US20140116082A1

US20140116082A1 - Heat exchange apparatus

Info

Publication number: US20140116082A1
Application number: US14/111,343
Authority: US
Inventors: Yoshiaki Kawakami; Yuki Jojima; Eizo Takahashi; Kousuke Sato; Kazuhide Uchida; Yuichi Ohno
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2011-04-13
Filing date: 2012-04-12
Publication date: 2014-05-01
Also published as: EP2697576A2; JP5718710B2; JP2012218673A; WO2012140492A2; WO2012140492A3; CN103477162A

Abstract

A heat exchange apparatus that performs heat exchange between a refrigerant and a temperature-adjusted unit includes: a compressor that circulates the refrigerant; a heat exchanger that performs heat exchange between the refrigerant and outside air; an expansion valve that reduces a pressure of the refrigerant; a heat exchanger that performs heat exchange between the refrigerant and air-conditioning air; a cooling passage that forms a path for the refrigerant to flow between the heat exchanger and the expansion valve; and a heating passage that forms a path for the refrigerant to flow between the expansion valve and the heat exchanger. The temperature-adjusted unit is disposed to be capable of exchanging heat with the refrigerant flowing through the cooling passage and to be capable of exchanging heat with the refrigerant flowing through the heating passage.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a heat exchange apparatus, and more particularly to a heat exchange apparatus that performs heat exchange between a refrigerant flowing through a vapor compression refrigeration cycle and a temperature-adjusted unit subjected to temperature adjustment.
2. Description of Related Art
In the related art pertaining to a motor cooling apparatus for cooling a drive motor, for example, Japanese Patent Application Publication No. 2005-218271 (JP 2005-218271 A) proposes a technique in which, when a temperature difference between a temperature of a drive motor and an oil temperature increases beyond a predetermined value, oil cooled by an oil cooler is supplied to the drive motor, and when the temperature difference between the temperature of the drive motor and the oil temperature falls to or below the predetermined value, oil cooling by the oil cooler is stopped.
In another proposed technique, a heat generating body is cooled using a vapor compression refrigeration cycle employed as a vehicle air-conditioning apparatus. For example, Japanese Patent Application Publication No. 2007-69733 (JP 2007-69733 A) discloses a system in which a heat exchanger that exchanges heat with air-conditioning air and a heat exchanger that exchanges heat with a heat generating body are disposed in parallel in a refrigerant passage extending from an expansion valve to a compressor, and the heat generating body is cooled by a refrigerant used in an air-conditioning apparatus. Japanese Patent Application Publication No. 2005-90862 (JP 2005-90862 A) discloses a cooling system in which heat generating body cooling means for cooling a heat generating body is provided in a bypass passage that bypasses a pressure reducer, an evaporator, and a compressor of an air-conditioning refrigeration cycle.
Japanese Patent Application Publication No. 11-223406 (JP 11-223406 A) discloses a configuration for causing a refrigerant of a heat pump cycle to absorb waste heat from a heat generating body such as a power transistor. Japanese Patent Application Publication No. 9-290622 (JP 9-290622 A) discloses a technique in which waste heat from a heat generating part installed in a vehicle is collected and absorbed into a refrigerant used for gas injection, thereby effectively improving a heating ability when an outside air temperature is low while suppressing an increase in power consumption.
As a method of cooling a transaxle installed in a vehicle, heat generated by a heat generating member such as a motor/generator or a gear constituting the transaxle may be collected in an Automatic Transmission Fluid (ATF). The ATF may then be pumped to a heat exchanger on the exterior of the transaxle in order to exchange heat with cooling water or a refrigerant used for air-conditioning. The ATF must be cooled in order to protect components such as a coil and a magnet of the motor/generator, suppress deterioration of the ATF, and so on. However, the ATF does not always need to be cooled. When the ATF is overcooled, a viscosity of the ATF increases, and as a result, the gear may be lubricated insufficiently and an increase in friction loss may occur. The ATF is therefore preferably warmed to an appropriate temperature.

SUMMARY OF THE INVENTION

The invention has been designed in consideration of the problem described above, and provides a heat exchange apparatus with which a temperature of a temperature-adjusted unit can be adjusted appropriately through heat exchange with a refrigerant.
According to an aspect of the invention, a heat exchange apparatus that performs heat exchange between a refrigerant and a temperature-adjusted unit includes: a compressor that compresses the refrigerant in order to circulate the refrigerant through the heat exchange apparatus; a first heat exchanger that performs heat exchange between the refrigerant and outside air; a first pressure reducer that reduces a pressure of the refrigerant; a second heat exchanger that performs heat exchange between the refrigerant and air-conditioning air; a first passage that forms a path for the refrigerant to flow between the first heat exchanger and the first pressure reducer; and a second passage that forms a path for the refrigerant to flow between the first pressure reducer and the second heat exchanger. The temperature-adjusted unit is disposed to be capable of exchanging heat with the refrigerant flowing through the first passage and to be capable of exchanging heat with the refrigerant flowing through the second passage.
The heat exchange apparatus described above may further include a four-way valve that switches between a refrigerant flow from the compressor to the first heat exchanger and a refrigerant flow from the compressor to the second heat exchanger.
The heat exchange apparatus described above may further include: a third passage connected in parallel with the first passage on the refrigerant path between the first heat exchanger and the first pressure reducer; and a first flow control valve that adjusts a flow rate of the refrigerant flowing through the first passage and a flow rate of the refrigerant flowing through the third passage.
The heat exchange apparatus described above may further include: a fourth passage connected in parallel with the second passage on the refrigerant path between the first pressure reducer and the second heat exchanger; and a second flow control valve that adjusts a flow rate of the refrigerant flowing through the second passage and a flow rate of the refrigerant flowing through the fourth passage.
The heat exchange apparatus described above may further include a first open/close valve that opens and closes the first passage, and a second open/close valve that opens and closes the second passage. The second open/close valve may be closed when the first open/close valve is open, and the second open/close valve may be open when the first open/close valve is closed.
The heat exchange apparatus described above may further include a second pressure reducer that is provided in the first passage between the first heat exchanger and the temperature-adjusted unit in order to reduce the pressure of the refrigerant.
The heat exchange apparatus described above may further include: a fifth passage that is connected in parallel with a path passing through the second pressure reducer on a path that forms a part of the first passage and passes through the temperature-adjusted unit and the first heat exchanger; and a third open/close valve that is provided in the fifth passage in order to open and close the fifth passage.
With the heat exchange apparatus according to the invention, the temperature of the temperature-adjusted unit can be adjusted appropriately by performing heat exchange between the refrigerant and the temperature-adjusted unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, advantages, and technical and industrial significance of this invention will be described in the following detailed description of example embodiments of the invention with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a schematic view showing a configuration of a heat exchange apparatus according to a first embodiment of the invention;

FIG. 2 is a Mollier chart showing states of a refrigerant during a cooling operation of a vapor compression refrigeration cycle according to the first embodiment;

FIGS. 3A, 3B, 3C and 3D are schematic views showing opening control of a flow control valve shown in FIG. 1;

FIG. 4 is a schematic view showing the heat exchange apparatus in a condition where a four-way valve shown in FIG. 1 has been switched;

FIG. 5 is a Mollier chart showing states of the refrigerant during a heating operation of the vapor compression refrigeration cycle according to the first embodiment;

FIG. 6 is a schematic view showing the heat exchange apparatus when a temperature-adjusted unit according to the first embodiment, shown in FIG. 4, is heated;

FIG. 7 is a Mollier chart showing states of the refrigerant used in the vapor compression refrigeration cycle according to the first embodiment when the temperature-adjusted unit is heated;

FIG. 8 is a schematic view showing a configuration of a heat exchange apparatus according to a second embodiment;

FIG. 9 is a Mollier chart showing states of a refrigerant during a cooling operation of a vapor compression refrigeration cycle according to the second embodiment;

FIG. 10 is a schematic view showing the heat exchange apparatus according to the second embodiment in a condition where a four-way valve shown in FIG. 9 has been switched;

FIG. 11 is a Mollier chart showing states of the refrigerant during a heating operation of the vapor compression refrigeration cycle according to the second embodiment;

FIG. 12 is a schematic view showing the heat exchange apparatus when a temperature-adjusted unit according to the second embodiment, shown in FIG. 10, is heated;

FIG. 13 is a Mollier chart showing states of the refrigerant used in the vapor compression refrigeration cycle according to the second embodiment when the temperature-adjusted unit is heated;

FIG. 14 is a schematic view showing a configuration of a heat exchange apparatus according to a third embodiment;

FIG. 15 is a Mollier chart showing states of a refrigerant during a cooling operation of a vapor compression refrigeration cycle according to the third embodiment;

FIG. 16 is a schematic view showing the heat exchange apparatus according to the third embodiment in a condition where a four-way valve shown in FIG. 14 has been switched; and

