JP2012180963A - Refrigeration cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an upper compressor discharge temperature without compressing a liquid in a heating operation in a two-stage boosting type refrigeration cycle.SOLUTION: The refrigeration cycle including a lower compressor 1, a higher compressor 2, a condenser 3 for exchanging heat of a high-pressure refrigerant discharged from the higher compressor 2 and radiating heat, a throttle mechanism 6 for decompressing and expanding the high-pressure refrigerant to be a low-pressure refrigerant, and an evaporator 7 absorbing heat by exchanging heat of the low-pressure refrigerant, and allowing the refrigerant absorbing heat, to be sucked to the lower compressor 1, further includes a heat exchanger 3a for radiating heat by exchanging heat of an intermediate-pressure refrigerant discharged from the lower compressor 1, and the intermediate-pressure refrigerant radiating heat by the heat exchanger 3a is sucked to the higher compressor 2.

Description

  The present invention relates to a refrigeration cycle, and in particular, to a refrigeration cycle having a low stage compressor and a high stage compressor.

  2. Description of the Related Art Conventionally, a two-stage boost refrigeration cycle is known that includes a low-stage compressor that compresses low-pressure refrigerant to an intermediate pressure and a high-stage compressor that compresses intermediate-pressure refrigerant discharged from the low-stage compressor to a higher pressure. . In this two-stage boost type refrigeration cycle, a high compression ratio can be realized, and the efficiency and capacity of the refrigeration cycle can be improved.

  In a two-stage boosting type refrigeration cycle, conventionally, a part of the refrigerant discharged from the high-stage compressor and condensed by the condenser is bypassed as liquid injection and mixed with the refrigerant discharged from the low-stage compressor. Inhalation into the stage compressor is carried out. Thereby, the temperature of the refrigerant | coolant suck | inhaled by a high stage compressor can be reduced, and the temperature of the refrigerant | coolant discharged from a high stage compressor can be reduced.

  For example, in Patent Document 1 below, when heating operation is performed in a two-stage boosting type refrigeration cycle, the temperature of the refrigerant discharged from the high-stage compressor can be further decreased by increasing the amount of liquid injection. Are listed.

JP 2009-270776 A

  However, in the liquid injection in the conventional two-stage boosting type refrigeration cycle, if all of the liquid refrigerant cannot evaporate before reaching the high stage compressor during heating operation, the high stage compressor is liquid compressed. There was a problem that a large load was applied to the compressor. In view of this problem, an object of the present invention is to provide a refrigeration cycle capable of reducing the discharge temperature of a high-stage compressor without causing liquid compression when heating operation is performed.

  The refrigeration cycle according to claim 1 of the present invention compresses a low-pressure compressor (1) that compresses low-pressure refrigerant and discharges it as intermediate-pressure refrigerant, and compresses the intermediate-pressure refrigerant discharged from the low-stage compressor (1). The high-stage compressor (2) discharged as a high-pressure refrigerant, the condenser (3) that radiates heat by exchanging heat from the high-pressure refrigerant discharged from the high-stage compressor (2), and flows out of the condenser (3) A throttle mechanism (6) that decompresses and expands the high-pressure refrigerant to form a low-pressure refrigerant, and a low-pressure refrigerant that flows out of the throttle mechanism (6) exchanges heat to absorb heat, and the absorbed refrigerant is converted into the low-stage compressor (1). And a heat exchanger (3a, 7a, 4) for radiating heat by exchanging the intermediate-pressure refrigerant discharged from the low-stage compressor (1). Provided with the intermediate pressure refrigerant radiated by the heat exchanger (3a, 7a, 4) Is sucked into the stage compressor (2). Thereby, the discharge temperature of a high stage compressor can be lowered | hung and the reliability of a compressor can be improved. Moreover, since it is not liquid injection, liquid compression can be avoided.

  In the refrigeration cycle according to claim 2 of the present application, the high-pressure refrigerant that has flowed out of the condenser (3) and a part of the high-pressure refrigerant that has flowed out of the condenser (3) are branched and decompressed and expanded to obtain an intermediate-pressure refrigerant. An internal heat exchanger (5) for exchanging heat with the branched refrigerant is provided, and the high-pressure refrigerant flowing out of the internal heat exchanger (5) flows into the throttle mechanism (6), and the internal heat exchanger ( The branched refrigerant flowing out from 5) is sucked into the high stage compressor (2). Thereby, the efficiency and capacity of the refrigeration cycle can be increased.

  In the refrigeration cycle according to claim 3 of the present application, the heat exchanger is arranged indoors together with the condenser (3), and the intermediate pressure refrigerant discharged from the low-stage compressor (1) is exchanged with indoor air. To do. By using a heat exchanger arranged indoors, the cycle efficiency can be improved.

