US20250067463A1 - Air conditioner - Google Patents

Air conditioner Download PDF

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US20250067463A1
US20250067463A1 US18/719,185 US202218719185A US2025067463A1 US 20250067463 A1 US20250067463 A1 US 20250067463A1 US 202218719185 A US202218719185 A US 202218719185A US 2025067463 A1 US2025067463 A1 US 2025067463A1
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Prior art keywords
refrigerant
heat exchanger
air conditioner
evaporator
flow channel
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US18/719,185
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English (en)
Inventor
Masanori Sato
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Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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Assigned to MITSUBISHI ELECTRIC CORPORATION reassignment MITSUBISHI ELECTRIC CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SATO, MASANORI
Publication of US20250067463A1 publication Critical patent/US20250067463A1/en
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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
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/70—Control systems characterised by their outputs; Constructional details thereof
    • F24F11/80—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air
    • F24F11/83—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers
    • 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
    • F25B40/00—Subcoolers, desuperheaters or superheaters
    • 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
    • F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
    • F25B2313/027—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means
    • F25B2313/02741—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means using one four-way valve
    • 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
    • F25B2400/12—Inflammable refrigerants
    • F25B2400/121—Inflammable refrigerants using R1234
    • 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
    • F25B2600/02—Compressor control
    • 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
    • F25B2600/25—Control of valves
    • 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
    • F25B2600/25—Control of valves
    • F25B2600/2513—Expansion valves

Definitions

  • the present disclosure relates to an air conditioner.
  • a refrigerant used in a refrigeration cycle of an air conditioner is required to have a low GWP (global warming potential).
  • WO 2020/144764 discloses an example of an air conditioner that uses such a refrigerant with a low GWP to improve the coefficient of performance.
  • the air conditioner includes an internal heat exchanger.
  • the problem is how to mix the refrigerants so as to improve the final coefficient of performance of the air conditioner.
  • the present disclosure has been made to solve the aforementioned problem, and an object of the present disclosure is to provide an air conditioner with an improved coefficient of performance.
  • the present disclosure relates to an air conditioner.
  • the air conditioner includes a refrigerant, a refrigerant circuit, a heat exchanger, and a controller.
  • the refrigerant circuit includes at least a compressor, a condenser and an evaporator, and is configured to circulate the refrigerant.
  • the heat exchanger includes a first flow channel through which the refrigerant that has passed through the condenser flows and a second flow channel through which the refrigerant to be sucked into the compressor flows, and is configured to exchange heat between the refrigerant passing through the first flow channel and the refrigerant passing through the second flow channel.
  • the controller is configured to control the refrigerant circuit so as to bring a degree of superheat of the refrigerant flowing through an outlet of the evaporator to 5 degrees or less.
  • the air conditioner according to the present disclosure can ensure the degree of superheat of the sucked refrigerant without decreasing the heat exchange performance of the evaporator. This improves the coefficient of performance of the air conditioner that uses an internal heat exchanger to exchange heat between the refrigerant that has passed through the condenser and the refrigerant to be sucked into the compressor.
  • FIG. 1 is a diagram illustrating a configuration of an air conditioner 1000 according to a first embodiment
  • FIG. 2 is a diagram illustrating a comparison of theoretical coefficients of performance (hereinafter referred to as “theoretical COP”) of the air conditioner when various types of refrigerant are used;
  • FIG. 3 is a PH diagram of a refrigeration cycle apparatus that uses R290 as a refrigerant and is not provided with an internal heat exchanger;
  • FIG. 4 is a PH diagram of a refrigeration cycle apparatus that uses R290 as a refrigerant and is provided with an internal heat exchanger;
  • FIG. 5 is a graph illustrating the relationship between the fraction of R32 in a refrigerant mixture R32/R1234yf and the theoretical COP ratio
  • FIG. 6 is a graph illustrating the relationship between the fraction of R32 in the refrigerant mixture R32/R1234yf and the saturation temperature at standard atmospheric pressure and the GWP value;
  • FIG. 7 is a graph illustrating the relationship between the saturation temperature of various refrigerants at standard atmospheric pressure and the theoretical COP ratio
  • FIG. 8 is a graph illustrating the relationship between the GWP values of various refrigerants and the theoretical COP ratios
  • FIG. 9 is a diagram illustrating a modification of the air conditioner illustrated in FIG. 1 ;
  • FIG. 10 is a flowchart illustrating the control of the expansion valve 230 ;
  • FIG. 11 is a diagram illustrating a configuration of an air conditioner according to a second embodiment
  • FIG. 12 is a cross-sectional view illustrating a specific example of a pressure-reducing heat exchanger 270 ;
  • FIG. 13 is a diagram illustrating another specific example of the pressure-reducing heat exchanger 270 ;
  • FIG. 14 is a diagram illustrating a configuration of a modification of the air conditioner illustrated in FIG. 11 ;
  • FIG. 15 is a cross-sectional view illustrating a configuration example of a pressure-reducing heat exchanger 280 .
