EP3306230A1 - Kältemittelkreislaufsystem und steuerungsverfahren - Google Patents

Kältemittelkreislaufsystem und steuerungsverfahren Download PDF

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Publication number
EP3306230A1
EP3306230A1 EP17194420.0A EP17194420A EP3306230A1 EP 3306230 A1 EP3306230 A1 EP 3306230A1 EP 17194420 A EP17194420 A EP 17194420A EP 3306230 A1 EP3306230 A1 EP 3306230A1
Authority
EP
European Patent Office
Prior art keywords
refrigerant
expansion valve
heat exchanger
utilization
side heat
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP17194420.0A
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English (en)
French (fr)
Inventor
Masashi Maeno
Shigeru Yoshida
Gaku Nakano
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Heavy Industries Thermal Systems Ltd
Original Assignee
Mitsubishi Heavy Industries Thermal Systems Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mitsubishi Heavy Industries Thermal Systems Ltd filed Critical Mitsubishi Heavy Industries Thermal Systems Ltd
Publication of EP3306230A1 publication Critical patent/EP3306230A1/de
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • F25B30/00—Heat pumps
    • F25B30/02—Heat pumps of the compression type
    • 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
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/30—Expansion means; Dispositions thereof
    • F25B41/39—Dispositions with two or more expansion means arranged in series, i.e. multi-stage expansion, on a refrigerant line leading to the same evaporator
    • 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
    • F25B2339/00—Details of evaporators; Details of condensers
    • F25B2339/04—Details of condensers
    • F25B2339/047—Water-cooled condensers
    • 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
    • F25B2400/04—Refrigeration circuit bypassing means
    • F25B2400/0411—Refrigeration circuit bypassing means for the expansion valve or capillary tube
    • 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
    • F25B2600/2501—Bypass 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 invention relates to a refrigerant circuit system and a control method.
  • a water heater using a heat pump has a once-through system which supplies hot water obtained by heating low temperature feed water to a target temperature and a circulation system which heats circulated feed water to a target temperature and then supplies the heated water.
  • the feed water having an arbitrary temperature (for example, 5°C) varying according to an external air temperature or the like is heated to a set temperature (for example, 80°C).
  • a set temperature for example, 80°C
  • warm water having a predetermined temperature for example, 75°C
  • the set temperature for example, 80°C.
  • the refrigerant circuit includes a condenser, a receiver, an evaporator, a compressor and the like which increases the temperature of the feed water and further includes expansion valves which are located on a downstream side of the condenser and an upstream side of the evaporator with the receiver interposed therebetween.
  • this refrigerant circuit since there is a change (for example, 5°C and 75°C) in a utilization-side inlet temperature of the condenser, it is necessary to use a heat exchanger having a capacity capable of responding to the change in the utilization-side inlet temperature in the condenser.
  • Patent Document 1 discloses a refrigeration cycle apparatus which is capable of switching between a two-stage compression operation and a single-stage compression operation according to a load.
  • Patent Document 1 Japanese Unexamined Patent Application, First Publication No. 2007-10282
  • the utilization-side inlet temperature is low (for example, 5°C)
  • a pressure difference between a front and a rear of the expansion valve on the downstream side of the condenser is increased.
  • the pressure difference is large, the flow rate of a refrigerant can be secured by a small-diameter expansion valve.
  • the utilization-side inlet temperature is high (for example, 75°C)
  • the pressure difference between the front and the rear of the expansion valve on the downstream side of the condenser is reduced. Therefore, a large-diameter expansion valve is required to secure the required flow rate of the refrigerant.
  • a large-diameter flow rate control valve may be used in the expansion valve on the downstream side of the condenser, but when the pressure difference is large, a flow rate adjustment at a low opening degree is required.
  • the control of the large-diameter flow rate control valve in a low opening degree range has a large amount of change per pulse and thus stable control is difficult.
  • cost is increased when the large-diameter flow rate control valve is used.
  • a first aspect of the present invention is a refrigerant circuit system including one or a plurality of compressors configured to compress a refrigerant, a utilization-side heat exchanger configured to condense the refrigerant compressed by the compressor, a first expansion valve configured to depressurize the refrigerant introduced from the utilization-side heat exchanger, a receiver configured to store some of the refrigerant depressurized by the first expansion valve, a second expansion valve configured to depressurize the refrigerant flowing out from the receiver, a heat source-side heat exchanger configured to evaporate the refrigerant depressurized by the second expansion valve, a first bypass circuit configured to bypass the flow of the refrigerant passing through the first expansion valve, and a control device configured to control opening and closing of the first bypass circuit.
