US20110209485A1 - Suction superheat conrol based on refrigerant condition at discharge - Google Patents

Suction superheat conrol based on refrigerant condition at discharge Download PDF

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Publication number
US20110209485A1
US20110209485A1 US12/671,970 US67197010A US2011209485A1 US 20110209485 A1 US20110209485 A1 US 20110209485A1 US 67197010 A US67197010 A US 67197010A US 2011209485 A1 US2011209485 A1 US 2011209485A1
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United States
Prior art keywords
refrigerant
set forth
compressor
discharge
refrigerant system
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.)
Abandoned
Application number
US12/671,970
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English (en)
Inventor
Alexander Lifson
Michael F. Taras
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Carrier Corp
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Carrier Corp
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Filing date
Publication date
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Assigned to CARRIER CORPORATION reassignment CARRIER CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LIFSON, ALEXANDER, TARAS, MICHAEL F.
Publication of US20110209485A1 publication Critical patent/US20110209485A1/en
Abandoned 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
    • 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
    • F25B2600/00—Control issues
    • F25B2600/21—Refrigerant outlet evaporator temperature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/19—Pressures
    • F25B2700/193—Pressures of the compressor
    • F25B2700/1933—Suction pressures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2115—Temperatures of a compressor or the drive means therefor
    • F25B2700/21152—Temperatures of a compressor or the drive means therefor at the discharge side of the compressor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2117—Temperatures of an evaporator

