JP4897284B2 - Refrigeration cycle - Google Patents

Description

  The present invention relates to a vapor compression refrigeration cycle, and particularly to a refrigeration cycle suitable for application to a cycle using a refrigerant that is also used in a supercritical region such as a natural refrigerant.

  In the vapor compression refrigeration cycle, the compressed refrigerant is generally cooled by a radiator, the compressed refrigerant is decompressed, and the refrigerant at a low pressure is evaporated by an evaporator to obtain a refrigeration capacity. There is (for example, Patent Document 1).

  In the above-described vapor compression refrigeration cycle, compared with the conventional refrigeration cycle using a chlorofluorocarbon refrigerant, in the refrigeration cycle using a natural system refrigerant such as carbon dioxide, the high-pressure side pressure is set to be higher than the critical pressure of the refrigerant. There is a problem that the efficiency of the refrigeration cycle is low because the required power of the compressor becomes large.

  In a refrigeration cycle using a conventional chlorofluorocarbon refrigerant, it is desirable to control the degree of superheat of the evaporator outlet refrigerant to 5 to 10 deg in order to efficiently exhibit the performance of the evaporator. Therefore, the amount of refrigerant in the evaporator is adjusted so that the dryness of the refrigerant becomes 1 before the outlet of the evaporator. However, in the case of a refrigeration cycle using carbon dioxide as a refrigerant, if the dryness of the refrigerant in the evaporator is increased as usual due to the difference in refrigerant physical properties, the heat transfer coefficient of the evaporator is greatly reduced and the efficiency of the cooling performance is poor. Thus, the efficiency of the refrigeration cycle is also deteriorated. Under such circumstances, research on the refrigeration cycle using carbon dioxide as a refrigerant and its components has been actively conducted, and the relationship between dryness and heat transfer coefficient has been grasped as well as the characteristics of the evaporator and the Mollier diagram. It's getting on.

A conventional refrigeration cycle 101 is configured, for example, as shown in FIG. 10, and includes a compressor 102 that compresses refrigerant, a radiator 103 that cools refrigerant flowing out from the compressor 102, and a high pressure that flows out from the radiator 103. An internal heat exchanger 105 that performs heat exchange between the low-pressure refrigerant that has flowed out of the refrigerant and the accumulator 104 (also serving as a gas-liquid separator) and supplies the low-pressure refrigerant heat-exchanged with the high-pressure refrigerant to the compressor 102; A decompressor 106 that depressurizes the high-pressure refrigerant that has flowed out of the internal heat exchanger 105, an evaporator 107 that evaporates the low-pressure refrigerant that has flowed out of the decompressor 106, and a two-phase liquid phase gas phase and gas phase refrigerant that have flowed out of the evaporator 107 The accumulator 104 is provided that stores the refrigerant and supplies the gas-phase refrigerant to the internal heat exchanger 105. In such a refrigeration cycle 101, a Mollier diagram representing the relationship between enthalpy and pressure is, for example, as shown in FIG.
JP 11-193967 A

  An object of the present invention is to provide a refrigeration cycle in which the performance of an evaporator is more efficiently exhibited in view of the above-described conventional technology, and preferably (2) decompress the refrigerant. An object of the present invention is to provide a highly efficient refrigeration cycle in which expansion energy generated at the time is regenerated and used for the operation of the refrigeration cycle, and the power consumption of the refrigeration cycle can be substantially reduced.