  • a second aspect of the present invention is a refrigerant circuit system including one or a plurality of compressors configured to compress a refrigerant, a utilization-side heat exchanger configured to condense the refrigerant compressed by the compressor, a first expansion valve configured to depressurize the refrigerant introduced from the utilization-side heat exchanger, a receiver configured to store some of the refrigerant depressurized by the first expansion valve, a second expansion valve configured to depressurize the refrigerant flowing out from the receiver, a heat source-side heat exchanger configured to evaporate the refrigerant depressurized by the second expansion valve, a second bypass circuit configured to bypass the flow of the refrigerant passing through the second expansion valve, and a control device configured to control opening and closing of the second bypass circuit.
  • a third aspect of the present invention is a refrigerant circuit system including one or a plurality of compressors configured to compress a refrigerant, a utilization-side heat exchanger configured to condense the refrigerant compressed by the compressor, a first expansion valve configured to depressurize the refrigerant introduced from the utilization-side heat exchanger, a receiver configured to store some of the refrigerant depressurized by the first expansion valve, a second expansion valve configured to depressurize the refrigerant flowing out from the receiver, a heat source-side heat exchanger configured to evaporate the refrigerant depressurized by the second expansion valve, a first bypass circuit configured to bypass the flow of the refrigerant passing through the first expansion valve, a second bypass circuit configured to bypass the flow of the refrigerant passing through the second expansion valve, and a control device configured to control opening and closing of the first bypass circuit and opening and closing of the second bypass circuit.
  • the control device in a fourth aspect of the present invention may control the opening and closing of the first bypass circuit on the basis of an outlet side temperature of the utilization-side heat exchanger or an outlet side supercooling degree of the utilization-side heat exchanger and an opening degree of the first expansion valve.
  • the control device in a fifth aspect of the present invention may control the opening and closing of the second bypass circuit on the basis of the outlet side superheat degree of the heat source-side heat exchanger or a suction side superheat degree of the compressor and an opening degree of the second expansion valve.
  • a sixth aspect of the present invention is a refrigerant circuit system described in one of the above aspects wherein the compressors include a high stage-side compressor and a low stage-side compressor, and which further includes an injection circuit configured to supply the refrigerant flowing out from the receiver to a high stage-side compressor, a third expansion valve provided at a middle portion of the injection circuit, and a third bypass circuit configured to bypass the flow of the refrigerant passing through the injection circuit in the refrigerant circuit system, and wherein the control device also controls the opening and closing of the third bypass circuit.
  • the compressors include a high stage-side compressor and a low stage-side compressor, and which further includes an injection circuit configured to supply the refrigerant flowing out from the receiver to a high stage-side compressor, a third expansion valve provided at a middle portion of the injection circuit, and a third bypass circuit configured to bypass the flow of the refrigerant passing through the injection circuit in the refrigerant circuit system, and wherein the control device also controls the opening and closing of the third bypass circuit
  • a seventh aspect of the present invention is a control method in a refrigerant circuit system which includes one or a plurality of compressors configured to compress a refrigerant, a utilization-side heat exchanger configured to condense the refrigerant compressed by the compressor, a first expansion valve configured to depressurize the refrigerant introduced from the utilization-side heat exchanger, a receiver configured to store some of the refrigerant depressurized by the first expansion valve, a second expansion valve configured to depressurize the refrigerant flowing out from the receiver, a heat source-side heat exchanger configured to evaporate the refrigerant depressurized by the second expansion valve, and a first bypass circuit configured to bypass the flow of the refrigerant passing through the first expansion valve, wherein opening and closing of the first bypass circuit is controlled on the basis of the outlet side temperature of the utilization-side heat exchanger or an outlet side supercooling degree of the utilization-side heat exchanger and an opening degree of the first expansion valve.
  • An eighth aspect of the present invention is a control method in a refrigerant circuit system which includes one or a plurality of compressors configured to compress a refrigerant, a utilization-side heat exchanger configured to condense the refrigerant compressed by the compressor, a first expansion valve configured to depressurize the refrigerant introduced from the utilization-side heat exchanger, a receiver configured to store some of the refrigerant depressurized by the first expansion valve, a second expansion valve configured to depressurize the refrigerant flowing out from the receiver, a heat source-side heat exchanger configured to evaporate the refrigerant depressurized by the second expansion valve, and a second bypass circuit configured to bypass the flow of the refrigerant passing through the second expansion valve, wherein opening and closing of the second bypass circuit is controlled on the basis of the outlet side superheat degree of the heat source-side heat exchanger or the suction side superheat degree of the compressor and the opening degree of the second expansion valve.
  • an efficient operation can be allowed using a flow rate control valve having a predetermined diameter in the expansion valve even if the utilization-side inlet temperature is changed.
  • FIGS. 1 to 5 a refrigerant circuit system according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 5 .
  • FIG. 1 is a first diagram showing an example of a refrigerant circuit system in a first embodiment of the present invention.
  • a refrigerant circuit system 1 is a refrigerant circuit used for a water heater.
