EP0564123A1 - Kühlsystem - Google Patents

Kühlsystem Download PDF

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Publication number
EP0564123A1
EP0564123A1 EP93302023A EP93302023A EP0564123A1 EP 0564123 A1 EP0564123 A1 EP 0564123A1 EP 93302023 A EP93302023 A EP 93302023A EP 93302023 A EP93302023 A EP 93302023A EP 0564123 A1 EP0564123 A1 EP 0564123A1
Authority
EP
European Patent Office
Prior art keywords
compressor
economizer
capacity
refrigeration system
trapped
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Withdrawn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
EP93302023A
Other languages
English (en)
French (fr)
Inventor
David Norton Shaw
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.)
Carrier Corp
Original Assignee
Carrier Corp
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 Corp filed Critical Carrier Corp
Publication of EP0564123A1 publication Critical patent/EP0564123A1/de
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
    • F04C28/10—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by changing the positions of the inlet or outlet openings with respect to the working chamber
    • 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
    • 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
    • F25B49/022—Compressor control arrangements
    • 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
    • F25B2400/13—Economisers
    • 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
    • F25B2400/23—Separators

Definitions

  • This invention relates to refrigeration systems.
  • Positive displacement compressors are designed for a particular capacity but are normally operated over a range of capacities, usually less than the designed capacity, and thus require some means for modifying their operation if efficient operation is to be maintained. Often, the operation of a compressor at other than design conditions is inefficient due to overcompression or the like. It is also desirable to be able to unload a compressor to various percentages of capacity in fixed increments or over an entire range. Simultaneously, it is desirable to efficiently maintain the desired discharge pressure to suction pressure ratio, or V i , for meeting system requirements. To meet these various requirements, a number of individual controls are used. In screw compressors, for example, capacity control is conventionally achieved by the use of a slide valve as well as by individual bypass valves.
  • a slide valve When a slide valve is used, it is located in and reciprocates in the cusp of the housing formed between the intersecting bores for the two rotors.
  • the slide valve thus defines a portion of each bore and thereby compromises the integrity of the housing as well as making for a complicated device.
  • the slide valve is reciprocatably positionable with respect to the axes of the rotors and can thus effectively change the start of compression by changing the closing point of the suction stroke and thereby controlling the amount of gas trapped and compressed.
  • the present invention is directed to V i and capacity variation. Where, for example, V i must be 3 to 1 under full load highest head conditions, the challenge is to avoid overcompression losses when the head pressure falls significantly.
  • the present invention provides a refrigeration system as described in claim 1 of the accompanying claims.
  • the present invention provides a method for operating a refrigeration system as described in claim 4 of the accompanying claims.
  • the present invention is directed to compensating for falling head pressure when full load V i is 3 or some other number dependent upon the application. This may be initially achieved by bypassing economizer flow to suction thus reducing the maximum volume/mass flow induced pressure buildup in the machine. The next step is to unload the compressor in order to further reduce the effective V i . Assuming only a fixed discharge port and full load V i of 3, V i will be 2.25 at 75% load and 1.5 at 50% load. What this means is that the compressor should be unloaded as the head pressure falls but that it should be done by limiting the maximum load as a function of the condensing pressure.
  • V i is always directly proportional to capacity so that as capacity drops, V i drops. As an economizer is bypassed, V i drops. Thus, V i can be changed in two ways.
  • V i is needed in hot weather which is also when the highest capacity is needed.
  • V i may be controlled by controlling capacity in combination with an economizer control which can be used to inject refrigerant at some stage of the compression process, bypass to suction or be disabled.
  • A-B represents the suction stroke when gas at suction pressure (P s ) is drawn into the compressor.
  • P s suction pressure
  • the suction stroke ceases and the compression stroke is initiated.
  • the gas taken in on the suction stroke is compressed and the pressure of the gas is increased from P s to Pd1, the discharge pressure.
  • the trapped, compressed gas becomes exposed to the fixed discharge port and the discharge stroke begins.
  • the actual discharge pressure will be a function of factors such as the head against which discharge takes place, but, ideally, the discharge stroke takes place at a constant pressure.
  • From C to D discharge takes place until, nominally, all of the compressed trapped fluid is delivered.
  • the discharge path is shut off and the trapped volume becomes exposed to suction causing the cycle to return to point A and be completed.
  • economizer injection is employed. Specifically, as described above, compression starts at point B but, when the cycle reaches point E, economizer injection takes place. Economizer injection is the adding of additional mass to the trapped volume and takes place during compression over the portion of the cycle represented by E-F. The economizer injection ceases at point F and compression continues until point G where the trapped, compressed gas becomes exposed to the fixed discharge port and the discharge stroke begins. Because more mass is within the trapped volume due to the economizer injection, the compression process from F to G results in a higher discharge pressure, Pd2, at the time that the trapped volume is exposed to the fixed discharge port. Discharge takes place from G to H. Because there is more mass compressed to a higher pressure at point G than at point C, the cycle capacity is increased beyond the nominal design reference designated by cycle A-B-C-D-A.