In order to solve the above problems, the present invention provides an evaporator for evaporating a refrigerant, a compressor for compressing and discharging the refrigerant, a radiator for cooling the refrigerant discharged from the compressor, and cooling by the radiator. The expander for decompressing the expanded refrigerant, the refrigerant flowing out from the expander and the refrigerant flowing in from the evaporator are separated into a liquid phase refrigerant and a gas phase refrigerant, and the liquid phase refrigerant is discharged to the evaporator side. and having a gas-liquid separator to flow out the vapor-phase refrigerant to the compressor side, and a refrigeration cycle high pressure side is that Do a critical pressure or more,
A pump means is provided between the gas-liquid separator and the evaporator to pump the liquid-phase refrigerant flowing out from the gas-liquid separator to the evaporator side, and the drive source of the pump means is a refrigerant that is expanded by the expander. Expansion energy ,
A bypass passage is provided between the radiator and the gas-liquid separator to allow a part of the refrigerant to flow by bypassing the expander, and the refrigerant flow rate in the bypass passage is determined based on information on the state of the refrigeration cycle. A refrigerant flow rate adjusting means for adjusting
Provided is a refrigeration cycle comprising refrigerant flow rate control means for controlling the refrigerant flow rate adjustment means so that the pressure in the gas-liquid separator is equal to or lower than the critical pressure of the refrigerant .

  Further, a decompressor for decompressing the refrigerant pumped by the pump means may be provided between the pump means and the evaporator. This decompressor corresponds to the second decompressor in the first embodiment described above.

  In this case, the decompressor may be configured to include a decompression amount adjusting unit that determines the degree of decompression based on information on the state of the refrigeration cycle.

  The decompression amount adjusting means preferably has a mechanism for determining the degree of decompression based on information relating to the state of the refrigeration cycle.

  The expander can be configured from an impeller, for example, a turbine impeller similar to an exhaust gas turbine supercharger used in an engine.

  Such a refrigeration cycle according to the present invention is particularly suitable when the refrigerant is carbon dioxide, which is a natural refrigerant. The refrigeration cycle according to the present invention is particularly suitable when used as a refrigeration cycle for a vehicle air conditioner.

According to the refrigeration cycle according to the present invention, the pump means is provided so that the liquid phase refrigerant is intentionally efficiently supplied to the evaporator. Therefore, in particular, in the refrigeration cycle using the refrigerant that operates in the supercritical region. Efficiency can be improved. Further, the supply of the liquid-phase refrigerant. Thus utilizing expansion energy of the refrigerant in the system, it is possible to reduce the power consumption of the refrigerating cycle, to further achieve a high refrigerating cycle efficiency It becomes possible.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with respect to a vapor compression refrigeration cycle using carbon dioxide, which is a natural refrigerant.

< Reference Example 1>
FIG. 1 shows a refrigeration cycle according to Reference Example 1 of the present invention. The refrigeration cycle 1 shown in FIG. 1 cools a compressor 2 that compresses and discharges a refrigerant, and cools the refrigerant discharged from the compressor 2. The radiator 3, the first decompressor 4 that decompresses the refrigerant cooled by the radiator 3, the refrigerant that flows out of the first decompressor 4, and the refrigerant that flows in from the evaporator 7 are combined into a liquid-phase refrigerant and a gas-phase refrigerant. The gas-liquid separator 5 that causes the liquid-phase refrigerant to flow out to the evaporator 7 side and the gas-phase refrigerant to flow to the compressor 2 side, and the liquid-phase refrigerant that has flowed out from the gas-liquid separator 5 evaporate. The vapor phase refrigerant is provided as an evaporator 7, and the liquid phase refrigerant that is between the gas-liquid separator 5 and the evaporator 7 and separated and discharged from the gas-liquid separator 5 is pumped toward the evaporator 7. The pump means 6 is provided. The refrigerant flowing out from the gas-liquid separator 5 toward the evaporator 7 may be a two-phase refrigerant that is a mixed refrigerant of a liquid-phase refrigerant and a gas-phase refrigerant. Since they are separated, even when they become two-phase refrigerant, most of the outflow refrigerant is liquid refrigerant, and the liquid refrigerant is pumped by the pump means 6 toward the evaporator 7 side. The compressor 1 and the pump means 6 are driven by different driving sources, and also have compression function force control means capable of independently controlling the refrigerant pumping ability.