  • FIG. 1 is a diagram illustrating a configuration of an air conditioner 1000 according to a first embodiment.
  • the air conditioner 1000 illustrated in FIG. 1 includes a refrigerant circuit 500 , an internal heat exchanger 250 , and a controller 100 .
  • the refrigerant circuit 500 includes at least a compressor 200 , an outdoor heat exchanger 210 , an expansion valve 230 and an indoor heat exchanger 110 , and is configured to circulate the refrigerant.
  • the refrigerant used in the present embodiment has a GWP value or a saturation temperature at standard atmospheric pressure in a certain range to be described later in detail.
  • the refrigerant circuit 500 includes a compressor 200 , an outdoor heat exchanger 210 , an outdoor blower 220 , an expansion valve 230 , a four-way valve 240 , an indoor heat exchanger 110 , and an indoor blower 120 .
  • the four-way valve 240 has ports P 1 to P 4 .
  • a linear expansion valve (LEV) for example, can be used as the expansion valve 230 .
  • the refrigerant circuit 500 is divided into an outdoor unit 1001 and an indoor unit 1002 .
  • the outdoor unit 1001 includes a compressor 200 , a four-way valve 240 , an outdoor heat exchanger 210 , an outdoor blower 220 , an expansion valve 230 , a controller 100 , and an internal heat exchanger 250 .
  • the indoor unit 1002 includes an indoor heat exchanger 110 and an indoor blower 120 .
  • the outdoor unit 1001 and the indoor unit 1002 are connected by a pipe 310 and a pipe 320 .
  • the compressor 200 is configured to change the operating frequency according to a control signal received from the controller 100 .
  • the compressor 200 incorporates an inverter-controlled drive motor with variable rotation speed, and the rotational speed of the drive motor changes as the operating frequency is changed.
  • the output of the compressor 200 is adjusted by changing the operating frequency of the compressor 200 .
  • the compressor 200 may be any type of compressors such as a rotary compressor, a reciprocating compressor, a scroll compressor, or a screw compressor.
  • the four-way valve 240 is controlled by a control signal received from the controller 100 to switch the operation mode of the air conditioner to a cooling operation mode or a heating operation mode.
  • the port P 1 communicates with the port P 4
  • the port P 2 communicates with the port P 3
  • the port P 1 communicates with the port P 3
  • the port P 2 communicates with the port P 4 .
  • the internal heat exchanger 250 includes a flow channel R 1 and a flow channel R 2 .
  • high-pressure high-temperature refrigerant that has passed through the condenser (the outdoor heat exchanger 210 ) flows through the flow channel R 1 .
  • low-pressure and low-temperature refrigerant to be sucked into the compressor 200 flows through the flow channel R 2 .
  • the internal heat exchanger 250 exchanges heat between the high-pressure high-temperature refrigerant that has passed through the condenser (the outdoor heat exchanger 210 ) and the low-pressure low-temperature refrigerant to be sucked into the compressor 200 .
  • the air conditioner 1000 further includes temperature sensors 262 to 265 .
  • the temperature sensor 262 is disposed in the indoor heat exchanger 110 , and is configured to measure a refrigerant temperature T 262 which is an evaporation temperature of the refrigerant during the cooling operation or a condensation temperature of the refrigerant during the heating operation.
  • the temperature sensor 263 is disposed in a pipe that connects the indoor heat exchanger 110 to the port P 3 of the four-way valve 240 , and is configured to measure a temperature T 263 of the refrigerant.
  • the temperature sensor 264 is disposed in the outdoor heat exchanger 210 , and is configured to measure a refrigerant temperature T 264 which is a condensation temperature of the refrigerant during the cooling operation or an evaporation temperature of the refrigerant during the heating operation.
  • the temperature sensor 265 is disposed in a pipe connecting the outdoor heat exchanger 210 and the port P 4 of the four-way valve 240 , and is configured to measure a temperature T 265 of the refrigerant.