Definitions

  • This application relates to a refrigerant superheat control to enhance system performance and improve compressor reliability, which relies upon a refrigerant thermodynamic condition at discharge to provide reliable suction superheat control.
  • a superheat of the refrigerant leaving an evaporator needs to be closely controlled.
  • Refrigerant leaves the evaporator normally at the superheated thermodynamic state, where its actual temperature is higher than the corresponding saturation temperature (a superheat is defined as the difference between these two temperatures).
  • a certain (positive) superheat is typically required to ensure that little or no liquid refrigerant enters the compressor and system operation is stable. If a significant amount of liquid refrigerant enters the compressor, an undesirable condition known as “flooding” will occur. Flooding could cause “liquid hammer” conditions damaging or breaking compression elements, dilute lubrication oil and wash it off the bearing surfaces, pump lubrication oil out of the compressor sump, and eventually degrade refrigerant system performance and operation.
  • the present invention utilizes a realization that a given change in the suction superheat will result in an expected change in a discharge temperature (or superheat) of the refrigerant leaving the compressor. That is, there is an approximately linear relationship between the suction superheat and the discharge temperature (or superheat) for the refrigerant leaving the compressor. This relationship is essentially linear at any given system operating suction and discharge pressure.
  • the system can be reliably operated at a desired low suction superheat or have a minimal controlled amount of liquid refrigerant entering the compressor suction port.
  • the control of the suction superheat that is based on discharge temperature (or superheat) can, for example, be accomplished by varying the opening of an expansion valve or a suction modulation valve.
  • the relationship between the discharge temperature (or superheat) and suction superheat can be determined experimentally or can be developed analytically. Further, the relationship can be periodically tested/verified during operation to ensure that the relationship still holds, or any small adjustments need to be made to this relation based on these periodic tests.
  • the present invention allows for operation at the superheat levels that are substantially lower than the superheat levels in the 5 to 10° F. range reliably achievable in the past.
  • the superheat levels leaving the evaporator can be as low as 1 to 2° F., or with appropriate control, some minimal amount of liquid refrigerant can be allowed to enter the compressor suction port.
  • FIG. 1 is a view of a refrigerant system incorporating the present invention.
  • FIG. 2 is a chart showing changes in discharge temperature as a function of suction superheat.
  • FIG. 3 shows the system efficiency with respect to suction superheat and discharge temperature.
  • a basic refrigerant system 20 is illustrated in FIG. 1 and incorporates a compressor 22 delivering compressed refrigerant downstream to a heat rejection heat exchanger 24 (a condenser for subcritical applications and a gas cooler for transcritical applications).
  • An expansion device 26 is preferably an electronic expansion device, and is generally known in the industry. Refrigerant having passed through the expansion device 26 flows in sequence through an evaporator 28 , through an optional suction modulation valve 30 , and through a suction line 38 back to the compressor 22 .
  • a temperature sensor 46 is placed on or inside the discharge line leaving the compressor. The temperature sensor 46 can also be positioned to measure the discharge temperature on the compressor shell or inside the compressor shell.
  • the temperature sensor 46 communicates with an electronic controller 32 , which in turn controls the electronic expansion device 26 , or/and the optional suction modulation valve 30 to adjust and control the suction superheat.
  • a sensor 56 measuring the suction superheat value that is placed between the expansion device 26 and compressor 22 . More preferably, the sensor 56 is placed on the suction line 38 between the exit from the evaporator 28 and inlet to the compressor 22 .
  • the sensor 56 can be a sensor that directly measures superheat (the difference between the actual and saturated refrigerant temperatures at approximately the same location).
  • the sensor 56 can be a temperature sensor.
  • the temperature sensor 56 for example, can be of a thermocouple or thermistor type.
  • an additional temperature sensor 58 may be placed within the evaporator 28 (in the refrigerant flow or externally on the evaporator surface) within the two-phase region to determine the saturated refrigerant temperature in the evaporator. The difference between these two temperature measurements provided by the temperature sensors 56 and 58 would determine the suction superheat value.
  • a pressure type sensor 60 may be utilized that would determine pressure of the refrigerant at or near the location where the superheat value is to be obtained (e.g. suction side of the refrigerant system 20 ).
  • the refrigerant pressure value is measured by the pressure sensor 60 , it can be converted to a corresponding saturated temperature value, as known.
  • the suction superheat value is then simply calculated by subtracting the obtained saturated refrigerant temperature from the measured actual refrigerant temperature.
  • the temperature sensors 56 and 58 can be installed on the external surface (e.g. air side) of the tubing, compressor, heat exchanger, etc. These sensors can also be installed internally or within the refrigerant flow (so-called in-flow sensors). In the latter case, the in-flow sensors would measure the temperature of the refrigerant directly. If the temperature sensors are installed externally, they are preferably insulated or shielded from the ambient environment to reduce the measurement error.
  • the present invention allows achieving very low superheat values or controlled flooded conditions for the refrigerant prior to entering the compression chambers by relying upon a relationship that is illustrated in FIGS. 2 .