  In the refrigeration cycle 1, the first pressure reducer 4 includes a first pressure reduction amount adjusting means capable of adjusting the degree of pressure reduction. The first pressure reduction amount adjusting means reduces the pressure based on information on the state of the refrigeration cycle 1. It has what has a mechanism in which a degree is determined. The mechanism of the first decompression amount adjusting means in the first decompressor 4 may operate autonomously based on the difference between the refrigerant pressures before and after the first decompressor 4, or by an external electric or pressure signal It may work.

  Further, the refrigeration cycle 1 includes first decompressor control means for controlling the first decompression amount adjusting means so that the pressure in the gas-liquid separator 5 becomes equal to or lower than the critical pressure of the refrigerant. The first pressure reducer control means controls the first pressure reducer 4 with an electric signal so that the pressure in the gas-liquid separator 5 is equal to or lower than the critical pressure of the refrigerant, and the refrigeration cycle 1 The degree of pressure reduction is adjusted so that the efficiency of the above becomes better.

FIG. 2 is a pressure-enthalpy diagram (Mollier diagram) in the refrigeration cycle of Reference Example 1 shown in FIG. 1, and the operation of each device in FIG. 1 is made to correspond by attaching the reference numerals shown in FIG. . The refrigerant flowing out of the radiator 3 is depressurized to form a low-pressure refrigerant, which is separated into a gas-phase refrigerant and a liquid-phase refrigerant by the gas-liquid separator 5, and only the liquid-phase refrigerant is intentionally efficient using the pump means 6. The refrigerant in the evaporator 7 is brought into a state with a low dryness and a high heat transfer coefficient in the relationship diagram between the dryness and the heat transfer coefficient shown in FIG. Can do. As a result, it is possible to avoid the deterioration of the efficiency of the cooling performance and the deterioration of the refrigeration cycle efficiency, which is the conventional problem described above.

FIG. 4 shows a modification of the refrigeration cycle according to the reference example 1. In the refrigeration cycle 1 shown in FIG. 1, the pump means 6 is further pumped between the pump means 6 and the evaporator 7. A second decompressor 8 is provided for decompressing the generated refrigerant. The second decompressor 8 includes a second decompression amount adjusting unit that can adjust the decompression degree. The second decompression amount adjusting unit is a mechanism in which the decompression degree is determined based on information on the state of the refrigeration cycle 1. It consists of what has. The mechanism of the second decompression amount adjusting means in the second decompressor 8 may operate autonomously based on the difference between the refrigerant pressures before and after the second decompressor 8 or by an external electric or pressure signal. It may work.

FIG. 5 is a pressure-enthalpy diagram (Mollier diagram) in a refrigeration cycle according to a modification of Reference Example 1 shown in FIG. 4, and the operation of each device in FIG. 4 is denoted by the reference numerals shown in FIG. It corresponds. The refrigerant flowing out of the radiator 3 is depressurized to form a low-pressure refrigerant, which is separated into a gas-phase refrigerant and a liquid-phase refrigerant by the gas-liquid separator 5, and the liquid-phase refrigerant is pumped and pumped using the pump means 6. The liquid refrigerant is further depressurized by the second decompressor 8 before reaching the evaporator 7. As a result, the vapor phase refrigerant from the gas-liquid separator 5 is intentionally and efficiently sent to the evaporator 7 using the pump means 6 while being decompressed by the second decompressor 8. It is possible to more effectively avoid the above-described conventional problem, that is, the deterioration in efficiency of the cooling performance and the deterioration in the efficiency of the refrigeration cycle.

