WO2010010414A1 - Procédés et systèmes d'utilisation d'un compresseur - Google Patents

Procédés et systèmes d'utilisation d'un compresseur Download PDF

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Publication number
WO2010010414A1
WO2010010414A1 PCT/IB2008/001908 IB2008001908W WO2010010414A1 WO 2010010414 A1 WO2010010414 A1 WO 2010010414A1 IB 2008001908 W IB2008001908 W IB 2008001908W WO 2010010414 A1 WO2010010414 A1 WO 2010010414A1
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WO
WIPO (PCT)
Prior art keywords
compressor
valve
refrigeration system
temperature
heat exchanger
Prior art date
Application number
PCT/IB2008/001908
Other languages
English (en)
Inventor
Fabienne Peyaud
Jean-Philippe Goux
David Veillon
Frederic Brisset
Original Assignee
Carrier Corporation
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 Carrier Corporation filed Critical Carrier Corporation
Priority to CN2008801304806A priority Critical patent/CN102105759B/zh
Priority to EP08788911.9A priority patent/EP2321595B1/fr
Priority to US13/003,942 priority patent/US20110113797A1/en
Priority to PCT/IB2008/001908 priority patent/WO2010010414A1/fr
Publication of WO2010010414A1 publication Critical patent/WO2010010414A1/fr
Priority to HK11113640.4A priority patent/HK1159234A1/xx

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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
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • 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
    • F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
    • F25B41/24—Arrangement of shut-off valves for disconnecting a part of the refrigerant cycle, e.g. an outdoor part
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/01—Heaters
    • 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
    • F25B2500/00—Problems to be solved
    • F25B2500/26—Problems to be solved characterised by the startup of the refrigeration cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2500/00—Problems to be solved
    • F25B2500/31—Low ambient temperatures
    • 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
    • F25B2600/025—Compressor control by controlling speed

Definitions

  • the present invention relates to methods and systems for compressor operation before and during compressor startup and/or shutdown and in particular to methods and systems for reliable startup of a compressor, even at low ambient temperatures.
  • Conventional refrigeration or airconditioning systems typically comprise a compressor, a heat rejecting heat exchanger or condenser, an expansion valve or device and a heat accepting heat exchanger or evaporator.
  • refrigerant is circulated through these components in a closed circuit.
  • the pressure and temperature of the refrigerant vapour is increased by the compressor before entering the heat rejecting heat exchanger where it is cooled.
  • the high pressure, lower temperature liquid is then expanded to a lower pressure by means of the expansion valve.
  • the refrigerant boils and absorbs heat from its surroundings.
  • the vapour at the heat accepting heat exchanger outlet is drawn into the compressor, completing the cycle.
  • a refrigeration system comprising a compressor, a heat rejecting heat exchanger, an expansion valve and a heat accepting heat exchanger.
  • the system further comprises a pressure equalisation valve (PEV) for equalising the pressure differential between the compressor suction and compressor discharge.
  • PEV pressure equalisation valve
  • the pressure equalisation valve comprises a bypass passage connecting the compressor suction to the compressor discharge and bypassing the compressor.
  • the system further comprises a liquid valve (LV), preferably a liquid solenoid valve (LSV), the liquid valve preferably arranged in a flow line between the heat rejecting heat exchanger and the expansion valve.
  • LV liquid valve
  • LSV liquid solenoid valve
  • a refrigeration system comprising a main refrigerant flow path from the compressor to the heat rejecting heat exchanger, from the heat rejecting heat exchanger to the liquid valve, from the liquid valve to the expansion valve and from the expansion valve to the heat accepting heat exchanger.
  • a bypass refrigerant path or other pressure equalisation valve is provided across the compressor, i.e. from the compressor suction to the compressor discharge that, when opened, bypasses refrigerant flow around the compressor and enables the pressure differential between the compressor suction and the compressor discharge to be minimised, or more preferably the suction and discharge pressures to be balanced, particularly on compressor shutdown and most preferably at or shortly before compressor startup.
  • the refrigeration system is operable in at least one of a plurality of predetermined sequences, and the particular sequence (or sequences) used is preferably determined based on at least one parameter of the refrigeration system.
  • the parameter (or parameters) comprises a system parameter measured by at least one sensor.
  • a preheating sequence is initiated in which one or more components of the compressor is heated.
  • the compressor body or shell, and/or the oil in the compressor, and/or the compressor motor, and/or any other suitable component is heated.
  • the component(s) is heated for a predetermined period of time, which may be determined based on one or more system parameters. In a preferred embodiment, the period for which the component is heated is determined based on the temperature of
  • the oil in the compressor, and/or the compressor shell temperature, and/or the compressor discharge temperature, and/or the temperature of the environment in which the compressor is located i.e. the ambient temperature
  • the period for which the component is heated is additionally or alternatively deterrnined based on the length of time for which the compressor has been shut down (for example if the compressor was only recently shut down, it may only be necessary to heat the component for a relatively short time, as the component may have retained some of the heat from its normal operating conditions and temperature).
  • Heating of the component(s) of the compressor is carried out in any suitable manner.
