerating cycle device concerning Embodiment 1 of the present invention. It is a PH diagram of the refrigerating cycle device concerning Embodiment 1 of the present invention. It is a refrigerant circuit figure of the refrigerating cycle device concerning Embodiment 2 of the present invention. It is a refrigerant circuit figure of the refrigerating cycle device concerning Embodiment 3 of the present invention. It is a refrigerant circuit figure of the refrigerating cycle device concerning Embodiment 4 of the present invention. It is a refrigerant circuit figure of the refrigerating cycle device concerning Embodiment 5 of the present invention. It is a work flow at the time of the refrigerant | coolant change which concerns on Embodiment 6 of this invention. It is a principal part schematic diagram of the inner surface cleaning apparatus which concerns on Embodiment 6 of this invention. It is a refrigerant circuit diagram of a general refrigeration cycle apparatus.

Explanation of symbols

  1 compressor, 2 four-way valve, 3 gas side shutoff valve, 4 heat source side heat exchanger, 5 expansion valve, 6 liquid side shutoff valve, 7 accumulator, 8 expansion valve, 9 liquid receiver, 10 use side heat exchanger, 21 Gas side existing piping, 22 Liquid side existing piping, 31 Refrigerant-refrigerant heat exchanger, 32 Branch part, 33 Branch part, 34 Branch pipe, 35 Compressor introduction pipe, 36 Injection pipe, 45 Expansion valve, 46 Oil separator, 47 capillary, 50 inner surface cleaning device, 51 rotating object, 52 variable fixing part, 53 piping.

Claims (11)

A primary refrigerant circuit in which a compressor, a heat source side heat exchanger, and a first pressure reducing means are sequentially connected;
A secondary side refrigerant circuit provided with a use side heat exchanger that is connected to the primary side refrigerant circuit by a connection pipe and through which the refrigerant discharged from the compressor circulates;
When replacing the refrigerant with a refrigerant having a low density at the same temperature from the hydrofluorocarbon-based refrigerant, the connection pipe is kept existing, and pressure loss in the pipe generated when the refrigerant flows through the connection pipe is suppressed. And a pressure suppressing means provided in the primary side refrigerant circuit. A branch pipe branched from between the heat source side heat exchanger and the first pressure reducing means;
Second decompression means for decompressing the refrigerant guided by the branch pipe;
A refrigerant-refrigerant heat exchanger for exchanging heat between the refrigerant decompressed by the second decompression means and the refrigerant before or after branching from the branch pipe through the heat source side heat exchanger;
The refrigeration cycle apparatus according to claim 1, wherein pressure loss is suppressed by providing a compressor introduction pipe that guides the refrigerant heat-exchanged by the refrigerant-refrigerant heat exchanger to the suction side of the compressor. The pressure suppression means is configured to put the refrigerant flowing in the secondary refrigerant circuit into a supercooled state and use the refrigerant flowing in the outlet side or the inlet side of the use side heat exchanger as superheated gas. The refrigeration cycle apparatus according to claim 1. A branch pipe branched from between the heat source side heat exchanger and the first pressure reducing means;
Second decompression means for decompressing the refrigerant guided to the branch pipe;
A refrigerant-refrigerant heat exchanger for exchanging heat between the refrigerant decompressed by the second decompression means and the refrigerant before or after branching from the branch pipe through the heat source side heat exchanger;
A compressor introduction pipe for guiding the refrigerant heat-exchanged by the refrigerant-refrigerant heat exchanger to the suction side of the compressor;
The refrigeration cycle apparatus according to claim 1, wherein pressure loss is suppressed by providing a liquid receiver connected between the refrigerant-refrigerant heat exchanger and the pressure reducing means. A branch pipe branched from between the heat source side heat exchanger and the first pressure reducing means;
The refrigeration cycle apparatus according to claim 1, wherein pressure loss is suppressed by providing an injection pipe that injects a refrigerant guided to the branch pipe into the compressor. The pressure loss is suppressed by providing an oil separator at the discharge port of the compressor. The refrigeration cycle apparatus according to any one of claims 1 to 5. As refrigerating machine oil used for lubricating the compressor,
The refrigeration cycle apparatus according to any one of claims 1 to 6, wherein a refrigeration oil having a lower oil viscosity than a refrigeration oil used in a refrigeration cycle apparatus using a hydrofluorocarbon-based refrigerant is used. The refrigeration cycle apparatus according to any one of claims 1 to 7, wherein the low-density refrigerant is a tetrafluoropropene refrigerant. In the refrigeration cycle apparatus according to any one of claims 1 to 8,
A pressure loss suppression method for a refrigeration cycle apparatus, wherein pressure loss is suppressed by cleaning an inner wall surface of the primary-secondary connection pipe. In the refrigeration cycle apparatus according to any one of claims 1 to 8,
A refrigeration cycle that suppresses pressure loss by removing deposits on the inner wall surface of the primary-secondary connection pipe using an inner surface cleaning device that penetrates the inner diameter of the primary-secondary connection pipe. Method for suppressing pressure loss of the apparatus. In the refrigeration cycle apparatus according to any one of claims 1 to 8,
Using an inner surface cleaning device that penetrates the inner diameter of the primary-secondary connection pipe, the inner wall surface of the primary-secondary connection pipe is cleaned and the pressure loss is suppressed by scraping the inner wall surface. A method for suppressing pressure loss in a refrigeration cycle apparatus.

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