JP2008121930A - Refrigeration system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigeration system capable of considerably improving the efficiency and durability of a refrigerating cycle by efficiently cooling a high temperature part of a compression refrigerating machine to a desired state, and shifting a working region to a lower temperature region by cooling. <P>SOLUTION: The refrigeration system is formed as a closed circuit filled with liquid and having an evaporating section and a condensing section for the liquid to cool the high temperature part of the compression refrigerating machine, and is provided with a thermal siphon for repeating a cycle of movement and phase change of the liquid in the closed circuit so that, after the liquid in the evaporating section receives heat and is evaporated, it is liquefied by heat radiation in the condensing section and returned to the evaporating section. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a refrigeration system, and more particularly, to a refrigeration system that can efficiently cool a high-temperature part of a compression refrigerator.

  In a compression type refrigerator using a carbon dioxide refrigerant which has been actively developed in recent years, it is common to provide an internal heat exchanger in the refrigeration cycle in order to ensure a good coefficient of performance COP. (For example, Patent Document 1), the suction gas temperature of the compressor is high and the specific heat ratio of the carbon dioxide refrigerant is large, so that the discharge gas temperature is very high, the power consumption of the compressor is large, and the compressor as a whole has high temperature and high pressure. Therefore, it is necessary to select materials and ensure strength to meet the requirements, which has been a factor in reducing cost and productivity.

  In a conventional refrigeration system using carbon dioxide refrigerant, for example, as shown in the example of the refrigeration system in the vehicle air conditioner, the carbon dioxide refrigerant compressed and discharged by the compressor 101 is sent to the gas cooler 102. After the high-pressure side refrigerant from the gas cooler 102 is heat-exchanged with the low-pressure side refrigerant by the internal heat exchanger 103, the refrigerant is sent to the evaporator 105 through the expansion valve 104, and the refrigerant from the evaporator 105 passes through the accumulator 106. After that, the internal heat exchanger 103 exchanges heat with the high-pressure side refrigerant and sucks it into the compressor 101.

  The refrigeration cycle in such a refrigeration system can be represented by a Mollier diagram as shown in FIG. 8, for example. In the compression refrigeration cycle using the carbon dioxide refrigerant shown in FIG. 8, between 1-2, the compression work of the compressor 101, 2-3, heat radiation by the gas cooler 102, 3-4, and 7-1 are internal. Heat exchange by the heat exchanger 103, expansion between 4-5 by expansion valve 104, and evaporation by evaporator 105 between 5-6 are shown, and 6 and 7 are gas-liquid separation in the accumulator 106 under the same pressure state. Is shown.

  In such a refrigeration system, as described above, since the compressor section is at a high temperature and a high pressure, it is desirable that the compressor is appropriately cooled in order to reduce power consumption. As for a compressor driven by an electric motor, one that cools the motor by suction gas is known. However, if this is done, the degree of superheat of the suction gas is substantially increased (at the same time there is a decrease in gas density). In some cases, the power consumption in the compressor increases and the discharge gas temperature rises. In addition, there is a system in which the motor is driven by an inverter in order to drive the motor efficiently, but this inverter also needs to be cooled, and the same thing as the above-mentioned motor may occur.

  In a cooling system for a compressor, particularly in a system using a carbon dioxide refrigerant, the discharge gas may be, for example, more than 150 ° C. and more than 12 MPa, and there is a concern that durability and strength may be reduced due to high temperature and pressure. In addition, a system that uses sensible heat of brine to cool electrical equipment, etc. (generally, water cooling) is also known, but additional equipment such as pumps is a concern, leading to increased costs, failure risks, and increased energy consumption. The Furthermore, in an electric motor integrated compressor, the degree of superheat of the suction gas increases (at the same time the gas density decreases) under the influence of motor waste heat and inverter waste heat, and compression efficiency may decrease. In particular, in a situation where the heat load is small, there is a concern that the amount of circulating refrigerant is small and the cooling of the motor or inverter becomes insufficient.

