JP2005098635A - Refrigeration cycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigeration cycle capable of preventing the increase of pressure loss of an internal heat exchanger, reducing the dimension and weight of necessary components, and reducing the cost in constructing a component for preventing the rise in a refrigerant discharge temperature from a compressor. <P>SOLUTION: This refrigeration cycle comprising the compressor 2 for rising a pressure of the refrigerant, a radiator 3 for cooling the refrigerant compressed by the compressor, an expansion device 4 for decompressing the refrigerant cooled by the radiator 3, an evaporator 5 for evaporating the refrigerant decompressed by the expansion device 4, an accumulator 6 for performing the gas/liquid separation of the refrigerant passed through the evaporator 5 and separating the oil in the refrigerant, and the internal heat exchanger 7 performing the heat exchange between the low-pressure refrigerant guided from the accumulator 6 to the compressor 2 and the high-pressure refrigerant guided from the radiator 3 to the expansion device, is provided with a recovering passage 10 for recovering the liquid refrigerant or the oil in the accumulator 6 between the internal heat exchanger 7 and the compressor 2 while bypassing the internal heat exchanger 7, and an adjustment valve 11 for adjusting the recovering quantity through the recovering passage 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a refrigeration cycle in which a supercritical fluid such as carbon dioxide (CO ₂ ) is used as a refrigerant.

  In this type of refrigeration cycle, the temperature of the refrigerant discharged from the compressor becomes very high when the load is high, and the durability of each member constituting the refrigeration cycle may be significantly impaired. In particular, in rubber materials and resin materials, the allowable temperature at which durability can be ensured is lower than that of other members. Therefore, when the load is high, the discharge refrigerant temperature will exceed this allowable temperature and may be damaged. Occurs.

  In a supercritical vapor compression refrigeration cycle using carbon dioxide or the like as a refrigerant, high-pressure refrigerant passed through a radiator and low-pressure sucked into the compressor for the purpose of increasing cooling capacity or preventing liquid compression by the compressor. An internal heat exchanger for exchanging heat with the refrigerant is provided.

For this reason, conventionally, as shown in Patent Document 1, the liquid refrigerant and oil separated by the accumulator are collected at the inlet side of the internal heat exchanger, and the superheat degree of the refrigerant sucked in the compressor is excessively increased. And those that collect the gas refrigerant in the accumulator between the outlet side of the internal heat exchanger and the suction side of the compressor, as shown in Patent Documents 2 and 3, etc. Yes.
JP 2002-228282 A JP 11-193967 A JP 11-151568 A

  However, in the configuration of Patent Document 1, since the liquid refrigerant or oil cooled in the accumulator is mixed with the refrigerant absorbed by the evaporator, the intake refrigerant temperature of the compressor is lowered, and the Although the discharge refrigerant temperature can be lowered, the liquid refrigerant and oil pass through the internal heat exchanger, so there is a disadvantage that the pressure loss in the internal heat exchanger increases.

  In the configurations of Patent Documents 2 and 3, the gas refrigerant in the accumulator is supplied by bypassing the internal heat exchanger and mixed with the gas refrigerant flowing out of the internal heat exchanger. In order to effectively collect the refrigerant, the adjustment valve for adjusting the pipe diameter of the bypass passage and the amount to be collected had to be enlarged, which was against the demand for miniaturization, weight reduction, and cost reduction. .

  Therefore, in the present invention, in the configuration for preventing the rise in the refrigerant discharge refrigerant temperature, the increase in pressure loss of the internal heat exchanger is prevented, and the size and weight of components required for constructing such a configuration are reduced. The main challenge is to provide a refrigeration cycle that can be reduced in cost and cost.

  To achieve the above object, a refrigeration cycle according to the present invention includes a compressor that boosts a refrigerant, a radiator that cools the refrigerant compressed by the compressor, and a refrigerant that is cooled by the radiator. An expansion device, an evaporator that evaporates the refrigerant decompressed by the expansion device, an accumulator that separates the refrigerant that has passed through the evaporator and separates oil in the refrigerant, and that is led from the accumulator to the compressor In a refrigeration cycle having a low-pressure refrigerant and an internal heat exchanger for exchanging heat between the low-pressure refrigerant and the high-pressure refrigerant guided from the radiator to the expansion device, the liquid refrigerant or oil in the accumulator bypasses the internal heat exchanger and A recovery passage that can be recovered between the internal heat exchanger and the compressor, and an adjustment valve that can adjust the amount of the liquid refrigerant or oil recovered through the recovery passage; It is characterized by comprising (claim 1).