  • the controller 100 controls the opening degree of the expansion valve 230 so as to adjust the SH (the degree of superheat) of the refrigerant at an outlet of the evaporator according to the outputs from the temperature sensors 262 to 265 .
  • the controller 100 includes a CPU (Central Processing Unit) 101 , a memory 102 (such as a ROM (Read Only Memory) or a RAM (Random Access Memory)), an input/output buffer (not shown), and the like.
  • the CPU 101 loads programs stored in the ROM into the RAM or the like and executes the programs.
  • the programs stored in the ROM are programs that describe the processing procedure of the controller 100 .
  • the controller 100 controls each device in the air conditioner 1000 in accordance with these programs. This control is not limited to being processed by software, but may be processed by dedicated hardware (electronic circuit).
  • the refrigerant circuit of the air conditioner 1000 includes the compressor 200 , the outdoor heat exchanger 210 , the outdoor blower 220 , the expansion valve 230 , the four-way valve 240 , the internal heat exchanger 250 , the indoor heat exchanger 110 , and the indoor blower 120 .
  • the internal heat exchanger 250 exchanges heat between the high-pressure refrigerant flowing out from the outdoor heat exchanger 210 through the flow channel R 1 and the low-pressure refrigerant flowing through the flow channel R 2 into the compressor 200 .
  • FIG. 2 is a diagram illustrating a comparison of theoretical coefficients of performance (hereinafter referred to as “theoretical COP”) of the air conditioner when various types of refrigerants are used.
  • the results of FIG. 2 are obtained through calculations by setting the supercooling degree (SC) to 0 degrees, the evaporation temperature (ET) to 17° C., the condensation temperature (CT) to 40° C. and the compressor efficiency to 1.
  • the theoretical COP of a hydrofluorocarbon refrigerant decreases as the degree of superheat (SH) of the refrigerant to be sucked into the compressor increases.
  • the theoretical COP of a hydrocarbon refrigerant such as R290 or R600a increases as the degree of superheat (SH) of the sucked refrigerant increases.
  • HFO refrigerant hydrofluoroolefin refrigerant
  • the air conditioner of the present embodiment in addition to controlling the degree of superheat at the outlet of the evaporator to 5 degrees or less and using an internal heat exchanger, by using a low GWP refrigerant that satisfies certain conditions, it is possible to make the air conditioner operate with high performance while preventing the performance of the evaporator from decreasing.
  • FIG. 3 is a PH diagram of a refrigeration cycle apparatus that uses R290 as a refrigerant and is not provided with an internal heat exchanger.
  • FIG. 4 is a PH diagram of a refrigeration cycle apparatus that uses R290 as a refrigerant and is provided with an internal heat exchanger.
  • the theoretical COP is equal to 10.82 in both the configuration where the internal heat exchanger is provided and the configuration where the internal heat exchanger is not provided.
  • the degree of superheat (SH) of the refrigerant at the outlet of the evaporator is equal to the degree of superheat of the refrigerant to be sucked into the compressor. Therefore, when the degree of superheat of the sucked refrigerant is 10 degrees, the degree of dryness of the refrigerant is equal to I before the outlet of the evaporator, and thereby, the performance of the evaporator decreases by an amount corresponding to a decrease in the heat exchange performance caused by the portion of the gas refrigerant.
  • the evaporation temperature ET becomes lower than 17° C.
  • a refrigerant is required to have such a characteristic that the theoretical COP increases as the superheating degree (SH) of the refrigerant to be sucked into the compressor increases.
  • a refrigerant is required to improve the actual COP when an internal heat exchanger is provided.
  • the theoretical COP decreases when the degree of superheat (SH) of the refrigerant to be sucked into the compressor increases, but in the case of an HFO refrigerant, the theoretical COP increases when the degree of superheat (SH) of the refrigerant to be sucked into the compressor increases.
  • an HFO refrigerant such as R1234yf is used in a car air conditioner or the like.
  • R32 which is an HFC refrigerant used in a residential air conditioner, as a mixture with R1234yf.
  • FIG. 5 is a graph illustrating the relationship between the fraction of R32 in the refrigerant mixture R32/R1234yf and the theoretical COP ratio.
  • the theoretical COP ratio is the ratio of the theoretical COP in the case where the internal heat exchanger is provided to the theoretical COP in the case where the internal heat exchanger is not provided.
  • the theoretical COP ratio is (the theoretical COP of the configuration with the internal heat exchanger)/(the theoretical COP of the configuration without the internal heat exchanger).
