CA2312175A1 - Improved air-to-air heat pump - Google Patents
Improved air-to-air heat pump Download PDFInfo
- Publication number
- CA2312175A1 CA2312175A1 CA 2312175 CA2312175A CA2312175A1 CA 2312175 A1 CA2312175 A1 CA 2312175A1 CA 2312175 CA2312175 CA 2312175 CA 2312175 A CA2312175 A CA 2312175A CA 2312175 A1 CA2312175 A1 CA 2312175A1
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- CA
- Canada
- Prior art keywords
- compressor
- air
- heat pump
- refrigerant
- accumulator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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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
- F25B13/00—Compression machines, plants or systems, with reversible cycle
-
- 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
- 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
- F25B2400/05—Compression system with heat exchange between particular parts of the system
- F25B2400/051—Compression system with heat exchange between particular parts of the system between the accumulator and another part of the cycle
-
- 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
- F25B2400/0751—Details of compressors or related parts with parallel compressors the compressors having different capacities
-
- 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
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/21—Temperatures
- F25B2700/2106—Temperatures of fresh outdoor air
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Compression-Type Refrigeration Machines With Reversible Cycles (AREA)
Abstract
An air-to-air heat pump having two compressors in parallel in the refrigerant circuit with one being a high temperature low volume compressor that operates in both the heating and cooling mode and the other a low temperature high volume compressor that operates by itself in the heating mode of the heat pump when the ambient air temperature drops below a selected value of about 20 degree F.
Description
Ti tle Air-To-Air Heat Franp Having a High and a Zow Temperature Compressor Field Of Invention This invention relates generally to air-to-air heat pumps and more particularly to an air-to-air heat pump having an additional compressor, in parallel with the conventionally used compressor, for use by itself in the heating mode of operation below a selected ambient temperature.
The second compressor is an off the shelf low temperature high volume co~rpressor with proven record and prow des improved efficiency and endurance in the hen ting mode .
Backcrround Of Invention Heat pumps are lazown but not extensively used because of high initial installation costs (eg ground source systems)to provide an efficient year round operating system or because of low operating efficiencies in the heating mode in less expensive systems (eg air-to-air systems) .
The second compressor is an off the shelf low temperature high volume co~rpressor with proven record and prow des improved efficiency and endurance in the hen ting mode .
Backcrround Of Invention Heat pumps are lazown but not extensively used because of high initial installation costs (eg ground source systems)to provide an efficient year round operating system or because of low operating efficiencies in the heating mode in less expensive systems (eg air-to-air systems) .
Ground source heat pumps operate with relatively good efficiency in both the winter heating mode and the sramaer cooling mode. These systems however require below ground piping for the refrigerant in a closed loop piping system or water pipes of a heat exchanger.
Operating efficiencies year round are reasonably good because of fairly constant and known below ground temperatures for which the system can be designed.
However ground piping is expensive to install and prohibitively expensive if repairs are required because of among other things difficulties in locating any below ground level leaks when they occur.
Air-to air heat pumps on the other hand are relatively inexpensive because of lower installation costs, compared to a ground source system, but a wide variance in outdoor temperatures cause them to have an overall year round low efficiency rating and therefore expensive operational costs. They are inefficient 3n the heating mode, particularly at ambient temperatures loner than 20 degrees F(-6.5 degrees C),and the efficiency drops off as the temperature drops. lost known air-to-,.
Operating efficiencies year round are reasonably good because of fairly constant and known below ground temperatures for which the system can be designed.
However ground piping is expensive to install and prohibitively expensive if repairs are required because of among other things difficulties in locating any below ground level leaks when they occur.
Air-to air heat pumps on the other hand are relatively inexpensive because of lower installation costs, compared to a ground source system, but a wide variance in outdoor temperatures cause them to have an overall year round low efficiency rating and therefore expensive operational costs. They are inefficient 3n the heating mode, particularly at ambient temperatures loner than 20 degrees F(-6.5 degrees C),and the efficiency drops off as the temperature drops. lost known air-to-,.
air heat pumps respond to an outdoor thezmostat that shu is the uai t do~rn a t -8 degrees C (+15 degrees F) and thus another substantial heating system is needed for cold weather heating.