On the other hand, a thermal siphon is known as a device capable of transferring heat by phase change of an encapsulating medium without external power and thereby cooling the device. However, there is no example in which a thermal siphon is applied to a refrigeration system having a compression refrigerator configuration.
JP 11-193967 A

  Therefore, the object of the present invention is to focus on the problems associated with insufficient cooling in the high temperature part of the compression refrigerator as described above and the characteristics of the thermal siphon capable of cooling a specific part with a simple configuration. An object of the present invention is to provide a refrigeration system capable of efficiently cooling a high temperature part to a desired state and shifting the use region to a lower temperature region by the cooling, thereby greatly improving the efficiency and durability of the refrigeration cycle.

  In order to solve the above problems, a refrigeration system according to the present invention is configured in a closed circuit having a liquid enclosed therein and a liquid evaporation unit and a condensation unit in order to cool a high-temperature part of a compression refrigerator. A thermal siphon that repeats the cycle of liquid movement and phase change in a closed circuit is provided so that the liquid inside the evaporation unit is vaporized by heat reception and then liquefied by heat dissipation in the condensation unit and returned to the evaporation unit. It consists of what to do.

  Here, what moves heat | fever by the phase change of the enclosure liquid as an enclosure medium without external power is called a thermal siphon. As a typical encapsulated liquid, the case of water will be described. Water boils at 87 ° C under a pressure of 66661 Pa. By using this in a thermal siphon closed circuit, it becomes possible to cool equipment that generates heat above 87 ° C to 87 ° C without power (however, the heat exchange efficiency with the thermal siphon system is 100%. Assumption). That is, the thermal siphon can be used on the secondary side of the binary refrigeration system, and further, for example, on the primary side, for example, for cooling the compressor.

  For example, the closed circuit is filled with pure water and the pressure is 66661 Pa. The boiling temperature of water in this state is 87 ° C. The atmospheric temperature of the condensing part is set to around 25 ° C., for example. Inside the evaporator part of the thermal siphon that comes into contact with the equipment in need of cooling exceeding 87 ° C, for example, water is distributed to a plurality of heat exchange pipe parts by the header part below the evaporator part, and the liquid is vaporized ( (Latent heat change). The water that is vaporized and has a reduced density rises and flows into the condensing part. When liquid remains inside the evaporation unit, a liquid level is formed in the header tank in the upper part of the evaporation unit and stays downward, so that it does not flow out to the condensing unit. Water is liquefied after heat dissipation in the condensing part, and returns to the evaporation part by gravity. The thermal siphon that repeats such a cycle of water movement and phase change makes it possible to efficiently cool the high-temperature portion of the compression refrigerator, particularly the compressor. The thermal siphon can be configured as a structure including a condensing unit and a full liquid evaporation unit that are composed of header sections arranged above and below and a plurality of pipe sections that perform heat exchange connecting the header sections. Since the thermal siphon increases the evaporation amount of the sealed liquid in accordance with the heat load, heat exchange corresponding to this can be performed in the condensing unit, and the heat exchange amount can be adjusted by the fan air volume, for example. In this case, the condensing unit may be arranged above the high-pressure side heat exchanger of the compression refrigerator and cooled by a common fan.

  In the refrigeration system according to the present invention, the thermal siphon may be configured such that the evaporation temperature of the liquid can be adjusted by adjusting the internal pressure. For example, a pressure adjustment chamber for adjusting the internal volume is provided in the thermal siphon, the internal pressure of the thermal siphon is increased or decreased, and the cooling temperature is adjusted. Specifically, for example, the thermal siphon adjusts the setting of the partition wall made of at least a flexible member, the partition wall support member that elastically changes the stroke according to the pressure in the partition wall, and the stroke setting of the partition wall support member. It is the form which has a pressure regulation chamber provided with the adjustment screw. More specifically, for example, a pressure regulating chamber including a partition wall formed of a flexible member such as rubber, a metal bellows, and a metal diaphragm and a partition wall support member (for example, a spring) formed of an elastic member is provided. When water is boiled at 100 ° C. or less, the differential pressure between the pressure in the partition wall and the atmospheric pressure is balanced by a spring and an adjusting screw. When water is boiled at 100 ° C. or higher, the spring mounting method is reversed.

