EP3173714B1 - Refrigerating cycle system and liquid flow-back prevention method - Google Patents
Refrigerating cycle system and liquid flow-back prevention method Download PDFInfo
- Publication number
- EP3173714B1 EP3173714B1 EP16198071.9A EP16198071A EP3173714B1 EP 3173714 B1 EP3173714 B1 EP 3173714B1 EP 16198071 A EP16198071 A EP 16198071A EP 3173714 B1 EP3173714 B1 EP 3173714B1
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- European Patent Office
- Prior art keywords
- refrigerant
- heating element
- electric heating
- pressure vessel
- compressor
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- 239000007788 liquid Substances 0.000 title claims description 100
- 238000000034 method Methods 0.000 title claims description 9
- 230000002265 prevention Effects 0.000 title claims description 8
- 239000003507 refrigerant Substances 0.000 claims description 177
- 238000005485 electric heating Methods 0.000 claims description 103
- 238000010438 heat treatment Methods 0.000 claims description 34
- 230000000994 depressogenic effect Effects 0.000 claims description 4
- 230000020169 heat generation Effects 0.000 claims description 4
- 238000001816 cooling Methods 0.000 description 21
- 238000004378 air conditioning Methods 0.000 description 20
- 238000012423 maintenance Methods 0.000 description 8
- 238000001514 detection method Methods 0.000 description 6
- 239000007791 liquid phase Substances 0.000 description 4
- 238000001704 evaporation Methods 0.000 description 3
- 230000005484 gravity Effects 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 230000002123 temporal effect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000004043 responsiveness Effects 0.000 description 2
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B43/00—Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat
- F25B43/006—Accumulators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B13/00—Compression machines, plants or systems, with reversible cycle
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/01—Heaters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/05—Refrigerant levels
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/04—Refrigerant level
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/21—Temperatures
- F25B2700/2113—Temperatures of a suction accumulator
Definitions
- the present invention relates to a refrigerating cycle system and a liquid flow-back prevention method for preventing liquid flow-back to a compressor.
- a pressure vessel shaped accumulator is connected to the suction side of a compressor that compresses and liquefies a gas refrigerant.
- the accumulator stores gas-liquid mixed refrigerant gas returned from an evaporator to a compressor once to perform gas-liquid separation by gravity therein, and makes the compressor suck only a vaporized refrigerant. Consequently, a phenomenon that a liquefied refrigerant is sucked by the compressor, called so-called liquid flow-back, is prevented, and breakage of the compressor by liquid compression is avoided.
- the accumulator is provided with a liquid level detector at a predetermined liquid level position such that the capacity of a stored liquefied refrigerant does not exceed.
- the liquid level detector is exposed inside a pressure vessel of the accumulator so as to be in contact with a liquefied refrigerant. When the liquid level reaches the position of the liquid level detector, the liquid level detector electrically outputs a detection signal.
- a controller of the air conditioning system takes a measure such as reduction in the rotational speed of the compressor, temporal shutdown of the compressor, and reduction in the opening of an expansion valve, and performs protection operation for lowering the liquid level of the liquefied refrigerant in the accumulator to prevent liquid flow-back.
- a controller of the air conditioning system takes a measure such as reduction in the rotational speed of the compressor, temporal shutdown of the compressor, and reduction in the opening of an expansion valve, and performs protection operation for lowering the liquid level of the liquefied refrigerant in the accumulator to prevent liquid flow-back.
- the present invention has been made in view of the above circumstances, and an object of the invention is to provide a refrigerating cycle system capable of preventing liquid flow-back so as to protect a compressor by a simple and low-cost configuration having high reliability and an excellent maintenance property, and a liquid flow-back prevention method.
- the present invention employs the following solutions.
- a refrigerating cycle system includes: a compressor that compresses a refrigerant; a condenser that condenses compressed refrigerant discharged from the compressor; an expansion valve that expands the compressed refrigerant condensed by the condenser; an evaporator that vaporizes the compressed refrigerant expanded by the expansion valve; and an accumulator that once stores a gas-liquid mixed refrigerant returned from the evaporator to the compressor, separates the gas-liquid mixed refrigerant into a liquefied refrigerant and a vaporized refrigerant, and makes the compressor suck only the vaporized refrigerant, wherein the accumulator includes: a pressure vessel; a refrigerant inflow section that allows the gas-liquid mixed refrigerant to flow into the pressure vessel; a refrigerant outflow section that allows the vaporized refrigerant to flow toward the compressor; and an electric heating element provided at a position of an allowable highest liquid level of
- a heating value of the electric heating element provided in the accumulator namely, power consumption (e.g., a current value) when the electric heating element is adjacent to the liquefied refrigerant having a larger specific heat is larger than power consumption when the electric heating element is adjacent to the vaporized refrigerant having a smaller specific heat. Therefore, when the liquid level of the liquefied refrigerant reaches the height of the electric heating element, the power consumption of the electric heating element is increased. Accordingly, the controller monitors the power consumption of the electric heating element, so that it is possible to determine whether the electric heating element is adjacent to the vaporized refrigerant or the liquefied refrigerant.
- power consumption e.g., a current value
- the controller When the power consumption of the electric heating element reaches a predetermined threshold value, the controller performs the protection operation for lowering the liquid level of the liquefied refrigerant. More specifically, a measure such as reduction in the rotational speed of the compressor, temporal shutdown of the compressor, and reduction in the opening of the expansion valve is taken, and the liquid level of the liquefied refrigerant in the accumulator is lowered. Consequently, it is possible to prevent liquid flow-back to protect the compressor.
- the electric heating element is not a sensor, and therefore it is possible to carry out this simple and low-cost configuration compared with a configuration in which a liquid level detector is provided in the accumulator like a conventional technology. Additionally, a failure rate is reduced, and therefore reliability of the refrigerating cycle system is also improved. Accordingly, with the simple and low-cost configuration having high reliability, it is possible to prevent liquid flow-back from the accumulator to protect the compressor.
- a voltage applied to the electric heating element is set in such a range that a temperature of the vaporized refrigerant is raised by heat generation of the electric heating element when the electric heating element is adjacent to the vaporized refrigerant, and the temperature of the electric heating element is lowered by cold heat of the liquefied refrigerant when the electric heating element is adjacent to the liquefied refrigerant.
- the heating value of the electric heating element can warm the vaporized refrigerant, but cannot warm the liquefied refrigerant, and becomes such a weak heating value that the electric heating element is cooled by the liquefied refrigerant. Even this enables determination between the vaporized refrigerant and the liquefied refrigerant, and therefore rise of the liquid level of the liquefied refrigerant can be detected by required minimum power, and liquid flow-back can be prevented.
- the heating value of the electric heating element is minimized, and therefore the gas-liquid refrigerant in the accumulator is not heated more than necessary. Accordingly, an excessive degree of superheat is not given to the refrigerant by the electric heating element, and the efficiency of the refrigerating cycle system can be prevented from lowering.