  • the refrigerant circuit system 1 heats feed water supplied from an outside to a predetermined temperature (for example, 80°C) and supplies the hot water to a user.
  • the embodiment provides the refrigerant circuit system 1 which is capable of efficiently supplying the hot water when the temperature of the feed water supplied from the outside is changed (for example, 5°C and 75°C).
  • the refrigerant circuit system 1 includes a compressor 10, a utilization-side heat exchanger (condenser) 11, a first expansion valve 12, a first bypass circuit 13, a receiver 14, a second expansion valve 15, a second bypass circuit 16, a heat source-side heat exchanger (evaporator) 17, an accumulator 18, a pipe 19 which connects the above-described elements, and a control device 100.
  • a first two-way valve 13A and a first capillary tube 13B are provided in first bypass circuit 13.
  • a second two-way valve 16A and a second capillary tube 16B are provided in the second bypass circuit 16.
  • the specific constitution of the refrigerant circuit system 1 shown in FIG. 1 schematically shows a basic constitution of the refrigerant circuit system 1 and may further include other elements.
  • the compressor 10 compresses a refrigerant and discharges a high-pressure refrigerant.
  • the high-pressure refrigerant is supplied to the utilization-side heat exchanger 11.
  • the utilization-side heat exchanger 11 serves as a condenser.
  • the high-pressure refrigerant supplied to the utilization-side heat exchanger 11 exchanges heat with the feed water used by the user, radiates heat and is condensed and liquefied. Meanwhile, the feed water supplied to the utilization-side heat exchanger 11 absorbs heat from the high-pressure refrigerant, is heated to a predetermined set temperature (utilization-side outlet temperature) and is provided to the user.
  • a dotted arrow indicates the flow direction of the feed water
  • a solid arrow indicates the flow direction of the refrigerant.
  • the high-pressure refrigerant after the heat exchange is depressurized and expanded in the first expansion valve 12 and is supplied to the receiver 14.
  • the receiver 14 is a pressure container which temporarily stores some of the supplied refrigerant.
  • a two-phase refrigerant in which a gas and a liquid are mixed is present.
  • the refrigerant flowing out from the receiver 14 is further depressurized and expanded in the second expansion valve 15 and becomes a low-pressure refrigerant.
  • the low-pressure refrigerant is supplied to the heat source-side heat exchanger 17.
  • the heat source-side heat exchanger 17 serves as an evaporator.
  • the low-pressure refrigerant supplied to the heat source-side heat exchanger 17 absorbs heat from a heat source such as external air so that a temperature thereof is increased, and thus the low pressure refrigerant is evaporated.
  • the low-pressure refrigerant is supplied to the accumulator 18.
  • the low-pressure refrigerant is separated into gas and liquid by the accumulator 18, and only the gas refrigerant is suctioned into the compressor 10.
  • the refrigerant is again made into a high pressure refrigerant by the compressor 10 and circulates through the above-described route.
  • the first expansion valve 12 and the second expansion valve 15 are flow rate control valves, and an opening degree thereof is adjusted by the control device 100.
  • the opening degree of the first expansion valve 12 is controlled with the goal of an outlet side temperature of the utilization-side heat exchanger 11 becoming higher than a utilization-side inlet temperature by a predetermined temperature (for example, 2°C).
  • the utilization-side inlet temperature is the temperature of the feed water flowing into the utilization-side heat exchanger 11.
  • the temperature of the feed water is, for example, 5 °C or 75°C (5°C in the case of a once-through system and 75°C in the case of a circulation system).
  • the control device 100 increases the opening degree of the first expansion valve 12 and performs control so that the outlet side temperature becomes the target temperature.
  • the first bypass circuit 13 is a circuit which bypasses the flow of the refrigerant passing through the first expansion valve 12.
  • the control device 100 performs the control to open the first two-way valve 13A.
  • the first two-way valve 13A is controlled to be in an open state
  • the refrigerant flowing out from the utilization-side heat exchanger 11 passes through the first expansion valve 12 and the first bypass circuit 13 and is supplied to the receiver 14.
  • the first capillary tube 13B is provided to adjust resistance such that the refrigerant does not flow into only the first bypass circuit 13 side.
  • the opening degree of the second expansion valve 15 is controlled with the goal of the outlet side temperature of the heat source-side heat exchanger 17 becoming a predetermined superheat degree (for example, 3K).
  • a predetermined superheat degree for example, 3K
  • the control device 100 performs control to increase the opening degree of the second expansion valve 15.
  • the second bypass circuit 16 is a circuit which bypasses the flow of the refrigerant passing through the second expansion valve 15.
  • the control device 100 opens the second bypass circuit 16 and secures the flow rate of the refrigerant flowing through the refrigerant circuit. Specifically, the control device 100 performs control so that the second two-way valve 16A is in the open state. In this case, the refrigerant flowing out from the receiver 14 passes through both the second expansion valve 15 and the second bypass circuit 16 and is supplied to the heat source-side heat exchanger 17.
