Vapor compression refrigerating systems

Abstract

 A vapor compression refrigerating system includes a compressor configured to compress a refrigerant, and a radiator connected to the compressor, in which the radiator is configured to receive the refrigerant from the compressor and to reduce a temperature of the refrigerant. The system also includes a pressure reducing mechanism connected to the radiator, and the pressure reducing mechanism is configured to receive the refrigerant from the radiator and to reduce a pressure of the refrigerant. The system also includes a separator connected to the pressure reducing mechanism and to the compressor, a pump connected to the separator, and an evaporator connected to the pump and to the separator. The separator is configured to receive the refrigerant from the pressure reducing mechanism, to separate a liquid portion of the refrigerant from a gas portion of the refrigerant, and to transmit the gas portion to the compressor. Moreover, the pump is configured to pump the liquid portion from the separator to the evaporator, and the evaporator is configured to evaporate the liquid portion into an evaporated portion, and to transmit the evaporated portion to the separator.

Description

[0001] The present invention relates generally to vapor compression refrigerating systems.

[0002] A known vapor compression refrigerating system obtains its refrigerating ability by cooling a compressed refrigerant, reducing the pressure of the compressed refrigerant by a radiator, e.g., a gas cooler, and evaporating the pressure reduced refrigerant by an evaporator. Such a known vapor compression refrigerating system is described in Japanese Patent Application No. JP-A-11-193967.

[0003] In such a known vapor compression refrigerating system which uses a natural-system refrigerant, such as carbon dioxide, it is necessary to increase a pressure of the refrigerant on the high-pressure side to at least a critical pressure of the refrigerant, which increases the amount of power required to operate the compressor, and decreases the efficiency of the system.

[0004] Moreover, in a refrigerating system which uses a fleon group refrigerant, it has been considered that it is desirable to control a degree of superheating of the refrigerant flowing out of the evaporator to be in a range between 5 and 10 degrees in order to maximize evaporator efficiently. Therefore, an amount of the refrigerant in the evaporator is adjusted so that a degree of dryness of the refrigerant before the refrigerant exits the evaporator is 1. Nevertheless, in a refrigerating system using a carbon dioxide refrigerant, because of the different properties of the carbon dioxide refrigerant, if the degree of dryness of the refrigerant in the evaporator is adjusted in the known manner, the coefficient of heat transfer of the evaporator is reduced greatly, such that the cooling ability thereof deteriorates, and the efficiency of the refrigerating system also deteriorates. Consequently, research has been conducted to develop refrigerating systems that may use carbon dioxide as a refrigerant, and properties with respect to evaporator, such as Mollier chart and a relationship between degree of dryness and coefficient of heat transfer, have been being recognized.

[0005] Referring to Fig. 10, a known vapor compression refrigerating system 101 comprises a compressor 102 for compressing refrigerant, a radiator 103 for cooling refrigerant which flows out of compressor 102, an inside heat exchanger 105 for performing heat exchange between high-pressure refrigerant which flows out of radiator 103 and low-pressure refrigerant which flows out of an accumulator 104 (formed also as a gas and liquid separator) and supplying low-pressure refrigerant heat exchanged with high-pressure refrigerant to compressor 102, a pressure reducing mechanism 106 for reducing a pressure of high-pressure refrigerant which flows out of inside heat exchanger 105, an evaporator 107 for evaporating low-pressure refrigerant which flows out of pressure reducing mechanism 106, and an accumulator 104 for storing two-phase refrigerant of liquid phase refrigerant and gas phase refrigerant which flows out of evaporator 107 and supplying gas phase refrigerant to inside heat exchanger 105. The Mollier chart for such a vapor compression refrigerating system 101, which expresses a relationship between enthalpy and pressure, is shown in Fig. 11.

[0006] Therefore, a need has arisen for vapor compression refrigerating systems which overcome these and other shortcomings of the related art. A technical advantage of the present invention is that drive energy may obtained when the refrigerant is expanded and may regenerated as an electric energy or a mechanical energy, and the regenerated energy is used as an energy of a drive source for a means for pumping the refrigerant, which results in a highly efficient vapor compression refrigerating system.