- the electric heating element may be a temperature measuring resistor that is utilizable also as a temperature sensor. Consequently, in a case of the refrigerating cycle system provided with the refrigerant temperature sensor in the accumulator, the single electric heating element can be used as both the liquid level detection sensor for the liquefied refrigerant, and the refrigerant temperature sensor, and it is possible to simplify a system configuration to reduce a cost and improve reliability.
- the electric heating element may be inserted into a recess from an outer side of the pressure vessel, the recess being provided in the pressure vessel and being depressed to an inner side from the outer side of the pressure vessel.
- the electric heating element can be detachably mounted from the outside of the pressure vessel of the accumulator, and therefore, for example, in a case where the electric heating element is replaced for maintenance, the refrigerant in the entire refrigerating cycle system does not have to be removed, and it is possible to greatly improve a maintenance property.
- a surface of the electric heating element is immersed with a wide area into the gas-liquid refrigerant through the recess of the pressure vessel, and therefore a heat-exchange rate between the electric heating element and the gas-liquid refrigerant can be increased compared to a case where the electric heating element is simply stuck to the side wall of the pressure vessel.
- a liquid flow-back prevention method includes: providing an electric heating element at a liquid level of a liquefied refrigerant in an accumulator, the accumulator separating a gas-liquid mixed refrigerant returned from an evaporator to a compressor into the liquefied refrigerant and a vaporized refrigerant in a refrigerating cycle system, the liquid level being a maximum storage amount of the liquefied refrigerant; detecting change of a heating value of the electric heating element by change of a current value; and detecting that the liquid level of the liquefied refrigerant reaches an allowable highest liquid level.
- the simple method of providing the electric heating element at the liquid level being the maximum storage amount of the accumulator, and monitoring the change of the power consumption it is possible to reliably detect that the liquid level of the liquefied refrigerant in the accumulator rises, perform operation for lowering this liquid level to prevent liquid flow-back, and protect the compressor.
- FIG. 1 is a circuit diagram illustrating a basic configuration of a heating and cooling air conditioning system 1 (an example of a refrigerating cycle system) according to embodiments of the present invention.
- This heating and cooling air conditioning system 1 is a heat pump type heating and cooling air conditioning system applied to a house, an office, a store, or the like, and has a general configuration including an outdoor unit 2 installed outdoor, and an indoor unit 3 installed indoor.
- a sealed electric compressor 4 that compresses a refrigerant
- a four-way valve 5 that controls flow of the refrigerant
- an outdoor heat exchanger 6 that functions as a condenser for condensing a refrigerant during cooling operation, and functions as an evaporator for evaporating a refrigerant during heating operation
- a receiver drier 7 that removes moisture in the refrigerant
- an expansion valve 8 that expands the refrigerant are connected in this order by a pipeline member 10. From the expansion valve 8, a pipeline member 11 extends to be connected to the indoor unit 3.
- An accumulator 12 is connected to the suction side of the electric compressor 4, and a cooling fan 13 is provided in the outdoor heat exchanger 6. Furthermore, a controller 14 that controls this heating and cooling air conditioning system 1 is installed. The controller 14 controls the electric compressor 4, the four-way valve 5, and the expansion valve 8 by sending control signals S1, S2, S3 to the electric compressor 4, the four-way valve 5, and the expansion valve 8, respectively.
- an indoor heat exchanger 15 that functions as an evaporator for evaporating a refrigerant during cooling operation, and functions as a condenser for condensing a refrigerant during heating operation is incorporated, and a blower fan 16 is provided along with the indoor heat exchanger 15.
- the pipeline member 11 extending from the outdoor unit 2 is connected to one end of the indoor heat exchanger 15, a pipeline member 17 extending from the other end of the indoor heat exchanger 15 is connected to the accumulator 12 through the four-way valve 5 inside the outdoor unit 2.
- the heating and cooling air conditioning system 1 When the four-way valve 5 is at the angle illustrated in FIG. 1 , the heating and cooling air conditioning system 1 is in a cooling operation mode, high temperature and high pressure refrigerant compressed by the electric compressor 4 to be discharged flows into the outdoor heat exchanger 6 through the four-way valve 5, and is heat-exchanged with outside air by the cooling fan 13 to be cooled in the outdoor heat exchanger 6, so that the cooled refrigerant is brought into a liquid phase state. Then, after moisture is removed by the receiver drier 7, the refrigerant is expanded by the expansion valve 8 to be set to suitable pressure.
- the refrigerant flows into the indoor heat exchanger 15 of the indoor unit 3 through the pipeline member 11, and is vaporized in the indoor heat exchanger 15, so that heat of the indoor heat exchanger 15 is eliminated.
- the blower fan 16 operates, so that indoor air is cooled by the indoor heat exchanger 15 to be blown into a room and used for indoor air cooling.
- the refrigerant vaporized by the indoor heat exchanger 15 is sucked into the electric compressor 4 again through the pipeline member 17, the four-way valve 5, and the accumulator 12.
- the heating and cooling air conditioning system 1 enters a heating operation mode. That is, the refrigerant compressed by the electric compressor 4 flows into the indoor heat exchanger 15 through the four-way valve 5 and the pipeline member 17, is heat-exchanged with indoor air in the indoor heat exchanger 15 by the blower fan 16 to be cooled, and is brought into the liquid phase state. At this time, air warmed by heat exchange with the refrigerant is brown into the room by the blower fan 16 to be used for indoor air heating. Then, the refrigerant that passes through the indoor heat exchanger 15 to be brought into the liquid phase state is expanded by the expansion valve 8, and is set to suitable pressure. Thereafter, after moisture is removed by the receiver drier 7, the refrigerant flows into the outdoor heat exchanger 6, is vaporized in the outdoor heat exchanger 6 to release heat to the outside, and is sucked into the electric compressor 4 again through the accumulator 12.
- FIG. 2 is a longitudinal sectional view illustrating a first embodiment of the accumulator 12.
- the accumulator 12 once stores a gas-liquid mixed refrigerant returned from the outdoor heat exchanger 6 or the indoor heat exchanger 15 to the electric compressor 4, and performs gas-liquid separation by gravity therein, makes the electric compressor 4 suck only a vaporized refrigerant, and stores a predetermined amount of liquefied refrigerant R.
- the accumulator 12 includes a tank-shaped pressure vessel 20 having predetermined capacity, a pipe-shaped refrigerant inflow section 21 and a pipe-shaped refrigerant outflow section 22 provided at a top of the pressure vessel 20, an electric heating element 23, and a temperature sensor 24.
- the refrigerant inflow section 21 is a short pipe member bent at a right angle, an inlet opening 21a provided in one end of the refrigerant inflow section 21 is connected to the four-way valve 5, and an outlet opening 21b provided in the other end of the refrigerant inflow section 21 penetrates a top board of the pressure vessel 20 to be opened downward at an upper section of the inside of the pressure vessel 20.