  • FIG. 2 the discharge temperature as a function of suction superheat is plotted for a particular operating condition.
  • FIG. 3 shows the system thermodynamic efficiency in relation to suction superheat and discharge temperature.
  • a change in suction superheat essentially results in a linear change in the discharge temperature until the compressor begins to experience a flooded condition.
  • the flooded condition is represented by a vertical line originating at the point “O” and extending downward.
  • the discharge temperature continues to decrease, while the suction superheat value remains at zero (when the superheat is zero, the actual temperature of the refrigerant is equal to the saturated temperature).
  • the most efficient compressor, evaporator and the entire refrigerant system operation is achieved in the region located between the points “C” and “G” shown on the graphs.
  • the point “C” corresponds to approximately 4° F. of suction superheat and point “G” corresponds to slight compressor flooding conditions.
  • the compressor operation is controlled based on the discharge temperature, and at 160° F. in particular, it will correspond to a condition that falls approximately in the middle of the most efficient region of the operation, the point “E”.
  • the point “E” is located approximately in the middle of the region defined by the points “C” and “G”.
  • the measurements error tolerance band for the discharge temperature is defined in the FIGS. 2 and 3 to be between the points “D” and “F”. Since the measurement error tolerance band falls within the region of the most efficient operation, it can be concluded that, by controlling the suction superheat based on the discharge temperature, the refrigerant system 20 can always operate at or near the most efficient point. Further, in this particular example, the refrigerant system 20 can be comfortably operated at the point “E” using the discharge temperature control, where the point “E” corresponds to only 1° F. of suction superheat.
  • the suction superheat has to be set to at least 5° F., as shown in FIG. 2 by the point “B”, to make sure that an uncontrolled flooding situation has not occurred (uncontrolled flooding would represent large amounts of liquid refrigerant reaching the compressor suction port).
  • the superheat value is set below 5° F., then with potential measurement errors, the actual operating point could be well bellow the point “H”, which corresponds to severe flooding conditions for the compressor, and its potential damage.
  • the minimum acceptable setting for the suction superheat using the prior art technique would be a value of 5° F.
  • operation at the point “B” is not nearly as efficient as operation at the point “E”.
  • the suction superheat value is increased from 1 to 5° F.
  • the refrigerant system performance reduction can be substantially higher, if for example, the actual superheat value to be set at the point “A”, if the prior art technique is employed.
  • the present invention allows the use of a discharge temperature sensor to precisely control suction superheat by utilizing a relation that defines suction superheat value based on the measurements of the discharge temperature.
  • the controller 32 for the refrigerant system 20 can utilize the sensed discharge temperature to predict an amount by which the discharge temperature must be changed to achieve a desired suction superheat value.
  • the controller 32 would then control the expansion device 26 , and/or the suction modulation valve 30 , to change the discharge temperature, and hence adjust the suction superheat of the refrigerant reaching the compressor.
  • the suction superheat can be lowered to the values below 2° F., in the disclosed embodiments, and may be kept at approximately 1° F.
  • the refrigerant system can be periodically tested, to assure that the FIG. 2 relationship holds, by raising the suction superheat from a lower level to a higher level, and then measuring an inter-relation between the change in the discharge temperature and the suction superheat, to ensure that the expected change is still taking place. This can occur at high enough values of suction superheat so that the suction temperature can be reliably measured.
  • the suction superheat can be changed from 1 to 16° F. and the corresponding discharge temperature changes can be measured at the 16° F. superheat region. Therefore, the refrigerant system may operate in the self-learning or adaptive manner to achieve the highest operational performance possible.
  • FIG. 2 shows the relation between discharge temperature and suction superheat for a particular suction and discharge pressures
  • similar graphs can be developed for other operating conditions. These graphs then can be used to control the suction superheat at any expected operating conditions. Instead of developing multiple graphs, the results can be assembled into look-up tables, and then interpolated as needed for actual values of suction and discharge pressures. Furthermore, instead of using the look-up tables or graphs, equations relating suction superheat to discharge temperature for a given suction and discharge pressures can be developed.
  • the refrigerant system can be self-learning such that, during the system operation, for a given suction and discharge pressures, the discharge temperature can be varied on an intermittent basis to establish a relation between the discharge temperature and suction superheat.
  • the refrigerant system can itself develop the graph of FIG. 2 during operation. Then the corresponding graph values can be stored in the memory of the refrigerant system controller as a function of suction and discharge pressures, and then retrieved by the controller from the memory on an as needed basis.
  • discharge side pressure or saturation temperature may be known, a similar relationship can be established between the suction and discharge superheat that can be used for identical purposes of the refrigerant system control.
  • compressor types could be used in this invention.
  • scroll, screw, rotary, or reciprocating compressors can be employed.
  • the refrigerant systems that utilize this invention can be used in many different applications, including, but not limited to, air conditioning systems, heat pump systems, marine container units, refrigeration truck-trailer units, and supermarket refrigeration systems.