[0007] According to an embodiment of the present invention, a vapor compression refrigerating system comprises a compressor configured to compress a refrigerant, and a radiator connected to the compressor, in which the radiator is configured to receive the refrigerant from the compressor and to reduce a temperature of the refrigerant. The system also comprises a particular pressure reducing mechanism connected to the radiator, and the particular pressure reducing mechanism is configured to receive the refrigerant from the radiator and to reduce a pressure of the refrigerant. The system further comprises a separator connected to the particular pressure reducing mechanism and to the compressor, means for pumping connected to the separator, and an evaporator operationally coupled to the means for pumping and connected to the separator. Moreover, the separator is configured to receive the refrigerant from the particular pressure reducing mechanism, to separate a liquid portion of the refrigerant from a gas portion of the refrigerant, and to transmit the gas portion to the compressor. In addition, the means for pumping is configured to pump the liquid portion from the separator to the evaporator, and the evaporator is configured to evaporate the liquid portion into an evaporated portion, and to transmit the evaporated portion to the separator.

[0008] According to another embodiment of the present invention, a vapor compression refrigerating system comprises a compressor configured to compress a refrigerant, and a radiator connected to the compressor, in which the radiator is configured to receive the refrigerant from the compressor and to reduce a temperature of the refrigerant. The system also comprises an expander connected to the radiator, and the expander is configured to receive the refrigerant from the radiator and to reduce a pressure of the refrigerant. The system further comprises a separator connected to the expander and to the compressor, means for pumping connected to the separator and to the expander, and an evaporator operationally coupled to the means for pumping and connected to the separator. The separator is configured to receive the refrigerant from the expander, to separate a liquid portion of the refrigerant from a gas portion of the refrigerant, and to transmit the gas portion to the compressor. Moreover, the means for pumping is configured to pump the liquid portion from the separator to the evaporator, and the evaporator is configured to evaporate the liquid portion into an evaporated portion, and to transmit the evaporated portion to the separator. In addition, the expander drives the means for pumping when the expander expands the refrigerant.

[0009] Other objects, features, and advantage will be apparent to persons of ordinary skill in the art from the following detailed description of the invention and the accompanying drawings.

[0010] For a more complete understanding of the present invention, needs satisfied thereby, and the objects, features, and advantages thereof, reference now is made to the following description taken in connection with the accompanying drawings.

Fig. 1 is a schematic diagram of a vapor compression refrigerating system, according to an embodiment of the present invention.

Fig. 2 is a Mollier chart of refrigerant in the vapor compression refrigerating system of Fig. 1.

Fig. 3 is a graph showing a relationship between a degree of dryness and a coefficient of heat transfer in an evaporator.

Fig. 4 is a schematic diagram of a vapor compression refrigerating system, according to another embodiment of the present invention.

Fig. 5 is a Mollier chart of refrigerant in the vapor compression refrigerating system of Fig. 4.

Fig. 6 is a schematic diagram of a vapor compression refrigerating system, according to a yet another embodiment of the present invention.

Fig. 7 is a schematic diagram of a vapor compression refrigerating system, according to still yet another embodiment of the present invention.

Fig. 8 is a schematic sectional view of an impeller and a housing showing an example of a structure of an expander.

Fig. 9 is a Mollier chart of refrigerant in the vapor compression refrigerating systems of Figs. 6 and 7.

Fig. 10 is a schematic diagram of a known refrigerating system.

Fig. 11 is a Mollier chart of refrigerant in the refrigerating system of Fig. 10.

[0011] Embodiments of the present invention, and their features and advantages, may be understood by referring to Figures 1-9, like numerals being used for like corresponding parts in the various drawings.

[0012] Fig. 1 depicts a vapor compression refrigerating system 1 according to an embodiment of the present invention. In this embodiment, vapor compression refrigerating system 1 may comprise a compressor 2, a radiator 3 connected to compressor 2, a first pressure reducing mechanism 4 connected to radiator 3, and a gas and liquid separator 5 connected to first pressure reducing mechanism 4 and to compressor 2. Vapor compression refrigerating system 1 also may comprise a means for pumping 6 connected to gas and liquid separator 4, and an evaporator 7 connected to means for pumping 6 and to gas and liquid separator 4. Each of the connections between the various components of vapor compression refrigerating system 1 may be made via a tube.