- the refrigerant outflow section 22 is a U-shaped pipe member longer than the refrigerant inflow section 21, and an inlet opening 22a provided in one end of the refrigerant outflow section 22 is opened upward at an upper section of the inside of the pressure vessel 20, and the other end of the refrigerant outflow section 22 penetrates the top board of the pressure vessel 20, an outlet opening 22b provided in this end is connected to the electric compressor 4.
- An intermediate section of the refrigerant outflow section 22 is deeply curved in a U-shape so as to protrude downward the inside the pressure vessel 20, and a curve section is located near a bottom of the pressure vessel 20.
- the height H2 of the inlet opening 22a of the refrigerant outflow section 22 is set to be lower than HI.
- the height H3 of the electric heating element 23 and the height H3 of the temperature sensor 24 are each set to further lower than H2. That is, the relation of these heights are HI > H2 > H3.
- the installation height H3 of each of the electric heating element 23 and the temperature sensor 24 is the allowable highest liquid level of the liquefied refrigerant R inside the pressure vessel 20.
- the gas-liquid mixed refrigerant returned from the outdoor heat exchanger 6 or the indoor heat exchanger 15 to the electric compressor 4 flows from the inlet opening 21a of the refrigerant inflow section 21, and flows down from the outlet opening 21b to enter the pressure vessel 20.
- This gas-liquid mixed refrigerant is separated by gravity, and the liquefied refrigerant R which is a liquid phase of the gas-liquid mixed refrigerant is stored in the pressure vessel 20 along with lubricant oil.
- the liquid level H4 of the liquefied refrigerant R stored in the pressure vessel 20 is adjusted so as to be lower than the height H3 of each of the electric heating element 23 and the temperature sensor 24 during normal operation of the heating and cooling air conditioning system 1. Therefore, during normal operation, the inlet opening 22a of the refrigerant outflow section 22 sufficiently protrudes above the liquid level of the liquefied refrigerant R.
- a vaporized refrigerant that is separated from the gas-liquid mixed refrigerant enters the refrigerant outflow section 22 from the inlet opening 22a, and flows out from the outlet opening 22b to be sucked into the electric compressor 4.
- the liquefied refrigerant R is stored in the pressure vessel 20, and only the vaporized refrigerant is sucked into the electric compressor 4, so that the liquefied refrigerant R is never sucked into the electric compressor 4.
- a recess 20b depressed to the inner side from the outer side of the pressure vessel 20 is formed on a side wall 20a forming a side surface of the pressure vessel 20, a recess 20b depressed to the inner side from the outer side of the pressure vessel 20 is formed.
- This recess 20b is formed by, for example, boring a through hole in the side wall 20a, and inserting a pipe material 20c having a closed tip into this through hole by a predetermined length to be welded. Then, the electric heating element 23 and the temperature sensor 24 are inserted into this recess 20b from the outer side of the pressure vessel 20.
- the temperature sensor 24 is not an essential element for carrying out the present invention, and therefore can be omitted.
- a pressure sensor may be provided along with the temperature sensor 24.
- the pressure sensor is provided, so that the pressure of the inside of the pressure vessel 20 is detected, and it is possible to determine to some extent whether or not the liquefied refrigerant R exists near the installation heights H3 of the electric heating element 23 and the temperature sensor 24, from a difference between the saturation evaporation temperature of the liquefied refrigerant R under the detected pressure, and an actual temperature measured by the temperature sensor 24.
- a voltage applied to the electric heating element 23 is set to such a constant voltage that the temperature of the vaporized refrigerant is raised by heat generation of the electric heating element 23 when the electric heating element 23 is adjacent to the vaporized refrigerant, and the temperature of the electric heating element 23 is lowered by cold heat of the liquefied refrigerant R when the electric heating element 23 is adjacent to the liquefied refrigerant R.
- the electric heating element 23 when the liquid level of the liquefied refrigerant R stored in the pressure vessel 20 is lower than the height H3 of the electric heating element 23, the electric heating element 23 is adjacent to the vaporized refrigerant, and the vaporized refrigerant in the pressure vessel 20 is warmed by heat generated by the electric heating element 23.
- the electric heating element 23 In a case where the liquid level of the liquefied refrigerant R reaches the height H3 of the electric heating element 23, the electric heating element 23 is adjacent to the liquefied refrigerant R, the electric heating element 23 is cooled by the cold heat of the liquefied refrigerant R having larger specific heat than the vaporized refrigerant.
- the controller 14 detects the above change of the heating value of the electric heating element 23 by change of power consumption. As illustrated in FIG. 3 , in a case where the power consumption reaches a predetermined threshold value A, protection operation for lowering the liquid level of the liquefied refrigerant R is performed.
- the heating value of the electric heating element 23 to which a constant voltage is supplied namely, a current value starts rising from a steady-state value N.
- a current amount required for generating the heat of the electric heating element 23 when the electric heating element 23 is adjacent to the liquefied refrigerant having a larger specific heat is larger than a current required for generating the heat of the electric heating element 23 when the electric heating element 23 is adjacent to the vaporized refrigerant R having a smaller specific heat.
- the controller 14 monitors the current amount of the electric heating element 23, so that it is possible to determine whether the electric heating element 23 is adjacent to the vaporized refrigerant or the liquefied refrigerant R.
- the controller 14 starts the protection operation. More specifically, a measure such as reduction in the rotational speed of the electric compressor 4 or temporal shutdown of the electric compressor 4, and reduction in the opening of the expansion valve 8 is taken (suitably selected in accordance with an operation state), and the liquid level of the liquefied refrigerant R in the accumulator 12 is lowered. Consequently, it is possible to prevent liquid flow-back to protect the electric compressor 4.
- the controller 14 ends the protection operation.
- the reason why the threshold value A when the protection operation is started is set to be lower than the threshold value B when the protection operation is ended is because when the current value rises or lowers near the threshold value A, the protection operation is prevented from frequently repeating the start and the end (hysteresis).
- the liquid level of the liquefied refrigerant R lowers to an initial value, and the current value is returned to the steady-state value N.
- the current value rises and lowers between the steady-state value N and the threshold value A.
- the electric heating element 23 is provided at the position of the allowable highest liquid level H3 of the liquefied refrigerant R in the accumulator 12 that makes the electric compressor 4 suck only the vaporized refrigerant, the change of the heating value of the electric heating element 23 is detected as the change of the power consumption by the controller 14, and the protection operation for lowering the liquid level is performed in a case where the power consumption reaches the predetermined threshold value A.
- the electric heating element 23 is not a sensor, and therefore it is possible to carry out this simple and low-cost configuration compared with a configuration in which a liquid level detector is provided in the accumulator 12 like a conventional technology. Additionally, a failure rate as a liquid level detection unit is reduced, and therefore it is possible to greatly improve reliability of the heating and cooling air conditioning system 1. Accordingly, with the simple and low-cost configuration having high reliability, it is possible to prevent liquid flow-back from the accumulator 12 to protect the electric compressor 4.