  Therefore, the liquid refrigerant or oil separated in the accumulator is collected between the internal heat exchanger and the compressor and mixed with the gas refrigerant that has passed through the internal heat exchanger, so that it is sucked into the compressor. It becomes possible to lower the refrigerant temperature and, in turn, lower the refrigerant discharge refrigerant temperature. Moreover, the liquid refrigerant or oil separated in the accumulator is recovered between the internal heat exchanger and the compressor by bypassing the internal heat exchanger, so that pressure loss in the internal heat exchanger can be avoided. In addition, since liquid refrigerant and oil are recovered through the recovery passage, the pipe diameter of the recovery passage can be made smaller than when the gas refrigerant is passed, and the size and weight can be reduced. It becomes.

The above-described configuration may be embodied by providing a discharge refrigerant temperature sensor that detects the discharge refrigerant temperature of the compressor and a control unit that controls the adjustment valve according to the discharge refrigerant temperature detected by the discharge refrigerant temperature sensor. (Claim 2) Based on the outside air temperature, the pressure in the cycle, the room temperature, and the like, it may be embodied by providing a control means for controlling the regulating valve when the cycle load is predicted to be high and the discharge temperature becomes high ( Claim 3). Furthermore, in order to realize light weight, downsizing, and low cost of the refrigeration cycle, an internal heat exchanger and a regulating valve may be built in the accumulator.
In addition, such a cycle configuration as described above is suitable for a supercritical vapor compression refrigeration cycle using carbon dioxide as a refrigerant, which has a very high discharge refrigerant temperature when the load is high.

  As described above, according to the present invention, in the refrigeration cycle including the internal heat exchanger for exchanging heat between the low-pressure refrigerant led from the accumulator to the compressor and the high-pressure refrigerant led from the radiator to the expansion device, The liquid refrigerant or oil is bypassed through the internal heat exchanger via the recovery passage, and can be recovered between the internal heat exchanger and the compressor, and the amount of liquid refrigerant or oil recovered through the recovery passage is reduced. Since the adjustment is made by the adjusting valve, the intake refrigerant temperature of the compressor can be lowered, and the discharge refrigerant temperature can be lowered. In addition, an increase in pressure loss in the internal heat exchanger can be avoided and the pipe diameter of the recovery passage can be set smaller than when the gas refrigerant is allowed to pass. It becomes possible to reduce the weight, size and cost of the cycle.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best embodiment of the present invention will be described below with reference to the accompanying drawings.

  In FIG. 1, a refrigeration cycle 1 includes a compressor 2 that boosts the refrigerant, a radiator 3 that cools the refrigerant compressed by the compressor 2, an expansion device 4 that decompresses the refrigerant cooled by the radiator 3, An evaporator 5 for evaporating and evaporating the refrigerant decompressed by the expansion device 4, an accumulator 6 for separating the refrigerant that has passed through the evaporator 5 into gas and liquid and separating oil (lubricating oil) mixed in the refrigerant, and an accumulator 6 And an internal heat exchanger 7 for exchanging heat between the low-pressure refrigerant led to the compressor 2 and the high-pressure refrigerant led from the radiator 3 to the expansion device 4.

  That is, in the refrigeration cycle 1, the discharge side of the compressor 2 is connected to the high-pressure channel 7 a of the internal heat exchanger 7 via the radiator 3, and the outflow side of the high-pressure channel 7 a is connected to the expansion device 4. Further, the outflow side of the expansion device 4 is connected to the inlet of the accumulator 6 via the evaporator 5, and the outlet of the accumulator 6 is connected to the suction side of the compressor 2 via the low-pressure channel 7 b of the internal heat exchanger 7. Has been. Therefore, the high pressure line 8 is constituted by a path from the discharge side of the compressor 2 to the expansion device 4 via the radiator 3 and the high pressure flow path 7a, and the evaporator 5, the accumulator 6, and the low pressure from the outflow side of the expansion device 4. A low-pressure line 9 is constituted by a path reaching the compressor 2 through the flow path 7b.

In the refrigeration cycle 1 described above, carbon dioxide (CO ₂ ) is used as a refrigerant, and the refrigerant whose pressure has been increased by the compressor 2 enters the radiator 3 as a high-temperature and high-pressure supercritical refrigerant and radiates heat here. And cooled. Thereafter, the refrigerant enters the high-pressure flow path 7a of the internal heat exchanger 7, exchanges heat with the low-temperature gas refrigerant flowing out of the accumulator 6, is further cooled, and is sent to the expansion device 4 without being liquefied. Then, the pressure is reduced in the expansion device 4 to become low-temperature and low-pressure wet steam, and in the evaporator 5, heat is exchanged with the air passing therethrough to evaporate and flow into the accumulator 6 as a two-phase refrigerant in which gas and liquid are mixed. .