[0013] In operation, compressor 2 may compress a refrigerant, such as a carbon dioxide refrigerant, which contracts the refrigerant and increases the temperature of the refrigerant. The refrigerant then may flow from compressor 2 to radiator 3, and radiator 3 may radiate the refrigerant to decrease the temperature of the refrigerant. The refrigerant then may flow from radiator 3 to first pressure reducing mechanism 4, and first pressure reducing mechanism 4 may expand the refrigerant and may reduce the pressure of the refrigerant. The refrigerant then may flow from first pressure reducing mechanism 4 to gas and liquid separator 5, and gas and liquid separator 5 may separate a gas portion of the refrigerant from a liquid portion of the refrigerant. The gas portion of the refrigerant may flow to compressor 2, and the liquid portion of the refrigerant may flow to evaporator 7 via means for pumping 6 which pumps the liquid portion of the refrigerant to evaporator 7. Evaporator 7 then may evaporate the liquid portion of the refrigerant into a gas, and the gas may flow to gas and liquid separator 5. Gas and liquid separator 5 then may combine the refrigerant from evaporator 7 and first pressure reducing mechanism 4, and may separate the liquid portion of the combined refrigerant from the gas portion of the combined refrigerant. This process then may be repeated.

[0014] In an embodiment of the present invention, compressor 2 may be driven by a first drive source, and means for pumping 6 may be driven by a second drive source which is different than the first drive source. Moreover, a means for controlling may be provided to independently control the ability of compressor 2 and means for pumping 6 to transmit the refrigerant within vapor compression refrigerating system 1.

[0015] In an embodiment of the present invention, first pressure reducing mechanism 4 may comprise a means for adjusting the degree of pressure reduction in the refrigerant. The means for adjusting may comprise a mechanism for determining a degree of pressure reduction based on information associated with a condition of vapor compression refrigerating system 1. The mechanism of the means for adjusting may be automatically operated based on a difference between the pressure of the refrigerant before the refrigerant enters first pressure reducing mechanism 4 and after the refrigerant leaves first pressure reducing mechanism 4, or may be operated by an external electric or pressure signal.

[0016] Vapor compression refrigerating system 1 also may comprise means for controlling the means for adjusting to maintain the pressure of the refrigerant within gas and liquid separator 5 to be less than or equal to a critical pressure of the refrigerant. The means for controlling may control first pressure reducing mechanism 4 by an electric signal, and may adjust the degree of pressure reduction, such that the pressure of the refrigerant in gas and liquid separator 5 is less than or equal to a critical pressure of the refrigerant, and the efficiency of vapor compression refrigerating system 1 is improved.

[0017] Fig. 2 is a pressure-enthalpy diagram (a Mollier chart) of refrigerant in vapor compression refrigerating system 1 of Fig. 1. In vapor compression refrigerating system 1 of Fig. 1, the refrigerant flows from radiator 3 and the pressure of the refrigerant is reduced, and the refrigerant then is separated into a gas portion of the refrigerant and a liquid portion of the refrigerant by gas and liquid separator 5. The liquid portion then flows to evaporator 7 by means for pumping 6. By this operation, the refrigerant in evaporator 7 may be controlled to have a small degree of dryness with respect to the degree of dryness and the coefficient of heat transfer depicted in Fig. 3, and may be controlled at a high coefficient of heat transfer. Consequently, deterioration of efficiency of cooling performance and deterioration of efficiency of refrigerating system substantially may be avoided.

[0018] Fig. 4 depicts a vapor compression refrigerating system 1 according to another embodiment of the present invention. The embodiment of the present invention depicted in Fig. 4 and the embodiment of the present invention depicted in Fig. 1 are substantially similar. Therefore, only those differences between the embodiment of the present invention depicted in Fig. 4 and the embodiment of the present invention depicted in Fig. 1 are discussed with respect to the embodiment of the present invention depicted in Fig. 4. In this embodiment, vapor compression refrigerating system 1 further comprises a second pressure reducing mechanism 8 which is connected to means for pumping 6 and to evaporator 7. Second pressure reducing mechanism 8 reduces the pressure of the refrigerant transmitted from means for pumping 6 to evaporator 7. Second pressure reducing mechanism 8 may be substantially the same as first pressure reducing mechanism 4. Therefore, second pressure reducing mechanism 8 is not discussed in further detail.