FIG. 17 is a schematic view showing the heat exchange apparatus when a temperature-adjusted unit according to the third embodiment, shown in FIG. 16, is heated.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the invention will be described below on the basis of the drawings. Note that in the following drawings, identical or corresponding parts have been allocated identical reference numerals, and description thereof has not been repeated.
FIG. 1 is a schematic view showing a configuration of a heat exchange apparatus according to a first embodiment. As shown in FIG. 1, a heat exchange apparatus 1 includes a vapor compression refrigeration cycle 10. The vapor compression refrigeration cycle 10 is installed in a vehicle in order to cool and heat a vehicle interior of the vehicle, for example. Cooling is performed using the vapor compression refrigeration cycle 10 when, for example, a switch for performing cooling is switched ON or an automatic control mode for adjusting a temperature in a passenger compartment of the vehicle to a set temperature automatically has been selected and the temperature in the passenger compartment is higher than the set temperature. Heating is performed using the vapor compression refrigeration cycle 10 when, for example, a switch for performing heating is switched ON or the automatic control mode has been selected and the temperature in the passenger compartment is lower than the set temperature.
The vapor compression refrigeration cycle 10 includes a compressor 12, a heat exchanger 14 serving as a first heat exchanger, an expansion valve 16 serving as an example of a pressure reducer, and a heat exchanger 18 serving as a second heat exchanger. The vapor compression refrigeration cycle 10 also includes a four-way valve 13. The four-way valve 13 is disposed to be capable of switching between a refrigerant flow traveling from the compressor 12 toward the heat exchanger 14 and a refrigerant flow traveling from the compressor 12 toward the heat exchanger 18.
The compressor 12 is operated using a motor or an engine installed in the vehicle as a power source to compress refrigerant gas adiabatically into superheated refrigerant gas. The compressor 12 aspirates and compresses a gas phase refrigerant that flows when the vapor compression refrigeration cycle 10 is operative, and discharges a high-temperature, high-pressure gas phase refrigerant. By discharging the refrigerant, the compressor 12 circulates the refrigerant through the vapor compression refrigeration cycle 10.
The heat exchangers 14, 18 respectively include a tube through which the refrigerant flows and a fin that performs heat exchange between the refrigerant flowing through the tube and air on the periphery of the heat exchangers 14, 18. The heat exchangers 14, 18 perform heat exchange between the refrigerant and either an air flow supplied by a natural breeze generated as the vehicle travels or an air flow supplied by a fan.
The expansion valve 16 expands a high-pressure liquid phase refrigerant by ejecting the liquid phase refrigerant through a small hole. As a result, the high-pressure liquid phase refrigerant is changed into a low-temperature, low-pressure mist-form refrigerant. The expansion valve 16 reduces a pressure of a condensed refrigerant liquid to generate wet vapor in a gas-liquid mixed state. Note that the pressure reducer for reducing the pressure of the refrigerant liquid is not limited to the expansion valve 16 that performs throttle expansion, and may also be a capillary tube.
The vapor compression refrigeration cycle 10 further includes refrigerant passages 21 to 26. The refrigerant passage 21 connects the compressor 12 to the four-way valve 13. The refrigerant flows from the compressor 12 to the four-way valve 13 through the refrigerant passage 21. The refrigerant passage 22 connects the four-way valve 13 to the heat exchanger 14. The refrigerant flows from one of the four-way valve 13 and the heat exchanger 14 to the other through the refrigerant passage 22. The refrigerant passage 23 connects the heat exchanger 14 to the expansion valve 16. The refrigerant flows from one of the heat exchanger 14 and the expansion valve 16 to the other through the refrigerant passage 23.
The refrigerant passage 24 connects the expansion valve 16 to the heat exchanger 18. The refrigerant flows from one of the expansion valve 16 and the heat exchanger 18 to the other through the refrigerant passage 24. The refrigerant passage 25 connects the heat exchanger 18 to the four-way valve 13. The refrigerant flows from one of the heat exchanger 18 and the four-way valve 13 to the other through the refrigerant passage 25. The refrigerant passage 26 connects the four-way valve 13 to the compressor 12. The refrigerant flows from the four-way valve 13 to the compressor 12 through the refrigerant passage 26.
The vapor compression refrigeration cycle 10 is formed by connecting the compressor 12, the heat exchanger 14, the expansion valve 16, and the heat exchanger 18 to each other using the refrigerant passages 21 to 26. Note that carbon dioxide, a hydrocarbon such as propane or isobutane, ammonia, water, or the like, for example, may be used as the refrigerant of the vapor compression refrigeration cycle 10.
A first passage and a refrigerant passage 23 a serving as a third passage are connected in parallel and provided on a path along which the refrigerant flows between the heat exchanger 14 and the expansion valve 16. The refrigerant passage 23 a forms a part of the refrigerant passage 23 serving as the refrigerant path between the heat exchanger 14 and the expansion valve 16. A heat exchange unit 30 is provided on the first passage. The heat exchange unit 30 is provided on the refrigerant path between the heat exchanger 14 and the expansion valve 16. The heat exchange unit 30 includes a temperature-adjusted unit 31 that is subjected to temperature adjustment, and a cooling passage 32 constituted by a pipe through which the refrigerant flows. The heat exchange apparatus 1 includes the refrigerant passage 23 a as a path that does not pass through the heat exchange unit 30, and includes refrigerant passages 52, 54, 55 and the cooling passage 32 as a path that passes through the heat exchange unit 30. The refrigerant path between the heat exchanger 14 and the expansion valve 16 bifurcates such that a part of the refrigerant flows to the heat exchange unit 30.
The refrigerant passages 52, 54, 55 are provided as a path along which the refrigerant flows to the cooling passage 32. One end portion of the cooling passage 32 is connected to the refrigerant passage 54, and another end portion of the cooling passage 32 is connected to the refrigerant passage 55. The refrigerant passage 52 and the refrigerant passage 54 communicate via an open/close valve 53. The refrigerant flows from the refrigerant passage 23 into the cooling passage 32 through either the refrigerant passages 52, 54 or the refrigerant passage 55. The refrigerant that flows through the cooling passage 32 exchanges heat with the temperature-adjusted unit 31, and then returns to the refrigerant passage 23 through the other of the refrigerant passages 52, 54 and the refrigerant passage 55. The first passage connected to the refrigerant passage 23 a in parallel therewith includes the refrigerant passages 52, 54 on the heat exchanger 14 side of the heat exchange unit 30, the cooling passage 32 provided in the heat exchange unit 30, and the refrigerant passage 55 on the expansion valve 16 side of the heat exchange unit 30. The open/close valve 53 opens and closes the first passage.
The refrigerant flowing between the heat exchanger 14 and the expansion valve 16 flows through the cooling passage 32. While flowing through the cooling passage 32, the refrigerant cools the temperature-adjusted unit 31 by drawing heat from the temperature-adjusted unit 31. The heat exchange unit 30 is structured such that heat exchange can be performed between the temperature-adjusted unit 31 and the refrigerant in the cooling passage 32. In this embodiment, the heat exchange unit 30 includes the cooling passage 32, which is formed such that an outer peripheral surface thereof directly contacts a casing of the temperature-adjusted unit 31, for example. The cooling passage 32 includes a part that is adjacent to the casing of the temperature-adjusted unit 31. In this part, heat exchange can be performed between the refrigerant flowing through the cooling passage 32 and the temperature-adjusted unit 31.
The temperature-adjusted unit 31 is cooled by being directly connected to the outer peripheral surface of the cooling passage 32 that forms a part of the refrigerant path extending from the heat exchanger 14 to the expansion valve 16 of the vapor compression refrigeration cycle 10. Since the temperature-adjusted unit 31 is disposed on an exterior of the cooling passage 32, the temperature-adjusted unit 31 does not interfere with the refrigerant flow flowing through the interior of the cooling passage 32. Accordingly, pressure loss in the vapor compression refrigeration cycle 10 does not increase, and therefore the temperature-adjusted unit 31 can be cooled without increasing a power of the compressor 12.
Alternatively, the heat exchange unit 30 may include an arbitrary conventional heat pipe that is interposed between the temperature-adjusted unit 31 and the cooling passage 32. In this case, the temperature-adjusted unit 31 is connected to the outer peripheral surface of the cooling passage 32 via the heat pipe and cooled by heat transferred from the temperature-adjusted unit 31 to the cooling passage 32 via the heat pipe. By setting the temperature-adjusted unit 31 as a heat pipe heating portion and setting the cooling passage 32 as a heat pipe cooling portion, a heat transfer efficiency between the cooling passage 32 and the temperature-adjusted unit 31 can be improved, leading to an improvement in an efficiency with which the temperature-adjusted unit 31 is cooled. A Wick Heating Pipe, for example, may be used.
Heat can be transferred reliably from the temperature-adjusted unit 31 to the cooling passage 32 using the heat pipe, and therefore the temperature-adjusted unit 31 and the cooling passage 32 may be distanced from each other, thereby eliminating the need to provide the cooling passage 32 in a complicated arrangement to ensure that the cooling passage 32 contacts the temperature-adjusted unit 31. As a result, a disposal freedom of the temperature-adjusted unit 31 can be improved.
The refrigerant passages 52, 54, 55 and the cooling passage 32 serving as the path that passes through the heat exchange unit 30 are provided in parallel with the refrigerant passage 23 a serving as the path that does not pass through the heat exchange unit 30 as the path along which the refrigerant flows between the heat exchanger 14 and the expansion valve 16. A cooling system for the temperature-adjusted unit 31, including the refrigerant passages 52, 54, 55, is connected in parallel with the refrigerant passage 23 a. By providing the path of the refrigerant that flows between the heat exchanger 14 and the expansion valve 16 without passing through the heat exchange unit 30 in parallel with the path of the refrigerant that passes through the heat exchange unit 30 and causing only a part of the refrigerant to flow to the refrigerant passages 52, 54, 55, only a part of the refrigerant flowing between the heat exchanger 14 and the expansion valve 16 is caused to flow to the heat exchange unit 30.
A situation in which an amount of refrigerant required to cool the temperature-adjusted unit 31 is caused to flow to the refrigerant passages 52, 54, 55 such that all of the refrigerant flows to the heat exchange unit 30 does not occur in the heat exchange unit 30. Hence, the temperature-adjusted unit 31 can be cooled appropriately, and overcooling of the temperature-adjusted unit 31 can be prevented. Further, pressure loss in the refrigerant flow to the cooling system for the temperature-adjusted unit 31, including the refrigerant passages 52, 54, 55 and the cooling passage 32, can be reduced, enabling a corresponding reduction in an amount of power required to operate the compressor 12 in order to circulate the refrigerant.
The temperature-adjusted unit 31 is, for example, an ATF cooler that cools ATF used as lubricating oil and hydraulic working oil for a transaxle installed in a vehicle by performing heat exchange with the ATF. The ATF is charged into the interior of the transaxle, not shown in the drawings, in order to cool and lubricate respective constituent members of the transaxle. For this purpose, the ATF flows to the temperature-adjusted unit 31 from the transaxle through a pipe, not shown in the drawings, exchanges heat with the refrigerant in the temperature-adjusted unit 31, and then returns to the transaxle through a pipe, not shown in the drawing.
The heat exchanger 18 is disposed inside a duct 40 through which air flows. The heat exchanger 18 adjusts a temperature of air-conditioning air flowing through the duct 40 by performing heat exchange between the refrigerant and the air-conditioning air. The duct 40 includes a duct inlet 41, which is an inlet through which the air-conditioning air flows into the duct 40, and a duct outlet 42, which is an outlet through which the air-conditioning air flows out of the duct 40. A fan 43 is disposed inside the duct 40 in the vicinity of the duct inlet 41.
When the fan 43 is driven, air flows through the duct 40. When the fan 43 is operative, the air-conditioning air flows into the interior of the duct 40 through the duct inlet 41. The air flowing into the duct 40 may be outside air or air in a passenger compartment of the vehicle. An arrow 45 in FIG. 1 indicates a flow of the air-conditioning air that flows through the heat exchanger 18 so as to exchange heat with the refrigerant of the vapor compression refrigeration cycle 10. In the heat exchanger 18 during a cooling operation, the air-conditioning air is cooled while the refrigerant receives heat transfer from the air-conditioning air so as to be heated. In the heat exchanger 18 during a heating operation, the air-conditioning air is heated while the refrigerant transfers heat to the air-conditioning air so as to be cooled. An arrow 46 indicates a flow of the air-conditioning air flowing out of the duct 40 through the duct outlet 42 after being subjected to temperature adjustment in the heat exchanger 18.
