WO2004057246A1 - Method of operation and regulation of a vapour compression system - Google Patents

Method of operation and regulation of a vapour compression system Download PDF

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Publication number
WO2004057246A1
WO2004057246A1 PCT/NO2003/000425 NO0300425W WO2004057246A1 WO 2004057246 A1 WO2004057246 A1 WO 2004057246A1 NO 0300425 W NO0300425 W NO 0300425W WO 2004057246 A1 WO2004057246 A1 WO 2004057246A1
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WIPO (PCT)
Prior art keywords
pressure
cop
temperature
refrigerant
parameter
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Ceased
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PCT/NO2003/000425
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French (fr)
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WO2004057246A8 (en
Inventor
Kåre AFLEKT
Armin Hafner
Arne Jakobsen
Petter NEKSÅ
Jostein Pettersen
Håvard REKSTAD
Geir Skaugen
Trond Andresen
Espen TØNDELL
Munan Elgsaether
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Sinvent AS
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Sinvent AS
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Priority to US10/539,611 priority Critical patent/US7621137B2/en
Priority to JP2004562129A priority patent/JP2006511778A/en
Priority to EP03813728A priority patent/EP1579157B1/en
Priority to DE60322588T priority patent/DE60322588D1/en
Priority to AU2003303148A priority patent/AU2003303148A1/en
Publication of WO2004057246A1 publication Critical patent/WO2004057246A1/en
Anticipated expiration legal-status Critical
Publication of WO2004057246A8 publication Critical patent/WO2004057246A8/en
Ceased 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
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
    • 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
    • F25B2309/00—Gas cycle refrigeration machines
    • F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
    • F25B2309/061—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide with cycle highest pressure above the supercritical pressure
    • 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
    • F25B2500/19—Calculation of parameters
    • 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
    • F25B2600/17—Control issues by controlling the pressure of the condenser