  • the second capillary tube 16B is provided to adjust the resistance such that the refrigerant does not flow into only the second bypass circuit 16 side.
  • a temperature sensor 31 is provided on an outlet side of the utilization-side heat exchanger 11, and a temperature sensor 32 and a pressure sensor 33 are provided on the outlet side of the heat source-side heat exchanger 17.
  • the control device 100 obtains the outlet side temperature of the utilization-side heat exchanger 11 which is measured by the temperature sensor 31, the outlet side temperature of the heat source-side heat exchanger 17 which is measured by the temperature sensor 32 and an outlet side pressure of the heat source-side heat exchanger 17 which is measured by the pressure sensor 33.
  • the control device 100 controls the valve opening degrees of the first expansion valve 12 and the second expansion valve 15.
  • the control device 100 controls opening and closing of the first two-way valve 13A on the basis of the valve opening degree of the first expansion valve 12 and the temperature measured by the temperature sensor 31.
  • control device 100 controls the opening and closing of the second two-way valve 16A on the basis of the valve opening degree of the second expansion valve 15, the temperature measured by the temperature sensor 32 and the pressure measured by the pressure sensor 33. Further, the control device 100 is a computer device such as a microcomputer.
  • FIG. 2 is a P-h diagram of the refrigerant circuit system in the first embodiment of the present invention.
  • FIG. 2 is a relationship diagram of the pressure and the enthalpy which indicates a refrigeration cycle of the refrigerant circuit system 1 according to the embodiment.
  • each symbol indicates the following state. That is, A1 indicates the state of the high temperature and high pressure refrigerant discharged from the compressor 10, A2 indicates the state of the refrigerant on the outlet side of the utilization-side heat exchanger 11 when the utilization-side inlet temperature is high (for example, 75°C), A3 indicates the state of the refrigerant on the outlet side of the first expansion valve 12 when the utilization-side inlet temperature is high, A4 indicates the state of the refrigerant on the outlet side of the second expansion valve 15 when the utilization-side inlet temperature is high, A5 indicates the state of the refrigerant on the outlet side of the utilization-side heat exchanger 11 when the utilization-side inlet temperature is low (for example, 5°C), A6 indicates the state of the refrigerant on the outlet side of the first expansion valve 12 when the utilization-side inlet temperature is low
  • the change in the control region of the first expansion valve 12 and the second expansion valve 15 corresponding to a change in the utilization-side inlet temperature are as follows.
  • the pressure difference between the front and the rear of the first expansion valve 12 is a low differential pressure (PH2).
  • the pressure difference between the front and the rear of the second expansion valve 15 is a high differential pressure (PL2). That is, the control region due to the second expansion valve 15 has the high differential pressure, and the control region due to the first expansion valve 12 has a low differential pressure.
  • the high temperature and high pressure refrigerant (state A1) discharged from the compressor 10 radiates a large amount of heat to the feed water in the utilization-side heat exchanger 11, is condensed and liquefied and becomes a high pressure liquid refrigerant (state A5).
  • the refrigerant (state A6) greatly depressurized (PH1) by passing through the first expansion valve 12 reaches the second expansion valve 15 via the receiver 14.
  • the refrigerant is slightly depressurized (PL1) (state A7) by the second expansion valve 15 and flows into the heat source-side heat exchanger 17.
  • the refrigerant is evaporated by the heat source-side heat exchanger 17 and becomes a low pressure gas refrigerant (state A8).
  • the low pressure gas refrigerant flows into the accumulator 18, only the gas refrigerant is suctioned into the compressor 10, and the same cycle is repeated again.
  • the pressure difference between the front and the rear of the first expansion valve 12 is a high differential pressure (PH1).
  • the pressure difference between the front and the rear of the second expansion valve 15 is a low differential pressure (PL1). That is, the control region due to the first expansion valve 12 has a high differential pressure, and the control region due to the second expansion valve 15 has a low differential pressure.
  • the pressure difference which should be controlled by the first expansion valve 12 is largely different between the case (PH2) in which the utilization-side inlet temperature is high and the case (PH1) in which the utilization-side inlet temperature is low.
  • the pressure difference which should be controlled by the second expansion valve 15 is largely different between the case (PL2) in which the utilization-side inlet temperature is high and the case (PL1) in which the utilization-side inlet temperature is low.
  • the flow rate of the refrigerant can be secured even if the flow rate control valve having a small diameter is used in the first expansion valve 12.
  • the flow rate of the refrigerant cannot be secured unless the flow rate control valve having a relatively large diameter is used in the first expansion valve 12.
  • the flow rate of the refrigerant can be secured even if the flow rate control valve having the small diameter is used in the second expansion valve 15.