< Reference Example 2>
6 shows a refrigeration cycle according to Reference Example 2 of the present invention. The refrigeration cycle 1 shown in FIG. 6 cools the compressor 2 that compresses and discharges the refrigerant, and the refrigerant discharged from the compressor 2. The radiator 3, the expander 9 that decompresses and expands the refrigerant cooled by the radiator 3, and the refrigerant that flows out of the expander 9 and the refrigerant that flows in from the evaporator 7 are converted into a liquid-phase refrigerant and a gas-phase refrigerant. While separating, the liquid-phase refrigerant is caused to flow to the evaporator 7 side, and the gas-liquid separator 5 that causes the gas-phase refrigerant to flow to the compressor 2 side, and the liquid-phase refrigerant that has flowed out from the gas-liquid separator 5 is evaporated. And a pump means for pumping the liquid-phase refrigerant flowing out of the gas-liquid separator 5 toward the evaporator 7 between the gas-liquid separator 5 and the evaporator 7. 10. The pump means 10 uses the drive source as the expansion energy of the refrigerant that expands in the expander 9. In this reference example, the pump means 10 is directly connected to the expander 9, and the rotation of the expander 9 driven by the expansion energy of the refrigerant is substantially transmitted to the pump means 10 as it is. Further, in the present embodiment, between the pump means 10 evaporator 7, but decompressor 11 for decompressing the refrigerant pumped by the pump means 10 is provided, this reference also without this pressure reducer 11 The example refrigeration cycle 1 is established. The decompressor 11 corresponds to the second decompressor 8 in the reference form shown in FIG.

The difference between the refrigeration cycle according to the reference example 2 and the reference example 1 described above is that the liquid phase refrigerant flowing out from the gas-liquid separator 5 is pumped by regenerating the expansion energy of the refrigerant. This eliminates the need to supply the driving power of the pump means 10 from outside the refrigeration cycle, so that the refrigeration cycle efficiency of Reference Example 1 can be further improved.

FIG. 7 shows an embodiment as a modified example of the refrigeration cycle according to the reference example 2, and in the refrigeration cycle 1 shown in FIG. 6, further between the radiator 3 and the gas-liquid separator 5. A bypass passage 12 for bypassing a part of the refrigerant to the passage provided with the expander 9 is provided, and the refrigerant flow rate in the bypass passage 12 is adjusted in the bypass passage 12 based on information on the state of the refrigeration cycle 1. The refrigerant flow rate adjusting means 13 is provided.

  The refrigerant flow rate adjusting unit 13 controls the refrigerant flow rate adjusting unit 13 so that the pressure in the gas-liquid separator 5 is equal to or lower than the critical pressure of the refrigerant and the efficiency of the refrigeration cycle 1 is improved. And a refrigerant flow rate control means.

  In addition, the decompressor 11 includes a decompression amount adjusting unit that determines the degree of decompression based on information on the state of the refrigeration cycle 1, and the decompression amount adjusting unit is based on information on the state of the refrigeration cycle 1. It has what has a mechanism in which a pressure reduction degree is determined. The mechanism of the decompression amount adjusting means in the decompressor 11 may operate autonomously based on the difference in refrigerant pressure before and after the decompressor 11 or may operate based on an external electric or pressure signal.

For example, as shown in FIG. 8, the expander 9 has a turbine impeller shape similar to that of an exhaust gas turbine supercharger used in an engine, and converts expansion energy of refrigerant into mechanical energy and takes it out. Since the mechanical energy is input to the pump unit 10, it is not necessary to supply the driving power of the pump unit 10 from outside the refrigeration cycle, so that the refrigeration cycle efficiency of Reference Example 1 can be further improved. That is, the drive energy obtained from the expander 9 is regenerated as electric energy or mechanical energy and used as a drive source for the pump means 10. When used as electric energy, it may be stored in a capacitor and then input to the drive motor of the pump means 10. When used as mechanical energy, the drive shaft of the expander 9 and the pump unit 10 may be connected to transmit the drive energy obtained from the expander 9 directly to the pump unit 10.

Reference Example shown in FIG. 6 2, pressure in the refrigeration cycle according to the embodiment shown in FIG. 7 - illustrates enthalpy diagram (the Mollier diagram) in Fig. As shown in the Mollier diagram of FIG. 9, the refrigerant flowing out of the radiator 3 is decompressed by the expander 9 or the expander 9 and the refrigerant flow rate adjusting means 13 to form a low-pressure refrigerant, which is the gas-liquid separator 5. Is separated into a gas-phase refrigerant and a liquid-phase refrigerant, and only the liquid-phase refrigerant is intentionally and efficiently sent to the evaporator 7 using the pump means 10, so that the refrigerant in the evaporator 7 has a low dryness and heat. A high transmission rate can be achieved. As a result, it is possible to efficiently avoid the deterioration of the cooling performance and the deterioration of the refrigeration cycle efficiency, which are the conventional problems described above.

