US20060010907A1 - Refrigerant system with tandem compressors and reheat function - Google Patents

Refrigerant system with tandem compressors and reheat function Download PDF

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Publication number
US20060010907A1
US20060010907A1 US10/891,938 US89193804A US2006010907A1 US 20060010907 A1 US20060010907 A1 US 20060010907A1 US 89193804 A US89193804 A US 89193804A US 2006010907 A1 US2006010907 A1 US 2006010907A1
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Prior art keywords
refrigerant
set forth
condenser
reheat coil
compressors
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Abandoned
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US10/891,938
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English (en)
Inventor
Michael Taras
Alexander Lifson
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Carrier Corp
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Carrier Corp
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Filing date
Publication date
Application filed by Carrier Corp filed Critical Carrier Corp
Priority to US10/891,938 priority Critical patent/US20060010907A1/en
Assigned to CARRIER CORPORATION reassignment CARRIER CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LIFSON, ALEXANDER, TARAS, MICHAEL F.
Priority to PCT/US2005/024950 priority patent/WO2006019885A2/fr
Publication of US20060010907A1 publication Critical patent/US20060010907A1/en
Abandoned legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F3/00—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
    • F24F3/12—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling
    • F24F3/14—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification
    • F24F3/153—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification with subsequent heating, i.e. with the air, given the required humidity in the central station, passing a heating element to achieve the required 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
    • 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
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
    • F25B41/24—Arrangement of shut-off valves for disconnecting a part of the refrigerant cycle, e.g. an outdoor part
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/07—Details of compressors or related parts
    • F25B2400/075—Details of compressors or related parts with parallel compressors
    • 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