  • the utilization-side inlet temperature is low (the control range has the low differential pressure)
  • the flow rate of the refrigerant cannot be secured unless the flow rate control valve having the relatively large diameter should be used in the second expansion valve 15.
  • the flow rate of the refrigerant cannot be secured, a problem that the superheat degree of the refrigerant due to the evaporator is increased and the coefficient of performance (COP) is lowered occurs.
  • the problem may be solved by using the flow rate control valve having the large diameter as both of the first expansion valve 12 and the second expansion valve 15.
  • the diameter of the flow rate control valve used in the first expansion valve 12 and the second expansion valve 15 is selected assuming the case of a normal differential pressure, and the bypass circuit (the first bypass circuit 13, the second bypass circuit 16) having a throttle function which can be opened and closed is provided in parallel with the first expansion valve 12 and the second expansion valve 15.
  • the flow rate of the refrigerant is secured by opening the bypass circuit and flowing the refrigerant to both of the flow rate control valve and the bypass circuit. That is, the necessary flow rate of the refrigerant is secured by reducing the flow rate of the refrigerant flowing through the flow rate control valve side and flowing the remaining refrigerant to the bypass circuit side.
  • the bypass circuit is closed so that the refrigerant flows through only the flow rate control valve, and thus the fine flow rate control is performed by the flow rate control valve.
  • the control device 100 determines whether the flow rate of the refrigerant is insufficient and performs control to open the first bypass circuit 13 (the first two-way valve 13A) when the flow rate of the refrigerant is insufficient. Also, when the utilization-side inlet temperature is low, the control device 100 performs control to open the second bypass circuit 16 (the second two-way valve 16A) if the refrigerant flow rate is insufficient.
  • FIG. 3 is a flowchart of the control device in the first embodiment of the present invention.
  • the control device 100 acquires information on the temperature measured by the temperature sensor 31 and the temperature sensor 32 at predetermined time intervals and records the acquired information on the temperature in a built-in memory part (not shown). Further, the control device 100 acquires information on the pressure measured by the pressure sensor 33 at predetermined time intervals and records the acquired information on the pressure in the memory part. Furthermore, the control device 100 controls the number of rotations (frequency) of the compressor 10 and the opening degree of each of the first expansion valve 12 and the second expansion valve 15, and these values during the operation are recorded in the memory part.
  • the opening and closing of the first expansion valve 12 is controlled on the basis of the valve opening degree of the first expansion valve 12 and the outlet side temperature of the utilization-side heat exchanger 11 which is measured by the temperature sensor 31 will be described as an example.
  • the control device 100 reads the valve opening degree of the first expansion valve 12 from the memory part.
  • the control device 100 determines whether the read valve opening degree is within a predetermined range (Step S11).
  • the predetermined range is, for example, 20% to 80%.
  • the control device 100 continues the normal operation (Step S17).
  • the control device 100 continues the adjustment of the valve opening degree so that the outlet side temperature of the utilization-side heat exchanger 11 is higher than the utilization-side inlet temperature by a predetermined temperature (for example, 2°C).
  • a pressure sensor is provided on the outlet side of the utilization-side heat exchanger 11, and the control device 100 may find a saturation temperature at the pressure indicated by a measurement result of the pressure sensor and may control the valve opening degree so that a supercooling degree which is a value obtained by subtracting the temperature measured by the temperature sensor 31 from the saturation temperature becomes a predetermined target value.
  • Step S12 determines whether the valve opening degree of the first expansion valve 12 is less than a lower limit.
  • the lower limit of the valve opening degree is, for example, 20%.
  • Step S13 determines whether a control value (the outlet side temperature or the outlet side supercooling degree of the utilization-side heat exchanger 11) has reached the target value (Step S13).
  • Step S13 determines whether the target value has been achieved.
  • Step S13 When the target value has not been achieved (Step S13; No), the control device 100 controls the first bypass circuit 13 to be closed (Step S14) because it is considered that the flow rate of the refrigerant is excessive and thus the target value cannot be achieved. Specifically, the control device 100 closes the first two-way valve 13A. The control device 100 controls the first bypass circuit 13 to be closed and then continues normal operation (Step S17).
  • Step S12 when the valve opening degree of the first expansion valve 12 is not less than the lower limit (Step S12; No), that is, when the valve opening degree of the first expansion valve 12 is higher than an upper limit (80%), the control device 100 determines whether the control value (the outlet side temperature or the outlet side supercooling degree of the utilization-side heat exchanger 11) has reached the target value (Step S15). When the target value has been achieved (Step S15; Yes), the control device 100 continues the normal operation (Step S17).