  As a high temperature part of the compression refrigerator cooled by the thermal siphon, the compressor can be a cooling target. Moreover, you may include the electric motor integrated in the compressor in the high temperature part of the compression refrigerator used as cooling object. Furthermore, you may include the inverter which controls the electric motor which drives a compressor in the high temperature part of the compression type refrigerator used as cooling object.

  When cooling the compressor part of such a compression type refrigerator, for example, the compressor may be cooled by the evaporation part of the thermal siphon through its wall surface. With such an arrangement, the compressor as a cooling target is efficiently cooled.

  Further, the liquid enclosed in the thermal siphon in the refrigeration system according to the present invention is not particularly limited as long as the target cooling is achieved in the present invention. However, the liquid is easy to handle and can clearly grasp the characteristics in advance. As described above, water or a liquid mainly composed of water is desirable. For example, it is preferably made of a liquid containing 50% or more of water.

  In addition, some thermal siphons have copper or aluminum tubes connected substantially in an endless manner and are filled with a refrigerant gas such as carbon dioxide or butane. (Or condensing temperature) is not in the room temperature range of −8 ° C., and a thermal siphon is established, which may cause a contradiction that the heat load of the compression refrigerator becomes higher. Therefore, from this aspect, it is preferable to select a sealed liquid capable of changing the phase of gas and liquid (latent heat change) at an appropriate temperature, for example, a liquid containing 50% or more of water as described above.

  The refrigerant used in the compression refrigerator in the present invention is not particularly limited, but in the present invention, since the high temperature portion of the compression refrigerator can be efficiently cooled, when the refrigerant is made of carbon dioxide, that is, in the refrigeration cycle. The present invention is particularly effective when it has a high-temperature and high-pressure part. In other words, the present invention is particularly effective when the refrigerant circulating in the compression refrigerator is a refrigerant having a global warming potential (GWP) of 150 or less. However, a compression refrigerator using a refrigerant such as HFC134a can also be the subject of the present invention.

  In the refrigeration system according to the present invention, it is particularly preferable that heat exchange corresponding to the compressor power of the compression chiller is performed by the thermal siphon. This makes it possible to realize an extremely efficient refrigeration cycle, as will be described with reference to the Mollier diagram to be described later. In some cases, there is a possibility that the gas cooler in the conventional cycle can be omitted.

  In addition, since the refrigeration system according to the present invention uses a thermal siphon that does not require any special external power, a refrigeration system used in a vehicle air conditioner or the like that is not particularly preferred to install a new power source or the like. It is suitable for. However, the refrigeration system according to the present invention is not limited to a vehicle air conditioner, and can be applied to cooling other devices such as electronic devices.

  The operation of the present invention will be described in the case where the sealed liquid is water. For example, in the case of a vehicle air conditioner, the lower limit of the compressor housing surface temperature is about 90 ° C. in the normal operation mode, and the rotational speed of the compressor is As it increases, it may rise up to 160 ° C depending on the conditions. However, when the thermal siphon according to the present invention operates, the temperature does not rise above the boiling temperature of water in the thermal siphon under any conditions. That is, appropriate cooling is performed to prevent an undesirably high temperature.

  In the case of a compression refrigerator using carbon dioxide as a refrigerant, the critical point is a low temperature of about 30 ° C. and a high pressure of about 7 MPa, and the cycle does not use a normal internal heat exchanger. In the configuration, the dryness at the evaporator inlet is large and the efficiency as a refrigeration system is not good. An internal heat exchanger provided to compensate for this raises the intake gas temperature of the compressor and thus the discharge gas temperature in order to bring the gas cooler downstream pipe and the evaporator downstream pipe into contact with each other. In the present invention, as will be described later, for example, a space (jacket) in which water circulates is provided so as to cover the wall surface of the compressor of the compression refrigerator, and is connected to the condenser portion of the thermal siphon above the jacket by piping. Configured. The water that has entered the jacket as a liquid from below is vaporized by the heat of the compressor. At this time, if the pressure in the jacket is 66661 Pa, the temperature is maintained at 87 ° C., and the high temperature as described above is surely prevented.