  In the refrigeration cycle according to claim 4, the heat exchanger is disposed outdoors together with the evaporator (7), and the intermediate-pressure refrigerant discharged from the low-stage compressor (1) is heat-exchanged with outdoor air. To do. Thereby, since the outdoor temperature is low during heating, the refrigerant temperature can be sufficiently lowered.

  In the refrigeration cycle according to claim 5 of the present application, the heat exchanger (7a) is arranged on the windward side of the evaporator (7). Thereby, the temperature of the air ventilated by the outdoor unit 7 can be raised, and heat absorption capability increases. Furthermore, adhesion of frost on the evaporator which is an outdoor unit can be suppressed.

  In the refrigeration cycle according to claim 6, the heat exchanger is the internal heat exchanger (4), and the intermediate pressure refrigerant discharged from the low-stage compressor (1) is mixed with the branch refrigerant. And flows into the internal heat exchanger (4). In the refrigeration cycle using the internal heat exchanger, since the internal heat exchanger is used as the heat exchanger of the present invention, there is an advantage that it is not necessary to arrange a new heat exchanger.

It is a figure which shows the 1st Embodiment of this invention. It is a figure which shows the 2nd Embodiment of this invention. It is a figure which shows the 3rd Embodiment of this invention. It is a figure which shows the outline of the Mollier diagram regarding the 3rd Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a first embodiment of the present invention. The present invention is suitable for a refrigeration cycle of an air conditioning facility that cools and heats a vehicle such as a bus, and particularly relates to a refrigeration cycle during heating. However, the application of the present invention is not limited to air conditioning of buses, and can be used for air conditioning of other passenger cars or houses.

  The refrigeration cycle of the present embodiment includes a closed circuit in which a refrigerant circulates, and is used to heat the outside to increase the refrigerant temperature, to dissipate heat in the room and to heat the room. Specifically, the outdoor unit 7 is an evaporator that is provided with a two-stage pressure increasing mechanism composed of a low-stage compressor 1 and a high-stage compressor 2 that sucks in a refrigerant, boosts and discharges the refrigerant, and exchanges heat with the outside air. The indoor unit 3, which is a condenser that absorbs heat and exchanges heat with the inside air, dissipates heat and raises the room temperature.

  The low-stage compressor 1 and the high-stage compressor 2 may be electric compressors that compress the refrigerant by driving the compressor with an electric motor built in each, and the two compressors are a single drive shaft. The compressor may be connected to the compressor. Any compressor that can compress the refrigerant in at least two stages can be used as the low-stage compressor 1 and the high-stage compressor 2 of the present invention. The refrigerant to be used may be a chlorofluorocarbon refrigerant or carbon dioxide in which the pressure of the refrigerant at the discharge port of the compressor is equal to or higher than the critical pressure (supercritical state).

  The low-stage compressor 1 sucks low-pressure refrigerant and discharges it as intermediate-pressure refrigerant. In the present embodiment, the intermediate pressure refrigerant discharged from the low stage compressor 1 passes through the indoor sub heat exchanger 3 arranged in the vicinity of the indoor unit 3 and is sucked into the high stage compressor. The indoor sub heat exchanger 3a exchanges heat with indoor air in the same manner as the indoor unit 3, and increases the indoor air temperature and decreases the temperature of the intermediate pressure refrigerant. In this example, the indoor sub heat exchanger 3a is disposed upstream of the electric fan 3b for sending air to the indoor unit 3, and both the indoor unit 3 and the indoor sub heat exchanger 3a are blown by the electric fan 3b. The

  The arrangement of the indoor unit 3 and the indoor sub heat exchanger 3a is not limited to the arrangement shown in FIG. The indoor unit 3 and the indoor sub heat exchanger 3a may be arranged in parallel, or may be arranged in different places in the room.

  The intermediate pressure refrigerant whose temperature has decreased after passing through the indoor sub heat exchanger 3a is sucked into the high stage compressor 2. Since the temperature of the intermediate pressure refrigerant sucked into the high stage compressor 2 is lowered, the temperature of the high pressure refrigerant discharged from the high stage compressor 2 can also be lowered.

  The high-pressure refrigerant discharged from the high-stage compressor 2 is heat-exchanged with the indoor air by the indoor unit 3 that is a condenser to increase the indoor temperature, and the high-pressure refrigerant is cooled and condensed. The cooled high-pressure refrigerant flows into one inlet 51 of the internal heat exchanger 5, and part of the high-pressure refrigerant flows into the auxiliary throttle 4 as a branched high-pressure refrigerant through the branch flow path 4a. The auxiliary throttle 4 depressurizes the flowing high-pressure refrigerant. The branched refrigerant that has been depressurized to an intermediate pressure flows into the other inlet 52 of the internal heat exchanger 5.