[0019] Fig. 5 is a pressure-enthalpy diagram (a Mollier chart) of refrigerant in vapor compression refrigerating system 1 of Fig. 4. In vapor compression refrigerating system 1 of Fig. 4, the refrigerant flows from radiator 3 and the pressure of the refrigerant is reduced, and the refrigerant then is separated into a gas portion of the refrigerant and a liquid portion of the refrigerant by gas and liquid separator 5. The pressure of the liquid portion then is reduced by second pressure reducing mechanism 8 and flows to evaporator 7 by means for pumping 6. Consequently, the refrigerant that flows from gas and liquid separator 5 is sent to evaporator 7 at a further reduced pressure, and deterioration of efficiency of cooling performance and deterioration of efficiency of refrigerating system may be substantially avoided.

[0020] Fig. 6 depicts a vapor compression refrigerating system 1 according to yet another embodiment of the present invention. In this embodiment, vapor compression refrigerating system 1 may comprise a compressor 2, a radiator 3 connected to compressor 2, an expander 9 connected to radiator 3, and a gas and liquid separator 5 connected to expander 9 and to compressor 2. Vapor compression refrigerating system I also may comprise a means for pumping 10 connected to expander 9 and to gas and liquid separator 5, a pressure reducing mechanism 11 connected to means for pumping 10, and an evaporator 7 connected to pressure reducing mechanism 11 and gas and liquid separator 5. Each of the connections between the various components of vapor compression refrigerating system 1 may be made via a tube.

[0021] In operation, compressor 2 may compress a refrigerant, such as a carbon dioxide refrigerant, which contracts the refrigerant and increases the temperature of the refrigerant. The refrigerant then may flow from compressor 2 to radiator 3, and radiator 3 may radiate the refrigerant to decrease the temperature of the refrigerant. The refrigerant then may flow from radiator 3 to expander 9, and expander 9 may expand the refrigerant and may reduce the pressure of the refrigerant. The refrigerant then may flow from expander 9 to gas and liquid separator 5, and gas and liquid separator 5 may separate a gas portion of the refrigerant from a liquid portion of the refrigerant. The gas portion of the refrigerant may flow to compressor 2, and the liquid portion of the refrigerant may flow to pressure reducing mechanism 11 via means for pumping 10 which pumps the liquid portion of the refrigerant to pressure reducing mechanism 11. Pressure reducing mechanism 11 may reduce the pressure of the liquid portion of the refrigerant, and the liquid portion of the refrigerant may flow to evaporator 7. Evaporator 7 then may evaporate the liquid portion of the refrigerant into a gas, and the gas may flow to gas and liquid separator 5. Gas and liquid separator 5 then may combine the refrigerant from evaporator 7 and first pressure reducing mechanism 4, and may separate the liquid portion of the combined refrigerant from the gas portion of the combined refrigerant. This process then may be repeated. In a modification of this embodiment of the present invention, pressure reducing mechanism I 1 may be omitted, and the liquid portion of the refrigerant may flow to evaporator 7 via means for pumping 10

[0022] In this embodiment of the present invention, means for pumping 10 may be directly connected to expander 9, and the rotation of expander 9 driven by the expansion energy of the refrigerant substantially may be transmitted to means for pumping 10, such that means for pumping 10 may be driven by regeneration of expansion energy of the refrigerant. Consequently, it may not be necessary to provide an outside driving source for means for pumping 10, which increases the efficiency of the refrigerating system.