  • the stator windings of a motor associated with the compressor for example the internal electric alternating current motor (synchronous or asynchronous) of the compressor are electrically connected to an electrical source, e.g. a direct current source, to thereby heat the windings and thus heat the compressor.
  • the pressure equalisation valve can be opened prior to compressor start up, but in preferred embodiments the pressure equalisation valve is opened when the compressor is started (preferably at substantially the same time as the compressor is started).
  • the pressure equalisation valve is a bypass passage, the passage is opened as the compressor is started to allow pressure balancing between the compressor suction and discharge by bypassing the compressor.
  • the pressure equalisation valve is opened after the preheating steps discussed above.
  • the compressor is started slowly, e.g. at a speed or frequency considerably lower than a standard operating frequency.
  • Starting the compressor and opening the pressure equalisation valve allows oil in the compressor to be mixed. This is advantageous because in a shutdown compressor the temperature of the oil is not homogeneous in the compressor shell.
  • the oil and other parts of the compressor are heated by the refrigerant that bypasses the compressor via the pressure equalisation valve, the vapour refrigerant from the discharge valve in the compressor being hotter than the actual suction gas refrigerant and when passing through the bypass and the compressor suction, the vapour heats the mechanical parts of the compressor and the oil. That is the bypass line generally emits heat to the compressor and heats the oil that is circulating in the compressor. Pressure in the compressor body or shell is limited by the bypass.
  • the oil temperature of the compressor is maintained above the saturated discharge temperature of the refrigerant in the compressor shell. At temperatures below the saturated discharge temperature the vapour refrigerant condenses and if the oil temperature is below the saturated-discharge temperature, refrigerant will condense into the oil.
  • the compressor shell temperature is also maintained above the saturated discharge temperature of the refrigerant. If the oil, and preferably also the mechanical components and the shell of the compressor, are. above the saturated discharge temperature refrigerant will not condense in the compressor.
  • the speed of the compressor at startup is lower than the normal running speed of the compressor as previously mentioned.
  • the compressor at startup operates at a frequency of 30 Hz.
  • Low compressor speed is desirable at startup because a low flow rate through the compressor minimises refrigerant condensation in the compressor.
  • the liquid valve is closed prior to and during compressor startup.
  • the liquid valve closes as the compressor stops and remains closed during compressor shutdown. Closing the liquid valve on compressor shutdown limits ' the flow of refrigerant into the compressor limiting condensation in the compressor oil.
  • the liquid valve is opened. Therefore the system is operating in some states with both the pressure equalisation valve and the liquid valve open and the compressor operating at low frequency. This enables increased flow of refrigerant at the compressor suction, although the refrigerant flow is still lower than during normal system operation because the pressure equalisation valve is open (i.e. the compressor remains bypassed at this stage).
  • the liquid valve is opened when it is determined that a system parameter is at a desired level.
  • the system parameter is the oil temperature and when the oil temperature is determined (for example by measurement with a temperature sensor) to be sufficiently high (for example above a predetermined limit, and/or above the saturated discharge temperature of the refrigerant in the compressor, etc.), then the liquid valve is opened.
  • the parameter is alternatively or additionally the pressure in the compressor shell.
  • the liquid valve could instead or additionally be opened in response to other events, for example after a predetermined period of time (e.g. from compressor startup, and/or from opening of the pressure equalisation valve, or from any other action or event, etc.).
  • the pressure equalisation valve is closed. This occurs in response to any one or more of the following: after a predetermined period of time since opening the liquid valve; after a period of time has elapsed following any other suitable event; after a period of time has elapsed following one or more system parameters being determined to have reached a particular level; immediately after opening the liquid valve; etc.
  • the system parameter comprises either the compressor discharge temperature or the oil temperature and when the temperature is determined (for example by measurement with a temperature sensor) to be sufficiently high (for example above a predetermined limit, and/or above the saturated discharge temperature in the compressor, etc.);, then the pressure equalisation valve is closed.
  • the pressure of the suction and discharge of the compressor are therefore no longer balanced and refrigerant passes through the compressor at a greater flow rate than-wheirtbre ⁇ pressure-- equalisation valve was open (e.g. refrigerant no longer bypasses the compressor).
  • the compressor speed is preferably then increased, either immediately or preferably in response to a measured system parameter reaching a predetermined limit and/or after a period of time has elapsed, etc.
  • the compressor speed is slowly increased, preferably by a predetermined amount and/or at a predetermined rate, until a maximum or optimum speed is achieved and/or a predetermined time period has elapsed.
  • the compressor speed may be set to the maximum (i.e. standard) operating speed (which is preferably after a period of slow increase in compressor speed from the initial startup speed).
  • the compressor discharge temperature and/or oil temperature of the compressor has reached a predetermined level, the compressor is controlled to operate at normal operating speeds.
  • the above preferred systems and operational steps provide compressor starting sequences that enable a compressor to be started with minimal risk of failure which otherwise might occur due to condensation of refrigerant in the compressor, particularly at low ambient temperatures, after compressor shutdown.
  • Refrigerant condensation is detrimental in a compressor because condensed refrigerant can become mixed with oil in the compressor sump, and if the oil temperature in the compressor is below the saturated discharge temperature of the refrigerant then refrigerant can condense in the oil.