  • the control value the outlet side temperature or the outlet side supercooling degree of the utilization-side heat exchanger 11
  • Step S15 When the target value has not been achieved (Step S15; No), the control device 100 controls the first bypass circuit 13 to be opened (Step S16) because it is considered that the target value cannot be achieved due to an insufficient flow rate of the refrigerant despite the valve opening degree of the first expansion valve 12 being sufficient. Specifically, the control device 100 opens the first two-way valve 13A. The control device 100 opens the first bypass circuit 13 and then continues the normal operation (Step S17).
  • Step S18 the control device 100 determines whether the operation is to be continued. For example, when an instruction to stop the operation is input, the control device 100 determines to stop the operation. Further, when an operation instruction is input, the control device 100 determines to continue the operation. When it is determined that the operation is to be continued (Step S18; Yes), the processing from Step S11 is repeated. When it is determined that the operation is to be stopped (Step S18; No), the processing flow ends.
  • Step S13 and Step S15 the control device 100 compares the outlet side superheat degree of the heat source-side heat exchanger 17 or the suction side superheat degree of the compressor 10 with the target values thereof and determines whether the target value is achieved or not yet achieved. For example, in the case of the superheat degree on the outlet side of the heat source-side heat exchanger 17, the control device 100 finds a saturation temperature at the pressure measured by the pressure sensor 33 and calculates the superheat degree by subtracting the saturation temperature from the temperature measured by the temperature sensor 32. Further, in the memory part of the control device 100, a conversion table of the pressure and the saturation temperature is recorded, and the control device 100 calculates the saturation temperature from the pressure measured by the pressure sensor 33 and the conversion table.
  • the control device 100 opens the second bypass circuit 16 by opening the second two-way valve 16A. Further, the control device 100 closes the second bypass circuit 16 by closing the second two-way valve 16A. Also, in the operation of Step S17, the control device 100 controls the opening degree of the second expansion valve 15 so that the outlet side superheat degree of the heat source-side heat exchanger 17 or the suction side superheat degree of the compressor 10 becomes the target value thereof.
  • the flow rate of the refrigerant is ensured, and thus COP reduction in the refrigerant circuit system 1 and an increase in cost due to use of the large-diameter flow rate control valve can be prevented.
  • the utilization-side inlet temperature is low (e.g., 5°C)
  • an excessive increase in the outlet side superheat degree of the heat source-side heat exchanger (evaporator) 17 which causes a low COP can be prevented by opening the second bypass circuit.
  • FIG. 4 is a second diagram showing an example of the refrigerant circuit system in the first embodiment of the present invention.
  • the second bypass circuit 16 may not be provided in the refrigerant circuit system 1 of FIG. 1 , and only the first bypass circuit 13 may be provided.
  • a refrigerant circuit system 1A as shown in FIG. 4 can be used in the water heater.
  • the control device 100 performs only the opening and closing control of the first two-way valve 13A according to the control method of the flowchart described in FIG. 3 .
  • opening the first two-way valve 13A opening the first bypass circuit 13
  • the flow rate of the refrigerant can be ensured and the refrigerant circuit system 1A can be efficiently operated even if the first expansion valve 12 side has the low differential pressure.
  • FIG. 5 is a third diagram showing an example of the refrigerant circuit system in the first embodiment of the present invention.
  • the first bypass circuit 13 may not be provided in the refrigerant circuit system 1 of FIG. 1 , and only the second bypass circuit 16 may be provided.
  • a refrigerant circuit system 1B as shown in FIG. 5 can be used in the water heater.
  • the control device 100 performs only the opening and closing control of the second two-way valve 16A according to the control method of the flowchart described in FIG. 3 .
  • FIG. 6 is a view showing an example of a refrigerant circuit system in a second embodiment of the present invention.
  • a refrigerant circuit system 1C includes a high stage-side compressor 10A, a low stage-side compressor 10B, a utilization-side heat exchanger (condenser) 11, a first expansion valve 12, a first bypass circuit 13, a receiver 14, a second expansion valve 15, a second bypass circuit 16, a heat source-side heat exchanger (evaporator) 17, an accumulator 18, a pipe 19 which connects the elements, an intermediate heat exchanger 20, a third expansion valve 21, a third bypass circuit 22, an injection circuit 23, and a control device 100.
  • a first two-way valve 13A and a first capillary tube 13B are provided in the first bypass circuit 13.
  • a second two-way valve 16A and a second capillary tube 16B are provided in the second bypass circuit 16.
  • a third two-way valve 22A and a third capillary tube 22B are provided in the third bypass circuit 22.
  • the third expansion valve is provided in the middle of the injection circuit 23.
  • the high stage-side compressor 10A and the low stage-side compressor 10B are connected in series.
  • a suction side of the low stage-side compressor 10B is connected to the accumulator 18. Further, an outlet side of the low stage-side compressor 10B is connected to a suction side of the high stage-side compressor 10A.
  • the low stage-side compressor 10B suctions and compresses a low pressure refrigerant and discharges an intermediate pressure refrigerant to the high stage-side compressor 10A side.