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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)
US12/671,970 2007-10-10 2007-10-10 Suction superheat conrol based on refrigerant condition at discharge Abandoned US20110209485A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2007/080876 WO2009048466A1 (fr) 2007-10-10 2007-10-10 Commande de surchauffe à l'aspiration basée sur une condition de fluide frigorigène à la décharge

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US20110209485A1 true US20110209485A1 (en) 2011-09-01

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US (1) US20110209485A1 (fr)
EP (1) EP2198212A4 (fr)
CN (1) CN101842646B (fr)
HK (1) HK1148810A1 (fr)
WO (1) WO2009048466A1 (fr)

Cited By (15)

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US20130243032A1 (en) * 2012-03-16 2013-09-19 Dunan Microstaq, Inc. Superheat Sensor
US20140069120A1 (en) * 2012-09-12 2014-03-13 Mitsubishi Heavy Industries, Ltd. Control apparatus and method for parallel-type chiller, and computer-readable recording medium in which program for parallel-type chiller is stored
US20140260380A1 (en) * 2013-03-15 2014-09-18 Energy Recovery Systems Inc. Compressor control for heat transfer system
US9016074B2 (en) 2013-03-15 2015-04-28 Energy Recovery Systems Inc. Energy exchange system and method
JP2015148387A (ja) * 2014-02-06 2015-08-20 株式会社富士通ゼネラル 空気調和装置
US9234686B2 (en) 2013-03-15 2016-01-12 Energy Recovery Systems Inc. User control interface for heat transfer system
US9791175B2 (en) 2012-03-09 2017-10-17 Carrier Corporation Intelligent compressor flooded start management
WO2018102380A1 (fr) * 2016-11-30 2018-06-07 DC Engineering, P.C. Procédé et système d'amélioration du rendement d'un systeme de réfrigération
US10047990B2 (en) * 2013-03-26 2018-08-14 Aaim Controls, Inc. Refrigeration circuit control system
US10260775B2 (en) 2013-03-15 2019-04-16 Green Matters Technologies Inc. Retrofit hot water system and method
US10648719B2 (en) * 2017-12-14 2020-05-12 Dunan Microstaq, Inc. Heating, ventilating, air conditioning, and refrigeration system with simultaneous sub-cooling and superheat control
US10801762B2 (en) 2016-02-18 2020-10-13 Emerson Climate Technologies, Inc. Compressor floodback protection system
US10969165B2 (en) 2017-01-12 2021-04-06 Emerson Climate Technologies, Inc. Micro booster supermarket refrigeration architecture
US20210197648A1 (en) * 2018-08-30 2021-07-01 Sanden Holdings Corporation Heat pump system for vehicle air conditioning devices
US11466911B2 (en) 2016-11-30 2022-10-11 Dc Engineering, Inc. Method and system for improving refrigeration system efficiency

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US7895003B2 (en) 2007-10-05 2011-02-22 Emerson Climate Technologies, Inc. Vibration protection in a variable speed compressor
US8539786B2 (en) 2007-10-08 2013-09-24 Emerson Climate Technologies, Inc. System and method for monitoring overheat of a compressor
US8459053B2 (en) 2007-10-08 2013-06-11 Emerson Climate Technologies, Inc. Variable speed compressor protection system and method
US8418483B2 (en) 2007-10-08 2013-04-16 Emerson Climate Technologies, Inc. System and method for calculating parameters for a refrigeration system with a variable speed compressor
US9541907B2 (en) 2007-10-08 2017-01-10 Emerson Climate Technologies, Inc. System and method for calibrating parameters for a refrigeration system with a variable speed compressor
CN104266426B (zh) * 2014-10-16 2016-06-15 珠海格力电器股份有限公司 判断气液分离器中液位的方法及系统
ES2834548T3 (es) 2015-06-24 2021-06-17 Emerson Climate Tech Gmbh Mapeo cruzado de componentes en un sistema de refrigeración
CN104964485A (zh) * 2015-07-03 2015-10-07 珠海格力电器股份有限公司 用于压缩机的调温装置和换热系统
US11206743B2 (en) 2019-07-25 2021-12-21 Emerson Climate Technolgies, Inc. Electronics enclosure with heat-transfer element