During the cooling operation, the refrigerant flows through the vapor compression refrigeration cycle 10 so as to pass sequentially through a point A, a point B, a point C, a point D, and a point E, as shown in FIG. 1. Thus, the refrigerant circulates between the compressor 12, the heat exchanger 14, the expansion valve 16, and the heat exchanger 18. The refrigerant circulates within the vapor compression refrigeration cycle 10 through a refrigerant circulation passage formed by connecting the compressor 12, the heat exchanger 14, the expansion valve 16, and the heat exchanger 18 in sequence using the refrigerant passages 21 to 26.
FIG. 2 is a Mollier chart showing states of the refrigerant during the cooling operation of the vapor compression refrigeration cycle 10 according to the first embodiment. An abscissa in FIG. 2 shows a specific enthalpy (unit: kJ/kg) of the refrigerant, while an ordinate shows an absolute pressure (unit: MPa) of the refrigerant. A curve in the diagram is a saturation vapor line and a saturation liquid line of the refrigerant. FIG. 2 shows a thermodynamic state of the refrigerant at each point (i.e. the points A, B, C, D, and E) of the vapor compression refrigeration cycle 10, in which the refrigerant flows from the compressor 12 into the refrigerant passage 23 via the heat exchanger 14, cools the temperature-adjusted unit 31, returns to the refrigerant passage 23, and then returns to the compressor 12 via the expansion valve 16 and the heat exchanger 18.
As shown in FIG. 2, the refrigerant (point A) that is aspirated into the compressor 12 in a superheated vapor state is adiabatically compressed in the compressor 12 along a geometric entropy line. As the refrigerant is compressed, the pressure and temperature thereof rise such that the refrigerant turns into high-temperature, high-pressure, highly superheated vapor (point B). The refrigerant then flows to the heat exchanger 14.
The high-pressure refrigerant vapor that flows into the heat exchanger 14 exchanges heat with outside air in the heat exchanger 14 and is cooled thereby. As a result, the refrigerant changes from superheated vapor into dry saturated vapor while remaining at a constant pressure. Latent heat of condensation is discharged such that the refrigerant gradually liquefies, thereby turning into wet vapor in a gas-liquid mixed state, and when the refrigerant is condensed entirely, a saturated liquid is formed. Further, sensible heat is discharged such that a supercooled liquid is formed (point C). The heat exchanger 14 forms a refrigerant liquid by isobarically discharging the heat of the superheated refrigerant gas compressed in the compressor 12 to an external medium. A gas phase refrigerant discharged from the compressor 12 is condensed (liquefied) by discharging the heat thereof to the periphery of the heat exchanger 14 such that the refrigerant is cooled. As a result of the heat exchange performed in the heat exchanger 14, the temperature of the refrigerant falls such that the refrigerant liquefies.
The high-pressure liquid phase refrigerant liquefied by the heat exchanger 14 flows to the heat exchange unit 30 through the refrigerant passage 52, the open/close valve 53, and the refrigerant passage 54, in that order, and cools the temperature-adjusted unit 31. As a result of the heat exchange performed with the temperature-adjusted unit 31, a degree of supercooling of the refrigerant decreases. More specifically, the temperature of the refrigerant in the supercooled liquid state rises upon reception of sensible heat from the temperature-adjusted unit 31 so as to approach a liquid refrigerant saturation temperature, whereby the refrigerant is heated to a temperature slightly below the saturation temperature (point D). Next, the refrigerant flows into the expansion valve 16 through the refrigerant passage 23. By passing through the expansion valve 16, the refrigerant in the supercooled liquid state is throttle-expanded such that the temperature and pressure of the refrigerant fall while the specific enthalpy thereof remains unchanged. As a result, the refrigerant turns into low-temperature, low-pressure wet vapor in a gas-liquid mixed state (point E).
The wet vapor state refrigerant discharged from the expansion valve 16 flows into the heat exchanger 18 through the refrigerant passage 24. The wet vapor state refrigerant flows into the tube of the heat exchanger 18. While flowing through the tube of the heat exchanger 18, the refrigerant absorbs heat from the air-conditioning via the fin as latent heat of evaporation, and as a result, the refrigerant evaporates while remaining at a constant pressure. When the refrigerant turns entirely into dry saturated vapor, the temperature of the refrigerant vapor is raised further by sensible heat, and as a result, superheated vapor is formed (point A). In the heat exchanger 18, the refrigerant absorbs peripheral heat so as to be heated. The vaporized refrigerant then flows into the four-way valve 13 through the refrigerant passage 25, and is then aspirated into the compressor 12 via the refrigerant passage 26. The compressor 12 compresses the refrigerant flowing from the heat exchanger 18. In accordance with this cycle, the refrigerant undergoes several changes of state, namely compression, condensation, throttle expansion, and evaporation, repeatedly and continuously.
Note that a theoretical refrigeration cycle was described in the above description of the vapor compression refrigeration cycle. Needless to mention, however, in the actual vapor compression refrigeration cycle 10, loss in the compressor 12 and pressure loss and heat loss in the refrigerant must be taken into account.
During the cooling operation, the heat exchanger 18 absorbs heat from peripheral air introduced so as to contact the heat exchanger 18 as the mist-form refrigerant flowing through the interior of the heat exchanger 18 vaporizes. The heat exchanger 18 uses the low-temperature, low-pressure refrigerant throttle-expanded and reduced in pressure by the expansion valve 16 to cool the passenger compartment of the vehicle by absorbing vaporization heat generated when the wet vapor of the refrigerant evaporates into a refrigerant gas from the air-conditioning air that flows into the passenger compartment of the vehicle. The air-conditioning air reduced in temperature when the heat thereof is absorbed by the heat exchanger 18 flows into the passenger compartment of the vehicle, and as a result, the passenger compartment of the vehicle is cooled.
While the vapor compression refrigeration cycle 10 is operative, the refrigerant cools the passenger compartment by absorbing vaporization heat from the air in the passenger compartment of the vehicle in the heat exchanger 18. In addition, the high-pressure liquid refrigerant discharged from the heat exchanger 14 flows into the heat exchange unit 30 and cools the temperature-adjusted unit 31 by exchanging heat with the temperature-adjusted unit 31. Therefore, the heat exchange apparatus 1 cools the temperature-adjusted unit 31 installed in the vehicle using the vapor compression refrigeration cycle 10 for air-conditioning the passenger compartment of the vehicle. Note that a temperature to which the temperature-adjusted unit 31 is to be cooled is preferably at least lower than an upper limit value of a target temperature range serving as a temperature range of the temperature-adjusted unit 31.
Returning to FIG. 1, the heat exchange apparatus 1 includes a flow control valve 51. The flow control valve 51 is disposed in the refrigerant passage 23 a forming a part of the refrigerant passage 23 between the heat exchanger 14 and the expansion valve 16. The pressure loss of the refrigerant flowing through the refrigerant passage 23 a is increased or reduced by varying a valve opening of the flow control valve 51, and as a result, the flow control valve 51 adjusts a flow rate of the refrigerant flowing through the refrigerant passage 23 a and a flow rate of the refrigerant flowing through the refrigerant passages 52, 54, 55 and the cooling passage 32 as desired.
For example, when the flow control valve 51 is fully closed such that the valve opening thereof is set at 0%, all of the refrigerant flowing between the heat exchanger 14 and the expansion valve 16 flows into the refrigerant passages 52, 54, 55 and the cooling passage 32. When the valve opening of the flow control valve 51 is increased, the flow rate of the refrigerant flowing through the refrigerant passage 23 a, of the refrigerant flowing between the heat exchanger 14 and the expansion valve 16, increases while the flow rate of the refrigerant flowing through the refrigerant passages 52, 54, 55 and the cooling passage 32 in order to cool the temperature-adjusted unit 31 decreases. When the valve opening of the flow control valve 51 is reduced, the flow rate of the refrigerant flowing through the refrigerant passage 23 a, of the refrigerant flowing between the heat exchanger 14 and the expansion valve 16, decreases while the flow rate of the refrigerant flowing through the refrigerant passages 52, 54, 55 and the cooling passage 32 in order to cool the temperature-adjusted unit 31 increases.
When the valve opening of the flow control valve 51 is increased, the flow rate of the refrigerant that cools the temperature-adjusted unit 31 decreases, leading to a reduction in the ability to cool the temperature-adjusted unit 31. When the valve opening of the flow control valve 51 is reduced, the flow rate of the refrigerant that cools the temperature-adjusted unit 31 increases, leading to an improvement in the ability to cool the temperature-adjusted unit 31. The amount of refrigerant that flows to the heat exchange unit 30 can be adjusted to an optimum amount using the flow control valve 51, and therefore overcooling of the temperature-adjusted unit 31 can be prevented reliably. Moreover, pressure loss in the flow of refrigerant through the refrigerant passages 52, 54, 55 and the cooling passage 32 and the power consumption of the compressor 12 required to circulate the refrigerant can be reliably reduced.
An example of control performed to adjust the valve opening of the flow control valve 51 will now be described. FIGS. 3A to 3D are schematic views showing opening control of the flow control valve 51. An abscissa of graphs shown in FIGS. 3A to 3D shows time. An ordinate of the graph in FIG. 3A shows the valve opening in a case where the flow control valve 51 is an electric expansion valve using a stepping motor. An ordinate of the graph in FIG. 3B shows the valve opening in a case where the flow control valve 51 is a temperature expansion valve that is operated to open and close in response to temperature variation. An ordinate of the graph in FIG. 3C shows the temperature of the temperature-adjusted unit 31. An ordinate of the graph in FIG. 3D shows a temperature difference between an outlet and an inlet of the temperature-adjusted unit 31.
The temperature-adjusted unit 31 is cooled as the refrigerant passes through the heat exchange unit 30. The opening of the flow control valve 51 is adjusted by monitoring the temperature of the temperature-adjusted unit 31 or the temperature difference between an outlet temperature and an inlet temperature of the temperature-adjusted unit 31, for example. Referring to the graph in FIG. 3C, for example, the temperature of the temperature-adjusted unit 31 is monitored by providing a temperature sensor that continuously measures the temperature of the temperature-adjusted unit 31. Further, referring to the graph in FIG. 3D, for example, the temperature difference between the outlet and the inlet of the temperature-adjusted unit 31 is monitored by providing a temperature sensor that measures the inlet temperature and the outlet temperature of the temperature-adjusted unit 31.
When the temperature of the temperature-adjusted unit 31 exceeds a target temperature or the outlet/inlet temperature difference of the temperature-adjusted unit 31 exceeds a target temperature difference (3 to 5° C., for example), the opening of the flow control valve 51 is reduced, as shown on the graphs in FIGS. 3A and 3B. As described above, when the opening of the flow control valve 51 is narrowed, the flow rate of the refrigerant flowing to the heat exchange unit 30 increases, and therefore the temperature-adjusted unit 31 can be cooled more effectively. As a result, the temperature of the temperature-adjusted unit 31 can be reduced to or below the target temperature, as shown on the graph in FIG. 3C, or the outlet/inlet temperature difference of the temperature-adjusted unit 31 can be reduced to or below the target temperature difference, as shown on the graph in FIG. 3D.
By adjusting the valve opening of the flow control valve 51 optimally in this manner, an amount of refrigerant for obtaining a radiation capacity required to keep the temperature-adjusted unit 31 in an appropriate temperature range can be secured, and as a result, the temperature-adjusted unit 31 can be cooled appropriately. Hence, situations in which the temperature-adjusted unit 31 is damaged through overheating can be suppressed reliably.
FIG. 4 is a schematic view showing the heat exchange apparatus 1 in a condition where the four-way valve 13 has been switched. Comparing FIGS. 1 and 4, the four-way valve 13 has been rotated 90°, thereby switching the path along which the refrigerant flowing into the four-way valve 13 from the outlet of the compressor 12 is discharged from the four-way valve 13. During the cooling operation shown in FIG. 1, the refrigerant compressed by the compressor 12 flows from the compressor 12 toward the heat exchanger 14. During the heating operation shown in FIG. 4, on the other hand, the refrigerant compressed by the compressor 12 flows from the compressor 12 toward the heat exchanger 18.
During the heating operation, the refrigerant flows through the vapor compression refrigeration cycle 10 so as to pass sequentially through a point A, a point B, a point E, a point D, and a point C, as shown in FIG. 4. Thus, the refrigerant circulates between the compressor 12, the heat exchanger 18, the expansion valve 16, and the heat exchanger 14. The refrigerant circulates within the vapor compression refrigeration cycle 10 through a refrigerant circulation passage formed by connecting the compressor 12, the heat exchanger 18, the expansion valve 16, and the heat exchanger 14 in sequence using the refrigerant passages 21 to 26.