Definitions

  • the present invention relates to compression refrigeration system including a compressor, a heat rejector, an expansion means and a heat absorber connected in a closed circulation circuit that may operate with supercritical high-side pressure, using carbon dioxide or a mixture containing carbon dioxide as the refrigerant in the system.
  • WO 94/14016 and WO 97/27437 both describe a simple circuit for realising such a system, in basis comprising a compressor, a heat rejector, an expansion means and an evaporator connected in a closed circuit.
  • CO 2 is the preferred refrigerant for both of them.
  • EP 0 604417 B 1 describe how different signals can be used as steering parameter for the high side pressure.
  • a suitable signal is the heat rejector refrigerant outlet temperature.
  • the relation between optimum high side pressure and the signal temperature is calculated in advance or measured. Densopatent describes more or less an analogous strategy. Different signals are used as input parameter to a controller, which based on the signals regulates the pressure to a predetermined level.
  • Liao & Jakobsen presented an equation, which calculates optimum pressure from theoretical input.
  • the equation does not take into account practical aspects which may affect the optimum pressure sicnificantly.
  • a major object of the present invention is to make a simple, efficient system that avoids the aforementioned shortcomings and disadvantages.
  • the invention is characterized by the features as defined in the accompanying independent claim 1.
  • the present invention is based on the system described above, comprising at least a compressor, a heat rejector, an expansion means and a heat absorber. It is a new and novel method for optimum operation of such a system with respect to energy efficiency.
  • the controller in the trans-critical vapour compression system can perform a perturbation of the high side pressure and thereby establish a correlation between the pressure and the energy efficiency, or a suitable parameter reflecting the energy efficiency. A relation between high side pressure and energy efficiency can then easily be mapped, and optimum pressure determined and used until operating conditions change. This is a simple method which will work for all designs of trans-critical vapour compression systems. No initial measurements have to be made, and practical aspects will be accounted for on site.
  • Fig. 1 illustrates a simple circuit for a vapour compression system.
  • Fig. 2 shows a temperature entropy diagram for carbon dioxide with an example of a typical trans-critical cycle.
  • Fig. 3 shows a schematic diagram showing the principle of optimum high side pressure determination. Temperature approach is used as COP reflecting parameter in the figure. Detailed description of the invention
  • Fig. 1 illustrates a conventional vapour compression system comprising a compressor 1, a heat rejector 2, an expansion means 3 and a heat absorber 4 connected in a closed circulation system.
  • Figure 2 shows a trans-critical CO 2 cycle in a temperature entropy diagram.
  • the compression process is indicated as isentropic from state a to b.
  • the refrigerant exit temperature out of the heat rejector c is regarded as constant. Specific work, specific cooling capacity and coefficient of performance are explained in the figure.
  • the optimum pressure is achieved when the marginal increase of capacity (change of h c at constant temperature) equals ⁇ times the marginal increase in work (change of h b at constant entropy).
  • Perturbation of the high side pressure is in principle a practical approach to use the equation above.
  • mapping the energy efficiency, or a parameter which reflects the energy efficiency, as function of high side pressure it is possible to establish the point where the marginal increase of capacity equals ⁇ times the marginal increase in work.
  • Example 1 Various parameters can be used as reflection for the energy efficiency.
  • Example 1 Various parameters can be used as reflection for the energy efficiency.
  • the temperature difference between refrigerant and heat sink at the cold end of the heat rejector 4 is often denoted as "temperature approach" for a trans-critical cycle.
  • temperature approach for a trans-critical cycle.
  • high side pressure An increase of the high side pressure will lead to a reduction of temperature approach.
  • the high side pressure can favourably be increased until a further increase does not lead to a significant reduction of temperature approach.
  • optimum high side pressure is then in practice established, and the system can be operated at optimum conditions, maximizing the system COP. This principle is illustrated in figure 3.
  • a perturbation of the high side pressure will produce a relation as indicated in figure 3.
  • a new perturbation can be made and a new updated relation established. In this way, the trans-critical system will always be able to operate close to optimum conditions.
  • COP is used as steering parameter, the optimum high side pressure will be established directly. If a COP reflecting parameter is used, an exact measure for the "marginal effect" on the parameter has to be quantified. This measure can however easily be estimated. Another possibility is to increase pressure until the parameter reaches a predetermined level.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Air Conditioning Control Device (AREA)
  • Reduction Or Emphasis Of Bandwidth Of Signals (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)
  • Control Of Eletrric Generators (AREA)
  • Control Of Positive-Displacement Air Blowers (AREA)
  • Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
  • Compression-Type Refrigeration Machines With Reversible Cycles (AREA)
  • Sorption Type Refrigeration Machines (AREA)

Abstract

A compression refrigeration system includes a compressor (1), heat rejector (2), expansion means (3) and a heat absorber (4) connected in a closed circulation circuit that may operate with supercritical high-side pressure.