  The internal heat exchanger 5 exchanges heat between the high-pressure refrigerant flowing from the inlet 51 and the intermediate-pressure branch refrigerant flowing from the inlet 52. The temperature of the high-pressure refrigerant decreases and the temperature of the branch refrigerant increases. The high-pressure refrigerant flowing out from one outlet 53 of the internal heat exchanger 5 is reduced in pressure through the main throttle 6, flows into the outdoor unit 7 that is an evaporator, and exchanges heat with the outside air. The fan 7 b blows outside air to the outdoor unit 7. The refrigerant flowing out of the outdoor unit 7 is sucked into the low stage compressor 1. The branched refrigerant flowing out from the other outlet 54 of the internal heat exchanger 5 is increased in temperature, gasified, and sucked into the high stage compressor 2.

  The auxiliary throttle 4 and the main throttle 6 can adjust the refrigerant amount by adjusting the opening degree using an electronic expansion valve. These throttles may be, for example, capillary tubes that provide a predetermined flow path resistance.

  As described above, the intermediate-pressure refrigerant that has passed through the indoor sub heat exchanger 3a is sucked into the high-stage compressor 2, and part of the high-pressure refrigerant that flows out of the indoor unit 3 is branched to reduce the intermediate pressure. The reduced pressure refrigerant is sucked. Since any refrigerant is gasified, it does not become liquid injection and does not cause liquid compression.

  In the present embodiment, the intermediate pressure refrigerant discharged from the low-stage compressor 1 is passed through the indoor sub heat exchanger 3a, and the temperature of the intermediate-pressure refrigerant is lowered and sucked into the high-stage compressor 2. Thereby, the discharge temperature of the high stage compressor 2 can be lowered | hung and the reliability of a compressor can be improved. Further, since liquid injection is not used, liquid compression can be avoided.

  FIG. 2 is a diagram showing a second embodiment of the present invention. In the second embodiment, a heat exchanger arranged outdoors is used as a heat exchanger that lowers the temperature of the intermediate pressure refrigerant discharged from the low-stage compressor 1. The same members and the same elements as those in the first embodiment shown in FIG.

  As shown in FIG. 2, the intermediate pressure refrigerant discharged from the low-stage compressor 1 passes through the outdoor sub heat exchanger 7 a disposed in the vicinity of the outdoor unit 7 and is sucked into the high-stage compressor 2. In the second embodiment, an outdoor sub heat exchanger 7a is used instead of the indoor sub heat exchanger 3a, and the rest is the same as that of the first embodiment. For example, a part of the high-pressure refrigerant that has passed through the indoor unit 3 becomes an intermediate-pressure refrigerant that has been gasified through the auxiliary throttle 4 and the internal heat exchanger 5, and is sucked into the high-stage compressor 2 according to the first embodiment. It is the same.

  In the second embodiment, the outdoor sub heat exchanger 7a disposed outside is used, and since the outdoor temperature is low during heating, the refrigerant temperature can be further lowered. Although arrangement | positioning of the outdoor sub heat exchanger 7a is not specifically limited, as shown in FIG. 2, the outdoor sub heat exchanger 7a is arrange | positioned between the electric fan 7b and the outdoor unit 7, and it winds up the outdoor unit 7. If it arrange | positions, the temperature of the air ventilated by the outdoor unit 7 can be raised, and it can be used as a heater of the outdoor unit 7. This increases the endothermic capacity. Furthermore, when the heating operation is performed, the outdoor unit 7 often has frost. However, since the outdoor sub-heat exchanger 7a can increase the temperature of the outdoor unit 7, the frost on the outdoor unit 7 can be suppressed. it can.

  FIG. 3 is a diagram showing a third embodiment of the present invention. The third embodiment uses an internal heat exchanger as a heat exchanger that reduces the temperature of the intermediate pressure refrigerant discharged from the low-stage compressor 1. The same members and the same elements as those in the first example shown in FIG. 1 are denoted by the same reference numerals.

  As shown in FIG. 3, the intermediate pressure refrigerant discharged from the low stage compressor 1 flows into the internal heat exchanger 5 from the refrigerant inlet 52 of the internal heat exchanger 5. A part of the high-pressure refrigerant that has passed through the indoor unit 3 is decompressed by the auxiliary throttle 4 and flows into the refrigerant inlet 52 as intermediate-pressure refrigerant. Therefore, the intermediate pressure refrigerant discharged from the low-stage compressor 1 is mixed with the intermediate pressure refrigerant flowing out from the auxiliary throttle 4 and flows into the internal heat exchanger 5. The intermediate pressure refrigerant gasified by exchanging heat with the high pressure refrigerant in the internal heat exchanger 5 flows out of the refrigerant outlet 54 and is sucked into the high stage compressor 2. In this case, the outflow side of the internal heat exchanger 5 can be controlled to a low temperature close to saturation. Therefore, also in the third example, the intake temperature of the high stage compressor 2 can be lowered, and the discharge temperature of the high stage compressor 2 can be lowered.