FIG. 5 is a Mollier chart showing states of the refrigerant during the heating operation of the vapor compression refrigeration cycle 10 according to the first embodiment. An abscissa in FIG. 5 shows the specific enthalpy (unit: kJ/kg) of the refrigerant, while an ordinate shows the absolute pressure (unit: MPa) of the refrigerant. A curve in the diagram is a saturation vapor line and a saturation liquid line of the refrigerant. FIG. 5 shows a thermodynamic state of the refrigerant at each point (i.e. the points A, B, E, D, and C) of the vapor compression refrigeration cycle 10, in which the refrigerant flows from the compressor 12 into the refrigerant passage 23 via the heat exchanger 18 and the expansion valve 16, cools the temperature-adjusted unit 31, returns to the refrigerant passage 23, and then returns to the compressor 12 via the heat exchanger 14.
As shown in FIG. 5, the refrigerant (point A) that is aspirated into the compressor 12 in a superheated vapor state is adiabatically compressed in the compressor 12 along a geometric entropy line. As the refrigerant is compressed, the pressure and temperature thereof rise such that the refrigerant turns into high-temperature, high-pressure, highly superheated vapor (point B). The refrigerant then flows to the heat exchanger 18.
The high-pressure refrigerant vapor that flows into the heat exchanger 18 is cooled in the heat exchanger 18 so as to change from superheated vapor into dry saturated vapor while remaining at a constant pressure. Latent heat of condensation is discharged such that the refrigerant gradually liquefies, thereby turning into wet vapor in a gas-liquid mixed state, and when the refrigerant is condensed entirely, a saturated liquid is formed. Further, sensible heat is discharged such that a supercooled liquid is formed (point E). The heat exchanger 18 forms a refrigerant liquid by isobarically discharging the heat of the superheated refrigerant gas compressed in the compressor 12 to an external medium. The gas phase refrigerant discharged from the compressor 12 is condensed (liquefied) by discharging the heat thereof to the periphery of the heat exchanger 18 such that the refrigerant is cooled. As a result of the heat exchange performed in the heat exchanger 18, the temperature of the refrigerant falls such that the refrigerant liquefies. Thus, the refrigerant is cooled by radiating the heat thereof to the periphery of the heat exchanger 18.
The high-pressure liquid phase refrigerant liquefied by the heat exchanger 18 flows into the expansion valve 16 through the refrigerant passage 24. In the expansion valve 16, the supercooled liquid state refrigerant is throttle-expanded such that the temperature and pressure of the refrigerant fall while the specific enthalpy thereof remains unchanged, and as a result, low-temperature, low-pressure wet vapor in a gas-liquid mixed state is formed (point D). The refrigerant reduced in temperature by the expansion valve 16 flows into the cooling passage 32 of the heat exchange unit 30 through the refrigerant passages 23, 55 and cools the temperature-adjusted unit 31. As a result of the heat exchange performed with the temperature-adjusted unit 31, the refrigerant is heated such that a dryness of the refrigerant increases. When the refrigerant receives latent heat from the temperature-adjusted unit 31, a part thereof vaporizes, leading to an increase in a proportion of saturated vapor in the wet vapor state refrigerant (point C).
The wet vapor state refrigerant discharged from the heat exchange unit 30 returns to the refrigerant passage 23 through the refrigerant passages 54, 52, and then flows into the heat exchanger 14. The wet vapor state refrigerant flows into the tube of the heat exchanger 14. While flowing through the tube, the refrigerant absorbs heat from the outside air via the fin as latent heat of evaporation, and as a result, the refrigerant evaporates while remaining at a constant pressure. When the refrigerant turns entirely into dry saturated vapor, the temperature of the refrigerant vapor is raised further by sensible heat, and as a result, the refrigerant vapor turns into superheated vapor (point A). The vaporized refrigerant is aspirated into the compressor 12 via the refrigerant passage 22. The compressor 12 compresses the refrigerant flowing from the heat exchanger 14. In accordance with this cycle, the refrigerant undergoes several changes of state, namely compression, condensation, throttle expansion, and evaporation, repeatedly and continuously.
During the heating operation, the heat exchanger 18 adds heat to the peripheral air introduced so as to contact the heat exchanger 18 as the refrigerant vapor flowing through the interior thereof is condensed. The heat exchanger 18 uses the high-temperature, high-pressure refrigerant adiabatically compressed by the compressor 12 to heat the passenger compartment of the vehicle by discharging condensation heat generated when the refrigerant gas condenses into refrigerant wet vapor to the air-conditioning air that flows into the passenger compartment of the vehicle. The air-conditioning air increased in temperature after receiving heat from the heat exchanger 18 flows into the passenger compartment of the vehicle, and as a result, the passenger compartment of the vehicle is heated.
In the heat exchange apparatus 1, a second passage and a refrigerant passage 24 a serving as a fourth passage are connected in parallel and provided on a path along which the refrigerant flows between the expansion valve 16 and the heat exchanger 18. The refrigerant passage 24 a forms a part of the refrigerant passage 24 forming the refrigerant path between the expansion valve 16 and the heat exchanger 18. The heat exchange unit 30 is provided to be capable of exchanging heat with the first passage, as described above, and also provided in the second passage to be capable of exchanging heat with the second passage. The heat exchange unit 30 is provided on the refrigerant path between the expansion valve 16 and the heat exchanger 18. The heat exchange unit 30 includes, in addition to the temperature-adjusted unit 31 and the cooling passage 32, a heating passage 33 constituted by a pipe through which the refrigerant flows. The heat exchange apparatus 1 includes the refrigerant passage 24 a as a path that does not pass through the heat exchange unit 30, and includes refrigerant passages 62, 64, 65 and the heating passage 33 as a path that passes through the heat exchange unit 30. The refrigerant path between the expansion valve 16 and the heat exchanger 18 bifurcates such that a part of the refrigerant flows to the heat exchange unit 30.
The refrigerant passages 62, 64, 65 are provided as a path along which the refrigerant flows to the heating passage 33. One end portion of the heating passage 33 is connected to the refrigerant passage 64, and another end portion of the heating passage 33 is connected to the refrigerant passage 65. The refrigerant passage 62 and the refrigerant passage 64 communicate via an open/close valve 63. The refrigerant flows from the refrigerant passage 24 into the heating passage 33 through either the refrigerant passages 62, 64 or the refrigerant passage 65. The refrigerant that flows through the heating passage 33 exchanges heat with the temperature-adjusted unit 31, and then returns to the refrigerant passage 24 through the other of the refrigerant passages 62, 64 and the refrigerant passage 65. The second passage connected to the refrigerant passage 24 a in parallel therewith includes the refrigerant passages 62, 64 on the heat exchanger 18 side of the heat exchange unit 30, the heating passage 33 provided in the heat exchange unit 30, and the refrigerant passage 65 on the expansion valve 16 side of the heat exchange unit 30. The open/close valve 63 opens and closes the second passage.
FIG. 6 is a schematic view showing the heat exchange apparatus 1 when the temperature-adjusted unit 31 is heated. When the temperature-adjusted unit 31 shown in FIGS. 1 and 4 is to be cooled, the open/close valve 53 is opened and the open/close valve 63 is closed. When the open/close valve 53 is open, the open/close valve 63 is closed. Accordingly, the refrigerant flows through the cooling passage 32 but does not flow through the heating passage 33. Heat is transferred to the refrigerant flowing through the cooling passage 32 from the temperature-adjusted unit 31, and as a result, the temperature-adjusted unit 31 is cooled. When the temperature-adjusted unit 31 shown in FIG. 6 is to be heated, on the other hand, the open/close valve 63 is opened and the open/close valve 53 is closed. When the open/close valve 53 is closed, the open/close valve 63 is open. Accordingly, the refrigerant flows through the heating passage 33 but does not flow through the cooling passage 32. Heat is transferred from the refrigerant flowing through the heating passage 33 to the temperature-adjusted unit 31, and as a result, the temperature-adjusted unit 31 is heated.
As shown in FIG. 6, when the refrigerant flowing between the expansion valve 16 and the heat exchanger 18 via the heating passage 33 flows through the heating passage 33, heat is applied to the temperature-adjusted unit 31, thereby raising the temperature of the temperature-adjusted unit 31. The heat exchange unit 30 is structured such that heat exchange can be performed between the temperature-adjusted unit 31 and the refrigerant in the heating passage 33. Similarly to the disposition of the temperature-adjusted unit 31 in the cooling passage 32, an outer peripheral surface of the heating passage 33 may contact the casing of the temperature-adjusted unit 31 directly. Alternatively, a heat pipe may be disposed between the temperature-adjusted unit 31 and the heating passage 33 such that the heating passage 33 is set as a heat pipe heating portion and the temperature-adjusted unit 31 is set as a heat pipe cooling portion. Since the temperature-adjusted unit 31 is disposed on the exterior of the heating passage 33, pressure loss in the vapor compression refrigeration cycle 10 does not increase, and therefore the temperature-adjusted unit 31 can be heated without increasing the power of the compressor 12.
The refrigerant passages 62, 64, 65 and the heating passage 33 serving as the path that passes through the heat exchange unit 30 are provided in parallel with the refrigerant passage 24 a serving as the path that does not pass through the heat exchange unit 30 as the path along which the refrigerant flows between the expansion valve 16 and the heat exchanger 18. A heating system for the temperature-adjusted unit 31, including the refrigerant passages 62, 64, 65, is connected in parallel with the refrigerant passage 24 a. By providing the path of the refrigerant that flows between the heat expansion valve 16 and the heat exchanger 18 without passing through the heat exchange unit 30 in parallel with the path of the refrigerant that passes through the heat exchange unit 30 and causing only a part of the refrigerant to flow to the refrigerant passages 62, 64, 65, only a part of the refrigerant flowing between the expansion valve 16 and the heat exchanger 18 is caused to flow to the heat exchange unit 30.
A situation in which an amount of refrigerant required to heat the temperature-adjusted unit 31 is caused to flow to the refrigerant passages 62, 64, 65 such that all of the refrigerant flows to the heat exchange unit 30 does not occur in the heat exchange unit 30. Hence, the temperature-adjusted unit 31 can be heated appropriately, and overheating of the temperature-adjusted unit 31 can be prevented. Further, pressure loss in the refrigerant flow to the heating system for the temperature-adjusted unit 31, including the refrigerant passages 62, 64, 65 and the heating passage 33, can be reduced, enabling a corresponding reduction in the amount of power required to operate the compressor 12 in order to circulate the refrigerant.
A flow control valve 61 is disposed in the refrigerant passage 24 a as another flow control valve differing from the flow control valve 51. Similarly to the flow control valve 51 described above, the pressure loss of the refrigerant flowing through the refrigerant passage 24 a is increased or reduced by varying a valve opening of the flow control valve 61, and as a result, the flow control valve 61 adjusts the flow rate of the refrigerant flowing through the refrigerant passage 24 a and the flow rate of the refrigerant flowing through the refrigerant passages 62, 64, 65 and the heating passage 33 as desired.
When the valve opening of the flow control valve 61 is increased, the flow rate of the refrigerant for heating the temperature-adjusted unit 31 decreases, leading to a reduction in an ability to raise the temperature of the temperature-adjusted unit 31. When the valve opening of the flow control valve 61 is reduced, the flow rate of the refrigerant used to heat the temperature-adjusted unit 31 increases, leading to improvement in the ability to raise the temperature of the temperature-adjusted unit 31. Using the flow control valve 61, the amount of refrigerant flowing to the heat exchange unit 30 can be adjusted to an optimum amount, and therefore overheating of the temperature-adjusted unit 31 can be prevented reliably. In addition, pressure loss in the refrigerant flow through the refrigerant passages 62, 64, 65 and the heating passage 33 and the amount of power consumed by the compressor 12 to circulate the refrigerant can be reduced reliably.
Note that when the temperature-adjusted unit 31 is cooled, the flow control valve 61 is maintained in a fully open condition while the opening of the flow control valve 51 is controlled as described with reference to FIG. 3. By closing the open/close valve 63, the refrigerant can be reliably prevented from flowing into the heating passage 33, and by fully opening the flow control valve 61, pressure loss in the refrigerant flowing through the refrigerant passage 24 a can be minimized. When the temperature-adjusted unit 31 is heated, on the other hand, the flow control valve 51 is maintained in a fully open condition while the opening of the flow control valve 61 is controlled similarly to the opening control of the flow control valve 51 described with reference to FIG. 3, i.e. such that the flow rate of the refrigerant flowing through the heating passage 33 in order to heat the temperature-adjusted unit 31 can be maintained at an appropriate level. By closing the open/close valve 53, the refrigerant can be reliably prevented from flowing into the cooling passage 32, and by fully opening the flow control valve 51, pressure loss in the refrigerant flowing through the refrigerant passage 23 a can be minimized.