[0023] Fig. 7 depicts a vapor compression refrigerating system 1 according to another embodiment of the present invention. The embodiment of the present invention depicted in Fig. 7 and the embodiment of the present invention depicted in Fig. 6 are substantially similar. Therefore, only those differences between the embodiment of the present invention depicted in Fig. 7 and the embodiment of the present invention depicted in Fig. 6 are discussed with respect to the embodiment of the present invention depicted in Fig. 7. In this embodiment, vapor compression refrigerating system 1 further comprises a bypass passage 12 positioned between radiator 3 and gas and liquid separator 5 for bypassing a portion of the refrigerant away from the passage with expander 9, and a means for adjusting the rate of refrigerant flow 13 provided on bypass passage 12 for adjusting a flow rate of refrigerant flowing in bypass passage 12 based on information associated with a condition of vapor compression refrigerating system 1. The means for adjusting 13 has a means for controlling the means for adjusting 13, such that a pressure of the refrigerant in gas and liquid separator 5 is less than or equal to a critical pressure. Consequently, the efficiency of vapor compression refrigerating system 1 may be further improved.

[0024] Moreover, pressure reducing mechanism 11 may operate substantially the same as first pressure reducing mechanism 4 and second pressure reducing mechanism 8. Therefore, pressure reducing mechanism 11 is not discussed in further detail.

[0025] Referring to Fig. 8, expander 9 may have a turbine impeller similar to that of an exhaust gas turbine supercharger used for an engine. In expander 9, the expansion energy of the refrigerant is removed after converting it into a mechanical energy, and the mechanical energy is inputted into means for pumping 10. In such a mechanism, because it is not necessary to provide an outside driving force for means for pumping 10, the efficiency of vapor compression refrigerating system 1 may be further improved. Specifically, the drive energy obtained from expander 9 is regenerated as an electric energy or a mechanical energy, and the regenerated energy is used as an energy of a drive source for means for pumping 10. When the energy is used as an electric energy, it may be inputted to a drive motor for means for pumping 10 after being stored in a battery. When the energy is used as a mechanical energy, as depicted in Fig. 8, the drive shafts of expander 9 and means for pumping 10 may be coupled to each other, and a driving energy obtained from expander 9 may be transmitted directly to means for pumping 10.

[0026] Fig. 9 is a pressure-enthalpy diagram (a Mollier chart) of refrigerant in vapor compression refrigerating system 1 of Figs. 6 and 7. In vapor compression refrigerating system I of Figs. 6 and 7, the refrigerant flows from radiator 3 and the pressure of the refrigerant is reduced by expander 9 and adjusting means 13, and the refrigerant then is separated into a gas portion of the refrigerant and a liquid portion of the refrigerant by gas and liquid separator 5. The liquid portion then flows to evaporator 7 by means for pumping 10. By this operation, the refrigerant in evaporator 7 may be controlled to have a small degree of dryness, and a high coefficient of heat transfer may be maintained. Consequently, deterioration of efficiency of cooling performance and deterioration of efficiency of refrigerating system substantially may be avoided.

[0027] The vapor compression refrigerating system according to the present invention may be particularly suitable for an air conditioning system of a vehicle, such as an air conditioning system which uses carbon dioxide as a refrigerant.

Claims

1. A vapor compression refrigerating system comprising:

a compressor configured to compress a refrigerant;

a radiator connected to the compressor, wherein the radiator is configured to receive the refrigerant from the compressor and to reduce a temperature of the refrigerant;

a particular pressure reducing mechanism connected to the radiator, wherein the particular pressure reducing mechanism is configured to receive the refrigerant from the radiator and to reduce a pressure of the refrigerant;

a separator connected to the particular pressure reducing mechanism and to the compressor;

means for pumping connected to the separator; and

an evaporator operationally coupled to the means for pumping and connected to the separator, wherein the separator is configured to receive the refrigerant from the particular pressure reducing mechanism, to separate a liquid portion of the refrigerant from a gas portion of the refrigerant, and to transmit the gas portion to the compressor, wherein the means for pumping is configured to pump the liquid portion from the separator to the evaporator, and the evaporator is configured to evaporate the liquid portion into an evaporated portion, and to transmit the evaporated portion to the separator.

2. The vapor compression refrigerating system of claim 1, wherein the compressor is driven by a first drive source, and the means for pumping is driven by a second drive source, wherein the first drive source is different than the second drive source.

3. The vapor compression refrigerating system of claim 1, further comprising means for independently controlling the compressor and the means for pumping.

4. The vapor compression refrigerating system of claim 1, wherein the particular pressure reducing mechanism comprises means for adjusting a degree of pressure reduction by the particular pressure reducing mechanism.