  Further, by providing the pressure adjusting chamber, even if the amount of gas after boiling when the thermal load on the thermal siphon increases, the boiling point does not fluctuate and stable cooling performance can be obtained. If this is used to cool the high-pressure side equipment of a compression refrigerator using a carbon dioxide refrigerant whose high-pressure side is supercritical, the high-pressure side pressure will be stable and stable operation will be possible without advanced control. Become.

  As described above, according to the refrigeration system of the present invention, the boiling temperature (condensation temperature) determined by the pressure in the closed circuit is used in order to use the latent heat at the time of the phase change of the liquid enclosed in the thermal siphon. ), The temperature of the cooled part can be maintained at a desired constant temperature, and the target cooling can be performed efficiently and reliably.

  For the compressor housing of the compression refrigerator, a light alloy material is generally used because of its good formability and machinability and high thermal conductivity. However, light alloys have the property that the strength decreases significantly as the temperature rises. As a result of the cooling according to the present invention, the compressor housing temperature can be lowered, so that it can be used in a substantially high strength region.

  Moreover, if the cooling characteristic that keeps the temperature of the thermal siphon constant is utilized, the high temperature deterioration of the seal material can be prevented.

  Further, if the cooling characteristic for keeping the temperature of the thermal siphon constant is utilized, the lubricating oil film thickness is secured by preventing the refrigerating machine oil viscosity from being lowered, so that the durability of the seal sliding portion and the bearing portion can be improved.

  Since this thermal siphon has no moving parts, it is extremely reliable and quiet. Further, since no special external drive source is required, the present invention can be implemented at low cost and without requiring a large space.

  Further, since the thermal siphon operates at a pressure lower than the atmospheric pressure, there is no leakage to the outside, and this aspect is extremely reliable.

  Further, by appropriate cooling by the thermal siphon, it is possible to reduce the high-pressure side heat exchanger of the compression refrigeration machine, and it is possible to reduce the amount of enclosed refrigerant accordingly.

  Further, even when a compression type refrigerator having a compressor integrated with an electric motor is used in a state where the heat load is small, there is no deterioration in the performance and durability of the compressor.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a device arrangement when a refrigeration system according to an embodiment of the present invention is applied to a vehicle air conditioner. In FIG. 1, the carbon dioxide refrigerant compressed and discharged by the compressor 11 is sent to the gas cooler 12, and after the high-pressure side refrigerant from the gas cooler 12 is heat-exchanged with the low-pressure side refrigerant by the internal heat exchanger 13, the expansion valve 14, the refrigerant from the evaporator 15 passes through the accumulator 16, and is then heat-exchanged with the high-pressure side refrigerant by the internal heat exchanger 13 and sucked into the compressor 11. The thermal siphon 17 according to the present invention is provided for the compressor 11 of the refrigeration system configured as described above, or a portion thereof. The thermal siphon 17 includes an evaporation unit 19 for the sealed liquid formed in the form of a jacket 18 around the compressor 11 and a condensing unit 20 positioned above. The evaporator 19 is disposed around the compressor 11, but the condenser 20 is disposed above the compressor 11.