FIG. 7 is a Mollier chart showing states of the refrigerant used in the vapor compression refrigeration cycle 10 according to the first embodiment when the temperature-adjusted unit 31 is heated. An abscissa in FIG. 7 shows a specific enthalpy (unit: kJ/kg) of the refrigerant, while an ordinate shows an absolute pressure (unit: MPa) of the refrigerant. A curve in the diagram is a saturation vapor line and a saturation liquid line of the refrigerant. FIG. 7 shows a thermodynamic state of the refrigerant at each point (i.e. the points A, B, E, F, and D) of the vapor compression refrigeration cycle 10, in which the refrigerant flows from the compressor 12 into the refrigerant passage 24 via the heat exchanger 18, heats the temperature-adjusted unit 31, returns to the refrigerant passage 24, and then returns to the compressor 12 via the expansion valve 16 and the heat exchanger 14.
As shown in FIG. 7, the refrigerant (point A) that is aspirated into the compressor 12 in a superheated vapor state is adiabatically compressed in the compressor 12 along a geometric entropy line. As the refrigerant is compressed, the pressure and temperature thereof rise such that the refrigerant turns into high-temperature, high-pressure, highly superheated vapor (point B). The refrigerant then flows to the heat exchanger 18.
The high-pressure refrigerant vapor that flows into the heat exchanger 18 is cooled in the heat exchanger 18 so as to change from superheated vapor into dry saturated vapor while remaining at a constant pressure. Latent heat of condensation is discharged such that the refrigerant gradually liquefies, thereby turning into wet vapor in a gas-liquid, mixed state (point E). The heat exchanger 18 forms a refrigerant liquid by isobarically discharging the heat of the superheated refrigerant gas compressed in the compressor 12 to an external medium. The gas phase refrigerant discharged from the compressor 12 is condensed (liquefied) by discharging the heat thereof to the periphery of the heat exchanger 18 such that the refrigerant is cooled. As a result of the heat exchange performed in the heat exchanger 18, the temperature of the refrigerant falls such that the refrigerant liquefies. Thus, the refrigerant is cooled by radiating the heat thereof to the periphery of the heat exchanger 18.
The wet vapor state refrigerant flowing out of the heat exchanger 18 flows into the heating passage 33 of the heat exchange unit 30 via the refrigerant passages 24, 62, 64 in order to heat the temperature-adjusted unit 31. Having exchanged heat with the temperature-adjusted unit 31, the refrigerant is cooled and condensed. When the refrigerant is condensed entirely in the heat exchange unit 30, the refrigerant forms a saturated liquid. Further, the refrigerant discharges sensible heat so as to form a supercooled liquid (point F).
The high-pressure liquid phase refrigerant liquefied by the heat exchange unit 30 flows into the expansion valve 16 through the refrigerant passages 65, 24. In the expansion valve 16, the supercooled liquid state refrigerant is throttle-expanded such that the temperature and pressure of the refrigerant fall while the specific enthalpy thereof remains unchanged. As a result, the refrigerant turns into low-temperature, low-pressure wet vapor in a gas-liquid mixed state (point D).
The refrigerant lowered in temperature in the expansion valve 16 flows into the heat exchanger 14 through the refrigerant passage 23. The wet vapor state refrigerant flows into the tube of the heat exchanger 14. While flowing through the tube, the refrigerant absorbs heat from the outside air via the fin as latent heat of evaporation, and as a result, the refrigerant evaporates while remaining at a constant pressure. When the refrigerant turns entirely into dry saturated vapor, the temperature of the refrigerant vapor is raised further by sensible heat, and as a result, superheated vapor is formed (point A). The vaporized refrigerant is then aspirated into the compressor 12 via the refrigerant passage 22. The compressor 12 compresses the refrigerant flowing from the heat exchanger 14. In accordance with this cycle, the refrigerant undergoes several changes of state, namely compression, condensation, throttle expansion, and evaporation, repeatedly and continuously.
If, as described with reference to FIGS. 4 and 5, low-temperature refrigerant is caused to flow to the cooling passage 32 of the heat exchange unit 30 in order to cool the temperature-adjusted unit 31 during a heating operation performed in a cold period, the temperature-adjusted unit 31 is cooled to an extremely low temperature. In a case where the temperature-adjusted unit 31 is an ATF cooler, the ATF is preferably not cooled excessively so that fuel efficiency deterioration can be suppressed and gear lubrication can be secured. Hence, when the ATF temperature is low, high-pressure refrigerant is introduced into the heating passage 33 of the heat exchange unit 30 in order to exchange heat with the temperature-adjusted unit 31, as shown in FIGS. 6 and 7, and as a result, the ATF can be actively heated. Since the temperature of the ATF can be raised to an appropriate level, a viscosity of the ATF does not increase, and therefore problems such as insufficient gear lubrication and an increase in friction loss can be avoided. Further, the ATF can be warmed up quickly when the temperature of the ATF is low, and as a result, a fuel efficiency can be improved and gear lubrication can be secured.
As described above, the heat exchange apparatus 1 according to this embodiment includes the vapor compression refrigeration cycle 10, which is provided to cool and heat the passenger compartment of the vehicle by performing heat exchange with the air-conditioning air in the hear exchanger 18. By switching a flow direction of the refrigerant through the vapor compression refrigeration cycle 10 between the cooling operation and the heating operation using the four-way valve 13, the temperature of the air-conditioning air flowing into the passenger compartment of the vehicle can be adjusted appropriately using the single heat exchanger 18 during both the cooling operation and the heating operation. Since there is no need to provide two heat exchangers to exchange heat with the air-conditioning air, reductions in both the cost and the size of the heat exchange apparatus 1 can be achieved.
During the cooling operation, the refrigerant has a temperature and a pressure at the outlet of the expansion valve 16 required originally to cool the passenger compartment of the vehicle. A radiation capacity of the heat exchanger 14 is determined such that the refrigerant can be cooled sufficiently. When the refrigerant is used to cool the temperature-adjusted unit 31 after passing through the expansion valve 16, an ability of the heat exchanger 18 to cool the air-conditioning air deteriorates, leading to a reduction in a passenger compartment cooling ability. With the heat exchange apparatus 1 according to this embodiment, on the other hand, the refrigerant is cooled to a sufficiently supercooled state in the heat exchanger 14, and the high-pressure refrigerant at the outlet of the heat exchanger 14 is used to cool the temperature-adjusted unit 31. Therefore, the temperature-adjusted unit 31 can be cooled without affecting the ability to cool the air in the passenger compartment.
Specifications of the heat exchanger 14 (more specifically, a size or a heat exchange performance of the heat exchanger 14) are determined such that the temperature of the liquid phase refrigerant after passing through the heat exchanger 14 is lower than a temperature required to cool the passenger compartment. The specifications of the heat exchanger 14 are determined such that the heat exchanger 14 has a radiation capacity which is greater than that of a heat exchanger of a vapor compression refrigeration cycle used in a case where the temperature-adjusted unit 31 is not cooled by an amount of heat assumed to be received by the refrigerant from the temperature-adjusted unit 31. The heat exchange apparatus 1 including the heat exchanger 14 having these specifications can cool the temperature-adjusted unit 31 appropriately while maintaining a superior cooling performance with respect to the passenger compartment of the vehicle and without increasing the power of the compressor 12.
During the heating operation, the refrigerant is heated in the heat exchange unit 30 by heat absorbed from the temperature-adjusted unit 31, and heated further in the heat exchanger 14 by heat absorbed from the outside air. When the refrigerant is heated by both the heat exchange unit 30 and the heat exchanger 14, the refrigerant can be heated to a sufficient superheated vapor state at the outlet of the heat exchanger 14, and therefore the temperature-adjusted unit 31 can be cooled appropriately while maintaining a superior heating performance with respect to the passenger compartment of the vehicle. Since the refrigerant is heated by the heat exchange unit 30 and waste heat from the temperature-adjusted unit 31 is used effectively to heat the passenger compartment, an improvement can be achieved in a coefficient of performance, leading to a reduction in an amount of power consumed to compress the refrigerant adiabatically in the compressor 12 during the heating operation.
Furthermore, during a heating operation performed in a cold period, the high-temperature, high-pressure refrigerant pressurized by the compressor 12 is used to heat the air-conditioning air and the temperature-adjusted unit 31. During the heating operation, the temperature of the temperature-adjusted unit 31 may be measured by a thermistor or the like such that when the temperature of the temperature-adjusted unit 31 is high, the temperature-adjusted unit 31 can be cooled by opening the open/close valve 53 and closing the open/close valve 63, and when the temperature of the temperature-adjusted unit 31 is low, the temperature-adjusted unit 31 can be heated by opening the open/close valve 63 and closing the open/close valve 53. The temperature-adjusted unit 31 is disposed so that it can be cooled by the refrigerant flowing through the cooling passage 32 and heated by the refrigerant flowing through the heating passage 33, and the refrigerant flow through the cooling passage 32 and the heating passage 33 is switched by opening and closing the open/ close valves 53, 63. Hence, the temperature-adjusted unit 31 can be cooled or heated freely using a simple configuration and simple control, and as a result, the temperature of the temperature-adjusted unit 31 can be adjusted to an optimum level easily.
In the heat exchange apparatus 1, the temperature-adjusted unit 31 is cooled and heated using the vapor compression refrigeration cycle 10. Therefore, a dedicated cooling device such as a water circulation pump or a cooling fan is not required to cool the temperature-adjusted unit 31, and a dedicated heating device such as a heater is not required to heat the temperature-adjusted unit 31. Accordingly, a number of configurations required to adjust the temperature of the temperature-adjusted unit 31 can be reduced, enabling simplification of the apparatus configuration, and as a result, a manufacturing cost of the heat exchange apparatus 1 can be reduced. Furthermore, there is no need to operate a power source of a pump, a cooling fan, a heater, or the like for adjusting the temperature of the temperature-adjusted unit 31, and therefore no power need be consumed to operate such a power source. As a result, a reduction can be achieved in the amount of power consumed to heat and cool the temperature-adjusted unit 31.
FIG. 8 is a schematic view showing a configuration of the heat exchange apparatus 1 according to a second embodiment. The heat exchange apparatus 1 according to the second embodiment differs from that of the first embodiment in that a heat exchanger 15 serving as a third heat exchanger is disposed on the refrigerant path between the heat exchange unit 30 and the expansion valve 16.
By providing the heat exchanger 15, the refrigerant path between the heat exchanger 14 and the expansion valve 16 is divided into the refrigerant passage 23 on the heat exchanger 14 side of the heat exchanger 15 and a refrigerant passage 27 on the expansion valve 16 side of the heat exchanger 15. The refrigerant passage 23 is provided as a path for the refrigerant flowing between the heat exchanger 14 and the heat exchanger 15. The first passage serving as the cooling system for the temperature-adjusted unit 31, which includes the cooling passage 32, is connected in parallel with the refrigerant passage 23 a forming a part of the refrigerant passage 23.
During the cooling operation, the refrigerant flows through the vapor compression refrigeration cycle 10 so as to pass sequentially through a point A, a point B, a point C, a point D, a point G, and a point E, as shown in FIG. 8. Thus, the refrigerant circulates between the compressor 12, the heat exchangers 14, 15, the expansion valve 16, and the heat exchanger 18. The refrigerant circulates within the vapor compression refrigeration cycle 10 through a refrigerant circulation passage formed by connecting the compressor 12, the heat exchangers 14, 15, the expansion valve 16, and the heat exchanger 18 in sequence using the refrigerant passages 21 to 27.
FIG. 9 is a Mollier chart showing states of the refrigerant during the cooling operation of the vapor compression refrigeration cycle 10 according to the second embodiment. An abscissa in FIG. 9 shows the specific enthalpy (unit: kJ/kg) of the refrigerant, while an ordinate shows the absolute pressure (unit: MPa) of the refrigerant. A curve in the diagram is a saturation vapor line and a saturation liquid line of the refrigerant. FIG. 9 shows the thermodynamic state of the refrigerant at each point (i.e. the points A, B, C, D, G, and E) of the vapor compression refrigeration cycle 10, in which the refrigerant flows from the compressor 12 into the refrigerant passage 23 via the heat exchanger 14, cools the temperature-adjusted unit 31, returns to the refrigerant passage 23, flows into the refrigerant passage 27 via the heat exchanger 15, and then returns to the compressor 12 via the expansion valve 16 and the heat exchanger 18.
