EP2623900A1 - Verfahren zur Steuerung des Gasdrucks in einer Kühlanlage - Google Patents

Verfahren zur Steuerung des Gasdrucks in einer Kühlanlage Download PDF

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Publication number
EP2623900A1
EP2623900A1 EP12000707.5A EP12000707A EP2623900A1 EP 2623900 A1 EP2623900 A1 EP 2623900A1 EP 12000707 A EP12000707 A EP 12000707A EP 2623900 A1 EP2623900 A1 EP 2623900A1
Authority
EP
European Patent Office
Prior art keywords
capacity
compressors
pressure
heat exchanger
cooling medium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP12000707.5A
Other languages
English (en)
French (fr)
Inventor
Kenneth Bank Madsen
Frede Schmidt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Danfoss AS
Original Assignee
Danfoss AS
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 Danfoss AS filed Critical Danfoss AS
Priority to EP12000707.5A priority Critical patent/EP2623900A1/de
Priority to EP12772209.8A priority patent/EP2764303B1/de
Priority to PL12772209T priority patent/PL2764303T3/pl
Priority to US14/349,749 priority patent/US9885509B2/en
Priority to PCT/DK2012/000109 priority patent/WO2013050035A1/en
Priority to CN201280049297.XA priority patent/CN103842749B/zh
Publication of EP2623900A1 publication Critical patent/EP2623900A1/de
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/005—Arrangement or mounting of control or safety devices of safety devices
    • 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
    • F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
    • F25B2313/031—Sensor arrangements
    • F25B2313/0313—Pressure sensors near the outdoor heat exchanger
    • 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
    • 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
    • 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