  • the injection circuit 23 which diverges some of the refrigerant from a main flow circuit connected to the second expansion valve 15 and the heat source-side heat exchanger 17 and then supplies the diverged refrigerant to the suction side of the high stage-side compressor 10A is provided on a downstream side of the receiver 14.
  • the intermediate heat exchanger 20 which exchanges heat between the refrigerant flowing through the injection circuit 23 and depressurized in the third expansion valve 21 and the refrigerant flowing through the main flow circuit is provided in the injection circuit 23.
  • the diverged refrigerant is depressurized by the third expansion valve 21, then exits from an outlet of the intermediate heat exchanger 20 on the high stage-side compressor side, is returned to the high stage-side compressor 10A and is then recompressed.
  • the injection circuit 23 can improve the COP of the refrigeration cycle as is well known.
  • the third bypass circuit 22 is a circuit for bypassing the flow of the refrigerant passing through the third expansion valve 21.
  • the third bypass circuit 22 of the embodiment is controlled to be in an open state when a pressure difference between a front and a rear of the third expansion valve 21 is a low differential pressure and the flow rate of the refrigerant returned to the high stage-side compressor 10A through the injection circuit 23 cannot be secured.
  • Other constitutions are the same as those in the first embodiment.
  • FIG. 7 is a P-h diagram of the refrigerant circuit system in the second embodiment of the present invention.
  • FIG. 7 is a relationship diagram of the pressure and the enthalpy which indicates a refrigeration cycle of a refrigerant circuit system 1C according to the embodiment.
  • each symbol indicates the following state. That is, A1 indicates the state of the refrigerant discharged from the high stage-side compressor 10A, A2 indicates the state of the refrigerant on the outlet side of the utilization-side heat exchanger 11 when the utilization-side inlet temperature is high (e.g., 75°C), A3 indicates the state of the refrigerant on the outlet side of the first expansion valve 12 when the utilization-side inlet temperature is high, A4 indicates the state of the refrigerant on the inlet side of the second expansion valve 15 when the utilization-side inlet temperature is high, A5 indicates the state of the refrigerant on the outlet side of the second expansion valve 15 when the utilization-side inlet temperature is high, A6 indicates the state of the refrigerant on the outlet side of the heat source-side heat exchanger 17, A7 indicates the state of the refrigerant on the
  • B2 indicates the state of the refrigerant on the outlet side of the utilization-side heat exchanger 11 when the utilization-side inlet temperature is low (e.g., 5°C)
  • B3 indicates the state of the refrigerant on the outlet side of the first expansion valve 12 when the utilization-side inlet temperature is low
  • B4 indicates the state of the refrigerant on the inlet side of the second expansion valve 15 when the utilization-side inlet temperature is low
  • B5 indicates the state of the refrigerant on the outlet side of the second expansion valve 15 when the utilization-side inlet temperature is low
  • B8 indicates the state of the refrigerant on the outlet side of the third expansion valve 21 when the utilization-side inlet temperature is low.
  • the change in the control region of the first expansion valve 12, the second expansion valve 15 and the third expansion valve 21 corresponding to a change in the utilization-side inlet temperature are as follows.
  • PL4 depressurized
  • the low pressure gas refrigerant is boosted to an intermediate pressure by the low stage-side compressor 10B (state A7) and is supplied to the suction side of the high stage-side compressor 10A.
  • the refrigerant diverged to the injection circuit 23 is depressurized (PM4) to the intermediate pressure (state A8) by the third expansion valve 21, absorbs heat through the intermediate heat exchanger 20 and is supplied to the suction side of the high stage-side compressor 10A.
  • the intermediate pressure refrigerant whose temperature is lowered (state A9) by mixing the refrigerant supplied through the injection circuit 23 and the refrigerant compressed by the low stage-side compressor 10B is supplied to the high stage-side compressor 10A.
  • the high stage-side compressor 10A compresses the intermediate pressure refrigerant and discharges the high temperature and high pressure refrigerant (state A1). The same cycle is repeated thereafter.
  • the pressure difference between the front and the rear of the first expansion valve 12 is a low differential pressure (PH4).
  • the pressure difference between the front and the rear of the second expansion valve 15 is a high differential pressure (PL4).
  • the pressure difference between the front and the rear of the third expansion valve 21 is a high differential pressure (PM4).
  • the low pressure gas refrigerant is compressed to an intermediate pressure by the low stage-side compressor 10B (state A7) and is supplied to the suction side of the high stage-side compressor 10A.
  • the refrigerant diverged to the injection circuit 23 is depressurized (PM3) to the intermediate pressure (state B8) by the third expansion valve 21, absorbs heat through the intermediate heat exchanger 20 and is supplied to the suction side of the high stage-side compressor 10A.