  • refrigerant in the oil is pumped by the oil pump and may fail.
  • a method of optimising compressor startup for a compressor of a refrigeration system comprising the steps of: preheating at least one component of a compressor in a refrigeration system; opening a pressure equalisation valve that connects a suction and a discharge of the compressor to thereby reduce " the pressure differential therebetween; starting the compressor, preferably with a predetermined frequency ft, preferably at substantially the same time as opening the pressure equalisation valve.
  • the method further comprises the steps of opening a liquid valve that is located in a refrigerant flow path of the system in response to a first event, closing the pressure equalisation valve in response to a second event, and increasing the frequency of operation of the compressor.
  • the starting speed of the compressor is less than the compressor standard operating speed f s .
  • ft is about 30 Hz.
  • fs is about 60 Hz, preferably about 65 Hz or greater.
  • the method comprises the further steps of: further increasing the frequency of operation of the compressor to a standard operating frequency, preferably in response to a third event.
  • the first event comprises at least one of a first predetermined period of time elapsing and a measured compressor oil temperature being deterr ⁇ med— to be above a predetermined threshold.
  • the second event comprises at least one of a second predetermined period of time elapsing and a measured compressor oil temperature being determined to be above a predetermined threshold.
  • the method further comprises the steps of providing at least one system sensor and measuring at least one parameter of the system with the sensor, and operating the system in at least one of a plurality of predetermined sequences based on the at least one parameter measured by the sensor.
  • the step of preheating at least one component of the compressor comprises the steps of providing means for heating at least one component of the compressor, and activating the heating means to heat the component when it is determined that compressor startup is required.
  • the means for heating at least one component of the compressor comprises means for heating at least one of the compressor body or shell, the oil in the compressor, and the compressor motor:
  • the heating means comprises means for supplying DC electricity to the stator windings of an internal AC motor of the compressor.
  • the method further comprises providing at least one sensor and measuring at least one parameter of the system with the sensor, and the heating means is activated for a predetermined period of time based on the at least one parameter.
  • the predetermined period is based on at least one of the temperature of the oil in the compressor, the compressor shell temperature;, the compressor discharge temperature, the ambient temperature and the length of time for which the compressor has been inactive.
  • the method further comprises the steps - ef-m-easurmg the- temperature of oil in the compressor, determining the saturated discharge temperature of refrigerant in the compressor, and heating at least one component of the compressor such that die oil is maintained at a temperature above the saturated discharge temperature.
  • preheating a refrigeration system prior to compressor start up and controlling a liquid valve and a pressure equalisation valve before and during start up can advantageously reduce or eliminate refrigerant condensation problems, particularly in low ambient temperatures.
  • the above system may experience failure or other problems on compressor startup for further reasons on or after compressor shutdown.
  • a refrigeration system comprising a compressor, a heat rejecting heat exchanger, an expansion valve and a heat accepting heat exchanger.
  • the system further comprises a liquid valve (LV), preferably a liquid solenoid valve (LSV) or an electronic expansion valve (EXV), the liquid valve arranged in a flow line between the heat rejecting heat exchanger and the expansion valve, and a check valve arranged in a flow line between the heat rejecting heat exchanger and the compressor.
  • LV liquid valve
  • LSV liquid solenoid valve
  • EXV electronic expansion valve
  • the refrigeration system is advantageous in that when the compressor is shut down the liquid valve is actuated to close and the check valve is also closed.
  • the check valve is closed by the pressure differential between the high pressure side of the system and the compressor.
  • the check valve is a solenoid valve and is actuated to close.
  • the check valve comprises a combination of a solenoid valve and a pressure-actuated -valver- -In a standard circuit without this valve arrangement the pressure differential would cause refrigerant to migrate to the compressor from the high side, e.g. from the- condenser and also from the evaporator, particularly during long periods of compressor shutdown, for example 12 hours or more. Any refrigerant that migrates to the compressor during shutdown can condense in the compressor or otherwise migrate into the compressor oil, which can lead to compressor failure on start up, for example due to the low oil viscosity.
  • the system of the embodiments of this aspect of the present • invention advantageously reduces the amount of, or even prevents, refrigerant reaching the compressor during shutdown and therefore little or no refrigerant can mix with the compressor oil.
  • This is advantageous because the amount of refrigerant in the oil is minimised and therefore the oil viscosity will remain sufficiently high, whereas low viscosity oil is dangerous for the compressor.
  • the check valve is configured such that a pressure differential between the valve inlet and the valve outlet is required to open the check valve, preferably a significant pressure differential.
  • the system of this embodiment is further advantageous in that the check valve in combination with the liquid valve will maintain the refrigerant in the condenser (and in any other component that may be present between the check valve and the liquid valve, such as in preferred embodiments an accumulator and/or a dryer, etc.).
  • the check valve is configured such that if the pressure at the inlet and the outlet of the check valve is balanced, which may occur over time after the compressor is shut down, the valve remains closed. That is in preferred embodiments the check valve is configured such that refrigerant can pass ⁇ titi-rough-the valve- only when the valve inlet pressure is higher than the valve outlet pressure, for example when the compressor is started.