The vapor compression refrigeration cycle 10 according to the second embodiment is identical to that of the first embodiment except for a system extending from the heat exchanger 14 to the expansion valve 16. More specifically, the refrigerant states from the point D to the point B via the points E and A on the Mollier chart shown in FIG. 2 are identical to the refrigerant states from the point G to the point B via the points E and A on the Mollier chart shown in FIG. 9. Therefore, refrigerant states from the point B to the point G, which are unique to the vapor compression refrigeration cycle 10 according to the second embodiment, will be described below.
The refrigerant (point B) adiabatically compressed into high-temperature, high-pressure superheated vapor by the compressor 12 is cooled in the heat exchanger 14. As a result, the refrigerant discharges sensible heat while remaining at a constant pressure so as to change from superheated vapor into dry saturated vapor. Latent heat of condensation is then discharged such that the refrigerant gradually liquefies, thereby turning into wet vapor in a gas-liquid mixed state, and when the refrigerant is condensed entirely, it turns into a saturated liquid (point C).
The saturated liquid state refrigerant that flows out of the heat exchanger 14 flows into the heat exchange unit 30 through the refrigerant passages 52, 54. In the heat exchange unit 30, heat is discharged to the liquid refrigerant condensed while passing through the heat exchanger 14, whereby the temperature-adjusted unit 31 is cooled. The refrigerant is heated by the heat exchange performed with the temperature-adjusted unit 31, and as a result, the dryness of the refrigerant increases. When the refrigerant receives latent heat from the temperature-adjusted unit 31 so as to undergo partial vaporization, the refrigerant turns into wet vapor intermixing saturated liquid and saturated vapor (point D).
The refrigerant then flows into the heat exchanger 15. The wet vapor of the refrigerant exchanges heat with the outside air in the heat exchanger 15 so as to be condensed again, and when condensed entirely, the refrigerant forms a saturated liquid. Further, the refrigerant discharges sensible heat so as to form a supercooled liquid (point G). The refrigerant then passes through the expansion valve 16 so as to form low-temperature, low-pressure wet vapor (point E).
In the vapor compression refrigeration cycle 10, the high-pressure refrigerant discharged from the compressor 12 is condensed by both the heat exchanger 14 and the heat exchanger 15. When the refrigerant is cooled sufficiently in the heat exchanger 15, the refrigerant has the temperature and pressure originally required to cool the passenger compartment of the vehicle at the outlet of the expansion valve 16. Accordingly, the amount of heat received by the refrigerant from the outside while evaporating in the heat exchanger 18 can be made sufficiently large. By determining the radiation capacity of the heat exchanger 15 so that the refrigerant can be cooled sufficiently in this manner, the temperature-adjusted unit 31 can be cooled without affecting the ability to cool the air in the passenger compartment. As a result, both the ability to cool the temperature-adjusted unit 31 and the ability to cool the passenger compartment can be secured reliably.
In the vapor compression refrigeration cycle 10 according to the first embodiment, the heat exchanger 14 is disposed between the compressor 12 and the expansion valve 16 such that during the cooling operation, an amount of heat exchange corresponding to cooling of the passenger compartment and cooling of the temperature-adjusted unit 31 must be performed by the heat exchanger 14. Accordingly, the refrigerant must be cooled further from the saturated liquid state in the heat exchanger 14 until the refrigerant exhibits a predetermined degree of supercooling. When the refrigerant in the supercooled liquid state is cooled, the temperature of the refrigerant approaches an atmospheric temperature, leading to a reduction in a cooling efficiency of the refrigerant, and therefore a capacity of the heat exchanger 14 must be increased. As a result, a size of the heat exchanger 14 increases, which is disadvantageous for the vehicle-installed heat exchange apparatus 1. When the size of the heat exchanger 14 is reduced to facilitate vehicle installation, on the other hand, the radiation capacity of the heat exchanger 14 deteriorates. As a result, it may be impossible to reduce the temperature of the refrigerant at the outlet of the expansion valve 16 sufficiently, leading to a deficiency in the ability to cool the passenger compartment.
With the vapor compression refrigeration cycle 10 according to the second embodiment, however, the heat exchangers 14, 15 are disposed in two stages between the compressor 12 and the expansion valve 16, and the heat exchange unit 30 serving as the cooling system for the temperature-adjusted unit 31 is provided between the heat exchanger 14 and the heat exchanger 15. As shown in FIG. 9, the refrigerant need only be cooled to a saturated liquid state in the heat exchanger 14. The wet vapor state refrigerant that is partially vaporized after receiving latent heat of evaporation from the temperature-adjusted unit 31 is then cooled again in the heat exchanger 15. The state of the refrigerant is changed at a constant temperature until the wet vapor state refrigerant has been completely condensed into a saturated liquid. Furthermore, the heat exchanger 15 cools the refrigerant to a degree of supercooling required to cool the passenger compartment of the vehicle. Therefore, in comparison with the first embodiment, there is no need to increase the degree of supercooling of the refrigerant, and the capacity of the heat exchangers 14, 15 can be reduced accordingly. Hence, the ability to cool the passenger compartment can be secured, and the size of the heat exchangers 14, 15 can be reduced. As a result, the heat exchange apparatus 1 obtained herein is small enough to be suitable for installation in a vehicle.
When the refrigerant flowing into the heat exchange unit 30 from the heat exchanger 14 cools the temperature-adjusted unit 31, the refrigerant is heated by heat received from the temperature-adjusted unit 31. When the refrigerant is heated to or above a vapor saturation temperature in the heat exchange unit 30 such that the refrigerant vaporizes entirely, an amount of heat exchange between the refrigerant and the temperature-adjusted unit 31 decreases so that the temperature-adjusted unit 31 can no longer be cooled efficiently and pressure loss occurring in the refrigerant while flowing through pipes increases. Therefore, the refrigerant is preferably cooled sufficiently in the heat exchanger 14 to ensure that the refrigerant does not vaporize entirely after cooling the temperature-adjusted unit 31.
More specifically, the state of the refrigerant at the outlet of the heat exchanger 14 is caused to approach a saturated liquid such that typically, the state of the refrigerant exists on the saturation liquid line at the outlet of the heat exchanger 14. When the heat exchanger 14 is provided with the ability to cool the refrigerant sufficiently in this manner, the radiation capacity of the heat exchanger 14 for discharging heat from the refrigerant improves beyond the radiation capacity of the heat exchanger 15. By cooling the refrigerant sufficiently in the heat exchanger 14 having a relatively large radiation capacity, the refrigerant can be kept in the wet vapor state after receiving heat from the temperature-adjusted unit 31, thereby avoiding a reduction in the amount of heat exchange between the refrigerant and the temperature-adjusted unit 31, and as a result, the temperature-adjusted unit 31 can be cooled efficiently and sufficiently. After cooling the temperature-adjusted unit 31, the wet vapor state refrigerant is efficiently cooled again in the heat exchanger 15 to a supercooled liquid state slightly below the saturation temperature. Hence, with the heat exchange apparatus 1 provided herein, both the ability to cool the passenger compartment and the ability to cool the temperature-adjusted unit 31 can be secured.
FIG. 10 is a schematic view showing the heat exchange apparatus 1 according to the second embodiment in a condition where the four-way valve 13 has been switched. Comparing FIGS. 8 and 10, the four-way valve 13 has been rotated 90°, thereby switching the path along which the refrigerant flowing into the four-way valve 13 from the outlet of the compressor 12 is discharged from the four-way valve 13. During the cooling operation shown in FIG. 8, the refrigerant compressed by the compressor 12 flows from the compressor 12 toward the heat exchanger 14. During the heating operation shown in FIG. 10, on the other hand, the refrigerant compressed by the compressor 12 flows from the compressor 12 toward the heat exchanger 18.
During the heating operation, the refrigerant flows through the vapor compression refrigeration cycle 10 so as to pass sequentially through a point A, a point B, a point E, a point G, a point D, and a point C, as shown in FIG. 10. Thus, the refrigerant circulates between the compressor 12, the heat exchanger 18, the expansion valve 16, and the heat exchangers 15, 14. The refrigerant circulates within the vapor compression refrigeration cycle 10 through a refrigerant circulation passage formed by connecting the compressor 12, the heat exchanger 18, the expansion valve 16, and the heat exchangers 15, 14 in sequence using the refrigerant passages 21 to 27.
FIG. 11 is a Mollier chart showing states of the refrigerant during the heating operation of the vapor compression refrigeration cycle 10 according to the second embodiment. An abscissa in FIG. 11 shows the specific enthalpy (unit: kJ/kg) of the refrigerant, while an ordinate shows the absolute pressure (unit: MPa) of the refrigerant. A curve in the diagram is a saturation vapor line and a saturation liquid line of the refrigerant. FIG. 11 shows the thermodynamic state of the refrigerant at each point (i.e. the points A, B, E, G, D, and C) of the vapor compression refrigeration cycle 10, in which the refrigerant flows from the compressor 12 into the refrigerant passage 23 via the heat exchanger 18, the expansion valve 16, and the heat exchanger 15, cools the temperature-adjusted unit 31, returns to the refrigerant passage 23, and then returns to the compressor 12 via the heat exchanger 14.
The vapor compression refrigeration cycle 10 according to the second embodiment is identical to that of the first embodiment except for a system extending from the expansion valve 16 to the heat exchanger 14. More specifically, the refrigerant states from the point A to the point D via the points B and E on the Mollier chart shown in FIG. 5 are identical to the refrigerant states from the point A to the point G via the points B and E on the Mollier chart shown in FIG. 11. Therefore, refrigerant states from the point G to the point A, which are unique to the vapor compression refrigeration cycle 10 according to the second embodiment, will be described below.
The refrigerant (point G) reduced in temperature by the expansion valve 16 flows into the heat exchanger 15 through the refrigerant passage 27. The wet vapor state refrigerant flows into the tube of the heat exchanger 15. While flowing through the tube, the refrigerant absorbs heat from the outside air via the fin as latent heat of evaporation, and as a result, the refrigerant evaporates while remaining at a constant pressure. The refrigerant is then heated through heat exchange with the outside air in the heat exchanger 15, whereby the dryness of the refrigerant increases. When the refrigerant receives the latent heat in the heat exchanger 15, a part thereof vaporizes, leading to an increase in the proportion of saturated vapor in the wet vapor state refrigerant (point D).
The wet vapor state refrigerant discharged from the heat exchanger 15 flows into the cooling passage 32 of the heat exchange unit 30 through the refrigerant passages 23, 55, and cools the temperature-adjusted unit 31. In the heat exchange unit 30, heat is discharged to the wet vapor state refrigerant intermixing saturated liquid and saturated vapor, whereby the temperature-adjusted unit 31 is cooled. The refrigerant is heated by the heat exchange performed with the temperature-adjusted unit 31, and as a result, the dryness of the refrigerant increases. When the refrigerant receives latent heat from the temperature-adjusted unit 31, a part thereof vaporizes, leading to a further increase in the proportion of saturated vapor in the wet vapor state refrigerant (point C).
The wet vapor state refrigerant discharged from the heat exchange unit 30 returns to the refrigerant passage 23 through the refrigerant passages 54, 52, and then flows into the heat exchanger 14. The wet vapor state refrigerant flows into the tube of the heat exchanger 14. While flowing through the tube, the refrigerant absorbs heat from the outside air via the fin as latent heat of evaporation, and as a result, the refrigerant evaporates while remaining at a constant pressure. When the refrigerant has turned entirely into dry saturated vapor, the temperature of the refrigerant vapor is raised further by sensible heat, and as a result, the refrigerant vapor turns into superheated vapor (point A).
During the heating operation, the refrigerant is heated by heat absorbed from the outside air in the two heat exchangers 14, 15, and then heated further by heat absorbed from the temperature-adjusted unit 31 in the heat exchange unit 30. By heating the refrigerant in both the heat exchange unit 30 and the heat exchangers 14, 15, the refrigerant can be heated to a sufficient superheated vapor state at the outlet of the heat exchanger 14, and therefore the temperature-adjusted unit 31 can be cooled appropriately while maintaining a superior heating performance with respect to the passenger compartment of the vehicle. Since the refrigerant is heated by the heat exchange unit 30 and waste heat from the temperature-adjusted unit 31 is used effectively to heat the passenger compartment, the amount of power consumed to compress the refrigerant adiabatically in the compressor 12 during the heating operation can be reduced.