  • FIG. 5 shows the calculation result when the temperature at the inlet of the internal heat exchanger changes by 10 degrees due to heat exchange.
  • the mass fraction of R32 exceeds 30%, the theoretical COP of the configuration where the internal heat exchanger is provided will not increase.
  • the effective range W 1 of the mass fraction of R32 in the case where the internal heat exchanger is provided is 0% to 30%.
  • FIG. 6 is a graph illustrating the relationship between the fraction of R32 in the refrigerant mixture R32/R1234yf and the saturation temperature at standard atmospheric pressure and the GWP value.
  • the saturation temperature of a refrigerant depends on the dryness of the refrigerant at the same pressure but with a temperature gradient.
  • the results illustrated in FIG. 6 represent the saturation temperature at the standard atmospheric pressure when the dryness is 0.5.
  • a refrigerant has a saturated temperature of ⁇ 44.4° C. or more at the standard atmospheric pressure, it is effective in the case where the internal heat exchanger is provided.
  • a refrigerant has a GWP of 205 or less, it is effective in the case where the internal heat exchanger is provided.
  • FIG. 7 is a graph illustrating the relationship between the saturation temperature of various refrigerants at standard atmospheric pressure and the theoretical COP ratio.
  • FIG. 8 is a graph illustrating the relationship between the GWP values of various refrigerants and the theoretical COP ratio.
  • the COP in the case where the internal heat exchanger is not provided was calculated by assuming the degree of superheat (SH) of the sucked refrigerant is 10 degrees, the degree of supercooling (SC) is 0 degrees, the evaporation temperature (ET) is 17° C., the condensation temperature (CT) is 40° C., and the compressor efficiency is 1.
  • the COP in the case where the internal heat exchanger is provided was calculated by assuming that the capacity of the evaporator is the same, the degree of superheat (SH) of the refrigerant at the outlet of the evaporator is controlled at 0 degrees by using the expansion valve, and the internal heat exchanger exchanges an amount of heat of 10° C.
  • the saturation temperature range W 3 and the GWP value range W 4 which are obtained by applying the range W 1 to FIG. 6 and effective in the case where the internal heat exchanger is provided are generally true for various refrigerants except for R32 and R410A.
  • the refrigerant suitably used in the present embodiment has such a characteristic that the saturated temperature at the standard atmospheric pressure is ⁇ 44.4° C. or more or the GWP is 205 or less.
  • the developer or the user of the air conditioner may use this characteristic as an indicator to select a refrigerant.
  • the internal heat exchanger 250 is configured to operate mainly during the cooling operation, it also may be configured to operate mainly during the heating operation. Alternatively, as illustrated in the following modifications, an expansion valve may be further provided.
  • FIG. 9 is a diagram illustrating a modification of the air conditioner illustrated in FIG. 1 .
  • the air conditioner 1010 illustrated in FIG. 9 includes a refrigerant circuit 510 instead of the refrigerant circuit 500 .
  • the refrigerant circuit 510 further includes a second expansion valve 231 inside the outdoor unit 1011 as compared with the refrigerant circuit 500 .
  • An electronic expansion valve can be used as the expansion valve 231 .
  • the expansion valve 231 is connected between the first flow channel R 1 of the internal heat exchanger 250 and the outdoor heat exchanger 210 .
  • the controller 100 fully opens the second expansion valve 231 and controls the superheat (SH) of the refrigerant at the outlet of the evaporator with the expansion valve 230 during the cooling operation, and fully opens the expansion valve 230 and controls the superheat (SH) of the refrigerant at the outlet of the evaporator with the second expansion valve 231 during the heating operation. This makes it possible to improve the efficiency of heat exchange in the internal heat exchanger 250 during both the cooling operation and the heating operation.
  • the internal heat exchanger 250 may be any heat exchanger as long as it exchanges heat between the high-pressure refrigerant that has passed through the condenser and the low-pressure refrigerant to be sucked into the compressor, and for example, it may be a double-tube heat exchanger composed of an inner pipe and an outer pipe, or may be a heat exchanger in which the high-pressure pipe and the low-pressure pipe are brazed and brought into contact with each other by soldering or the like to perform heat exchange.
  • the air conditioner illustrated in FIGS. 1 and 9 is provided with a four-way valve, the air conditioner may not be provided with a four-way valve and thereby is used exclusively for cooling.