  • the check valve comprises a resilient means such as a spring or the like that biases the valve into a closed position when the pressure at the inlet and the outlet of the check valve is balanced.
  • a resilient means such as a spring or the like that biases the valve into a closed position when the pressure at the inlet and the outlet of the check valve is balanced.
  • the above preferred refrigeration system prevents or substantially reduces refrigerant migration from the condenser and other high side components of the system, and/or from the low side of the system, to the compressor after compressor shutdown and thus enables the compressor to be started, even after a long shutdown period, with minimised risk of failure from refrigerant having mixed with the compressor oil.
  • a method of controlling a refrigeration system comprising the step of: initiating shutdown of a compressor of the system, closing a check valve provided in a flow line between the compressor and a heat rejecting heat exchanger of the system, and closing a liquid valve of the system that is located in a flow path between the heat rejecting heat exchanger and an expansion device of the system.
  • a pressure differential between the condenser and the compressor that occurs on shutdown is such that the pressure on the condenser side of the check valve is higher than the pressure on the compressor side of the check valve after shutdown and this closes the check valve to preventHfow-of refrigerant therethrough.
  • the check valve comprises a solenoid valve and preferably both valves are closed as soon as possible after compressor shutdown and preferably at substantially the same time as each other to prevent refrigerant migration.
  • the. method further comprises the steps of: starting the compressor thereby causing a pressure differential between the condenser and the compressor and opening the check valve provided in the flow line therebetween, and opening the liquid valve.
  • the pressure differential between the condenser and the compressor is such that the pressure on the condenser side of the check valve (e.g. the outlet) is lower than the pressure on the compressor side of the check valve (e.g. the inlet) after the compressor is restarted.
  • the method further comprises the step of biasing the check valve into a closed position, wherein the biasing force must be overcome in order to open the valve.
  • providing a liquid valve and a check valve of the present invention enables the system to be operated to prevent or substantially reduce refrigerant migration from the condenser and other high side and/or low side components of the system to the compressor after compressor shutdown.
  • the compressor can therefore be restarted and the risk of compressor failure due to the presence of refrigerant in the oil after refrigerant migration is minimised.
  • the above system may experience failure or other problems on compressor start up due to a further effect that also arises from compressor shut down.
  • a refrigeration system comprising a compressor, a heat rejecting heat exchanger, an expansion valve and a heat accepting heat exchanger.
  • the system further comprises a pressure equalisation valve (PEV) for equalising the pressure differential between the compressor suction and compressor discharge.
  • PEV pressure equalisation valve
  • the pressure equalisation valve is operable to open after or at the same time as the compressor is shutdown, preferably substantially immediately after compressor shutdown is effected.
  • the pressure equalisation valve comprises a bypass passage connecting the compressor suction to the compressor discharge and bypassing the compressor.
  • the pressure differential between the compressor suction and discharge is balanced as quickly as possible.
  • This is advantageous because a high pressure differential between the compressor suction and discharge on compressor shutdown causes oil from the compressor to migrate towards the suction side of the compressor, leaving the compressor and entering the suction line, whereas in the present invention, equalisation or balancing of the discharge and suction pressures prevents such migration. It is undesirable for oil to leave the compressor as upon restarting the compressor., little or no oil is available for compressor lubrication. Furthermore upon restart the compressor has a mixture of oil and refrigerant in the suction line, which can lead to compressor failure as the mixture is sucked into the compressor.
  • the oil that leaves the compressor and enters the suction line can migrate to the evaporator which can cause -further failure and also if the expansion valve is controlled in relation to the evaporator temperature (e.g. the evaporator outlet temperature) then the presence of oil at the sensor can lead to opening of the expansion valve even though the system is shut down.
  • the embodiments of the present invention provide an improved refrigeration system in which migration of oil from the compressor to the low side of the system is minimised or prevented after compressor shutdown by equalising the pressure differential between the compressor discharge and suction just after compressor shutdown.
  • a method of carrying out the invention is also envisaged and therefore from a further broad aspect of the present invention, there is provided a method of controlling a refrigeration system comprising the steps of: initiating shutdown of a compressor of the system; and opening a pressure equalisation valve (PEV) for equalising the pressure differential between a compressor suction and a compressor discharge.
  • PEV pressure equalisation valve
  • the pressure equalisation valve is opened preferably as or just after the compressor is shutdown, preferably substantially immediately after compressor shutdown is effected, thereby substantially equalising the high side discharge pressure and the low side suction pressure of the compressor.
  • the pressure equalisation valve comprises a bypass passage connecting the compressor suction to the compressor discharge and bypassing the compressor.
  • Figure 1 shows a schematic representation a refrigeration system in accordance with an embodiment of the present inventions
  • Figure 2 shows a flow diagram illustrating the modes of operation of a refrigeration system in accordance with an embodiment of the present invention
  • Figure 3 shows a first, standard operating sequence for starting a compressor of a refrigeration system in accordance with an embodiment of the present invention
  • Figure 4 shows a second, long operating sequence for starting a compressor of a refrigeration system in accordance with an embodiment of the present invention
  • Figure 5 shows a third, short operating sequence for starting a compressor of a refrigeration system in accordance with an embodiment of the ' present invention
  • FIG. 6 shows a schematic representation of another refrigeration system in accordance with an embodiment of the present invention.