Description

Method of operation and regulation of a vapour compression system
Field of invention
The present invention relates to compression refrigeration system including a compressor, a heat rejector, an expansion means and a heat absorber connected in a closed circulation circuit that may operate with supercritical high-side pressure, using carbon dioxide or a mixture containing carbon dioxide as the refrigerant in the system.
Description of prior art and background of the invention
Conventional vapour compression systems reject heat by condensation of the refrigerant at subcritical pressure given by the saturation pressure at the given temperature. When using a refrigerant with low critical temperature, for instance CO2, the pressure at heat rejection will be supercritical if the temperature of the heat sink is high, for instance higher than the critical temperature of the refrigerant, in order to obtain efficient , operation of the system. The cycle of operation will then be transcritical, for instance as known from WO 90/07683. Temperature and the high-pressure side will be independent variables contrary to conventional systems.
WO 94/14016 and WO 97/27437 both describe a simple circuit for realising such a system, in basis comprising a compressor, a heat rejector, an expansion means and an evaporator connected in a closed circuit. CO2 is the preferred refrigerant for both of them.
The system coefficient of performance (COP) for trans-critical vapour compression systems is strongly affected by the level of the high side pressure. This is thoroughly explained by Pettersen & Skaugen (1994), who also presents a mathematical expression for the optimum pressure. Based on the fact that the high side pressure is independent from temperature, high side pressure can be controlled in order to achieve optimum energy efficiency. The next step is to determine optimum pressure for given operating conditions. Several publications and patents are published, which suggests different strategies to determine the optimum high side pressure. Inokuty (1922) published a graphic method already in 1922, but it is not applicable for the present digital controllers.
EP 0 604417 B 1 describe how different signals can be used as steering parameter for the high side pressure. A suitable signal is the heat rejector refrigerant outlet temperature. The relation between optimum high side pressure and the signal temperature is calculated in advance or measured. Densopatent describes more or less an analogous strategy. Different signals are used as input parameter to a controller, which based on the signals regulates the pressure to a predetermined level.
Among others, Liao & Jakobsen (1998) presented an equation, which calculates optimum pressure from theoretical input. The equation does not take into account practical aspects which may affect the optimum pressure sicnificantly.
Most methods for optimum pressure determination described above, has a theoretical approach. This means that they are not able to compensate for practical aspects like varying operating conditions, influence of oil in the system, ... Optimum pressure will then most probably be different from the calculated one. There is also a risk for a "wind up" and lack of control. The temperature signal gives a feedback to the controller, which adjust the pressure with some delay. If conditions change quit rapidly, the controller will never establish a constant pressure, and cooling capacity will vary.
As explained above, it is a possibility to run tests and measure optimum high side pressure relations. But this is time consuming, expensive. Furthermore, it is hard, if not impossible, to cover all operating conditions. And the measurements has to be performed for all new designs.
Summary of the invention
A major object of the present invention is to make a simple, efficient system that avoids the aforementioned shortcomings and disadvantages. The invention is characterized by the features as defined in the accompanying independent claim 1.
Advantageous features of the invention are further defined in the accompanying independent claims 2—8.
The present invention is based on the system described above, comprising at least a compressor, a heat rejector, an expansion means and a heat absorber. It is a new and novel method for optimum operation of such a system with respect to energy efficiency.
When operating conditions change, the controller in the trans-critical vapour compression system can perform a perturbation of the high side pressure and thereby establish a correlation between the pressure and the energy efficiency, or a suitable parameter reflecting the energy efficiency. A relation between high side pressure and energy efficiency can then easily be mapped, and optimum pressure determined and used until operating conditions change. This is a simple method which will work for all designs of trans-critical vapour compression systems. No initial measurements have to be made, and practical aspects will be accounted for on site.
Brief description of the drawings.
The invention will be further described in the following by way of examples only, and with reference to the drawings in which,
Fig. 1 illustrates a simple circuit for a vapour compression system.
Fig. 2 shows a temperature entropy diagram for carbon dioxide with an example of a typical trans-critical cycle.
Fig. 3 shows a schematic diagram showing the principle of optimum high side pressure determination. Temperature approach is used as COP reflecting parameter in the figure. Detailed description of the invention
Fig. 1 illustrates a conventional vapour compression system comprising a compressor 1, a heat rejector 2, an expansion means 3 and a heat absorber 4 connected in a closed circulation system.
Figure 2 shows a trans-critical CO2 cycle in a temperature entropy diagram. The compression process is indicated as isentropic from state a to b. The refrigerant exit temperature out of the heat rejector c is regarded as constant. Specific work, specific cooling capacity and coefficient of performance are explained in the figure.
As mentioned above, there is a mathematical expression for high optimum high side pressure in a trans-critical vapour compression system. The expression is as follows:
Figure imgf000005_0001
The optimum pressure is achieved when the marginal increase of capacity (change of hc at constant temperature) equals ε times the marginal increase in work (change of hb at constant entropy).
Perturbation of the high side pressure, is in principle a practical approach to use the equation above. By mapping the energy efficiency, or a parameter which reflects the energy efficiency, as function of high side pressure, it is possible to establish the point where the marginal increase of capacity equals ε times the marginal increase in work.
Various parameters can be used as reflection for the energy efficiency. Example 1
The temperature difference between refrigerant and heat sink at the cold end of the heat rejector 4, is often denoted as "temperature approach" for a trans-critical cycle. There is a correlation between high side pressure and the temperature approach. An increase of the high side pressure will lead to a reduction of temperature approach. The high side pressure can favourably be increased until a further increase does not lead to a significant reduction of temperature approach. At this point, optimum high side pressure is then in practice established, and the system can be operated at optimum conditions, maximizing the system COP. This principle is illustrated in figure 3.
A perturbation of the high side pressure will produce a relation as indicated in figure 3. When operating conditions change, or for other reasons, a new perturbation can be made and a new updated relation established. In this way, the trans-critical system will always be able to operate close to optimum conditions.
Example 2
Instead of using the temperature approach, it is an option to use the gas cooler outlet temperature as parameter for reflection of energy efficiency.
Example 3
By online measurements of system pressures and temperatures, it is possible to automatically calculate the enthalpies for a trans-critical cycle at the points 1 to 4 indicated in figure 2, if the refrigerant properties can be provided from property a library. The enthalpies can be used for calculation of the system coefficient of performance. A perturbation of the high side pressure will then produce a relation between COP and the high side pressure directly.
If COP is used as steering parameter, the optimum high side pressure will be established directly. If a COP reflecting parameter is used, an exact measure for the "marginal effect" on the parameter has to be quantified. This measure can however easily be estimated. Another possibility is to increase pressure until the parameter reaches a predetermined level.