Definitions

  • This invention relates to refrigerant cycles incorporating a reheat coil, and wherein a tandem compressor arrangement is utilized.
  • the resulting cycles provide an enhanced control over both humidity and temperature in the conditioned space as well as improve efficiency, reliability and life-cycle cost of the equipment.
  • Refrigerant cycles are utilized to change the temperature and humidity, or otherwise control the environment, in the conditioned space.
  • a refrigerant cycle will typically include a compressor delivering a compressed refrigerant to a condenser, and from the condenser to an expansion device.
  • the refrigerant exchanges heat with an outdoor environment at the condenser, and is expanded in the expansion device to a lower pressure and temperature.
  • the refrigerant continues to an evaporator at which it exchanges heat with an indoor environment, or an environment to be conditioned. From the evaporator, the refrigerant returns to the compressor.
  • the amount of cooling that can be supplied by a refrigerant cycle is known as its “capacity.”
  • capacity There are numerous ways to provide control over the capacity for a refrigerant cycle.
  • One way is to substitute multiple compressors acting in tandem for a single compressor. In such an arrangement, the compressors can be selectively operated or shut down in response to an external heat load demand.
  • tandem compressors of different sizes can be utilized such that the various steps in the total capacity can be achieved.
  • both economized and conventional compressors can be employed in the tandem configuration, allowing for switching between various compressor modes of operation and further increasing a number of the unloading steps.
  • the tandem compressor configuration can be selectively chosen for any of the independent circuits of a multi-circuit system.
  • a reheat coil is provided in the path of air that has been blown over the evaporator.
  • the air passes over the reheat coil to regain heat from a refrigerant that is at a temperature hotter than the temperature of air leaving the evaporator.
  • the reheat coil is thus able to raise the temperature of the air leaving the evaporator.
  • the air dehumidified and overcooled in the evaporator is reheated back to a comfortable temperature level in the reheat coil.
  • the humidity in the conditioned space is mainly controlled by the evaporator and its temperature—by the reheat coil.
  • the reheat coil has not been utilized in a combination with tandem compressors, however.
  • the refrigerant cycles with tandem compressors have not had as complete control over temperature and humidity levels as may be desired.
  • this invention is not related to any particular reheat concept or tandem compressor configuration, but rather provides advantages, that could not be obtained before for a refrigerant system, by integrating both design features in a single cycle. Consequently, a system with any reheat schematic or tandem compressor configuration can take advantages from the invention.
  • a refrigerant system incorporates tandem compressors. At least two compressors each separately compress a refrigerant and deliver it into the refrigerant cycle.
  • a reheat coil is also incorporated into the refrigerant system, and receives air having passed over the evaporator to reheat the air to a desired temperature when required.
  • the reheat coil is positioned in the refrigerant cycle to receive a hot gas. Other embodiments may position the reheat coil such that it utilizes a two-phase mixture of refrigerant, or a liquid refrigerant.
  • some embodiments allow the condenser to be bypassed by at least a portion of refrigerant flow, when desired.
  • the reheat cycle may be incorporated in a system utilizing either economized or conventional tandem compressors, or a combination of both, in other embodiments.
  • at least one compressor may be unloaded to provide even greater capacity control.
  • FIG. 1 shows a first embodiment of the present invention.
  • FIG. 2 shows a second embodiment of the present invention.
  • FIG. 3 shows a third embodiment of the present invention.
  • FIG. 1 shows a refrigerant system 20 incorporating a pair of conventional tandem compressors 22 and 24 for compressing a refrigerant and passing the refrigerant downstream to a discharge manifold 30 , and then to condenser 36 .
  • the compressors 22 and 24 may or may not have oil equalization line 12 and pressure equalization line 13 connecting the two compressors for the purpose of potentially improving the oil management in the connected compressors.
  • compressors 22 and 24 can be of different sizes and may have shutoff or check valves 32 located on the compressor discharge line to enhance system performance upon shutdown of one of the compressors.
  • a three-way valve 34 selectively communicates at least a portion of the refrigerant to a reheat coil 44 .
  • the valve 34 can be of a fixed orifice design, a regulating device, or can be substituted by a pair of solenoid valves.
  • the refrigerant passes to a line 39 downstream of the reheat coil 44 through the check valve 46 , and rejoins the main refrigerant circuit at point 41 .
  • Point 41 is upstream of condenser 36 .
  • a main expansion device 38 , and an evaporator 40 are downstream of condenser 36 .
  • refrigerant flows from the main expansion device 38 to the evaporator 40 , and then is returned to a suction manifold 26 , communicating through lines 28 to the suction port of each compressor 22 and 24 .
  • an indoor airflow 45 is driven over the evaporator 40 .
  • the moisture content in the air stream is typically reduced, and, thus, the air supplied to the conditioned space has been dehumidified.
  • reheat coil 44 is utilized to reheat the air stream 45 to a required temperature level.
  • air moving device 42 drives air stream 45 .
  • a control 19 for the refrigerant system 20 can operate the system to achieve various goals.
  • one or both of the compressors 22 and 24 can be operated by controlling motors and closing shut-off valves 32 .
  • the total amount of refrigerant being compressed and circulated throughout the refrigerant system can be controlled to achieve different capacity levels.
  • the three-way valve 34 may be controlled to direct at least a portion of refrigerant into the reheat coil 44 . Under many conditions it is not necessary to circulate refrigerant through the reheat coil.
  • each of the tandem compressors 22 and 24 may be provided with a means of unloading, where part of the compressed refrigerant is by-passed back to the compressor suction (internal or external of compressor) and allow for additional steps in capacity control. This is particularly true when the capacities of the two compressors are selected to be different.
  • Control 19 can close either shut-off valve 32 or leave both valves open (in conjunction to controlling the respective compressor motor shutdowns) to achieve several capacity steps. Further, at each capacity step, there is greater humidification control by selectively opening valve 34 , utilizing the reheat coil 44 .
  • more than two compressors can be configured into a tandem arrangement offering multiple steps of unloading and control over various system operation parameters.
  • FIG. 2 shows another embodiment 50 .
  • Compressors 22 and 24 also have intermediate pressure, or economizer, ports communicating through lines 61 and economizer manifold 57 to the refrigerant system.
  • Economizer lines 61 may incorporate shutoff valves 59 in order to switch between economizer and conventional modes of operation for each individual compressor.