- the voltage applied to the electric heating element 23 is set in such a range that the temperature of the vaporized refrigerant is raised by the heat generation of the electric heating element 23 when the electric heating element 23 is adjacent to the vaporized refrigerant, and the temperature of the electric heating element 23 is lowered by the cold heat of the liquefied refrigerant R when the electric heating element 23 is adjacent to the liquefied refrigerant R.
- the heating value of the electric heating element 23 can warm the vaporized refrigerant, but cannot warm the liquefied refrigerant, and becomes such a weak heating value that the electric heating element 23 is cooled. Even this enables sufficient determination between the vaporized refrigerant and the liquefied refrigerant R, and therefore rise of the liquid level of the liquefied refrigerant R can be detected by required minimum power, and liquid flow-back can be prevented.
- the heating value of the electric heating element 23 is minimized, and therefore the gas-liquid refrigerant in the accumulator 12 is not heated more than necessary. Accordingly, an excessive degree of superheat is not given to the refrigerant by the electric heating element 23, and the efficiency of the heating and cooling air conditioning system 1 can be prevented from lowering.
- the electric heating element 23 is inserted, from the outer side, into the recess 20b provided in the side wall 20a of the accumulator 12 (pressure vessel 20) and depressed to the inner side from the outer side of the pressure vessel 20.
- the electric heating element 23 can be detachably mounted from the outside of the pressure vessel 20, and therefore, for example, in a case where the electric heating element 23 is replaced for maintenance, the refrigerant in the entire heating and cooling air conditioning system 1 does not have to be removed, and it is possible to greatly improve a maintenance property.
- a surface of the electric heating element 23 is immersed with a wide area into the gas-liquid refrigerant through the recess 20b of the pressure vessel 20, and therefore a heat-exchange rate between the electric heating element 23 and the gas-liquid refrigerant can be increased compared to a case where the electric heating element 23 is simply stuck to the side wall 20a of the pressure vessel 20.
- FIG. 4 is a longitudinal sectional view illustrating a second embodiment of an accumulator.
- This accumulator 12A is different from the accumulator 12 of the first embodiment illustrated in FIG. 2 in two points, namely in that an electric heating element 23A is a temperature measuring resistor which is utilizable also as a temperature sensor, and the temperature sensor 24 illustrated in FIG. 2 is not provided.
- Other components are the same as the components of the accumulator 12 illustrated in FIG. 2 , and therefore are denoted by the same reference numerals, and description thereof will be omitted.
- a constant voltage is supplied to the electric heating element 23A by use of a temperature measuring resistor as the electric heating element 23A, similarly to the first embodiment, so that the electric heating element 23A can be used as a liquid level detection sensor of a liquefied refrigerant R.
- temperature data detected by the electric heating element 23A is sent to a controller 14, so that the temperature of a refrigerant can be detected.
- the single electric heating element 23A can be used as both the liquid level detection sensor for the liquefied refrigerant R, and the refrigerant temperature sensor, and it is possible to simplify a system configuration to reduce a cost and improve reliability.
- the recess 20b into which the electric heating element 23, 23A is inserted is not always provided in the side wall 20a of the pressure vessel 20.
- the recess 20b may be formed so as to be suspended toward the inner section of the pressure vessel 20 of the top board of the pressure vessel 20, and the electric heating element 23, 23A may be inserted into the inner section.
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Description
- The present invention relates to a refrigerating cycle system and a liquid flow-back prevention method for preventing liquid flow-back to a compressor.
- In an air conditioning system used in a store, an office, a house, or the like, a pressure vessel shaped accumulator is connected to the suction side of a compressor that compresses and liquefies a gas refrigerant. The accumulator stores gas-liquid mixed refrigerant gas returned from an evaporator to a compressor once to perform gas-liquid separation by gravity therein, and makes the compressor suck only a vaporized refrigerant. Consequently, a phenomenon that a liquefied refrigerant is sucked by the compressor, called so-called liquid flow-back, is prevented, and breakage of the compressor by liquid compression is avoided.
- As disclosed in Japanese Unexamined Patent Application, Publication No.
2001-27460 claim 1, the accumulator is provided with a liquid level detector at a predetermined liquid level position such that the capacity of a stored liquefied refrigerant does not exceed. The liquid level detector is exposed inside a pressure vessel of the accumulator so as to be in contact with a liquefied refrigerant. When the liquid level reaches the position of the liquid level detector, the liquid level detector electrically outputs a detection signal. - When receiving this detection signal, a controller of the air conditioning system takes a measure such as reduction in the rotational speed of the compressor, temporal shutdown of the compressor, and reduction in the opening of an expansion valve, and performs protection operation for lowering the liquid level of the liquefied refrigerant in the accumulator to prevent liquid flow-back. In an air conditioning system of Japanese Unexamined Patent Application, Publication No.
2001-27460 - {PTL 1}
Japanese Unexamined Patent Application, Publication No.2001-27460 - However, as disclosed in Japanese Unexamined Patent Application, Publication No.
2001-27460 - The present invention has been made in view of the above circumstances, and an object of the invention is to provide a refrigerating cycle system capable of preventing liquid flow-back so as to protect a compressor by a simple and low-cost configuration having high reliability and an excellent maintenance property, and a liquid flow-back prevention method.
- In order to solve the above problem, the present invention employs the following solutions.
- A refrigerating cycle system according to the present invention includes: a compressor that compresses a refrigerant; a condenser that condenses compressed refrigerant discharged from the compressor; an expansion valve that expands the compressed refrigerant condensed by the condenser; an evaporator that vaporizes the compressed refrigerant expanded by the expansion valve; and an accumulator that once stores a gas-liquid mixed refrigerant returned from the evaporator to the compressor, separates the gas-liquid mixed refrigerant into a liquefied refrigerant and a vaporized refrigerant, and makes the compressor suck only the vaporized refrigerant, wherein the accumulator includes: a pressure vessel; a refrigerant inflow section that allows the gas-liquid mixed refrigerant to flow into the pressure vessel; a refrigerant outflow section that allows the vaporized refrigerant to flow toward the compressor; and an electric heating element provided at a position of an allowable highest liquid level of the liquefied refrigerant in the pressure vessel, of the pressure vessel, the refrigerating cycle system further including a controller that detects change of a heating value of the electric heating element by change of power consumption, and performs protection operation for lowering the liquid level of the liquefied refrigerant in a case where the power consumption reaches a predetermined threshold value.