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US20120011866A1 (en) * 2009-04-09 2012-01-19 Carrier Corporation Refrigerant vapor compression system with hot gas bypass

Cited By (22)

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Publication number Priority date Publication date Assignee Title
US9791175B2 (en) 2012-03-09 2017-10-17 Carrier Corporation Intelligent compressor flooded start management
US9140613B2 (en) * 2012-03-16 2015-09-22 Zhejiang Dunan Hetian Metal Co., Ltd. Superheat sensor
US20130243032A1 (en) * 2012-03-16 2013-09-19 Dunan Microstaq, Inc. Superheat Sensor
US9772235B2 (en) 2012-03-16 2017-09-26 Zhejiang Dunan Hetian Metal Co., Ltd. Method of sensing superheat
US9404815B2 (en) 2012-03-16 2016-08-02 Zhejiang Dunan Hetian Metal Co., Ltd. Superheat sensor having external temperature sensor
US9453670B2 (en) * 2012-09-12 2016-09-27 Mitsubishi Heavy Industries, Ltd. Control apparatus and method for parallel-type chiller, and computer-readable recording medium in which program for parallel-type chiller is stored
US20140069120A1 (en) * 2012-09-12 2014-03-13 Mitsubishi Heavy Industries, Ltd. Control apparatus and method for parallel-type chiller, and computer-readable recording medium in which program for parallel-type chiller is stored
US20140260380A1 (en) * 2013-03-15 2014-09-18 Energy Recovery Systems Inc. Compressor control for heat transfer system
US9016074B2 (en) 2013-03-15 2015-04-28 Energy Recovery Systems Inc. Energy exchange system and method
US9234686B2 (en) 2013-03-15 2016-01-12 Energy Recovery Systems Inc. User control interface for heat transfer system
US10260775B2 (en) 2013-03-15 2019-04-16 Green Matters Technologies Inc. Retrofit hot water system and method
US10047990B2 (en) * 2013-03-26 2018-08-14 Aaim Controls, Inc. Refrigeration circuit control system
JP2015148387A (ja) * 2014-02-06 2015-08-20 株式会社富士通ゼネラル 空気調和装置
US10801762B2 (en) 2016-02-18 2020-10-13 Emerson Climate Technologies, Inc. Compressor floodback protection system
US11573037B2 (en) 2016-02-18 2023-02-07 Emerson Climate Technologies, Inc. Compressor floodback protection system
WO2018102380A1 (fr) * 2016-11-30 2018-06-07 DC Engineering, P.C. Procédé et système d'amélioration du rendement d'un systeme de réfrigération
US10760842B2 (en) 2016-11-30 2020-09-01 Dc Engineering, Inc. Method and system for improving refrigeration system efficiency
US11466911B2 (en) 2016-11-30 2022-10-11 Dc Engineering, Inc. Method and system for improving refrigeration system efficiency
US10969165B2 (en) 2017-01-12 2021-04-06 Emerson Climate Technologies, Inc. Micro booster supermarket refrigeration architecture
US10648719B2 (en) * 2017-12-14 2020-05-12 Dunan Microstaq, Inc. Heating, ventilating, air conditioning, and refrigeration system with simultaneous sub-cooling and superheat control
US20210197648A1 (en) * 2018-08-30 2021-07-01 Sanden Holdings Corporation Heat pump system for vehicle air conditioning devices
US11794555B2 (en) * 2018-08-30 2023-10-24 Sanden Corporation Heat pump system for vehicle air conditioning devices

Also Published As

Publication number Publication date
CN101842646B (zh) 2013-06-12
HK1148810A1 (en) 2011-09-16
EP2198212A1 (fr) 2010-06-23
EP2198212A4 (fr) 2014-01-22
WO2009048466A1 (fr) 2009-04-16
CN101842646A (zh) 2010-09-22

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