FIG. 12 is a schematic view showing the heat exchange apparatus 1 when the temperature-adjusted unit 31 according to the second embodiment is heated. Similarly to the first embodiment, by switching the open/closed conditions of the open/ close valves 53, 63 such that the open/close valve 53 is closed and the open/close valve 63 is open, a condition in which the refrigerant flows through the heating passage 33 but does not flow through the cooling passage 32 is established. At this time, heat is transferred to the temperature-adjusted unit 31 from the refrigerant flowing through the heating passage 33, and as a result, the temperature-adjusted unit 31 is heated.
FIG. 13 is a Mollier chart showing states of the refrigerant used in the vapor compression refrigeration cycle 10 according to the second embodiment when the temperature-adjusted unit 31 is heated. An abscissa in FIG. 13 shows a specific enthalpy (unit: kJ/kg) of the refrigerant, while an ordinate shows an absolute pressure (unit: MPa) of the refrigerant. A curve in the diagram is a saturation vapor line and a saturation liquid line of the refrigerant. FIG. 13 shows a thermodynamic state of the refrigerant at each point (i.e. the points A, B, E, F, and D) of the vapor compression refrigeration cycle 10, in which the refrigerant flows from the compressor 12 into the refrigerant passage 24 via the heat exchanger 18, heats the temperature-adjusted unit 31, returns to the refrigerant passage 24, and then returns to the compressor 12 via the expansion valve 16 and the heat exchangers 15, 14.
The vapor compression refrigeration cycle 10 according to the second embodiment is identical to that of the first embodiment except for the system extending from the expansion valve 16 to the heat exchanger 14. More specifically, the refrigerant states from the point A to the point D via the points B, E, and F on the Mollier chart shown in FIG. 7 are identical to the refrigerant states from the point A to the point G via the points B, E, and F on the Mollier chart shown in FIG. 13. Therefore, refrigerant states from the point G to the point A, which are unique to the vapor compression refrigeration cycle 10 according to the second embodiment, will be described below.
The refrigerant (point G) reduced in temperature by the expansion valve 16 flows into the heat exchanger 15 through the refrigerant passage 27. The wet vapor state refrigerant intermixing saturated liquid and saturated vapor flows into the tube of the heat exchanger 15. While flowing through the tube, the refrigerant absorbs heat from the outside air via the fin as latent heat of evaporation, and as a result, the refrigerant evaporates while remaining at a constant pressure. The refrigerant is then heated through heat exchange with the outside air in the heat exchanger 15, whereby the dryness of the refrigerant increases. When the refrigerant receives the latent heat in the heat exchanger 15, a part thereof vaporizes, leading to an increase in the proportion of saturated vapor in the wet vapor state refrigerant (point D).
The wet vapor state refrigerant discharged from the heat exchanger 15 flows into the heat exchanger 14 through the refrigerant passage 23. The wet vapor state refrigerant intermixing saturated liquid and saturated vapor flows into the tube of the heat exchanger 14. While flowing through the tube, the refrigerant absorbs heat from the outside air via the fin as latent heat of evaporation, and as a result, the refrigerant evaporates while remaining at a constant pressure. When the refrigerant has turned entirely into dry saturated vapor, the temperature of the refrigerant vapor is raised further by sensible heat, and as a result, the refrigerant vapor turns into superheated vapor (point A).
During a heating operation performed in a cold period, the air-conditioning air is heated, and the temperature-adjusted unit 31 is heated by causing the high-pressure refrigerant to flow into the heat exchange unit 30 and exchange heat with the temperature-adjusted unit 31. In a case where the temperature-adjusted unit 31 is an ATF cooler, the ATF can be actively heated such that the temperature of the ATF is raised to an appropriate level. As a result, the viscosity of the ATF does not increase, and therefore problems such as insufficient gear lubrication and an increase in friction loss can be avoided. After passing through the expansion valve 16, the low-temperature, low-pressure refrigerant is heated at two stages by the two heat exchangers 15, 14, respectively and therefore respective heat exchange capacities of the heat exchangers 14, 15 can be reduced. The size of the heat exchangers 14, 15 can therefore be reduced accordingly, and as a result, the heat exchange apparatus 1 obtained herein is small enough to be suitable for installation in a vehicle.
FIG. 14 is a schematic view showing a configuration of the heat exchange apparatus 1 according to a third embodiment. The heat exchange apparatus 1 according to the third embodiment differs from those of the first and second embodiments in that an expansion valve 56 is provided on the refrigerant path between the heat exchanger 14 and the heat exchange unit 30 as a second pressure reducer differing from the first pressure reducer (the expansion valve 16) in place of the open/close valve 53 that sets the refrigerant passages 52, 54 in a communicative or non-communicative condition. Similarly to the expansion valve 16, the expansion valve 56 reduces the temperature and pressure of the refrigerant by expanding the high-pressure liquid phase refrigerant that is discharged from the heat exchanger 14. The heat exchange apparatus 1 also includes a refrigerant passage 57 serving as a refrigerant path that bypasses the expansion valve 56, and an open/close valve 58 provided in the refrigerant passage 57 to switch the refrigerant flow to the refrigerant passage 57.
During the cooling operation, as shown in FIG. 14, the open/close valve 58 is closed. Accordingly, the refrigerant condensed in the heat exchanger 14 flows toward the heat exchange unit 30 through the refrigerant passage 52, the expansion valve 56, and the refrigerant passage 54. The refrigerant that flows into the heat exchange unit 30 so as to pass through the cooling passage 32 cools the temperature-adjusted unit 31 by drawing heat from the temperature-adjusted unit 31. Hence, the heat exchange unit 30 cools the temperature-adjusted unit 31 using the low-temperature, low-pressure refrigerant discharged from the heat exchanger 14 and reduced in pressure by the expansion valve 56.
FIG. 15 is a Mollier chart showing states of the refrigerant during the cooling operation of the vapor compression refrigeration cycle 10 according to the third embodiment. An abscissa in FIG. 15 shows the specific enthalpy (unit: kJ/kg) of the refrigerant, while an ordinate shows the absolute pressure (unit: MPa) of the refrigerant. A curve in the diagram is a saturation vapor line and a saturation liquid line of the refrigerant. FIG. 15 shows the thermodynamic state of the refrigerant at each point (i.e. points A, B, H, C, D, G, and E) of the vapor compression refrigeration cycle 10, in which the refrigerant flows into the refrigerant passage 52 from the refrigerant passage 23 at the outlet of the heat exchanger 14, flows through the refrigerant passage 54 after being expanded in the expansion valve 56, cools the temperature-adjusted unit 31, and then returns to the refrigerant passage 23 at the inlet of the heat exchanger 15 from the refrigerant passage 55.
The vapor compression refrigeration cycle 10 according to the third embodiment is identical to that of the second embodiment except for the system extending from the heat exchanger 14 to the expansion valve 16. More specifically, the refrigerant states from the point E to the point C via the points A and B on the Mollier chart shown in FIG. 9 are identical to the refrigerant states from the point E to the point H via the points A and B on the Mollier chart shown in FIG. 15. Therefore, refrigerant states from the point H to the point E, which are unique to the vapor compression refrigeration cycle 10 according to the third embodiment, will be described below.
The refrigerant (point H) liquefied in the heat exchanger 14 flows into the expansion valve 56 through the refrigerant passages 23, 52. In the expansion valve 56, the saturated liquid-form refrigerant is throttle-expanded such that the temperature and pressure of the refrigerant fall while the specific enthalpy thereof remains unchanged. As a result, the refrigerant turns into wet vapor intermixing saturated liquid and saturated vapor (point C). The refrigerant reduced in temperature in the expansion valve 56 flows into the cooling passage 32 of the heat exchange unit 30 via the refrigerant passage 54, and cools the temperature-adjusted unit 31. The refrigerant is heated by the heat exchange performed with the temperature-adjusted unit 31, and as a result, the dryness of the refrigerant increases. The refrigerant receives latent heat from the temperature-adjusted unit 31 so as to undergo partial vaporization, leading to an increase in the proportion of saturated vapor in the wet vapor state refrigerant (point D).
The refrigerant then flows into the heat exchanger 15. The wet vapor of the refrigerant is condensed again in the heat exchanger 15, and when condensed entirely, the refrigerant forms a saturated liquid. Further, the refrigerant discharges sensible heat so as to form a supercooled liquid (point G). The refrigerant then passes through the expansion valve 16, in which the supercooled liquid state refrigerant is throttle-expanded such that the temperature and pressure of the refrigerant fall while the specific enthalpy thereof remains unchanged. As a result, the refrigerant forms low-temperature, low-pressure wet vapor in a gas-liquid mixed state (point E).
In the heat exchange apparatus 1 according to the third embodiment, the temperature-adjusted unit 31 can be cooled during the cooling operation using refrigerant that has been expanded by the expansion valve 56 so as to decrease in temperature, and therefore the temperature-adjusted unit 31 can be cooled more efficiently. By selecting optimal specifications for the expansion valve 56, the temperature of the refrigerant that cools the temperature-adjusted unit 31 can be adjusted as desired by the heat exchange unit 30. Hence, the temperature-adjusted unit 31 can be cooled by supplying refrigerant having a lower temperature, which is more suitable for cooling the temperature-adjusted unit 31, to the heat exchange unit 30.
FIG. 16 is a schematic view showing the heat exchange apparatus according to the third embodiment in a condition where the four-way valve has been switched. When a heating operation is performed using the heat exchange apparatus 1 according to the third embodiment, the expansion valve 56 is fully closed (set at opening 0%) and the open/close valve 58 is opened. Accordingly, the refrigerant flows through the vapor compression refrigeration cycle 10 so as to pass sequentially through a point A, a point B, a point E, a point G, a point D, and a point C, as shown in FIG. 16. Thus, the refrigerant circulates between the compressor 12, the heat exchanger 18, the expansion valve 16, and the heat exchangers 15, 14.
At this time, the refrigerant circulates through the vapor compression refrigeration cycle 10 while the state thereof is varied in a similar manner to that shown in FIG. 11. Hence, similarly to the second embodiment, the refrigerant is heated by both the heat exchange unit 30 and the heat exchangers 14, 15 such that the refrigerant can be heated to a sufficient superheated vapor state at the outlet of the heat exchanger 14, and therefore the temperature-adjusted unit 31 can be cooled appropriately while maintaining a superior heating performance with respect to the passenger compartment of the vehicle.
FIG. 17 is a schematic view showing the heat exchange apparatus 1 when the temperature-adjusted unit 31 according to the third embodiment is heated. When the temperature-adjusted unit 31 is heated during a heating operation performed in a cold period using the heat exchange apparatus 1 according to the third embodiment, the expansion valve 56 is fully closed (set at opening 0%), the open/close valve 58 is closed, and the open/close valve 63 is opened. Accordingly, the refrigerant flows through the vapor compression refrigeration cycle 10 so as to pass sequentially through points A, B, E, F, G, and D, as shown in FIG. 17. Thus, the refrigerant circulates between the compressor 12, the heat exchanger 18, the expansion valve 16, and the heat exchangers 15, 14.
At this time, the refrigerant circulates through the vapor compression refrigeration cycle 10 while the state thereof is varied in a similar manner to that shown in FIG. 13. Hence, similarly to the second embodiment, during a heating operation performed in a cold period, the air-conditioning air can be heated, and the temperature-adjusted unit 31 can be heated by introducing the high-pressure refrigerant into the heat exchange unit 30. In a case where the temperature-adjusted unit 31 is an ATF cooler, the ATF can be actively heated, whereby the temperature of the ATF can be raised to an appropriate level. As a result, the viscosity of the ATF does not increase, and therefore problems such as insufficient gear lubrication and an increase in friction loss can be avoided.
Note that in the first to third embodiments, the heat exchange apparatus 1 that adjusts the temperature of the temperature-adjusted unit installed in the vehicle to an optimum temperature was described using an ATF cooler as an example. However, the temperature-adjusted unit 31 subjected to temperature adjustment by the heat exchange apparatus 1 according to the invention is not limited to an ATF cooler installed in a vehicle, and any device that requires cooling or heating in accordance with various conditions such as outside air temperature, or a heat generating part of such a device, may be used instead.
Embodiments of the invention were described above, but the configurations of the respective embodiments may be combined appropriately. Further, the embodiments disclosed herein are examples with respect to all points, and are not therefore to be considered limiting. The scope of the invention is defined by the scope of the claims rather than the above description, and is intended to include equivalent definitions to the scope of the claims and all modifications within that scope.
The heat exchange apparatus according to the invention is particularly suitable for use in adjusting the temperature of a temperature-adjusted unit, such as an ATF cooler that requires cooling or heating, using a vapor compression refrigeration cycle that heats and cools a vehicle interior of a vehicle.