  • the intermediate pressure refrigerant whose temperature is lowered (state A9) by mixing the refrigerant supplied through the injection circuit 23 and the refrigerant compressed by the low stage-side compressor 10B is supplied to the high stage-side compressor 10A.
  • the high stage-side compressor 10A compresses the intermediate pressure refrigerant and discharges the high temperature and high pressure refrigerant (state A1). The same cycle is repeated thereafter.
  • the pressure difference between the front and the rear of the first expansion valve 12 is a high differential pressure (PH3).
  • the pressure difference between the front and the rear of the second expansion valve 15 is a low differential pressure (PL3).
  • the pressure difference between the front and the rear of the third expansion valve 21 is a low differential pressure (PM3).
  • the control device 100 opens the third bypass circuit 22, for example, in the case of the third expansion valve 21 and controls the necessary amount of refrigerant to flow through the injection circuit 23.
  • the control of the first bypass circuit 13 is the same as in the first embodiment.
  • the control device 100 controls the opening and closing of the first two-way valve 13A on the basis of the valve opening degree of the first expansion valve 12 and the outlet side temperature or supercooling degree of the utilization-side heat exchanger 11.
  • the control of the second bypass circuit 16 is the same as in the first embodiment.
  • the control device 100 controls the opening and closing of the second two-way valve 16A on the basis of the valve opening degree of the second expansion valve 15 and the outlet side superheat degree of the heat source-side heat exchanger 17 or the suction side superheat degree of the low stage-side compressor 10B.
  • the control of the third bypass circuit 22 is also the same.
  • the control device 100 controls the opening and closing of the third two-way valve 22A, for example, on the basis of the valve opening degree of the third expansion valve 21 and the outlet side temperature of the intermediate heat exchanger 20 measured by a temperature sensor 34. Details of the control are as described in the flowchart of FIG. 3 . Therefore, even if the flow rate of the refrigerant passing through the third expansion valve 21 is small, the refrigerant flowing into the injection circuit 23 is also supplied from the third bypass circuit 22, and thus the flow rate of the intermediate pressure refrigerant supplied from the injection circuit 23 to the high stage-side compressor 10A can be secured.
  • the embodiment even if the pressure difference between the front and the rear of each of the first expansion valve 12, the second expansion valve 15 and the third expansion valve 21 is the low differential pressure, the flow rate of the refrigerant is ensured, and thus the COP reduction in the refrigerant circuit system 1C and an increase in cost due to the use of the large-diameter flow rate control valve in each of the expansion valves can be prevented. Also, in the refrigerant circuit system 1C shown in FIG. 6 , the case in which the first bypass circuit 13, the second bypass circuit 16 and the third bypass circuit 22 are provided has been described. However, only one or two of the three bypass circuits may be provided according to the width of the control range of the first expansion valve 12, the second expansion valve 15 and the third expansion valve 21.
  • the two-way valve and the capillary tube are combined as an example of the constitution of the first bypass circuit 13, the second bypass circuit 16 and the third bypass circuit 22.
  • this combination may be replaced with a single flow rate control valve, and in the first bypass circuit 13 or the like, the flow rate of the refrigerant may be secured by adjusting the valve opening degree of the flow rate control valve used as a replacement.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Air Conditioning Control Device (AREA)
EP17194420.0A 2016-10-05 2017-10-02 Kältemittelkreislaufsystem und steuerungsverfahren Withdrawn EP3306230A1 (de)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2016197358A JP2018059665A (ja) 2016-10-05 2016-10-05 冷媒回路システム及び制御方法

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EP3306230A1 true EP3306230A1 (de) 2018-04-11

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007010282A (ja) 2005-07-04 2007-01-18 Hitachi Ltd 二段圧縮式冷凍サイクル装置
JP2007155230A (ja) * 2005-12-06 2007-06-21 Hitachi Appliances Inc 空気調和機
EP2224187A2 (de) * 2004-10-18 2010-09-01 Mitsubishi Denki Kabushiki Kaisha Kühl-/Klimaanlage
WO2013061365A1 (ja) * 2011-10-26 2013-05-02 三菱電機株式会社 空気調和装置
EP2722616A1 (de) * 2011-06-14 2014-04-23 Mitsubishi Electric Corporation Klimaanlage

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2224187A2 (de) * 2004-10-18 2010-09-01 Mitsubishi Denki Kabushiki Kaisha Kühl-/Klimaanlage
JP2007010282A (ja) 2005-07-04 2007-01-18 Hitachi Ltd 二段圧縮式冷凍サイクル装置
JP2007155230A (ja) * 2005-12-06 2007-06-21 Hitachi Appliances Inc 空気調和機
EP2722616A1 (de) * 2011-06-14 2014-04-23 Mitsubishi Electric Corporation Klimaanlage
WO2013061365A1 (ja) * 2011-10-26 2013-05-02 三菱電機株式会社 空気調和装置

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