  • the flow of the refrigerant in the heating operation mode is indicated by a solid line
  • the flow of the refrigerant in the cooling operation mode is indicated by a broken line.
  • the controller 100 changes the frequency of the compressor 200 so as to bring the indoor temperature to a target (set) temperature.
  • FIG. 10 is a flowchart illustrating the control of the expansion valve 230 .
  • step S 21 the controller 100 sets the opening degree of the expansion valve 230 to a predefined value. After a certain period of time has elapsed, in step S 22 , the controller 100 initializes the variable Count to 0. Thereafter, in step S 23 , the controller 100 decreases the opening degree of the expansion valve 230 by a certain value. After a certain period of time has elapsed, in step S 24 , the controller 100 determines whether or not the degree of superheat (SH) of the refrigerant at the outlet of the evaporator has changed.
  • SH superheat
  • the degree of superheat (SH) of the refrigerant at the outlet of the evaporator is calculated by subtracting the evaporation temperature of the refrigerant obtained by the temperature sensor 262 from the refrigerant temperature at the outlet of the evaporator obtained by the temperature sensor 263 .
  • the degree of refrigerant superheat (SH) at the outlet of the evaporator is calculated by subtracting the evaporation temperature of the refrigerant obtained by the temperature sensor 264 from the refrigerant temperature at the outlet of the evaporator obtained by the temperature sensor 265 .
  • step S 24 determines whether the degree of superheat (SH) of the refrigerant at the outlet of the evaporator is not changed, since the state of the refrigerant at the outlet of the evaporator is not changed from the gas-liquid two-phase state.
  • the controller 100 adds 1 to the variable Count in step S 25 , returns the procedure to step S 23 , and decreases the opening degree of the expansion valve 230 by a certain value.
  • step S 24 the controller 100 proceeds the procedure to step S 26 to determine whether or not the variable Count is 0.
  • step S 26 If the determination result is NO in step S 26 , in other words, if the variable Count is not 0, since the degree of superheat (SH) of the refrigerant at the outlet of the evaporator has been appropriately controlled in steps S 23 to S 25 , the controller 100 ends the procedure of this flowchart. On the other hand, if the determination result is YES in step S 26 , since the variable Count is 0, the procedure passes step S 24 once without going through step S 25 .
  • SH degree of superheat
  • the controller 100 Since the refrigerant at the outlet of the evaporator is in a superheated gas state at the default opening degree in step S 21 , and the degree of superheat (SH) of the refrigerant is further increased as a result of the process in step S 23 from that state, the state cannot be regarded as an appropriate state. Thus, the controller 100 increases the opening degree of the expansion valve 230 by a certain value in step S 27 . After a certain period of time has elapsed, in step S 28 , the controller 100 determines whether or not the degree of superheat (SH) of the refrigerant at the outlet of the evaporator has changed.
  • step S 28 If the determination result is NO in step S 28 , in other words, if the degree of superheat (SH) of the refrigerant at the outlet of the evaporator has changed, since there is a change in the degree of superheat (SH) of the refrigerant at the outlet of the evaporator, the process returns to step S 27 where the controller 100 increases the opening degree of the expansion valve 230 by a certain value.
  • the degree of superheat (SH) of the refrigerant at the outlet of the evaporator can be brought to an optimum state where the degree of superheat is substantially zero.
  • step S 28 if there is no change in the degree of superheat (SH) of the refrigerant at the outlet of the evaporator, it can be determined that the refrigerant at the outlet of the evaporator is in a gas-liquid two-phase state (the degree of superheat is 0), and the heat exchange efficiency of the evaporator is good, the controller 100 ends the procedure of this flowchart.
  • SH degree of superheat
  • the procedure of the flowchart in FIG. 10 is performed again, whereby the opening degree of the expansion valve 230 is set to bring the degree of superheat of the refrigerant at the outlet of the evaporator to substantially zero.
  • the opening degree of the expansion valve 230 determined in a previous procedure may be used as the predefined value in step S 21 .
  • the degree of superheat (SH) of the refrigerant at the outlet of the evaporator is controlled to approach the target value (zero), however, the target value of the degree of superheat (SH) of the refrigerant discharged from the compressor 200 or the target value of the temperature of the refrigerant discharged from the compressor 200 corresponding to the degree of superheat (SH) of the refrigerant at the outlet of the evaporator may be determined in advance, and the degree of superheat (SH) or the temperature of the refrigerant discharged from the compressor may be controlled to be the target value. Also, the expansion valve 231 in the configuration of FIG. 9 during the heating operation may be controlled in the same manner as in FIG. 10 with the expansion valve 230 fixed to fully open.