  • Figure 7A shows a schematic representation of another refrigeration system in accordance with an embodiment of the present invention after compressor shutdown
  • Figure 7B shows a system, that does not have the pressure equalisation valve of the embodiment of figure 7A, in two states, the first being shortly after compressor shutdown and the second being some time after compressor shutdown;
  • Figure 8 shows a schematic representation of a refrigeration system in accordance with another embodiment of the present invention.
  • the principles of the present invention can be incorporated within any suitable system.
  • suitable systems include refrigeration and airconditioning systems and particularly, although not exclusively, transport or truck refrigeration systems.
  • the specific embodiments discussed herein are described with reference to a refrigeration system suitable for a transport refrigeration unit or the like.
  • FIG. 1 schematically shows a refrigeration system 10 having a refrigerant cycle or circuit 20 such that refrigerant can flow around the system.
  • the system comprises a compressor 12 connected from an outlet or discharge 13 thereof via flow path 22 to a heat rejecting heat exchanger, which in this embodiment is -a condenser 14.
  • the condenser 14 is connected via flow path 24 to expansion device 16, which is connected via flow path 26 to a heat accepting heat exchanger, which in this embodiment is an evaporator 18.
  • the evaporator 18 is connected to the compressor 12 at an inlet or suction 11 thereof via flow path 28.
  • the expansion device 16 is preferably a thermostatic expansion valve and in this embodiment is controlled in response to conditions of the system 10 via control line 36.
  • the system condition which controls opening of the expansion valve 16 could for example be the temperature of the evaporator 18, or a related temperature such as a bulb temperature at the evaporator outlet, etc.
  • additional optional components accumulator 32 and dryer 34 are also provided on flow path 24 between the condenser 14 and the valve 16.
  • the system 10 further comprises a pressure equalisation valve (PEV) across the compressor 12, i.e. connecting the compressor suction 11 to the discharge 13.
  • PEV pressure equalisation valve
  • the PEV comprises a bypass passage 40 and means 42, such as a valve, for opening and closing the passage 40.
  • the system 10 further comprises a liquid valve (LV), which in preferred embodiments is a liquid solenoid valve 44, in the flow path 24 between the condenser 14 and the expansion valve 16.
  • LV liquid valve
  • the LV 44 can be energised to open or close as required, thereby opening or closing the flow path 24 to enable or disable refrigerant flow around the circuit 20.
  • high pressure and high temperature refrigerant vapour exits the compressor 12 and enters the condenser 14 where it is cooled to a lower temperature, high pressure liquid refrigerant.
  • This liquid is then expanded to a_ lower pressure by the expansion valve 16 and passes to the evaporator 18 where the refrigerant boils and absorbs heat from its surroundings.
  • the vapour at the evaporator 18 outlet is drawn into the compressor 12, completing the cycle.
  • refrigerant may be present in the compressor 12 and, particularly if the compressor 12 is shut down for prolonged periods, additional refrigerant can migrate from the condenser 14 to the compressor 12 as discussed in more detail below.
  • the refrigerant in the compressor 12 may condense on the compressor shell, particularly at low ambient temperatures, and the condensed refrigerant will mix with the compressor oil which has an affinity for refrigerant. If the compressor oil temperature is below the saturated discharge temperature of the refrigerant, the refrigerant can condense in the oil. The refrigerant dilutes the oil and, when the compressor 12 is restarted, the diluted oil is less effective at lubricating the components of the compressor 12, which may lead to damage. Furthermore the compressor oil pump will draw in refrigerant which may also lead to damage.
  • FIG. 2 is a flow diagram of one embodiment of the present invention in which a control means or the like determines the state of a system 10 (for example the system 10 of any of figures 1, 6, 7 A or 8) and in particular the length of time T S to P that the compressor has been shut down and the discharge temperature T re f of the compressor 12. If the compressor 12 is shut down for a reasonably long period of time, the discharge temperature T re f is substantially equal to the ambient temperature. In other embodiments the ambient temperature may be measured. The control means determines from these parameters what steps before and during compressor startup should be taken to minimise or eliminate the problems of refrigerant condensation in the compressor 12.
  • a control means or the like determines the state of a system 10 (for example the system 10 of any of figures 1, 6, 7 A or 8) and in particular the length of time T S to P that the compressor has been shut down and the discharge temperature T re f of the compressor 12. If the compressor 12 is shut down for a reasonably long period of time, the discharge temperature T re f is substantially equal to the ambient
  • the sequence begins at step 1.1 and the time since the compressor 12 stopped Tstop ' is determined in step 1.2. If it is less than 1 hour, the time is further determined in step 2.1 and still further in step 3.2 if Tstop is less than 1/2 hour. For shutdown periods less than 1/2 hour, it is determined unnecessary to preheat the compressor 12 and a normal starting sequence (for example as shown in figure 3) begins in step 4.3.