  The refrigerant flowing into the accumulator 6 is separated from gas and liquid and oil mixed in the refrigerant. The separated liquid refrigerant and oil remain in the accumulator, and the gas refrigerant exchanges heat internally. The heat is exchanged with the high-temperature refrigerant flowing out from the radiator 3 to further absorb heat and returned to the compressor 2 in a completely gasified state.

  By the way, in this structure, as FIG. 2 also shows, with respect to the refrigerating cycle 1 mentioned above, one end opens to the bottom part of the accumulator 6, and the other end compresses with the low pressure flow path 7b of the internal heat exchanger 7. A recovery passage 10 connected to the suction side of the machine 2 is provided, and the opening degree of the recovery passage 10 is adjusted by an adjustment valve 11 formed of an electromagnetic valve.

  A discharge refrigerant temperature sensor 12 detects the discharge refrigerant temperature Td of the compressor 2, and a temperature signal output from the discharge refrigerant temperature sensor 12 is input to the control unit 13. The control unit 13 includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), an input / output port, and the like, and a drive circuit that drives and controls the regulating valve 11. The control valve 11 is controlled by the control routine shown in FIG. 3 executed at predetermined intervals. That is, the discharge refrigerant temperature Td is input at a predetermined interval (step 50), it is determined whether or not the input discharge refrigerant temperature Td is equal to or higher than a specified temperature (step 52), and it is determined to be equal to or higher than the predetermined temperature. If the discharge refrigerant temperature Td increases, the opening degree of the regulating valve 11 increases (so that the amount of oil or liquid refrigerant recovered through the recovery passage 10 increases) according to the discharge refrigerant temperature Td. The opening degree of the adjusting valve 11 is adjusted (step 54).

  Therefore, as shown in FIG. 2, the oil 20a separated in the accumulator 6 has a specific gravity greater than that of the liquid refrigerant 20b, and therefore accumulates below the liquid refrigerant 20b. Therefore, the recovery passage 10 is opened by the regulating valve 11. If it will be in a state, it will be collect | recovered between the internal heat exchanger 7 and the compressor 2 via the collection | recovery channel | path 10 ahead of a liquid refrigerant. Further, after the oil 20a in the accumulator 6 is recovered, the liquid refrigerant 20b is recovered between the internal heat exchanger 7 and the compressor 2 through the recovery passage 10 and passes through the internal heat exchanger 7. It will be mixed with the refrigerant and recovered to the compressor 2. For this reason, the low-pressure gas refrigerant that has passed through the internal heat exchanger 7 exchanges heat with the high-temperature high-pressure gas refrigerant, so that the temperature is raised, but by mixing with the cooled oil 20a or liquid refrigerant 20b in the accumulator 6, It will be cooled again, and the suction temperature of the compressor 2 can be lowered.

  The above mechanism will be described with reference to the Mollier diagram of FIG. 4. In the conventional configuration without the recovery passage 10, the A1 → B1 → C → D → E → A1 changes in the Mollier diagram. , The low-temperature oil 20a or liquid refrigerant 20b recovered through the recovery passage 10 is mixed with the gas refrigerant that has passed through the internal heat exchanger 7, so that the enthalpy once increased by the internal heat exchanger 7 is increased. It will fall from A1 to A2. Therefore, in this refrigeration cycle, the refrigeration effect hardly changes depending on the presence or absence of the oil 10a or the liquid refrigerant 10b recovered through the recovery passage 10, but the enthalpy on the discharge side of the compressor is reduced from B1 to B2. Become. Therefore, in the above-described configuration, the intake refrigerant temperature of the compressor 2 can be lowered, and thus the discharge refrigerant temperature of the compressor 2 can be lowered.

  Actually, the oil from the accumulator 6 is bypassed through the internal heat exchanger 7 under the condition that the discharged refrigerant temperature Td becomes high, and is recovered between the internal heat exchanger and the compressor. As shown in FIG. 5, it was possible to lower the discharged refrigerant temperature as the oil recovery amount increased. Further, it was confirmed that the change in the cooling capacity at that time was maintained almost equal regardless of the oil recovery amount, as shown in FIG.