Claims

Claims
1. A compression refrigeration system including at least a compressor (1), a heat rejector (2), an expansion means (3) and a heat absorber (4) connected in a closed circulation circuit that may operate with supercritical high-side pressure, characterized in that an online estimation of coefficient of performance (COP) , or a parameter reflecting the COP, can be used as a signal for optimum regulation and operation of the compression refrigeration system.
2. System according to claim 1, characterized in that carbon dioxide or a refrigerant mixture containing carbon dioxide is applied as the refrigerant in the system.
3. System according to any of the preceding claims 1-4, characterized in that a regulation system may vary pressure on the high pressure side in order to map the COP or the COP reflecting parameter as function of pressure for a given operation condition.
4. System according to any of the preceding claims 1-3, characterized in that the temperature difference between the refrigerant and heat sink at the cold end (temperature approach) can be used as a signal for optimum regulation and operation of the compression refrigeration system.
5. System according to any of the preceding claims 1-4, characterized in that pressure on the high pressure side of the system can be increased until the increase has marginal effect on the temperature approach.
6. System according to any of the preceding claims 1-5, characterized in that pressure on the high pressure side of the system can be increased until temperature approach is equal or lower than a predetermined level.
7. System according to the preceding claims 6, characterized in that the predetermined level may vary with varying operation conditions.
8. System according to the preceding claims 1-7, characterized in that the heat rejector outlet temperature can be used as COP reflecting parameter.
PCT/NO2003/000425 2002-12-23 2003-12-17 Method of operation and regulation of a vapour compression system Ceased WO2004057246A1 (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US10/539,611 US7621137B2 (en) 2002-12-23 2003-12-17 Method of operation and regulation of a vapour compression system
JP2004562129A JP2006511778A (en) 2002-12-23 2003-12-17 Operation and adjustment method of vapor compression system
EP03813728A EP1579157B1 (en) 2002-12-23 2003-12-17 Method of operation and regulaton of a vapour compression system
DE60322588T DE60322588D1 (en) 2002-12-23 2003-12-17 METHOD FOR OPERATING AND REGULATING A STEAM COMPRESSION SYSTEM
AU2003303148A AU2003303148A1 (en) 2002-12-23 2003-12-17 Method of operation and regulation of a vapour compression system

Applications Claiming Priority (2)

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NO20026232A NO317847B1 (en) 2002-12-23 2002-12-23 Method for regulating a vapor compression system
NO20026232 2002-12-23

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EP (1) EP1579157B1 (en)
JP (1) JP2006511778A (en)
CN (1) CN100501271C (en)
AT (1) ATE403122T1 (en)
AU (1) AU2003303148A1 (en)
DE (1) DE60322588D1 (en)
NO (1) NO317847B1 (en)
WO (1) WO2004057246A1 (en)

Cited By (3)