  • the cycle A-I-J-K-A represents a reduced capacity or loading cycle and is similar to A-B-C-D-A except that it has a shorter suction cycle and reduced discharge pressure.
  • the suction stroke takes place from A to I with I, as illustrated, representing a trapped volume which is 50% of that represented by point B.
  • Compression takes place from I to J where the trapped volume becomes exposed to the fixed discharge port. Because less mass is compressed, point J represents a lower discharge pressure, Pd3, than that at point C.
  • the capacity of the cycle represented by A-B-C-D-A can be reduced by economizer bypass in the cycle represented by A-B-E-L-M-N-A.
  • gas is removed from the trapped volume until point L is reached.
  • E-L is the reverse of E-F.
  • the remaining trapped volume is compressed until the trapped volume is exposed to the discharge port at point M.
  • the discharge pressure at point M is Pd4 and discharge takes place from M to N.
  • economizer bypass can be used to further reduce the capacity of the cycle represented by A-I-J-K-A.
  • Refrigerant circuit 10 generally designates a refrigeration circuit.
  • Refrigerant circuit 10 includes a compressor 12 which compresses suction gas to a higher temperature and pressure and delivers it via discharge line 14 to condenser 16.
  • the hot refrigerant gas gives up heat to the condenser air thereby cooling the compressed gas and changing the state of the refrigerant from a gas to a liquid.
  • Liquid refrigerant flows from condenser 16 via liquid line 18 to thermostatic expansion valve, TXV, 20. As the liquid refrigerant passes through the orifice of TXV 20, some of the liquid refrigerant vaporizes into a gas (flash gas).
  • the mixture of liquid and gaseous refrigerant then passes via distributor tubes 22 to the evaporator 24. Heat is absorbed by the refrigerant from the evaporator air by the balance of the liquid refrigerant causing it to vaporize in the coil of the evaporator 24. The vaporized refrigerant then flows via suction line 26 to compressor 12 to complete the fluid circuit.
  • the refrigeration system just described is conventional.
  • the present invention places an expansion device 28 and an economizer 30 in line 18 between condenser 16 and TXV 20.
  • Expansion device 28 may be an orifice, a valve responsive to the liquid level in condenser 16 or any other suitable device.
  • Economizer 30 is connected to port 12a of compressor 12 via line 32 which contains valve 34 which is under the control of microprocessor controller 36.
  • Valve 34 can be closed, provide fluid communication from economizer 30 to port 12a in compressor 12 which is in fluid communication with trapped volumes within compressor 12, or provide bypass from the trapped volumes via port 12a and bypass line 38 to suction line 26.
  • controller 36 controls valve 34. If valve 34 is closed then cycles exemplified by A-B-C-D-A and by A-I-J-K-A would occur based upon the position of the capacity valves if compressor 12 is a screw compressor or other positive displacement compressor. If valve 34 is opened to permit flow from economizer 30 to trapped volumes in the compressor 12 then a cycle exemplified by A-B-E-F-G-H-A would occur. However, if valve 34 is opened to permit flow from trapped volumes in compressor 12 to suction line 26 via bypass line 38, then a cycle exemplified by A-B-E-L-M-N-A would occur.
  • compressor 12 is a screw compressor and the numeral 41 represents the unwrapped male rotor while numeral 42 represents the unwrapped female rotor.
  • Axial suction port 44 is located in end wall 45 and is in fluid communication with suction line 26.
  • Axial discharge port 46 is located in end wall 47 and is in fluid communication with discharge line 14.
  • the chevron shaped areas represent trapped volumes at various stages in the compression process starting with the cutoff of suction port 44 and progressing to a point just prior to communication with axial discharge port 46.
  • Generally radial port 12a is in communication with essentially one trapped volume at a point in the compression process corresponding to point E and economizer injection or economizer bypass can take place under the control of valve 34 as described above.
  • a second radial port 12b may provide fluid communication with the same trapped volume as port 12a.
  • the numeral 112 generally designates a scroll compressor having a first wrap 141, which is a fixed wrap, and a second wrap 142.
  • wraps 141 and 142 coact to define a plurality of pairs of trapped volumes.
  • trapped volumes 101 and 102 form one pair as do trapped volumes 103 and 104.
  • the trapped volumes move towards the center of the scroll wraps 141 and 142 until they become exposed to outlet 146 which is connected to discharge line 14.
  • screw compressors have trapped volumes on each rotor in communication with each other such that a single port 12a can communicate with trapped volumes on both rotors, this is not true for scroll compressors.
  • port 112a is in fluid communication with trapped volume 101 whereas port 112b is in fluid communication with trapped volume.
  • Ports 112a and 112b are formed along the fixed wrap 141 and are of a width which is preferably somewhat less than the thickness of wrap 142. In the illustrated position, ports 112a and 112b are partially covered by wrap 142 but cannot communicate with trapped volumes 103 and 104 for any position of wrap 142. For symmetry of loading it is preferred that the trapped volumes in communication with ports 112a and 112b are subject to the same conditions. Thus both port 112a and 112b would be preferably commonly manifolded to valve 34, but, if necessary or desired, they can be separately controlled for more steps in capacity control.
  • the invention serves to: prevent severe overcompression in screw compression systems; ensure that screw compressors always operate at near optimum performance; and ensure that positive displacement compressors with V i tied into capacity level are capable of always operating at near optimum performance.
EP93302023A 1992-04-02 1993-03-17 Kühlsystem Withdrawn EP0564123A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US86247392A 1992-04-02 1992-04-02
US862473 1992-04-02