Claims

1. A heat exchange apparatus that performs heat exchange between a refrigerant and a temperature-adjusted unit, comprising:

a compressor configured to compress the refrigerant in order to circulate the refrigerant through the heat exchange apparatus;

a first heat exchanger configured to perform heat exchange between the refrigerant and outside air;

a first pressure reducer configured to reduce a pressure of the refrigerant;

a second heat exchanger configured to perform heat exchange between the refrigerant and air-conditioning air; and

a first flow control valve configured to adjust a flow rate of the refrigerant,

wherein a first passage provides a path for the refrigerant to flow between the first heat exchanger and the first pressure reducer, a second passage provides a path for the refrigerant to flow between the first pressure reducer and the second heat exchanger, a third passage is connected in parallel with the first passage on the refrigerant path between the first heat exchanger and the first pressure reducer, the first flow control valve adjusts the flow rate of the refrigerant flowing through the first passage and the flow rate of the refrigerant flowing through the third passage, and the temperature-adjusted unit is disposed to exchange heat with the refrigerant flowing through the first passage and to exchange heat with the refrigerant flowing through the second passage.

2. The heat exchange apparatus according to claim 1, further comprising:

a four-way valve configured to switch between a refrigerant flow from the compressor to the first heat exchanger and a refrigerant flow from the compressor to the second heat exchanger.

3. (canceled)

4. The heat exchange apparatus according to claim 1, further comprising:

a second flow control valve configured to adjust a flow rate of the refrigerant,

wherein a fourth passage is connected in parallel with the second passage on the refrigerant path between the first pressure reducer and the second heat exchanger; and

the second flow control valve adjusts the flow rate of the refrigerant flowing through the second passage and the flow rate of the refrigerant flowing through the fourth passage.

5. The heat exchange apparatus according to claim 1, further comprising:

a first open/close valve configured to open and close the first passage.

6. The heat exchange apparatus according to claim 4, further comprising:

a second open/close valve configured to open and close the second passage.

7. The heat exchange apparatus according to claim 6, wherein the second open/close valve is closed when the first open/close valve is open and the second open/close valve is open when the first open/close valve is closed.

8. The heat exchange apparatus according to claim 1, further comprising:

a second pressure reducer configured to reduce the pressure of the refrigerant, the second pressure reducer being provided in the first passage between the first heat exchanger and the temperature-adjusted unit.

9. The heat exchange apparatus according to claim 8, further comprising:

a third open/close valve configured to open and close a passage for the refrigerant, wherein a fifth passage is connected in parallel with a path passing through the second pressure reducer on a path that forms a part of the first passage and passes through the temperature-adjusted unit and the first heat exchanger, and the third open/close valve that is provided in the fifth passage in order to open and close the fifth passage.