Definitions

  • the invention relates to a method for controlling of gas pressure in a heat rejecting heat exchanger of a cooling plant.
  • the invention also relates to a control unit operating according to the method of the invention, and to a plant with such a control unit.
  • Fig. 1 is a log P-h diagram showing how a read-out of a slightly too high pressure (upper limit of ⁇ p) may result in the controller registering the pressure and/or the temperature at the outlet of the heat rejecting heat exchanger, for instance the gas cooler, to be at the optimal curve in point B in Fig. 1 , while the physical situation, or the actual condition, is shown in point A in Fig. 1 .
  • cooling plant While it is believed that the cooling plant is operated at near optimal conditions, it is in fact operated in a very energy inefficient manner.
  • the problem is sometimes referred to as gas loop operation and may occur, where the isothermal lines are approximately horizontal in the log P-h diagram, as illustrated in Fig. 1 .
  • Gas loop operation reduces the cooling capacity to almost zero. It will result in the controller increasing the capacity of the compressor to 100%, and after a couple of minutes, the controller will increase the reference of the gas cooler.
  • the present invention provides a method for monitoring gas pressure in a heat rejecting heat exchanger in a cooling circuit, said method comprising the steps of:
  • the term 'cooling circuit' should be interpreted to mean a refrigerant path in which refrigerant is alternatingly compressed and expanded.
  • a compressor, a heat rejecting heat exchanger, an expansion device and a heat consuming heat exchanger are arranged in the refrigerant path.
  • the compressor may be in the form of a single compressor or in the form of a rack of two or more compressors.
  • the heat rejecting heat exchanger may be in the form of a condenser or a gas cooler, depending on whether the cooling circuit is operated subcritically or transcritically.
  • the heat consuming heat exchanger may be an evaporator.
  • Refrigerant is compressed in the compressor before being supplied to the heat rejecting heat exchanger.
  • heat exchange takes place with a secondary fluid flow across the heat rejecting heat exchanger, in such a manner that the temperature of the refrigerant flowing through the heat rejecting heat exchanger, via the refrigerant path, is reduced.
  • the heat rejecting heat exchanger is a condenser
  • gaseous refrigerant which enters the heat rejecting heat exchanger is at least partly condensed.
  • the heat rejecting heat exchanger is a gas cooler, gaseous refrigerant which enters the heat rejecting heat exchanger remains gaseous, but the temperature of the refrigerant is reduced.
  • the cooling circuit is capable of providing heating for a closed volume, via the heat rejecting heat exchanger.
  • the refrigerant is then supplied to the expansion device, where it is expanded before being supplied to the heat consuming heat exchanger.
  • heat exchange takes place with a secondary fluid flow across the heat consuming heat exchanger, in such a manner that the temperature of the refrigerant flowing through the heat consuming heat exchanger, via the refrigerant path, is increased.
  • the heat consuming heat exchanger is an evaporator
  • liquid refrigerant entering the heat consuming heat exchanger is at least partly evaporated in the heat consuming heat exchanger.
  • the evaporated refrigerant may be heated further, in which case superheated refrigerant leaves the heat consuming heat exchanger.
  • the cooling circuit is capable of providing cooling for a closed volume, via the heat consuming heat exchanger. The refrigerant is then returned to the compressor, and the cycle is repeated.
  • the present capacity of one or more compressors in the cooling circuit compared to a maximum capacity is established.
  • the term 'capacity' should be interpreted to mean the work provided by the compressor(s).
  • the capacity may be expressed in terms of the electrical energy or power consumed by the compressor(s), in terms of the amount of refrigerant being compressed and displaced by the compressor(s), in terms of the cooling load on the cooling plant, or in any other suitable manner.
  • the present compressor capacity may be measured.
  • information regarding the present compressor capacity may be inherently present in the compressor controller, in which case the information is simply provided by the compressor controller.
  • the maximum capacity may be the rated capacity of the one or more compressors, the rated capacity being the maximum work which the compressor(s) is/are designed to deliver.
  • the maximum capacity may be a capacity limit which is defined by various operating conditions of the cooling circuit, such as the outdoor temperature, the indoor temperature, the design of the cooling plant, the installation site, the desired temperature of the equipment and/or goods to be cooled, etc.
  • the cooling plant may be over dimensioned in the sense that the compressor(s) is/are potentially capable of providing a significantly higher cooling capacity than will ever be necessary in order to meet the cooling load on the cooling plant.
  • the maximum capacity may be a specified percentage of the rated capacity, such as 75% of the rated capacity, 80% of the rated capacity, 90% of the rated capacity, or the like.
  • the maximum capacity may advantageously be a compressor capacity which is required when the cooling load on the cooling plant is at a maximum level.
  • the present capacity of the one or more compressors is at least at a level corresponding to a pre-set percentage of the maximum capacity, it is investigated when this level was reached, and for how long the compressor capacity has been at or above this level. In other words, it is investigated whether the one or more compressors is/are operating at a relatively high capacity, at or close to the maximum capacity as defined above, and has/have been doing so for a while. If the compressor(s) is/are operating at a high capacity level during a continuous time period, it is an indication that the cooling plant is operating inefficiently, and that the cooling medium may be in a gas loop operational mode.
  • the cooling medium is in a gas loop operational mode.
  • the method according to the first aspect of the invention allows a gas loop condition to be identified in an easy manner.
  • This allows the operation of the cooling plant to be adjusted in such a manner that the cooling medium is brought out of the gas loop operational mode.
  • the compressor capacity has to be at a high level for at least a pre-set period of time, it is ensured that short spikes of high capacity are not reacted upon. This is an advantage, because such short spikes may be the result of fluctuations, rather than indicating a gas loop operational mode.
  • the method may comprise the further step of increasing the pressure of the cooling medium inside the heat rejecting heat exchanger, if it is concluded that the cooling medium is in a gas loop operational mode.
  • the pressure of the cooling medium may be increased by 5-20 bars, such as by 7-15 bars, such as by 8-10 bars, such as approximately 10 bars, or approximately 5 bars, or approximately 20 bars.
  • the pressure of the cooling medium may be increased by 1 %-15%, such as by 2%-12%, such as by 5%-10%, such as by approximately 7%, or approximately 5%, or approximately 10%.
  • the step of increasing the pressure may result in a pressure increase which causes the present capacity of the one or more compressors to decrease to below 95% of the maximum capacity, possibly to below 90% of the maximum capacity, even possibly to below 80% of the maximum capacity.
  • the pressure increase moves the cooling medium out of the gas loop operation mode, and thereby operation of the compressor(s) is moved away from the very high capacity level.
  • the method may further comprise the step of decreasing the pressure of the cooling medium inside the heat rejecting heat exchanger, if it can be concluded that the cooling medium is no longer in a gas loop operational mode.
  • the increased pressure of the cooling medium inside the heat rejecting heat exchanger is only maintained as long as required in order to move the cooling medium out of the gas loop operational mode. Once this has been obtained, the pressure is once again reduced, and the cooling plant is returned to normal operation.
  • the duration within which the pressure of the cooling medium is increased may differ depending on which percentage of the maximum capacity is decided as being relatively high or full capacity of the one or more compressors. For instance, if the percentage of the maximum capacity is decided as being 90%, the increase in pressure will be terminated, when the present capacity decreases to below 90% of the maximum capacity.
  • the pre-set percentage of the maximum capacity of the one or more compressors may be at least 80% of the maximum capacity, possibly at least 90% of the maximum capacity, even possibly between 95% and 100% of the maximum capacity of the one or more compressors, even more possible 100% of the maximum capacity.
  • the present capacity of the one or more compressors should be very close to the maximum capacity for a significant period of time before it can be concluded that the cooling medium is in a gas loop operational mode.
  • the pre-set period of time of a certain duration may be at least one minute, preferably at least two minutes, possibly at least three minutes, even possible at least four minutes, and even more possible at least five minutes, possibly at the most 15 minutes.
  • the duration within which the one or more compressors of the cooling plant operate at a capacity decided as being maximum capacity, or close to maximum capacity, may differ depending on the installation site, the outdoor and indoor temperature, the desired temperature of the equipment and/or goods to be cooled, etc. Therefore, under some conditions, a shorter period of time is enough for concluding that the cooling medium is in a gas loop operational mode, and under other conditions a longer period of time is needed for concluding that the cooling medium is in a gas loop operational mode.
  • the present capacity of the one or more compressors may be established commonly for all the compressors of the cooling circuit. According to this embodiment, the combined capacity of all of the compressors is established in one go, and compared to the maximum combined capacity. Thus, the sum of capacity of the entire cooling plant is established for obtaining the capacity of all compressors, if the cooling plant comprises more than one compressor.
  • the present capacity of the one or more compressors may be established individually for each compressor of the cooling circuit. According to this embodiment, the capacity of each of the compressors is established and compared to the maximum capacity for that compressor.
  • the present invention provides a control unit for monitoring pressure in a heat rejecting heat exchanger of a cooling circuit comprising one or more compressors,
  • control unit is adapted to establish whether or not a cooling medium of a cooling circuit is in a gas loop operational mode, by means of the method according to the first aspect of the invention. Therefore the remarks set forth above are equally applicable here.
  • the present invention provides a plant with a cooling circuit comprising one or more compressors, said plant also comprising at least one heat rejecting heat exchanger and a controller for controlling pressure in the heat rejecting heat exchanger, and
  • Fig. 1 is a log P-h diagram illustrating a gas loop operational mode of a cooling medium in a cooling plant.
  • the cooling plant is operated transcritically, i.e. no phase transition takes place during heat exchange in the heat rejecting heat exchanger.
  • Fig. 1 illustrates that when the cooling medium is operated in a region where the isothermal curve is relatively flat, small variations in pressure results in large variations in enthalpy. Therefore a measurement of the pressure of the cooling medium leaving the gas cooler may lead the controller to believe that the cooling medium is at the optimal operating point B. However, due to a small error in the measurement ( ⁇ p), the cooling medium may in fact be at the very inefficient operating point A. As a consequence, the cooling plant is not operated in an optimal manner. Since this is not registered by the controller, the operation of the cooling plant continues to be inefficient. This situation is sometimes referred to as gas loop operation.
  • Fig. 2 is a log P-h diagram, similar to the diagram of Fig. 1 .
  • Fig. 2 also illustrates the gas loop operational mode described above with reference to Fig. 1 .
  • a small error ( ⁇ p) in the measurement of the pressure of the cooling medium leaving the gas cooler may lead the controller to believe that the cooling medium is at the optimal operating point A, while it is in fact at the very inefficient operating point B.