  The refrigeration cycle in the refrigeration system provided with the thermal siphon 17 as described above can be represented by, for example, a Mollier diagram as shown in FIG. In the compression refrigeration cycle using the carbon dioxide refrigerant shown in FIG. 2, boiling cooling of the liquid sealed in the thermal siphon 17 is used for cooling the compressor 11. In FIG. 2, a portion between 1-1 ′ and 2 is a portion equivalent to a compression work (virtual portion) by the compressor 11, but the compressor 11 is boiled and cooled by the thermal siphon 17 as between 1 ′ and 2 ′. As a result, the compressor 11 is prevented from being heated at a high temperature. Between 2'-3, heat is radiated by the gas cooler 12, between 3-4 and 7-1 is heat exchange by the internal heat exchanger 13, between 4-5 is expanded by the expansion valve 14, and between 5-6 is by the evaporator 15. Evaporation is shown, and 6 and 7 show gas-liquid separation in the accumulator 16 under the same pressure state. Thus, it is clear that the compressor 11 is efficiently cooled by the thermal siphon 17 even on the Mollier diagram. If 2 ′ is at the position 3, the gas cooler 12 may be omitted in some cases. It becomes possible.

  The thermal siphon 17 has a basic configuration as shown in FIG. 3, for example. That is, the evaporating part 19 in which the sealed liquid flows in the liquid phase is located on the lower side, and the condensing part 20 in which the sealed liquid flows in the gas phase and is liquefied by heat dissipation is disposed above it. These are configured in a closed circuit, and after the liquid in the evaporation unit 19 is heat-received and vaporized, the liquid moves and phase changes in the closed circuit so that it is liquefied by heat dissipation in the condensation unit 20 and returned to the evaporation unit 19. This cycle is repeated, and the high-temperature portion of the compression refrigerator is cooled by heat absorption due to vaporization (latent heat change) in the evaporation portion 19. In this manner, the encapsulated liquid circulates in the thermal siphon 17 without applying special external power.

  FIG. 4 illustrates a case where the pressure adjustment chamber 21 is provided in the thermal siphon 17. In this example, the pressure regulation chamber 21 is made of a flexible member, and a rubber or metal bellows 22 as a partition wall through which the liquid inside the thermal siphon 17 circulates, and the pressure in the bellows 22. A spring 23 serving as a partition wall supporting member that elastically changes the stroke and an adjusting screw 24 that adjusts the stroke setting of the spring 23 are provided. For example, in the case where water as the sealed liquid is boiled at 100 ° C. or lower, the difference between the pressure inside the bellows 22 and the atmospheric pressure may be balanced by the spring 23 and the adjusting screw 24. When the water is boiled at 100 ° C. or higher, the attachment method of the spring 23 is reversed.

  FIG. 5 shows an example of a conventional compressor 31 for comparison. The compressor 31 is formed by integrating a compression mechanism 32 and an electric motor 33 (for example, a DC brushless motor) that drives the compression mechanism 32, and the electric motor 33 is controlled by an inverter 34. In the compressor 31, the suction refrigerant 35 is sucked into the compression mechanism 32 through the electric motor 33, thereby cooling the electric motor 33 together with the compressor 31. The refrigerant compressed by the compression mechanism 32 is discharged as a compressed refrigerant 36.

  On the other hand, a compressor as a cooling target of a compression refrigerator to which the present invention is applied is configured as shown in FIG. 6, for example. FIG. 6 shows the compressor 11 shown in FIG. 1 and the configuration around it. Like the compressor 31 shown in FIG. 5, the compressor 11 is driven by an electric motor 42 with a built-in compression mechanism 41, but the suction refrigerant 43 is directly passed through the electric motor 42. The refrigerant introduced into the compression mechanism 41 and compressed by the compression mechanism 41 is discharged as the compressed refrigerant 44. And with respect to this compressor 11, the evaporation part 19 of the thermal siphon 17 is arrange | positioned by the structure of the above-mentioned jacket 18, Between the evaporation part 19 and the condensation part 20, circulation of the sealing liquid is carried out. That is, the liquid movement and the phase change cycle in the closed circuit as described above are repeated. In this example, the cooling jacket 18 is arranged so as to cool the electric motor 42 portion by covering the electric motor 42 portion, and is arranged so that the inverter 45 that controls the electric motor 42 can also be cooled. Thus, the compressor 11, the electric motor 42, and the inverter 45 are all efficiently cooled.