5. The vapor compression refrigerating system of claim 4, wherein the means for adjusting the degree of pressure reduction by the particular pressure reducing mechanism comprises a mechanism for determining a degree of pressure reduction based on information associated with a condition of the refrigerating system.

6. The vapor compression refrigerating system of claim 5, further comprising means for controlling the means for adjusting the degree of pressure reduction by the particular pressure reducing mechanism, such that a pressure of the refrigerant in the gas and liquid separator is less than or equal to a critical pressure.

7. The vapor compression refrigerating system of claim 1, further comprising a further pressure reducing mechanism connected to the means for pumping and to the evaporator, wherein the evaporator is coupled to the means for pumping via the further pressure reducing mechanism, and the further pressure reducing mechanism is configured to reducing a pressure of the liquid portion and to transmit the liquid portion to the evaporator.

8. The vapor compression refrigerating system of claim 7, wherein the further pressure reducing mechanism comprises means for adjusting a degree of pressure reduction by the further pressure reducing mechanism.

9. The vapor compression refrigerating system of claim 8, wherein the means for adjusting the degree of pressure reduction by the further pressure reducing mechanism comprises a mechanism for determining a degree of pressure reduction based on information associated with a condition of the vapor compression refrigerating system.

10. The vapor compression refrigerating system of claim 1, wherein the refrigerant comprises carbon dioxide.

11. An air conditioning system comprising the vapor compression refrigerating system of claim 1.

12. A vehicle comprising the air conditioning system of claim 11.

13. A vapor compression refrigerating system comprising:

a compressor configured to compress a refrigerant;

a radiator connected to the compressor, wherein the radiator is configured to receive the refrigerant from the compressor and to reduce a temperature of the refrigerant;

an expander connected to the radiator, wherein the expander is configured to receive the refrigerant from the radiator and to reduce a pressure of the refrigerant;

a separator connected to the expander and to the compressor;

means for pumping connected to the separator and to the expander; and

an evaporator operationally coupled to the means for pumping and connected to the separator, wherein the separator is configured to receive the refrigerant from the expander, to separate a liquid portion of the refrigerant from a gas portion of the refrigerant, and to transmit the gas portion to the compressor, wherein the means for pumping is configured to pump the liquid portion from the separator to the evaporator, and the evaporator is configured to evaporate the liquid portion into an evaporated portion, and to transmit the evaporated portion to the separator, wherein the expander drives the means for pumping when the expander expands the refrigerant.

14. The vapor compression refrigerating system of claim 13, further comprising a bypass passage provided between the radiator and the gas and liquid separator for flowing a portion of the refrigerant by bypassing the expander, wherein the bypass passage comprises means for adjusting the amount of refrigerant which flows through the bypass passage based on information associated with a condition of the vapor compression refrigerating system.

15. The vapor compression refrigerating system of claim 14, further comprising means for controlling the means for adjusting the amount of refrigerant which flows through the bypass passage, such that a pressure of the refrigerant in the gas and liquid separator is less than or equal to a critical pressure.

16. The vapor compression refrigerating system of claim 13, further comprising a pressure reducing mechanism connected to the means for pumping and to the evaporator, wherein the evaporator is coupled to the means for pumping via the pressure reducing mechanism, and the pressure reducing mechanism is configured to reducing a pressure of the liquid portion and to transmit the liquid portion to the evaporator.

17. The vapor compression refrigerating system of claim 16, wherein the pressure reducing mechanism comprises means for adjusting a degree of pressure reduction by the pressure reducing mechanism.

18. The vapor compression refrigerating system of claim 17, wherein the means for adjusting the degree of pressure reduction by the pressure reducing mechanism comprises a mechanism for determining a degree of pressure reduction based on information associated with a condition of the vapor compression refrigerating system.

19. The vapor compression refrigerating system of claim 13, wherein the expander comprises an impeller.

20. The vapor compression refrigerating system of claim 13, wherein the refrigerant comprises carbon dioxide.

21. An air conditioning system comprising the vapor compression refrigerating system of claim 13.

22. A vehicle comprising the air conditioning system of claim 21.

Drawing