  • T re f the discharge temperature
  • a short (3 minute) preheat of the compressor 12 is initiated in step 4.2 and as discussed below, before the normal starting sequence begins in step 5.2.
  • T re f is sufficiently high already, no preheat is required and a short starting sequence (for example as shown in figure 5) begins in step 4.1.
  • the discharge temperature T re f is determined in step 1.3 and dependent on the temperature, also in steps 1.4, 1.5. 1.6, 1.7 and 1.8. Furthermore, dependent on Tref, the compressor 12 is preheated for 12, 9, 6 or 3 minutes (steps 2.2, 2.3, 2.4 and 2.5 respectively) before a long starting sequence (for example as shown in figure 4) begins in step 3.3. However if T re f is sufficiently high (between 0 and 2O 0 C) as determined in step 1.7, a 3 minute preheat is initiated in step 2.6 before the normal starting sequence begins in step 3.4.
  • Tref is already even higher than 20°C as determined is steps 1.8 and 1.9, then no preheat is required and either a normal starting sequence is initiated in step 2.7 or for very high temperatures (greater than 4O 0 C) a short starting sequence is initiated in step 2.8.
  • the above sequences ensure that if the discharge temperature of the compressor 12 is low, the compressor 12 is heated, preferably prior to compressor startup, to raise the compressor temperature, including the oil temperature. This is advantageous not only because the viscosity of the oil is improved making the oil more suitable for lubricating the compressor components on startup, but also because a sufficiently high oil temperature (greater than the saturation discharge temperature of the refrigerant) reduces or eliminates refrigerant condensation in the compressor 12 that occurs when the compressor shell and oil are cool.
  • Figures 3 3 4 and 5 schematically illustrate preferred embodiments of the starting sequences for starting a compressor 12 after shutdown.
  • Figure 3 shows a "normal" or default starting sequence
  • figure 4 shows a long starting sequence
  • figure 5 shows a short starting sequence.
  • the starting sequences disclosed in figure 2 correspond with the figure 3, 4 and 5 sequences, but it is also envisaged that this could differ or be modified by the skilled person.
  • the preheat sequences disclosed in figures 3, 4 and 5 may correspond with the preheat. sequences of figure 2, or may differ or be modified.
  • FIG 3 shows a normal starting sequence for a compressor 12.
  • the discharge temperature of the compressor 12 is preferably at least 2O 0 C or the compressor shutdown period was less than 1/2 hour.
  • the pressure equalisation valve (PEV) 40, 42 is initially closed and so is the liquid valve (LV) 44.
  • the PEV is opened thereby opening a bypass of the compressor 12.
  • the compressor 12 is started, but with a relatively low frequency of about 30 Hz (which is significantly less than the full operating speed of the compressor 1,2).
  • the liquid valve is opened and the PEV remains open.
  • the refrigerant flow at the compressor suction 11 increases slightly, but -is still relatively low as the compressor 12 is still bypassed by the open PEV.
  • the PEV when it is again measured, determined and/or expected to be greater than the saturated discharge temperature of the refrigerant, and/or in this embodiment after it has been heated for a sufficient period of time which in the normal starting sequence is a further 20 seconds, the PEV is closed whilst the liquid . valve remains open. Refrigerant therefore flows around the circuit 20 of system 10 under the influence of the compressor 12, which is no longer bypassed.
  • the oil temperature in the compressor 12 is sufficiently high, e.g.
  • the speed of the compressor " 12 is ⁇ gra ⁇ d ⁇ rarllynncreased,- preferably by 5 Hz per second until an optimum or normal operating frequency is reached, after which standard compressor speed control is applied as is known in the art.
  • the standard operating speed control can be started after it is again determined or otherwise expected that the oil temperature is still higher than the saturated discharge temperature.
  • a normal starting sequence may not be appropriate under certain circumstances, for example when the temperature of the shutdown compressor 12 is low (e.g. less than about 5 0 C) and/or when the compressor 12 has been shutdown for a long period (more than about one hour).
  • a long starting sequence as shown in figure 4 may be more appropriate.
  • the long starting sequence differs from the normal starting sequence in that the periods between events are generally significantly longer. For example the LV is kept closed after compressor startup for 5 minutes rather than 20 seconds, thereby allowing the oil additional time to heat up. The delay before closing the PEV is also longer and is about 2 minutes thus allowing the system 10 to operate at a reduced flow rate for longer.
  • the period of time before the compressor frequency is increased is also longer and is about 2 1/2 minutes after which the frequency is increased more slowly than the normal starting sequence, at about 1 Hz per 5 seconds.
  • the long starting sequence differs at this stage from the normal starting sequence in that an additional step is included before standard compressor speed control is initiated, during which the compressor is operated at a maximum frequency of 60 Hz for 1 minute.
  • the long starting sequence is significantly slower than the normal starting sequence thereby allowing the system temperature to increase gradually before fully loading the compressor 12, which is appropriate in -eelde ⁇ - conditions, particularly if the compressor 12 has been inactive for a long period of time.
  • a normal nor a long starting sequence may be appropriate, for example when the temperature of the shutdown compressor 12 is relatively high (e.g. more than about 40 0 C) and/or when the compressor 12 has been shutdown for only a brief period (less than an hour).