  The present invention can be applied to a vapor compression refrigeration cycle, and is particularly suitable for a refrigeration cycle using carbon dioxide, which is a natural refrigerant, as a refrigerant.

It is a schematic block diagram of the refrigerating cycle which concerns on the reference example 1 of this invention. FIG. 2 is a Mollier diagram of the refrigeration cycle of FIG. 1. It is a related figure of the dryness in an evaporator, and a heat transfer rate. It is a schematic block diagram of the refrigerating cycle which concerns on the modification of the reference example 1 of this invention. FIG. 5 is a Mollier diagram of the refrigeration cycle of FIG. 4. It is a schematic block diagram of the refrigerating cycle which concerns on the reference example 2 of this invention. It is a schematic block diagram of the refrigerating cycle which concerns on the Example as a modification of the reference example 2 of this invention. It is sectional drawing of the impeller which shows the specific example of an expander, and its housing. FIG. 8 is a Mollier diagram of the refrigeration cycle of FIGS. 6 and 7. It is a schematic block diagram of the conventional refrigeration cycle. FIG. 11 is a Mollier diagram of the refrigeration cycle of FIG. 10.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Refrigeration cycle 2 Compressor 3 Radiator 4 First decompressor 5 Gas-liquid separator 6 Pump means 7 Evaporator 8 Second decompressor 9 Expander 10 Pump means 11 Decompressor 12 Bypass passage 13 Flow rate adjusting means

Claims (7)

An evaporator for evaporating the refrigerant, a compressor for compressing and discharging the refrigerant, a radiator for cooling the refrigerant discharged from the compressor, an expander for decompressing and expanding the refrigerant cooled by the radiator, The refrigerant flowing out of the expander and the refrigerant flowing in from the evaporator are separated into a liquid phase refrigerant and a gas phase refrigerant, the liquid phase refrigerant is made to flow out to the evaporator side, and the gas phase refrigerant is moved to the compressor side. a gas-liquid separator to flow out, and a refrigeration cycle high pressure side is that Do a critical pressure or more,
A pump means is provided between the gas-liquid separator and the evaporator to pump the liquid-phase refrigerant flowing out from the gas-liquid separator to the evaporator side, and the drive source of the pump means is a refrigerant that is expanded by the expander. Expansion energy ,
A bypass passage is provided between the radiator and the gas-liquid separator to allow a part of the refrigerant to flow by bypassing the expander, and the refrigerant flow rate in the bypass passage is determined based on information on the state of the refrigeration cycle. A refrigerant flow rate adjusting means for adjusting
A refrigeration cycle comprising refrigerant flow rate control means for controlling the refrigerant flow rate adjusting means so that the pressure in the gas-liquid separator is equal to or lower than the critical pressure of the refrigerant. Between the evaporator and the pumping means, characterized in that a pressure reducer for reducing the pumped refrigerant by the pump means, wherein the refrigeration cycle to claim 1. The refrigeration cycle according to claim 2 , wherein the decompressor includes a decompression amount adjusting means capable of adjusting a degree of decompression. The refrigeration cycle according to claim 3 , wherein the decompression amount adjusting means has a mechanism for determining a degree of decompression based on information relating to a state of the refrigeration cycle. The refrigeration cycle according to any one of claims 1 to 4 , wherein the expander includes an impeller. It said refrigerant characterized in that it consists of carbon dioxide, a refrigeration cycle according to claim 1-5. Characterized in that it is used as a refrigeration cycle of a vehicular air conditioner, refrigeration cycle according to claim 1-6.

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