Publications (1)

Publication Number Publication Date
EP0564123A1 true EP0564123A1 (de) 1993-10-06

Family

ID=25338579

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93302023A Withdrawn EP0564123A1 (de) 1992-04-02 1993-03-17 Kühlsystem

Country Status (1)

Country Link
EP (1) EP0564123A1 (de)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995021359A1 (en) * 1994-02-03 1995-08-10 Svenska Rotor Maskiner Ab Refrigeration system and a method for regulating the refrigeration capacity of such a system
EP0703419A3 (de) * 1994-09-20 1997-05-07 Microtecnica Kälteanlage
EP1132621A1 (de) * 1999-09-22 2001-09-12 Daikin Industries, Ltd. Schraubenverdichter und kühlgerät
WO2005119141A1 (en) * 2004-05-28 2005-12-15 York International Corporation System and method for controlling an economizer circuit
WO2006015629A1 (en) * 2004-08-09 2006-02-16 Carrier Corporation Flashgas removal from a receiver in a refrigeration circuit
WO2008112568A2 (en) * 2007-03-09 2008-09-18 Johnson Controls Technology Company Compressor with multiple inlets
EP3557062A1 (de) * 2018-04-20 2019-10-23 Trane International Inc. Schraubenverdichter mit synchronisierten vorwärmeranschlüssen
DE10334947B4 (de) * 2003-07-31 2019-11-07 Gea Refrigeration Germany Gmbh Verdichter für transkritische Kälteanlagen

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4727725A (en) * 1985-05-20 1988-03-01 Hitachi, Ltd. Gas injection system for screw compressor
DE3705849A1 (de) * 1987-02-24 1988-09-01 Sueddeutsche Kuehler Behr Kaelteanlage
US4947655A (en) * 1984-01-11 1990-08-14 Copeland Corporation Refrigeration system
US4989414A (en) * 1988-10-26 1991-02-05 Hitachi, Ltd Capacity-controllable air conditioner

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4947655A (en) * 1984-01-11 1990-08-14 Copeland Corporation Refrigeration system
US4727725A (en) * 1985-05-20 1988-03-01 Hitachi, Ltd. Gas injection system for screw compressor
DE3705849A1 (de) * 1987-02-24 1988-09-01 Sueddeutsche Kuehler Behr Kaelteanlage
US4989414A (en) * 1988-10-26 1991-02-05 Hitachi, Ltd Capacity-controllable air conditioner

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995021359A1 (en) * 1994-02-03 1995-08-10 Svenska Rotor Maskiner Ab Refrigeration system and a method for regulating the refrigeration capacity of such a system
US5816055A (en) * 1994-02-03 1998-10-06 Svenska Rotor Maskiner Ab Refrigeration system anad a method for regulating the refrigeration capacity of such a system
EP0703419A3 (de) * 1994-09-20 1997-05-07 Microtecnica Kälteanlage
EP1132621A1 (de) * 1999-09-22 2001-09-12 Daikin Industries, Ltd. Schraubenverdichter und kühlgerät
EP1132621A4 (de) * 1999-09-22 2002-01-23 Daikin Ind Ltd Schraubenverdichter und kühlgerät
DE10334947B4 (de) * 2003-07-31 2019-11-07 Gea Refrigeration Germany Gmbh Verdichter für transkritische Kälteanlagen
US7895852B2 (en) 2004-05-28 2011-03-01 York International Corporation System and method for controlling an economizer circuit
US7353659B2 (en) 2004-05-28 2008-04-08 York International Corporation System and method for controlling an economizer circuit
KR100888384B1 (ko) * 2004-05-28 2009-03-13 요크 인터내셔널 코포레이션 이코노마이저 회로 제어 시스템 및 방법
CN100526765C (zh) * 2004-05-28 2009-08-12 约克国际公司 控制节能器回路的系统和方法
WO2005119141A1 (en) * 2004-05-28 2005-12-15 York International Corporation System and method for controlling an economizer circuit
WO2006015629A1 (en) * 2004-08-09 2006-02-16 Carrier Corporation Flashgas removal from a receiver in a refrigeration circuit
WO2008112568A2 (en) * 2007-03-09 2008-09-18 Johnson Controls Technology Company Compressor with multiple inlets
WO2008112568A3 (en) * 2007-03-09 2008-12-24 Johnson Controls Tech Co Compressor with multiple inlets
EP3557062A1 (de) * 2018-04-20 2019-10-23 Trane International Inc. Schraubenverdichter mit synchronisierten vorwärmeranschlüssen
CN110388319A (zh) * 2018-04-20 2019-10-29 特灵国际有限公司 具有同步节能器端口的螺杆压缩机
US10895259B2 (en) 2018-04-20 2021-01-19 Trane International Inc. Screw compressor having synchronized economizer ports

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