- In a case of the above configuration, a heating value of the electric heating element provided in the accumulator, namely, power consumption (e.g., a current value) when the electric heating element is adjacent to the liquefied refrigerant having a larger specific heat is larger than power consumption when the electric heating element is adjacent to the vaporized refrigerant having a smaller specific heat. Therefore, when the liquid level of the liquefied refrigerant reaches the height of the electric heating element, the power consumption of the electric heating element is increased. Accordingly, the controller monitors the power consumption of the electric heating element, so that it is possible to determine whether the electric heating element is adjacent to the vaporized refrigerant or the liquefied refrigerant.
- When the power consumption of the electric heating element reaches a predetermined threshold value, the controller performs the protection operation for lowering the liquid level of the liquefied refrigerant. More specifically, a measure such as reduction in the rotational speed of the compressor, temporal shutdown of the compressor, and reduction in the opening of the expansion valve is taken, and the liquid level of the liquefied refrigerant in the accumulator is lowered. Consequently, it is possible to prevent liquid flow-back to protect the compressor.
- The electric heating element is not a sensor, and therefore it is possible to carry out this simple and low-cost configuration compared with a configuration in which a liquid level detector is provided in the accumulator like a conventional technology. Additionally, a failure rate is reduced, and therefore reliability of the refrigerating cycle system is also improved. Accordingly, with the simple and low-cost configuration having high reliability, it is possible to prevent liquid flow-back from the accumulator to protect the compressor.
- In the above configuration, it is considered that a voltage applied to the electric heating element is set in such a range that a temperature of the vaporized refrigerant is raised by heat generation of the electric heating element when the electric heating element is adjacent to the vaporized refrigerant, and the temperature of the electric heating element is lowered by cold heat of the liquefied refrigerant when the electric heating element is adjacent to the liquefied refrigerant.
- Consequently, the heating value of the electric heating element can warm the vaporized refrigerant, but cannot warm the liquefied refrigerant, and becomes such a weak heating value that the electric heating element is cooled by the liquefied refrigerant. Even this enables determination between the vaporized refrigerant and the liquefied refrigerant, and therefore rise of the liquid level of the liquefied refrigerant can be detected by required minimum power, and liquid flow-back can be prevented.
- Moreover, the heating value of the electric heating element is minimized, and therefore the gas-liquid refrigerant in the accumulator is not heated more than necessary. Accordingly, an excessive degree of superheat is not given to the refrigerant by the electric heating element, and the efficiency of the refrigerating cycle system can be prevented from lowering.
- In the above configuration, the electric heating element may be a temperature measuring resistor that is utilizable also as a temperature sensor. Consequently, in a case of the refrigerating cycle system provided with the refrigerant temperature sensor in the accumulator, the single electric heating element can be used as both the liquid level detection sensor for the liquefied refrigerant, and the refrigerant temperature sensor, and it is possible to simplify a system configuration to reduce a cost and improve reliability.
- In the above configuration, the electric heating element may be inserted into a recess from an outer side of the pressure vessel, the recess being provided in the pressure vessel and being depressed to an inner side from the outer side of the pressure vessel.
- According to this configuration, the electric heating element can be detachably mounted from the outside of the pressure vessel of the accumulator, and therefore, for example, in a case where the electric heating element is replaced for maintenance, the refrigerant in the entire refrigerating cycle system does not have to be removed, and it is possible to greatly improve a maintenance property.
- Moreover, a surface of the electric heating element is immersed with a wide area into the gas-liquid refrigerant through the recess of the pressure vessel, and therefore a heat-exchange rate between the electric heating element and the gas-liquid refrigerant can be increased compared to a case where the electric heating element is simply stuck to the side wall of the pressure vessel.
- Consequently, when the liquid level of the liquefied refrigerant in the pressure vessel rises to reach the height of the electric heating element, time until the power consumption of the electric heating element is increased is shortened. Accordingly, time until the protection operation by the controller is started is also shortened. Therefore, it is possible to improve control responsiveness to prevent liquid flow-back, and reliably protect the compressor.
- That is, a liquid flow-back prevention method according to the present invention includes: providing an electric heating element at a liquid level of a liquefied refrigerant in an accumulator, the accumulator separating a gas-liquid mixed refrigerant returned from an evaporator to a compressor into the liquefied refrigerant and a vaporized refrigerant in a refrigerating cycle system, the liquid level being a maximum storage amount of the liquefied refrigerant; detecting change of a heating value of the electric heating element by change of a current value; and detecting that the liquid level of the liquefied refrigerant reaches an allowable highest liquid level.
- According to the above liquid flow-back prevention method, by the simple method of providing the electric heating element at the liquid level being the maximum storage amount of the accumulator, and monitoring the change of the power consumption, it is possible to reliably detect that the liquid level of the liquefied refrigerant in the accumulator rises, perform operation for lowering this liquid level to prevent liquid flow-back, and protect the compressor.
- As described above, according to the refrigerating cycle system and the liquid flow-back prevention method according to the present invention, it is possible to prevent liquid flow-back to protect a compressor by a simple and low-cost configuration having high reliability and an excellent maintenance property.
-
-
FIG. 1 is a circuit diagram illustrating a basic configuration of a heating and cooling air conditioning system according to embodiments of the present invention; -
FIG. 2 is a longitudinal sectional view of an accumulator illustrating a first embodiment of the present invention; -
FIG. 3 is a graph illustrating an example of change of a current value in an electric heating element; and -
FIG. 4 is a longitudinal sectional view of an accumulator illustrating a second embodiment of the present invention. - Hereinafter, embodiments according to the present invention will be described with reference to
FIG. 1 to FIG. 3 . -
FIG. 1 is a circuit diagram illustrating a basic configuration of a heating and cooling air conditioning system 1 (an example of a refrigerating cycle system) according to embodiments of the present invention. This heating and coolingair conditioning system 1 is a heat pump type heating and cooling air conditioning system applied to a house, an office, a store, or the like, and has a general configuration including anoutdoor unit 2 installed outdoor, and anindoor unit 3 installed indoor. - Inside the
outdoor unit 2, a sealed electric compressor 4 (compressor) that compresses a refrigerant, a four-way valve 5 that controls flow of the refrigerant, an outdoor heat exchanger 6 that functions as a condenser for condensing a refrigerant during cooling operation, and functions as an evaporator for evaporating a refrigerant during heating operation, areceiver drier 7 that removes moisture in the refrigerant, and anexpansion valve 8 that expands the refrigerant are connected in this order by apipeline member 10. From theexpansion valve 8, apipeline member 11 extends to be connected to theindoor unit 3. - An
accumulator 12 is connected to the suction side of theelectric compressor 4, and acooling fan 13 is provided in the outdoor heat exchanger 6. Furthermore, acontroller 14 that controls this heating and coolingair conditioning system 1 is installed. Thecontroller 14 controls theelectric compressor 4, the four-way valve 5, and theexpansion valve 8 by sending control signals S1, S2, S3 to theelectric compressor 4, the four-way valve 5, and theexpansion valve 8, respectively. - On the other hand, inside the