  Therefore, in the above-described configuration, it is possible to prevent damage to components due to an increase in the discharge refrigerant temperature Td of the compressor, and in order to reduce the discharge refrigerant temperature of the compressor 2, the oil 20a in the accumulator 6 is used. Alternatively, since the liquid refrigerant 20b is recovered by bypassing the internal heat exchanger 7, an increase in pressure loss due to the flow of oil or liquid refrigerant to the internal heat exchanger 7 can be avoided. Furthermore, since the fluid flowing through the recovery passage 10 is oil or liquid refrigerant, it is possible to reduce the diameter of the pipe constituting the recovery passage 10 compared to the pipe through which the gas refrigerant flows. The provided regulating valve 11 can also be reduced in size. For this reason, it is possible to reduce the size, weight, and cost of the component.

  In the above-described configuration, the recovery passage 10 is connected to the lower portion of the accumulator 6 to recover the oil 20a or liquid refrigerant 20b in the accumulator 6. However, the oil or liquid refrigerant in the accumulator 6 is recovered. However, the present invention is not limited to the above-described configuration, and a pipe constituting the recovery passage 10 may be inserted into the accumulator, and an adjustment valve for oil recovery or liquid refrigerant recovery may be provided in the inserted portion. .

  Further, the internal heat exchanger 7 may be built in the accumulator 6, and an oil or liquid refrigerant recovery passage and a regulating valve for adjusting the recovery amount may be provided inside the accumulator. In such a configuration, it is not necessary to add a new pipe outside the accumulator 6, so that the refrigeration cycle 1 can be easily reduced in weight, size, and cost.

  Further, in the above-described configuration, the recovery amount is adjusted when the discharge refrigerant temperature is equal to or higher than the predetermined value. If it is predicted that this will occur, the amount of recovery may be adjusted by controlling the adjustment valve. Specifically, the outlet air temperature of the evaporator 5 or the pressure of the low-pressure line is predetermined even if the recovery amount is adjusted when the indoor temperature, the outside air, or the inlet air temperature of the radiator 3 becomes equal to or higher than a predetermined temperature. The recovery amount may be adjusted when the value becomes equal to or greater than the value, or the recovery amount may be adjusted when the airflow rate of the air conditioning unit becomes equal to or greater than a predetermined air volume.

FIG. 1 is a diagram showing an example of the overall configuration of a refrigeration cycle according to the present invention. FIG. 2 is an enlarged view showing the vicinity of the accumulator and the internal heat exchanger of FIG. FIG. 3 is a flowchart showing an example of a control operation by the control unit of FIG. FIG. 4 is a Mollier diagram illustrating the operating mechanism of the refrigeration cycle. FIG. 5 is a graph showing the relationship between the amount of oil recovered from the accumulator and the refrigerant discharge refrigerant temperature. FIG. 6 is a graph showing the relationship between the amount of oil recovered from the accumulator and the refrigeration capacity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Refrigeration cycle 2 Compressor 3 Radiator 4 Expansion device 5 Evaporator 6 Accumulator 7 Internal heat exchanger 10 Recovery passage 11 Adjustment valve 12 Discharge refrigerant temperature sensor

Claims (5)

A compressor for boosting the refrigerant; a radiator for cooling the refrigerant compressed by the compressor; an expansion device for decompressing the refrigerant cooled by the radiator; and an evaporation for evaporating the refrigerant decompressed by the expansion device An accumulator for separating the refrigerant that has passed through the evaporator from gas and liquid, and separating oil in the refrigerant, a low-pressure refrigerant that is led from the accumulator to the compressor, and a high-pressure refrigerant that is led from the radiator to the expansion device In a refrigeration cycle having an internal heat exchanger for exchanging heat,
A recovery passage that allows the liquid refrigerant or oil in the accumulator to be bypassed the internal heat exchanger and recovered between the internal heat exchanger and the compressor;
A refrigeration cycle, comprising: an adjustment valve capable of adjusting an amount of the liquid refrigerant or oil recovered through the recovery passage. A discharge refrigerant temperature sensor for detecting a discharge refrigerant temperature of the compressor;
2. The refrigeration cycle according to claim 1, further comprising control means for controlling the regulating valve in accordance with a discharge refrigerant temperature detected by the discharge refrigerant temperature sensor. 2. The refrigeration according to claim 1, further comprising control means for controlling the regulating valve when it is predicted that the cycle load is high and the discharge temperature is high based on the outside air temperature, the pressure in the cycle, the room temperature, and the like. cycle. The refrigeration cycle according to claim 1, wherein the internal heat exchanger and the regulating valve are built in the accumulator. The refrigeration cycle according to claim 7, wherein the refrigeration cycle is a supercritical vapor compression refrigeration cycle using carbon dioxide as a refrigerant.

Images