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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)
EP12000707.5A 2011-10-07 2012-02-02 Verfahren zur Steuerung des Gasdrucks in einer Kühlanlage Withdrawn EP2623900A1 (de)

Priority Applications (6)

Application Number Priority Date Filing Date Title
EP12000707.5A EP2623900A1 (de) 2012-02-02 2012-02-02 Verfahren zur Steuerung des Gasdrucks in einer Kühlanlage
EP12772209.8A EP2764303B1 (de) 2011-10-07 2012-10-05 Verfahren zur regelung des gasdrucks in einer kühlanlage
PL12772209T PL2764303T3 (pl) 2011-10-07 2012-10-05 Sposób sterowania ciśnieniem gazu w instalacji chłodniczej
US14/349,749 US9885509B2 (en) 2011-10-07 2012-10-05 Method for controlling gas pressure in cooling plant
PCT/DK2012/000109 WO2013050035A1 (en) 2011-10-07 2012-10-05 Method for controlling gas pressure in cooling plant
CN201280049297.XA CN103842749B (zh) 2011-10-07 2012-10-05 用于控制冷却设备中的气体压力的方法

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP12000707.5A EP2623900A1 (de) 2012-02-02 2012-02-02 Verfahren zur Steuerung des Gasdrucks in einer Kühlanlage

Publications (1)

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EP2623900A1 true EP2623900A1 (de) 2013-08-07

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EP12000707.5A Withdrawn EP2623900A1 (de) 2011-10-07 2012-02-02 Verfahren zur Steuerung des Gasdrucks in einer Kühlanlage

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1202004A1 (de) * 2000-10-30 2002-05-02 Calsonic Kansei Corporation Kühlungskreislauf und Steuerungsverfahren dafür
DE102006019082A1 (de) * 2005-04-25 2006-10-26 Denso Corp., Kariya Kühlkreisvorrichtung für ein Fahrzeug
US20070089439A1 (en) * 2005-10-21 2007-04-26 Abtar Singh Monitoring a condenser in a refrigeration system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1202004A1 (de) * 2000-10-30 2002-05-02 Calsonic Kansei Corporation Kühlungskreislauf und Steuerungsverfahren dafür
DE102006019082A1 (de) * 2005-04-25 2006-10-26 Denso Corp., Kariya Kühlkreisvorrichtung für ein Fahrzeug
US20070089439A1 (en) * 2005-10-21 2007-04-26 Abtar Singh Monitoring a condenser in a refrigeration system

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