indoor unit 3, anindoor heat exchanger 15 that functions as an evaporator for evaporating a refrigerant during cooling operation, and functions as a condenser for condensing a refrigerant during heating operation is incorporated, and ablower fan 16 is provided along with theindoor heat exchanger 15. Thepipeline member 11 extending from theoutdoor unit 2 is connected to one end of theindoor heat exchanger 15, apipeline member 17 extending from the other end of theindoor heat exchanger 15 is connected to theaccumulator 12 through the four-way valve 5 inside theoutdoor unit 2. - When the four-
way valve 5 is at the angle illustrated inFIG. 1 , the heating and coolingair conditioning system 1 is in a cooling operation mode, high temperature and high pressure refrigerant compressed by theelectric compressor 4 to be discharged flows into the outdoor heat exchanger 6 through the four-way valve 5, and is heat-exchanged with outside air by thecooling fan 13 to be cooled in the outdoor heat exchanger 6, so that the cooled refrigerant is brought into a liquid phase state. Then, after moisture is removed by thereceiver drier 7, the refrigerant is expanded by theexpansion valve 8 to be set to suitable pressure. Thereafter, the refrigerant flows into theindoor heat exchanger 15 of theindoor unit 3 through thepipeline member 11, and is vaporized in theindoor heat exchanger 15, so that heat of theindoor heat exchanger 15 is eliminated. At the same time, theblower fan 16 operates, so that indoor air is cooled by theindoor heat exchanger 15 to be blown into a room and used for indoor air cooling. The refrigerant vaporized by theindoor heat exchanger 15 is sucked into theelectric compressor 4 again through thepipeline member 17, the four-way valve 5, and theaccumulator 12. - When the four-
way valve 5 rotates clockwise or counterclockwise by 90 degrees from the angle illustrated inFIG. 1 , the heating and coolingair conditioning system 1 enters a heating operation mode. That is, the refrigerant compressed by theelectric compressor 4 flows into theindoor heat exchanger 15 through the four-way valve 5 and thepipeline member 17, is heat-exchanged with indoor air in theindoor heat exchanger 15 by theblower fan 16 to be cooled, and is brought into the liquid phase state. At this time, air warmed by heat exchange with the refrigerant is brown into the room by theblower fan 16 to be used for indoor air heating. Then, the refrigerant that passes through theindoor heat exchanger 15 to be brought into the liquid phase state is expanded by theexpansion valve 8, and is set to suitable pressure. Thereafter, after moisture is removed by the receiver drier 7, the refrigerant flows into the outdoor heat exchanger 6, is vaporized in the outdoor heat exchanger 6 to release heat to the outside, and is sucked into theelectric compressor 4 again through theaccumulator 12. -
FIG. 2 is a longitudinal sectional view illustrating a first embodiment of theaccumulator 12. - The
accumulator 12 once stores a gas-liquid mixed refrigerant returned from the outdoor heat exchanger 6 or theindoor heat exchanger 15 to theelectric compressor 4, and performs gas-liquid separation by gravity therein, makes theelectric compressor 4 suck only a vaporized refrigerant, and stores a predetermined amount of liquefied refrigerant R. Theaccumulator 12 includes a tank-shapedpressure vessel 20 having predetermined capacity, a pipe-shapedrefrigerant inflow section 21 and a pipe-shapedrefrigerant outflow section 22 provided at a top of thepressure vessel 20, anelectric heating element 23, and atemperature sensor 24. - The
refrigerant inflow section 21 is a short pipe member bent at a right angle, aninlet opening 21a provided in one end of therefrigerant inflow section 21 is connected to the four-way valve 5, and anoutlet opening 21b provided in the other end of therefrigerant inflow section 21 penetrates a top board of thepressure vessel 20 to be opened downward at an upper section of the inside of thepressure vessel 20. - The
refrigerant outflow section 22 is a U-shaped pipe member longer than therefrigerant inflow section 21, and aninlet opening 22a provided in one end of therefrigerant outflow section 22 is opened upward at an upper section of the inside of thepressure vessel 20, and the other end of therefrigerant outflow section 22 penetrates the top board of thepressure vessel 20, anoutlet opening 22b provided in this end is connected to theelectric compressor 4. An intermediate section of therefrigerant outflow section 22 is deeply curved in a U-shape so as to protrude downward the inside thepressure vessel 20, and a curve section is located near a bottom of thepressure vessel 20. - When the height of the outlet opening 21b of the
refrigerant inflow section 21 inside thepressure vessel 20 is denoted by HI, the height H2 of the inlet opening 22a of therefrigerant outflow section 22 is set to be lower than HI. The height H3 of theelectric heating element 23 and the height H3 of thetemperature sensor 24 are each set to further lower than H2. That is, the relation of these heights are HI > H2 > H3. The installation height H3 of each of theelectric heating element 23 and thetemperature sensor 24 is the allowable highest liquid level of the liquefied refrigerant R inside thepressure vessel 20. - In the
accumulator 12, the gas-liquid mixed refrigerant returned from the outdoor heat exchanger 6 or theindoor heat exchanger 15 to theelectric compressor 4 flows from the inlet opening 21a of therefrigerant inflow section 21, and flows down from the outlet opening 21b to enter thepressure vessel 20. This gas-liquid mixed refrigerant is separated by gravity, and the liquefied refrigerant R which is a liquid phase of the gas-liquid mixed refrigerant is stored in thepressure vessel 20 along with lubricant oil. Thus, the liquid level H4 of the liquefied refrigerant R stored in thepressure vessel 20 is adjusted so as to be lower than the height H3 of each of theelectric heating element 23 and thetemperature sensor 24 during normal operation of the heating and coolingair conditioning system 1. Therefore, during normal operation, the inlet opening 22a of therefrigerant outflow section 22 sufficiently protrudes above the liquid level of the liquefied refrigerant R. - A vaporized refrigerant that is separated from the gas-liquid mixed refrigerant enters the
refrigerant outflow section 22 from theinlet opening 22a, and flows out from the outlet opening 22b to be sucked into theelectric compressor 4. Thus, the liquefied refrigerant R is stored in thepressure vessel 20, and only the vaporized refrigerant is sucked into theelectric compressor 4, so that the liquefied refrigerant R is never sucked into theelectric compressor 4. - On a
side wall 20a forming a side surface of thepressure vessel 20, arecess 20b depressed to the inner side from the outer side of thepressure vessel 20 is formed. Thisrecess 20b is formed by, for example, boring a through hole in theside wall 20a, and inserting apipe material 20c having a closed tip into this through hole by a predetermined length to be welded. Then, theelectric heating element 23 and thetemperature sensor 24 are inserted into thisrecess 20b from the outer side of thepressure vessel 20. - The
temperature sensor 24 is not an essential element for carrying out the present invention, and therefore can be omitted. Alternatively, a pressure sensor may be provided along with thetemperature sensor 24. The pressure sensor is provided, so that the pressure of the inside of thepressure vessel 20 is detected, and it is possible to determine to some extent whether or not the liquefied refrigerant R exists near the installation heights H3 of theelectric heating element 23 and thetemperature sensor 24, from a difference between the saturation evaporation temperature of the liquefied refrigerant R under the detected pressure, and an actual temperature measured by thetemperature sensor 24. - During operation of the heating and cooling
air conditioning system 1 thus configured, power is supplied to theelectric heating element 23 from the controller 14 (or a power source not illustrated) through aharness 23a. At this time, a voltage applied to theelectric heating element 23 is set to such a constant voltage that the temperature of the vaporized refrigerant is raised by heat generation of theelectric heating element 23 when theelectric heating element 23 is adjacent to the vaporized refrigerant, and the temperature of theelectric heating element 23 is lowered by cold heat of the liquefied refrigerant R when theelectric heating element 23 is adjacent to the liquefied refrigerant R. - That is, as illustrated in
FIG. 2 , when the liquid level of the liquefied refrigerant R stored in thepressure vessel 20 is lower than the height H3 of theelectric heating element 23, theelectric heating element 23 is adjacent to the vaporized refrigerant, and the vaporized refrigerant in thepressure vessel 20 is warmed by heat generated by theelectric heating element 23. In a case where the liquid level of the liquefied refrigerant R reaches the height H3 of theelectric heating element 23, theelectric heating element 23 is adjacent to the liquefied refrigerant R, theelectric heating element 23 is cooled by the cold heat of the liquefied refrigerant R having larger specific heat than the vaporized refrigerant. - The