  In this way, by disposing the thermal siphon to the high temperature part of the compression refrigerator, the high temperature part that needs to be cooled is efficiently cooled, and the efficiency of the refrigeration cycle of the refrigeration system is greatly increased. Will be improved.

  In addition, although the said embodiment illustrated the case where this invention was applied to cooling of the compressor part in a vehicle tower air conditioner, this invention is applicable also to the other site | part of this apparatus, and also a vehicle tower Not only the air conditioner but also other refrigeration systems can be applied.

  The refrigeration system according to the present invention is particularly suitable for applications that are used at room temperature and require cooling to a room temperature level. For example, it is suitable for cooling an electronic device and a compressor constituting a compression refrigerator using a carbon dioxide refrigerant.

It is an equipment system diagram at the time of applying a refrigeration system concerning one embodiment of the present invention to a vehicle air conditioner. FIG. 2 is a Mollier diagram of the refrigeration system of FIG. 1. It is a schematic block diagram which shows the basic composition of the thermal siphon in FIG. It is a schematic block diagram which shows an example of the thermal siphon provided with the pressure regulation chamber. It is a schematic longitudinal cross-sectional view of the conventional compressor shown for the comparison. It is a schematic longitudinal cross-sectional view of the compressor part to which this invention is applied. It is an equipment distribution diagram showing an example of a vehicle air conditioner to which a conventional refrigeration system is applied. FIG. 8 is a Mollier diagram of the refrigeration system of FIG. 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Compressor 12 Gas cooler 13 Internal heat exchanger 14 Expansion valve 15 Evaporator 16 Accumulator 17 Thermal siphon 18 Jacket 19 Evaporating part 20 Condensing part 21 Pressure regulation chamber 22 Bellows 23 as a partition wall Spring 24 as a partition wall supporting member Adjustment screw 41 Compression Mechanism 42 Electric motor 43 Suction refrigerant 44 Compressed refrigerant 45 Inverter

Claims (11)

  In order to cool the high-temperature part of the compression refrigerator, the liquid is enclosed, and is configured in a closed circuit having an evaporation part and a condensation part of the liquid. A refrigeration system comprising a thermal siphon that repeats a liquid movement and phase change cycle in a closed circuit so as to be liquefied by heat radiation and returned to the evaporation section.   The refrigeration system according to claim 1, wherein the thermal siphon is configured to be capable of adjusting a liquid evaporation temperature by adjusting an internal pressure.   The thermal siphon includes a partition made of at least a flexible member, a partition support member that elastically changes its stroke in accordance with the pressure in the partition, and an adjustment screw that adjusts the stroke setting of the partition support member. The refrigeration system according to claim 2, comprising a pressure chamber.   The refrigeration system according to any one of claims 1 to 3, wherein a high-temperature portion of the compression refrigerator that is cooled by the thermal siphon is a compressor.   The refrigeration system according to any one of claims 1 to 4, wherein the high-temperature portion of the compression refrigerator that is cooled by the thermal siphon includes an electric motor integrated with the compressor.   The refrigeration system according to any one of claims 1 to 5, wherein the high-temperature portion of the compression refrigerator cooled by the thermal siphon includes an inverter that controls an electric motor that drives the compressor.   The refrigeration system according to any one of claims 1 to 6, wherein a compressor of the compression refrigerator is cooled by an evaporator unit of the thermal siphon through a wall surface thereof.   The refrigeration system according to any one of claims 1 to 7, wherein the liquid sealed in the thermal siphon is made of a liquid containing 50% or more of water.   The refrigeration system according to any one of claims 1 to 8, wherein a refrigerant used in the compression refrigerator is made of carbon dioxide.   The refrigeration system according to any one of claims 1 to 9, wherein heat exchange corresponding to compressor power of the compression refrigerator is performed by the thermal siphon.   The refrigeration system according to any one of claims 1 to 10, wherein the refrigeration system is used for a vehicle air conditioner.

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