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JP2006207929A (en) * 2005-01-28 2006-08-10 Daikin Ind Ltd Optimal operation control system and optimum operation control method for air conditioning system
US8578722B2 (en) 2007-06-29 2013-11-12 Sinvent As Closed circuit vapour compression refrigeration system and a method for operating the system
US9395112B2 (en) 2011-07-05 2016-07-19 Danfoss A/S Method for controlling operation of a vapour compression system in a subcritical and a supercritical mode

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US6505475B1 (en) 1999-08-20 2003-01-14 Hudson Technologies Inc. Method and apparatus for measuring and improving efficiency in refrigeration systems
FR2909439B1 (en) * 2006-12-01 2009-02-13 Commissariat Energie Atomique VAPOR COMPRESSION DEVICE AND METHOD OF REALIZING A TRANSCRITICAL CYCLE THEREFOR
EP2256422B1 (en) * 2008-03-27 2018-11-07 Mitsubishi Electric Corporation Air conditioning management system, air conditioning system, program, and recording medium
US8694131B2 (en) * 2009-06-30 2014-04-08 Mitsubishi Electric Research Laboratories, Inc. System and method for controlling operations of vapor compression system
US20120073316A1 (en) * 2010-09-23 2012-03-29 Thermo King Corporation Control of a transcritical vapor compression system
US10302342B2 (en) 2013-03-14 2019-05-28 Rolls-Royce Corporation Charge control system for trans-critical vapor cycle systems
US10132529B2 (en) 2013-03-14 2018-11-20 Rolls-Royce Corporation Thermal management system controlling dynamic and steady state thermal loads
WO2014143194A1 (en) 2013-03-14 2014-09-18 Rolls-Royce Corporation Adaptive trans-critical co2 cooling systems for aerospace applications
US9676484B2 (en) 2013-03-14 2017-06-13 Rolls-Royce North American Technologies, Inc. Adaptive trans-critical carbon dioxide cooling systems
US9718553B2 (en) 2013-03-14 2017-08-01 Rolls-Royce North America Technologies, Inc. Adaptive trans-critical CO2 cooling systems for aerospace applications
US9739200B2 (en) 2013-12-30 2017-08-22 Rolls-Royce Corporation Cooling systems for high mach applications
CA3020611C (en) * 2017-10-13 2024-03-26 Heating Solutions Llc Optimization sensor and pool heater utilizing same and related methods
US11800692B2 (en) * 2020-03-19 2023-10-24 Nooter/Eriksen, Inc. System and method for data center cooling with carbon dioxide
CN114992926B (en) * 2022-05-26 2023-04-28 西安交通大学 For transcritical CO 2 Control method and control system of air conditioning system
DE102023111158A1 (en) * 2023-04-28 2024-10-31 Denso Automotive Deutschland Gmbh Method for operating a supercritical refrigerant circuit

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DE10053203A1 (en) * 1999-10-28 2001-06-07 Denso Corp Refrigerant cycle system; has compressor at over-critical pressure and pressure-control valve to control refrigerant leaving compressor and cooler by decompressing refrigerant leaving cooler
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Cited By (3)

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Publication number Priority date Publication date Assignee Title
JP2006207929A (en) * 2005-01-28 2006-08-10 Daikin Ind Ltd Optimal operation control system and optimum operation control method for air conditioning system
US8578722B2 (en) 2007-06-29 2013-11-12 Sinvent As Closed circuit vapour compression refrigeration system and a method for operating the system
US9395112B2 (en) 2011-07-05 2016-07-19 Danfoss A/S Method for controlling operation of a vapour compression system in a subcritical and a supercritical mode

Also Published As

Publication number Publication date
US7621137B2 (en) 2009-11-24
CN100501271C (en) 2009-06-17
AU2003303148A1 (en) 2004-07-14
CN1735778A (en) 2006-02-15
US20060150646A1 (en) 2006-07-13
DE60322588D1 (en) 2008-09-11
JP2006511778A (en) 2006-04-06
NO317847B1 (en) 2004-12-20
EP1579157A1 (en) 2005-09-28
AU2003303148A8 (en) 2004-07-14
WO2004057246A8 (en) 2005-10-06
EP1579157B1 (en) 2008-07-30
ATE403122T1 (en) 2008-08-15
NO20026232D0 (en) 2002-12-23

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