  • Bypass valves 51 allow the compressors to be unloaded, such that either or both of the compressors can be operated at a reduced capacity.
  • An economizer loop is incorporated in the refrigerant system 50 downstream of the condenser 36 .
  • an economizer heat exchanger 52 receives a tapped refrigerant flow 54 , and a main refrigerant flow 55 .
  • the tapped refrigerant flow in this embodiment is tapped from the main refrigerant flow 55 downstream of condenser 36 .
  • the tapped refrigerant passes through an economizer expansion device 56 . After having passed through the economizer expansion device 56 , the tapped refrigerant is at a lower pressure and temperature, and is able to cool the main refrigerant flow 55 in the economizer heat exchanger 52 .
  • the flow of the tapped refrigerant through the economizer heat exchanger 52 is preferably in the reverse direction to that illustrated (that is in the opposed direction to the flow 55 ). However, the flows are illustrated in the same direction to simplify the drawing.
  • the tapped refrigerant is typically returned as a vapor to be injected into the compressors 22 and 24 through the economizer manifold 57 communicating with separate economizer return lines 61 , each having a shut off valve 59 .
  • control 19 has the ability to open the valves 59 and adjust expansion device 56 to control the economizer loop.
  • This control strategy is employed in combination with the abovementioned control methodology for operating the valves 32 to utilize either or both of the compressors.
  • bypass or unloader valves 51 provide further ability to reduce the refrigerant flow into the cycle. A worker of ordinary skill in the art would recognize the times when a controller would like to utilize each of these options. Valves 32 , 51 and 59 may be either shutoff valves or regulating flow control devices, allowing for more flexibility in the refrigerant flow control.
  • the economizer loop may or may not be engaged.
  • the economizer expansion device 56 may be closed down such that no refrigerant is tapped.
  • a respective valve 59 needs to be closed.
  • the three-way valve 58 may be moved to such a position that no refrigerant is tapped through the reheat coil 38 . It has to be noted, that the illustrated position of the reheat coil 60 and the economizer heat exchanger 52 is not critical to take advantage of the invention benefits, and various possible arrangements become obvious to a person ordinarily skilled in the art.
  • a bypass line 64 with a valve 65 selectively bypasses refrigerant around the condenser 36 .
  • the valve 65 preferably allows a metering of flow around the condenser 36 .
  • any of these reheat loop controls may be employed independent of each other, in combination with the economizer loop controls and tandem compressor control strategy, or none of them need be used.
  • the present invention is mainly directed to providing the ability to use all techniques in combination with each other, while providing better control over the humidity and temperature, while enhancing system efficiency by matching latent and sensible load demands more closely and improving component reliability by reducing a number of start-stop cycles.
  • the three-way valve 58 can be substituted by a pair of conventional valves. If the expansion device 56 is of such a type that it cannot be closed down completely, an additional shutoff valve may be placed on the tap line 54 .
  • both economizer expansion device 56 and the three-way valve 58 are moved to an open position to operate both the economizer heat exchanger 56 and the reheat coil 60 and both tandem compressors 22 and 24 are controlled to provide maximum refrigerant flow with valves 32 and 59 in open positions and valves 51 closed.
  • Refrigerant passing through the main line 55 will be subcooled by the refrigerant from the tap 54 .
  • that refrigerant will have a higher cooling capacity (both sensible and latent) when reaching the evaporator 40 . Consequently an air stream 45 leaving evaporator 40 can be cooled to a lower temperature.
  • refrigerant in the refrigerant cycle 50 passes through the reheat coil 60 , where its temperature is reduced further during the heat transfer interaction with the indoor air stream 46 leaving the evaporator 40 .
  • the refrigerant cooling capacity is boosted even further, allowing for even more dehumidification in the evaporator 40 .
  • This drier air then passes over the reheat coil 60 , which will have a higher temperature refrigerant, as it is positioned upstream of the main expansion device 38 .
  • An air moving device 42 shown schematically, drives air over the evaporator 40 and reheat coil 60 .
  • This hotter refrigerant in the reheat coil will reheat the air stream 45 such that the desired temperature is reached. Moisture has already been removed from this air stream in the evaporator 40 .
  • a refrigerant system designer is able to achieve both desired temperature and humidity levels, especially in hot and humid environments. Moreover, the higher efficiency levels are achieved due to implementation of the economizer cycle concept.
  • other external load demand scenarios can be considered along with corresponding control strategies for the refrigerant cycle 50 . These scenarios are well known to a person ordinarily skilled in the art.
  • this invention offers additional steps of unloading. Turning a tapped refrigerant flow in the economizer heat exchanger 26 on and off, the system capacity can be correspondingly increased or decreased, depending on the external load requirements. Also, one or both compressors 22 and 24 can be operated in the conventional, economized or unloaded modes. Again, this provides several distinct capacity control steps. This will allow matching the desired temperature and humidity levels with a greater precision as well as improve system reliability through the reduction of the start-stop cycles. Also it has to be understood that various configurations of this embodiment are possible including (but not limited to) more than two compressors, and more than one economizer heat exchanger.
  • FIG. 3 shows yet another embodiment 70 .
  • the reheat coil 74 communicates with the main cycle refrigerant by means of a three-way valve 72 downstream of the economizer heat exchanger 52 .
  • the compressors 22 and 24 are provided with a bypass line through valve 51 on only one of the two compressors (here compressor 24 ).
  • the economizer fluid is returned through line 28 to only one of the two compressors (here compressor 24 as well). While this embodiment does not provide the extreme number of steps of control provided by FIG. 2 embodiment, it does provide additional control when compared to a system that does not have tandem compressors, an economizer cycle or a reheat coil.
  • the two tandem compressors 24 and 22 can still be operated independently, or in combination.
  • the economizer cycle would only be utilized in combination with operation of compressor 24 .
  • Any number of economized and conventional compressors can be employed in this embodiment and will function and communicated to the refrigerant system 70 in the manner described above.
  • the invention presents a significantly enhanced control over temperature and humidity precisely satisfying latent and sensible capacity demands, while reaching superior efficiency and reliability levels and reducing life-cycle cost of equipment.
US10/891,938 2004-07-15 2004-07-15 Refrigerant system with tandem compressors and reheat function Abandoned US20060010907A1 (en)