  • a short starting sequence as shown in figure 5 may be more appropriate.
  • the short starting sequence differs from the normal starting sequence in that the periods between events are generally much shorter and in some embodiments, little or no delay between events is needed.
  • the LV is not kept closed after compressor startup but instead is opened up quickly as the oil perhaps does not need any additional time to heat up at the lower operating speed.
  • the delay before closing the PEV is also short or may not even be required and the PEV can be closed quickly after compressor startup.
  • the period of time before the compressor frequency is increased is also short and is about 5 seconds, after which the frequency is increased at a slower- rate than the normal starting sequence, at about 1 Hz per second.
  • the short starting sequence is significantly faster than the normal starting sequence as the system temperature does not need to increase gradually and the compressor 12 is capable of operating under full load relatively quickly. Furthermore it may not even be necessary to heat the oil prior to initiating the short starting sequence, as shown in figure 2.
  • Figure 6 schematically illustrates an -alternative embodiment of the present invention;, although this system 10 could be and preferably is combined with the system 10 shown in figure 1 simply by adding the PEV of figure 1 (for example as shown in figure 8) or indeed with figure 7A.
  • the components are mostly the same as those of the figure 1 embodiment and have like reference numerals.
  • the figure 6 embodiment further comprises a check valve 46 which is a one-way valve that prevents flow or migration of fluid in one direction (from the condenser 14 towards the compressor 12) but permits flow of fluid in the other direction (towards the condenser 14 from the compressor 12).
  • the system 10 of figure 6 operates as normal when the compressor 12 is running. However, in prior art systems when the compressor is shut down refrigerant migrates from the condenser and/or evaporator to the compressor due to the pressure and temperature differences, and the refrigerant can condense in the compressor and mix with the oil which is undesirable as discussed above. In the figure 6 embodiment however, refrigerant is effectively trapped between the check valve 46 and the liquid valve (LV) 44 and therefore does not reach the compressor 12. This embodiment operates as follows.
  • the LV When the compressor 12 is stopped, the LV is closed (preferably the LV is a liquid solenoid valve and the valve is closed by energising the solenoid) and the check valve 46 is closed (preferably the check valve is also a solenoid valve and the valve is closed by energising the solenoid, or the check valve may be closed by the pressure differential between the condenser 14 and the compressor 12.
  • Refrigerant that would otherwise migrate to the compressor 12, is therefore retained in the refrigerant circuit 20 between the two valves 44 ⁇ -46- — Even- if -the- pressure at the inlet and outlets of the check valve 46 are balanced, the check valve 46 will not open, because the check valve 46 in this embodiment comprises a spring inside (not shown) so that no leak occurs if the pressure is balanced.
  • the inlet pressure of the check valve 46 must be above the outlet pressure to permit circulation of the fluid. Any additional components such as an accumulator 32 and a dryer 34 in the circuit 20 help to store the refrigerant during compressor shutdown.
  • the LV is energised to be opened and the check valve 46 is energised or opens due to the changed pressure differential.
  • Figure 7A illustrates another embodiment of the present invention, which although as shown is a separate embodiment, it is within the scope of the invention for this system 10 to be combined with any one or more of the systems 10 shown in the other figures.
  • the system 10 comprises similar components as the other embodiments, including the pressure equalisation valve 40, 42 discussed with regard to figure 1 and the figure 1 embodiment can be operated in accordance with the following disclosure as well.
  • a conventional refrigeration system 110 is shown in figure 7B and is shown in a first state shortly after compressor shutdown and in a second state a longer time after shutdown.
  • the oil 100 can migrate and begin to fill the evaporator 118 and also the relatively hot oil can fill the bulb of the expansion valve 116 control means 136 that is located at the exit of the evaporator 118 (i.e. in line 128).
  • This can cause the expansion valve 116 to open even if that is not desired, further affecting the system performance on compressor startup and liquid in the compressor suction line can damage the compressor.
  • the refrigeration system 10 of the embodiment of figure 7 A overcomes this problem by provision of the PEV, which is opened during or preferably just after compressor shutdown. This equalises the pressure differential between the compressor suction 11 and discharge 13 and thus prevents migration of oil from the compressor to the low side of the system 10.
  • Figure 8 schematically illustrates another embodiment of the present invention.