controller 14 detects the above change of the heating value of theelectric heating element 23 by change of power consumption. As illustrated inFIG. 3 , in a case where the power consumption reaches a predetermined threshold value A, protection operation for lowering the liquid level of the liquefied refrigerant R is performed. - For example, when the liquid level of the liquefied refrigerant R in the
pressure vessel 20 of theaccumulator 12 rises to reach the height H3 of theelectric heating element 23 at a time point when time T1 elapses from operation start, the heating value of theelectric heating element 23 to which a constant voltage is supplied, namely, a current value starts rising from a steady-state value N. This is because a current amount required for generating the heat of theelectric heating element 23 when theelectric heating element 23 is adjacent to the liquefied refrigerant having a larger specific heat is larger than a current required for generating the heat of theelectric heating element 23 when theelectric heating element 23 is adjacent to the vaporized refrigerant R having a smaller specific heat. Accordingly, thecontroller 14 monitors the current amount of theelectric heating element 23, so that it is possible to determine whether theelectric heating element 23 is adjacent to the vaporized refrigerant or the liquefied refrigerant R. - When the current value reaches the predetermined threshold value A at time T2, the
controller 14 starts the protection operation. More specifically, a measure such as reduction in the rotational speed of theelectric compressor 4 or temporal shutdown of theelectric compressor 4, and reduction in the opening of theexpansion valve 8 is taken (suitably selected in accordance with an operation state), and the liquid level of the liquefied refrigerant R in theaccumulator 12 is lowered. Consequently, it is possible to prevent liquid flow-back to protect theelectric compressor 4. - Thereafter, when the current value exceeds a peak value and lowers, and drops to a threshold value B lower than the threshold value A at time T3, the
controller 14 ends the protection operation. Thus, the reason why the threshold value A when the protection operation is started is set to be lower than the threshold value B when the protection operation is ended is because when the current value rises or lowers near the threshold value A, the protection operation is prevented from frequently repeating the start and the end (hysteresis). - In
FIG. 3 , at time T4, the liquid level of the liquefied refrigerant R lowers to an initial value, and the current value is returned to the steady-state value N. However, during actual operation, the current value rises and lowers between the steady-state value N and the threshold value A. - Thus, in the heating and cooling
air conditioning system 1 of this embodiment, gas-liquid separation of the gas-liquid mixed refrigerant sucked into theelectric compressor 4 is performed, theelectric heating element 23 is provided at the position of the allowable highest liquid level H3 of the liquefied refrigerant R in theaccumulator 12 that makes theelectric compressor 4 suck only the vaporized refrigerant, the change of the heating value of theelectric heating element 23 is detected as the change of the power consumption by thecontroller 14, and the protection operation for lowering the liquid level is performed in a case where the power consumption reaches the predetermined threshold value A. - In a case of this configuration, the
electric heating element 23 is not a sensor, and therefore it is possible to carry out this simple and low-cost configuration compared with a configuration in which a liquid level detector is provided in theaccumulator 12 like a conventional technology. Additionally, a failure rate as a liquid level detection unit is reduced, and therefore it is possible to greatly improve reliability of the heating and coolingair conditioning system 1. Accordingly, with the simple and low-cost configuration having high reliability, it is possible to prevent liquid flow-back from theaccumulator 12 to protect theelectric compressor 4. - The voltage applied to the
electric heating element 23 is set in such a range that the temperature of the vaporized refrigerant is raised by the heat generation of theelectric heating element 23 when theelectric heating element 23 is adjacent to the vaporized refrigerant, and the temperature of theelectric heating element 23 is lowered by the cold heat of the liquefied refrigerant R when theelectric heating element 23 is adjacent to the liquefied refrigerant R. - Consequently, the heating value of the
electric heating element 23 can warm the vaporized refrigerant, but cannot warm the liquefied refrigerant, and becomes such a weak heating value that theelectric heating element 23 is cooled. Even this enables sufficient determination between the vaporized refrigerant and the liquefied refrigerant R, and therefore rise of the liquid level of the liquefied refrigerant R can be detected by required minimum power, and liquid flow-back can be prevented. - Moreover, the heating value of the
electric heating element 23 is minimized, and therefore the gas-liquid refrigerant in theaccumulator 12 is not heated more than necessary. Accordingly, an excessive degree of superheat is not given to the refrigerant by theelectric heating element 23, and the efficiency of the heating and coolingair conditioning system 1 can be prevented from lowering. - The
electric heating element 23 is inserted, from the outer side, into therecess 20b provided in theside wall 20a of the accumulator 12 (pressure vessel 20) and depressed to the inner side from the outer side of thepressure vessel 20. - According to this structure, the
electric heating element 23 can be detachably mounted from the outside of thepressure vessel 20, and therefore, for example, in a case where theelectric heating element 23 is replaced for maintenance, the refrigerant in the entire heating and coolingair conditioning system 1 does not have to be removed, and it is possible to greatly improve a maintenance property. - Moreover, a surface of the
electric heating element 23 is immersed with a wide area into the gas-liquid refrigerant through therecess 20b of thepressure vessel 20, and therefore a heat-exchange rate between theelectric heating element 23 and the gas-liquid refrigerant can be increased compared to a case where theelectric heating element 23 is simply stuck to theside wall 20a of thepressure vessel 20. - Consequently, when the liquid level of the liquefied refrigerant R in the
pressure vessel 20 rises to reach the height H3 of theelectric heating element 23, time until the power consumption of theelectric heating element 23 is increased (time between T1 and T2 inFIG. 3 ) is shortened. Accordingly, time until the protection operation by thecontroller 14 is started is also shortened. Therefore, it is possible to improve control responsiveness to prevent liquid flow-back, and reliably protect theelectric compressor 4. -
FIG. 4 is a longitudinal sectional view illustrating a second embodiment of an accumulator. - This
accumulator 12A is different from theaccumulator 12 of the first embodiment illustrated inFIG. 2 in two points, namely in that anelectric heating element 23A is a temperature measuring resistor which is utilizable also as a temperature sensor, and thetemperature sensor 24 illustrated inFIG. 2 is not provided. Other components are the same as the components of theaccumulator 12 illustrated inFIG. 2 , and therefore are denoted by the same reference numerals, and description thereof will be omitted. - Thus, a constant voltage is supplied to the
electric heating element 23A by use of a temperature measuring resistor as theelectric heating element 23A, similarly to the first embodiment, so that theelectric heating element 23A can be used as a liquid level detection sensor of a liquefied refrigerant R. - In a case of a heating and cooling air conditioning system in which a refrigerant temperature sensor is provided in the
accumulator 12A, temperature data detected by theelectric heating element 23A is sent to acontroller 14, so that the temperature of a refrigerant can be detected. - That is, the single
electric heating element 23A can be used as both the liquid level detection sensor for the liquefied refrigerant R, and the refrigerant temperature sensor, and it is possible to simplify a system configuration to reduce a cost and improve reliability. - As described above, according to the refrigerating cycle system and the liquid flow-back prevention method of this embodiment, it is possible to prevent liquid flow-back to protect a compressor by a simple and low-cost configuration having high reliability and an excellent maintenance property.