  • the method for calculating the degree of superheat (SH) of the refrigerant at the outlet of the evaporator described in the flowchart of FIG. 10 was based on temperature sensors.
  • the degree of superheat (SH) of the refrigerant changes.
  • the degree of superheat (SH) of the refrigerant at the outlet of the evaporator obtained by this method becomes smaller, and when the refrigerant has a larger temperature gradient, the degree of superheat (SH) of the refrigerant at the outlet of the evaporator obtained by this method becomes larger.
  • the degree of superheat (SH) is about 5 degrees, the performance of the evaporator does not drop that much, and thus, the degree of superheat (SH) may be controlled to 5 degrees or less to tolerate some error.
  • the air conditioner of the first embodiment it is possible to ensure the degree of superheat (SH) of the refrigerant to be sucked into the compressor without deteriorating the performance of the evaporator even when a low GWP refrigerant is used, which makes it possible to improve the COP of the air conditioner.
  • SH superheat
  • FIG. 11 is a diagram illustrating a configuration of an air conditioner according to a second embodiment.
  • the air conditioner 1100 illustrated in FIG. 11 includes a refrigerant circuit 600 instead of the refrigerant circuit 500 illustrated in FIG. 1 .
  • the refrigerant circuit 600 includes a pressure-reducing heat exchanger 270 inside the outdoor unit 1101 instead of the internal heat exchanger 250 and the expansion valve 230 in the refrigerant circuit 500 .
  • the internal heat exchanger 250 and the expansion valve 230 are replaced by a pressure-reducing heat exchanger 270 which solely performs pressure reduction and heat exchange of the high-pressure refrigerant.
  • the pressure-reducing heat exchanger 270 includes a low-pressure pipe 271 through which low-pressure refrigerant flows and a first medium-pressure pipe 272 through which medium-pressure refrigerant flows.
  • the inner diameter of the first medium-pressure pipe 272 is configured to be smaller than that of the low-pressure pipe 271 .
  • the inner diameter of the first medium-pressure pipe 272 is configured to be smaller than that of the pipes connected to both ends of the medium-pressure pipe 272 so as to reduce the pressure of the high-pressure refrigerant flowing out from the condenser.
  • the first low-pressure pipe 271 and the first medium-pressure pipe 272 are in contact with each other so as to exchange heat.
  • the two pipes are brazed by solder or the like, and are brought into contact with each other so as to exchange heat between the two pipes.
  • FIG. 12 is a cross-sectional view illustrating a specific example of the pressure-reducing heat exchanger 270 .
  • the diameter of the low-pressure pipe 271 is ⁇ 9.52, and the diameter of the first medium-pressure pipe 272 is ⁇ 3.0.
  • the diameter of the low-pressure pipe 271 is set larger so as to reduce the effect of the pressure loss, and the diameter of the medium-pressure pipe 272 is set smaller so as to reduce the pressure from high pressure to low pressure.
  • FIG. 13 is a diagram illustrating another specific example of the pressure-reducing heat exchanger 270 .
  • the first medium-pressure pipe 272 is spirally wound around the low-pressure pipe 271 . This increases the contact area of the first medium-pressure pipe 272 per unit length of the low-pressure pipe 271 , which improves the heat exchange efficiency. Accordingly, the length of the low-pressure pipe 271 for exchanging a required amount of heat in the pressure-reducing heat exchanger 270 can be made shorter than the length along which the medium-pressure pipe 272 is not wound. Since the length of the low-pressure pipe 271 is shortened, the pipe can be easily routed in a machine room. Further, since the pressure loss of the low-pressure pipe 271 is reduced by shortening the length, it is possible to reduce the diameter of the low-pressure pipe 271 .
  • the first medium-pressure pipe 272 is one pipe, and since one pipe can only form one fixed throttle, a plurality of pipes may be installed in parallel.
  • FIG. 14 is a diagram illustrating a configuration of a modification of the air conditioner illustrated in FIG. 11 .
  • the air conditioner 1110 illustrated in FIG. 14 includes a refrigerant circuit 601 instead of the refrigerant circuit 600 illustrated in FIG. 11 .
  • the refrigerant circuit 601 includes a pressure-reducing heat exchanger 280 inside the outdoor unit 1111 instead of the pressure-reducing heat exchanger 270 in the configuration of the refrigerant circuit 600 .