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PCT/US2005/024950 WO2006019885A2 (fr) 2004-07-15 2005-07-14 Systeme de refrigeration en tandem avec des compresseurs et une fonction de rechauffement

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060090502A1 (en) * 2004-10-28 2006-05-04 Carrier Corporation Hybrid tandem compressor system with economizer circuit and reheat function for multi-level cooling
ES2318941A1 (es) * 2006-02-21 2009-05-01 Aproalia, S.L. Sistema combinado de refrigeracion y climatizacion.
US20090260381A1 (en) * 2008-04-22 2009-10-22 Dover Systems, Inc. Free cooling cascade arrangement for refrigeration system
US20100199715A1 (en) * 2007-09-24 2010-08-12 Alexander Lifson Refrigerant system with bypass line and dedicated economized flow compression chamber
US20110146306A1 (en) * 2008-10-02 2011-06-23 Taras Michael F Start-up for refrigerant system with hot gas reheat
US20110167847A1 (en) * 2008-04-22 2011-07-14 Hill Phoenix, Inc. Free cooling cascade arrangement for refrigeration system
US20130098087A1 (en) * 2011-04-19 2013-04-25 Liebert Corporation Cooling system with tandem compressors and electronic expansion valve control
US20150013361A1 (en) * 2012-03-09 2015-01-15 Carrier Corporation Closed Loop Capacity And Power Management Scheme For Multi Stage Transport Refrigeration System
US20160363286A1 (en) * 2015-06-15 2016-12-15 J.W. Speaker Corporation Lens heating systems and methods for an led lighting system
US11149971B2 (en) 2018-02-23 2021-10-19 Emerson Climate Technologies, Inc. Climate-control system with thermal storage device
US11346583B2 (en) * 2018-06-27 2022-05-31 Emerson Climate Technologies, Inc. Climate-control system having vapor-injection compressors
US11585608B2 (en) 2018-02-05 2023-02-21 Emerson Climate Technologies, Inc. Climate-control system having thermal storage tank
US20230092476A1 (en) * 2021-09-17 2023-03-23 Addison Hvac Llc Air-conditioning system with variable subcooling

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7325414B2 (en) * 2004-10-28 2008-02-05 Carrier Corporation Hybrid tandem compressor system with economizer circuit and reheat function for multi-level cooling
US20060090502A1 (en) * 2004-10-28 2006-05-04 Carrier Corporation Hybrid tandem compressor system with economizer circuit and reheat function for multi-level cooling
ES2318941A1 (es) * 2006-02-21 2009-05-01 Aproalia, S.L. Sistema combinado de refrigeracion y climatizacion.
US20100199715A1 (en) * 2007-09-24 2010-08-12 Alexander Lifson Refrigerant system with bypass line and dedicated economized flow compression chamber
US9151521B2 (en) 2008-04-22 2015-10-06 Hill Phoenix, Inc. Free cooling cascade arrangement for refrigeration system
US20090260381A1 (en) * 2008-04-22 2009-10-22 Dover Systems, Inc. Free cooling cascade arrangement for refrigeration system
US7913506B2 (en) 2008-04-22 2011-03-29 Hill Phoenix, Inc. Free cooling cascade arrangement for refrigeration system
US20110167847A1 (en) * 2008-04-22 2011-07-14 Hill Phoenix, Inc. Free cooling cascade arrangement for refrigeration system
US20110146306A1 (en) * 2008-10-02 2011-06-23 Taras Michael F Start-up for refrigerant system with hot gas reheat
US20130098087A1 (en) * 2011-04-19 2013-04-25 Liebert Corporation Cooling system with tandem compressors and electronic expansion valve control
US8881541B2 (en) * 2011-04-19 2014-11-11 Liebert Corporation Cooling system with tandem compressors and electronic expansion valve control
US20150013361A1 (en) * 2012-03-09 2015-01-15 Carrier Corporation Closed Loop Capacity And Power Management Scheme For Multi Stage Transport Refrigeration System
US9908452B2 (en) * 2012-03-09 2018-03-06 Carrier Corporation Closed loop capacity and power management scheme for multi stage transport refrigeration system
US20160363286A1 (en) * 2015-06-15 2016-12-15 J.W. Speaker Corporation Lens heating systems and methods for an led lighting system
US11585608B2 (en) 2018-02-05 2023-02-21 Emerson Climate Technologies, Inc. Climate-control system having thermal storage tank
US11149971B2 (en) 2018-02-23 2021-10-19 Emerson Climate Technologies, Inc. Climate-control system with thermal storage device
US11346583B2 (en) * 2018-06-27 2022-05-31 Emerson Climate Technologies, Inc. Climate-control system having vapor-injection compressors
US20230092476A1 (en) * 2021-09-17 2023-03-23 Addison Hvac Llc Air-conditioning system with variable subcooling

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WO2006019885A2 (fr) 2006-02-23
WO2006019885A3 (fr) 2009-06-18

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