- The present invention is not limited to only the configurations of the above embodiments, changes or modifications can be suitably added to the embodiments, and embodiments including the changes or the modifications are included in the technical scope of the present invention.
- For example, the
recess 20b into which theelectric heating element side wall 20a of thepressure vessel 20. For example, therecess 20b may be formed so as to be suspended toward the inner section of thepressure vessel 20 of the top board of thepressure vessel 20, and theelectric heating element -
- 1
- Heating and cooling air conditioning system (refrigerating cycle system)
- 2
- Outdoor unit
- 3
- Indoor unit
- 4
- Electric compressor (compressor)
- 5
- Four-way valve
- 6
- Outdoor heat exchanger (condenser)
- 7
- Receiver drier
- 8
- Expansion valve
- 12, 12A
- Accumulator
- 14
- Controller
- 15
- Indoor heat exchanger (evaporator)
- 20
- Pressure vessel
- 20a
- Side wall of pressure vessel
- 20b
- Recess
- 20c
- Pipe material
- 21
- Refrigerant inflow section
- 22
- Refrigerant outflow section
- 23
- Electric heating element
- 23A
- Electric heating element (temperature measuring resistor)
- A
- Threshold value
- H3
- Allowable highest liquid level
- R
- Liquefied refrigerant
Claims (5)
- A refrigerating cycle system comprising:a compressor (4) configured to compress a refrigerant;a condenser (6) configured to condense compressed refrigerant discharged from the compressor (4);an expansion valve (8) configured to expand the compressed refrigerant condensed by the condenser (6);an evaporator (15) configured to vaporize the compressed refrigerant expanded by the expansion valve (8); andan accumulator (12, 12A) configured to, once a stored gas-liquid mixed refrigerant has returned from the evaporator (15) to the compressor (4), separate the gas-liquid mixed refrigerant into a liquefied refrigerant (R) and a vaporized refrigerant, and to make the compressor (4) suck only the vaporized refrigerant, whereinthe accumulator (12, 12A) includes:a pressure vessel (20);a refrigerant inflow section (21) configured to allow the gas-liquid mixed refrigerant to flow into the pressure vessel (20);a refrigerant outflow section (22) configured to allow the vaporized refrigerant to flow toward the compressor (4); andan electric heating element (23, 23A), characterized in that the electric heating element (23, 23A) is provided at a position of an allowable highest liquid level of the liquefied refrigerant (R) in the pressure vessel (20), of the pressure vessel (20), andin that the refrigerating cycle system further comprises a controller (14) configured to detect a change of a heating value of the electric heating element (23, 23A) by detecting a change of power consumption, and to perform protection operation for lowering the liquid level of the liquefied refrigerant (R) in a case where the power consumption reaches a predetermined threshold value.
- The refrigerating cycle system according to claim 1, wherein
a voltage applied to the electric heating element (23, 23A) is set in such a range that a temperature of the vaporized refrigerant is raised by heat generation of the electric heating element (23, 23A) when the electric heating element (23, 23A) is adjacent to the vaporized refrigerant, and the temperature of the electric heating element (23, 23A) is lowered by cold heat of the liquefied refrigerant (R) when the electric heating element (23, 23A) is adjacent to the liquefied refrigerant (R). - The refrigerating cycle system according to claim 1 or 2, wherein
the electric heating element (23, 23A) is a temperature measuring resistor (23A) that is utilizable also as a temperature sensor. - The refrigerating cycle system according to any of claims 1 to 3, wherein
the electric heating element (23, 23A) is inserted into a recess (20b) from an outer side of the pressure vessel (20), the recess (20b) being provided in the pressure vessel (20) and being depressed to an inner side from the outer side of the pressure vessel (20). - A liquid flow-back prevention method comprising:providing an electric heating element (23, 23A) at a liquid level of a liquefied refrigerant (R) in an accumulator (12, 12A), the accumulator (12, 12A) separating a gas-liquid mixed refrigerant returned from an evaporator (15) to a compressor (4) into the liquefied refrigerant (R) and a vaporized refrigerant in a refrigerating cycle system, the liquid level being a maximum storage amount of the liquefied refrigerant (R);detecting change of a heating value of the electric heating element (23, 23A) by change of a current value; anddetecting that the liquid level of the liquefied refrigerant (R) reaches an allowable highest liquid level.
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CN108759202B (en) * | 2018-07-30 | 2023-10-27 | 东莞市艾瑞科热能设备有限公司 | Gas-liquid separator |
WO2020066005A1 (en) * | 2018-09-28 | 2020-04-02 | 三菱電機株式会社 | Refrigeration cycle apparatus |
CN116972554A (en) * | 2019-02-28 | 2023-10-31 | 施耐德电气It公司 | Receiver for cooling system |
CN109990515B (en) * | 2019-04-30 | 2023-10-03 | 安徽美乐柯制冷空调设备有限公司 | Heat exchange gas-liquid separator with economizer function |
JP7262624B2 (en) * | 2020-01-21 | 2023-04-21 | 三菱電機株式会社 | Cold heat source unit and refrigeration cycle device |
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EP3173714A1 (en) | 2017-05-31 |
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