  • the pressure-reducing heat exchanger 280 further includes a second medium-pressure pipe 273 in addition to the low-pressure pipe 271 and the first medium-pressure pipe 272 .
  • the medium-pressure pipe 272 and the medium-pressure pipe 273 have different diameters.
  • the flow channel may be switched by the switching valve 232 so that the refrigerant flows through a pipe having an optimal inner diameter corresponding to the refrigerant circulation amount, or the pipe through which the refrigerant flows may be changed between the cooling operation and the heating operation.
  • the diameter of the medium-pressure pipe through which the refrigerant flows during the heating operation is smaller than the diameter of the medium-pressure pipe through which the refrigerant flows during the cooling operation.
  • the temperature difference between the air to be heat-exchanged by the indoor heat exchanger 110 and the air to be heat-exchanged by the outdoor heat exchanger 210 is larger during the heating operation than during the cooling operation, and thereby, it is suitable to increase the throttle amount in the medium-pressure pipe during the heating operation than during the cooling operation.
  • JIS Japan Industrial Standard
  • the air temperature at the inlet of the outdoor heat exchanger 210 is 35° C.
  • the air temperature at the inlet of the indoor heat exchanger 110 is 27° C.
  • the temperature difference between the two air temperatures is 8° C.
  • the air temperature at the inlet of the indoor heat exchanger 110 is 20° C.
  • the air temperature at the inlet of the outdoor heat exchanger 210 is 7° C.
  • the temperature difference between the two air temperatures is 13° C.
  • FIG. 15 is a cross-sectional view illustrating a configuration example of the pressure-reducing heat exchanger 280 .
  • the plurality of medium-pressure pipes are configured to have different diameters, and are disposed in contact with the low-pressure pipe to exchange heat.
  • the diameter of the low-pressure pipe 271 is ⁇ 9.52
  • the diameter of the first intermediate-pressure pipe 272 is ⁇ 3.0
  • the diameter of the second intermediate-pressure pipe 273 is ⁇ 2.5.
  • the diameter of the low-pressure pipe 271 should be larger to reduce the influence of the pressure loss, and the diameters of the medium-pressure pipes 272 and 273 should be smaller to reduce the pressure from a high pressure to a low pressure.
  • the refrigerant flows through the medium-pressure pipe 273 having a diameter of 2.5 mm during the heating operation, and flows through the medium-pressure pipe 272 having a diameter of 3.0 mm during the cooling operation.
  • the air conditioner of the second embodiment in addition to the effects exhibited by the air conditioner according to the first embodiment, since the temperature difference in the heat exchanger can always be ensured in either the cooling operation or the heating operation, the performance of the air conditioner can be improved in both the cooling operation and the heating operation. Further, since the expansion valve 230 is not provided, the air conditioner can be made cheaper.
  • the present disclosure relates to an air conditioner.
  • the air conditioner 1000 illustrated in FIG. 1 includes a refrigerant, a refrigerant circuit 500 , a heat exchanger 250 , and a controller 100 .
  • the refrigerant circuit 500 includes at least a compressor 200 , a condenser (an outdoor heat exchanger 210 ) and an evaporator (an indoor heat exchanger 110 ), and is configured to circulate the refrigerant.
  • the heat exchanger 250 includes a first flow channel R 1 through which the refrigerant that has passed through the condenser (the outdoor heat exchanger 210 ) flows and a second flow channel R 2 through which the refrigerant to be sucked into the compressor 200 flows, and is configured to exchange heat between the refrigerant passing through the first flow channel R 1 and the refrigerant passing through the second flow channel R 2 .
  • the controller 100 is configured to control the refrigerant circuit 500 so as to bring the degree of superheat of the refrigerant flowing through an outlet of the evaporator (the indoor heat exchanger 110 ) to 5 degrees or less.
  • the refrigerant circuit 500 illustrated in FIG. 1 further includes an expansion valve 230 configured to expand the refrigerant condensed in the condenser (the outdoor heat exchanger 210 ).
  • the controller 100 controls an opening degree of the expansion valve 230 to change the degree of superheat of the refrigerant flowing through the outlet of the evaporator (the indoor heat exchanger 110 ).
  • the condenser (the outdoor heat exchanger 210 ) is configured to condense the refrigerant
  • the evaporator (the indoor heat exchanger 110 ) is configured to evaporate the refrigerant.