  • the system 10 comprises a check valve 46, a liquid valve 44 and a pressure equalisation valve 40, 42. Therefore all of the advantages disclosed in relation to the. other embodiments and discussed above are provided by this system having the combination of all the valves.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Positive-Displacement Pumps (AREA)
  • Air Conditioning Control Device (AREA)
  • Compressor (AREA)

Abstract

L'invention concerne un système de réfrigération (10) comprenant un compresseur (12) comportant une aspiration (11) et une évacuation (13), un échangeur de chaleur rejetant la chaleur (14), une vanne de détente (16), et un échangeur de chaleur acceptant la chaleur (18). De préférence, le système (10) comprend un ou plusieurs des éléments suivants : une soupape d'égalisation de la pression (4O3 42) pour égaliser le différentiel de pression entre l'aspiration du compresseur (11) et l'évacuation du compresseur (13) ; une soupape pour liquide (44), de préférence un robinet électromagnétique pour liquide ou une vanne de détente électronique, la soupape pour liquide (44) étant disposée dans une ligne d'écoulement (24) entre l'échangeur de chaleur rejetant la chaleur (14) et la vanne de détente (16) ; et une soupape de retenue (46), de préférence un robinet électromagnétique ou une vanne de détente électronique, disposée dans une ligne d'écoulement (22) entre l'échangeur de chaleur rejetant la chaleur (14) et le compresseur (12). Les soupapes (40, 42, 44, 46) sont utilisées de plusieurs façons à l'arrêt et au démarrage du compresseur pour éviter l’endommagement des composants du compresseur (12). De préférence, le système comprend également un moyen pour chauffer au moins un composant du compresseur (12) et également de préférence un moyen de commande pour activer le moyen de chauffage quand cela est nécessaire, comme lorsque le démarrage du compresseur est requis, et au démarrage du compresseur après chauffage.
PCT/IB2008/001908 2008-07-23 2008-07-23 Procédés et systèmes d'utilisation d'un compresseur WO2010010414A1 (fr)

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CN2008801304806A CN102105759B (zh) 2008-07-23 2008-07-23 用于压缩机操作的方法和***
EP08788911.9A EP2321595B1 (fr) 2008-07-23 2008-07-23 Procédés et systèmes d'utilisation d'un compresseur
US13/003,942 US20110113797A1 (en) 2008-07-23 2008-07-23 Methods and systems for compressor operation
PCT/IB2008/001908 WO2010010414A1 (fr) 2008-07-23 2008-07-23 Procédés et systèmes d'utilisation d'un compresseur
HK11113640.4A HK1159234A1 (en) 2008-07-23 2011-12-16 Methods and systems for compressor operation

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EP2565323A4 (fr) * 2010-04-28 2015-06-03 Lg Electronics Inc Procédé de commande du fonctionnement d'un séchoir
CN105353796A (zh) * 2015-11-27 2016-02-24 珠海格力电器股份有限公司 制冷设备及其压缩机的加热控制电路及加热控制方法
EP2565322A4 (fr) * 2010-04-28 2017-12-27 LG Electronics Inc. Procédé de commande d'un séchoir
CN112594951A (zh) * 2020-12-14 2021-04-02 广东申菱环境***股份有限公司 一种空调机组制冷***及其控制方法
CN113758035A (zh) * 2021-09-18 2021-12-07 广东美芝制冷设备有限公司 一种制冷***

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KR102198326B1 (ko) * 2013-12-26 2021-01-05 엘지전자 주식회사 공기 조화기
CN104879881B (zh) * 2015-04-29 2017-06-27 广东美的制冷设备有限公司 一种定频空调器的控制方法、控制器及定频空调器
CN107850363B (zh) 2015-08-03 2020-10-30 开利公司 恒温膨胀阀和控制方法
CN105444448B (zh) * 2015-12-23 2018-02-06 广东美的暖通设备有限公司 制冷***及其控制方法
CN105526683B (zh) * 2016-02-19 2018-09-07 珠海格力电器股份有限公司 一种空调***的控制方法及装置
WO2018076364A1 (fr) * 2016-10-31 2018-05-03 合肥华凌股份有限公司 Appareil de réfrigération
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JP6601472B2 (ja) * 2017-10-30 2019-11-06 ダイキン工業株式会社 空調装置
CN107763776A (zh) * 2017-11-20 2018-03-06 珠海格力电器股份有限公司 空调机组及冷媒迁移控制方法
US11300339B2 (en) 2018-04-05 2022-04-12 Carrier Corporation Method for optimizing pressure equalization in refrigeration equipment
WO2019245675A1 (fr) 2018-06-22 2019-12-26 Carrier Corporation Système et procédé de commande d'huile pour système hvac
KR102067602B1 (ko) * 2018-08-20 2020-01-17 엘지전자 주식회사 리니어 압축기 및 리니어 압축기의 제어 방법
CN110594979B (zh) * 2018-11-12 2024-01-23 杭州三花微通道换热器有限公司 空调***的控制方法
IT202100007316A1 (it) * 2021-03-25 2022-09-25 Ariston S P A Metodo di gestione di una pompa di calore operante con un fluido operativo a basso impatto ambientale
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EP2565322A4 (fr) * 2010-04-28 2017-12-27 LG Electronics Inc. Procédé de commande d'un séchoir
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CN105353796A (zh) * 2015-11-27 2016-02-24 珠海格力电器股份有限公司 制冷设备及其压缩机的加热控制电路及加热控制方法
CN112594951A (zh) * 2020-12-14 2021-04-02 广东申菱环境***股份有限公司 一种空调机组制冷***及其控制方法
CN113758035A (zh) * 2021-09-18 2021-12-07 广东美芝制冷设备有限公司 一种制冷***

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US20110113797A1 (en) 2011-05-19
HK1159234A1 (en) 2012-07-27
CN102105759A (zh) 2011-06-22
CN102105759B (zh) 2013-11-13
EP2321595A1 (fr) 2011-05-18

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