  FIG. 4 is a diagram showing an outline of the Mollier diagram in the third embodiment. A broken line is a Mollier diagram of a conventional refrigeration cycle, and a solid line is a Mollier diagram according to the third embodiment. p1 to p2 to p3 indicate a compression process, and p2 indicates an intermediate pressure. p3 to p4 to p5 indicate a condensation process. p5 to p6 indicate an expansion process, and p6 to p1 indicate an evaporation process. Although the high stage discharge temperature is reduced in common with the first to third embodiments, the subcool degree (supercooling degree) on the condenser outlet side is reduced in the third embodiment. However, since the suction temperature of the high stage compressor 2 is low, the refrigerant density is high and the refrigerant flow rate is increased, so that the capacity of the refrigeration cycle is not greatly reduced. Although the capacity / coefficient of performance (COP) does not change compared to liquid injection, the inlet temperature of the high-stage compressor 2 can be reliably gasified by controlling the outlet temperature of the internal heat exchanger 5. There is no compression.

  Also in the third embodiment, the discharge temperature of the high stage compressor 2 can be lowered while preventing the occurrence of liquid compression. Moreover, since the internal heat exchanger 5 is utilized, it has the advantage that it is not necessary to arrange a new heat exchanger as compared with the first and second embodiments.

  In addition, although all the refrigerating cycle of embodiment described in this specification is provided with the internal heat exchanger 5, in 1st and 2nd embodiment, it is provided with the internal heat exchanger 5 and hence the auxiliary throttle 4. It is also possible to use a refrigeration cycle in which the refrigerant flowing out of the indoor unit 3 flows through the main throttle 6.

1 Low stage compressor 2 High stage compressor 3 Indoor unit (condenser)
3a Indoor sub heat exchanger 3b Fan 4 Auxiliary throttle 5 Internal heat exchanger 6 Main throttle 7 Outdoor unit (evaporator)
7a Outdoor sub heat exchanger 7b Fan

Claims (6)

A low-stage compressor (1) that compresses the low-pressure refrigerant and discharges it as an intermediate-pressure refrigerant;
A high-stage compressor (2) that compresses the intermediate-pressure refrigerant discharged from the low-stage compressor (1) and discharges it as a high-pressure refrigerant;
A condenser (3) for exchanging heat by exchanging heat from the high-pressure refrigerant discharged from the high-stage compressor (2);
A throttle mechanism (6) that expands the high-pressure refrigerant flowing out of the condenser (3) under reduced pressure to form a low-pressure refrigerant;
A refrigeration cycle comprising: an evaporator (7) that heat-exchanges the low-pressure refrigerant flowing out of the throttle mechanism (6) to absorb heat and sucks the absorbed refrigerant into the low-stage compressor (1),
A heat exchanger (3a, 7a, 4) for exchanging heat by exchanging the intermediate pressure refrigerant discharged from the low-stage compressor (1), and the intermediate pressure dissipated by the heat exchanger (3a, 7a, 4) A refrigeration cycle for sucking refrigerant into the high stage compressor (2).   Internal heat exchange between the high-pressure refrigerant that has flowed out of the condenser (3) and the branched refrigerant that has branched and decompressed and expanded part of the high-pressure refrigerant that has flowed out of the condenser (3). A high-pressure refrigerant that includes a heat exchanger (5), flows out from the internal heat exchanger (5), flows into the throttle mechanism (6), and the branched refrigerant that flows out from the internal heat exchanger (5) The refrigeration cycle according to claim 1, wherein the refrigeration cycle is sucked into the compressor (2).   The said heat exchanger is arrange | positioned indoors with the said condenser (3), and heat-exchanges the intermediate pressure refrigerant | coolant discharged from the said low stage compressor (1) with indoor air. Refrigeration cycle.   The said heat exchanger is arrange | positioned outdoors with the said evaporator (7), and heat-exchanges the intermediate pressure refrigerant | coolant discharged from the said low stage compressor (1) with outdoor air. Refrigeration cycle.   The refrigeration cycle according to claim 4, wherein the heat exchanger (7a) is arranged on the windward side of the evaporator (7).   The heat exchanger is the internal heat exchanger (4), and the intermediate pressure refrigerant discharged from the low-stage compressor (1) is mixed with the branched refrigerant to the internal heat exchanger (4). The refrigeration cycle according to claim 2, which flows in.

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