  • the refrigerant circuit 500 further includes a four-way valve 240 that changes the flow direction of the refrigerant passing through the condenser (the outdoor heat exchanger 210 ) and the evaporator (the indoor heat exchanger 110 ) from the flow direction during the cooling operation so as to cause the condenser (the outdoor heat exchanger 210 ) to evaporate the refrigerant and cause the evaporator (the indoor heat exchanger 110 ) to condense the refrigerant during the heating operation.
  • the first flow channel R 1 of the heat exchanger 250 is disposed between the condenser (the outdoor heat exchanger 210 ) and the expansion valve 230
  • the second flow channel R 2 of the heat exchanger 250 is disposed between the four-way valve 240 and the inlet of the compressor 200 .
  • the pressure of the refrigerant passing through the first flow channel (the middle-pressure pipe 272 ) is higher than the pressure of the refrigerant passing through the second flow channel (the low-pressure pipe 271 ), and the inner diameter of the pipe for the first flow channel (the middle-pressure pipe 272 ) is smaller than the inner diameter of the pipe for the second flow channel (the low-pressure pipe 271 ).
  • the condenser (the outdoor heat exchanger 210 ) is configured to condense the refrigerant
  • the evaporator (the indoor heat exchanger 110 ) is configured to evaporate the refrigerant.
  • the refrigerant circuit 600 further includes a four-way valve 240 that changes the flow direction of the refrigerant passing through the condenser (the outdoor heat exchanger 210 ) and the evaporator (the indoor heat exchanger 110 ) from the flow direction during the cooling operation so as to cause the condenser (the outdoor heat exchanger 210 ) to evaporate the refrigerant and cause the evaporator (the indoor heat exchanger 110 ) to evaporate the refrigerant during the heating operation.
  • the first flow channel (the middle-pressure pipe 272 ) of the pressure-reducing heat exchanger 270 is disposed between the condenser (the outdoor heat exchanger 210 ) and the evaporator (the indoor heat exchanger 110 ).
  • the second flow channel (the low-pressure pipe 271 ) of the pressure-reducing heat exchanger 270 is disposed between the four-way valve 240 and the inlet of the compressor 200 .
  • the first flow channel includes a first pipe (the medium-pressure pipe 272 ) and a second pipe (the medium-pressure pipe 273 ) which is provided in parallel with the first pipe (the medium-pressure pipe 272 ) and has an inner diameter smaller than that of the first pipe (the medium-pressure pipe 272 ).
  • the air conditioner 1110 further includes a switching valve 232 to switch the refrigerant to flow through the first pipe (the middle-pressure pipe 272 ) or the second pipe (the medium-pressure pipe 273 ).
  • the controller 100 controls the switching valve 232 to cause the refrigerant to flow through the first pipe (the medium-pressure pipe 272 ) during the cooling operation and cause the refrigerant to flow through the second pipe (the medium-pressure pipe 273 ) during the heating operation.
  • the degree of superheat of the refrigerant flowing through the outlet of the evaporator is 0 degrees, and the degree of superheat of the refrigerant to be sucked into the compressor 200 is greater than 0 degrees.
  • the refrigerant used in the refrigerant circuit 500 has a global warming coefficient of 205 or less, or a saturation temperature of ⁇ 44.4° C. or more at a standard atmospheric pressure.
  • the refrigerant has a global warming coefficient of 205 or less and a saturation temperature of ⁇ 44.4° C. or more at a standard atmospheric pressure.
  • the refrigerant includes R32 and R1234yf, and a mass fraction of R32 in the refrigerant is 30% or less.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Compression-Type Refrigeration Machines With Reversible Cycles (AREA)
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JPS60108655A (ja) * 1983-11-15 1985-06-14 三洋電機株式会社 ヒ−トポンプ式冷凍装置
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JP4952830B2 (ja) * 2005-04-01 2012-06-13 株式会社デンソー エジェクタ式冷凍サイクル
JP4884365B2 (ja) * 2007-12-28 2012-02-29 三菱電機株式会社 冷凍空調装置、冷凍空調装置の室外機および冷凍空調装置の制御装置
JP6794964B2 (ja) * 2017-08-31 2020-12-02 株式会社デンソー 冷凍サイクル装置
WO2019198175A1 (ja) * 2018-04-11 2019-10-17 三菱電機株式会社 冷凍サイクル装置
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JPWO2020188756A1 (ja) * 2019-03-19 2021-04-30 日立ジョンソンコントロールズ空調株式会社 ルームエアコン

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