There are proposals directed at improving the coefficient of performance (COP) in the heating mode that include booster compressors and cascading compressor systems and there are sir-to-air heat pump systems proposed using parallel compressors. In all instances known to applicant all compressors of a multi-compressor system are operating in the heating mode when the ambient temperature is low. Nome of the knowra proposals have compressors dedicated to the respective operational modes above and below a selected ambient tempera tore .
USA Patent 4,586,361 issued May 6~, 1986 to Yoshinobu Igarashi et a1 and Entitled "SAT Pllb~ WIT8 MULTIPLE CG~RESSORS" aliscloses two co~pressors in parallel in which the compressors 'maybe operated both at the same time or only one at a time, depending on the heating or cooling mode". For the compressors to operate at the same time they must both be the same i.e. either bo th high or bo th low tempera tore compressors . The patent is silent as to the type of compressor and obviously was of no concern to the patentees because the patent is directed to an oil management system for multiple compressors.
USA patent 5, 927, 088 issued July 27,1999 to David N
Shaw and entitled "BOOSTED AIR SODRCE SAT Pig"
discloses multiple stage compression(which always requires de-superheating) and in which, in the heating mode, the booster compressor is brought into operation.
The operation always requires one compressor or both compressors. There is no suggestion of having either one or the other of the compressors operating when the system is in the heating mode and below a selected ambient air temperature.
Other references include:
USP's 5, 029, 449 Issued July 9,1991 to R 8 i~ilkinson;
4, 347, 714 issued Sept . 7, 1982 to R K Kinsell et al;
4,777,805 Issued Oct.18,1988 to K Hashizume;
There are proposals directed at improving the coefficient of performance (COP) in the heating mode that include booster compressors and cascading compressor systems and there are sir-to-air heat pump systems proposed using parallel compressors. In all instances known to applicant all compressors of a multi-compressor system are operating in the heating mode when the ambient temperature is low. Nome of the knowra proposals have compressors dedicated to the respective operational modes above and below a selected ambient tempera tore .
USA Patent 4,586,361 issued May 6~, 1986 to Yoshinobu Igarashi et a1 and Entitled "SAT Pllb~ WIT8 MULTIPLE CG~RESSORS" aliscloses two co~pressors in parallel in which the compressors 'maybe operated both at the same time or only one at a time, depending on the heating or cooling mode". For the compressors to operate at the same time they must both be the same i.e. either bo th high or bo th low tempera tore compressors . The patent is silent as to the type of compressor and obviously was of no concern to the patentees because the patent is directed to an oil management system for multiple compressors.
USA patent 5, 927, 088 issued July 27,1999 to David N
Shaw and entitled "BOOSTED AIR SODRCE SAT Pig"
discloses multiple stage compression(which always requires de-superheating) and in which, in the heating mode, the booster compressor is brought into operation.
The operation always requires one compressor or both compressors. There is no suggestion of having either one or the other of the compressors operating when the system is in the heating mode and below a selected ambient air temperature.
Other references include:
USP's 5, 029, 449 Issued July 9,1991 to R 8 i~ilkinson;
4, 347, 714 issued Sept . 7, 1982 to R K Kinsell et al;
4,777,805 Issued Oct.18,1988 to K Hashizume;
5, 056, 329 Issued Oct .15,1991 to Tip 8 pilkinson;
5,582,022 issued Dec.10,1996 to A D 8einrichs;
x,100,763 issued July 18,1978 to 8 M Brody;
5 5,211,031 issued may 18, 1993 to A Murayama et al;
and 4,528,823 issued July 16,1985 to T Mochizuki et el.
SU~.RY OF INVENTION
An object of the present invention is to provide an air-to-air heat pump that has an improved efficiency in the hea ting mode .
A principal object of the present invention is to provide a relatively inexpensive but effective means of improving the COP of an air-to-air heat pump in the heating mode of operation at lower ambient temperatures.
A further object of the present invention is to provide a simple retro-fit to existing air-to-air heat pumps to improve their COP in the low ambient temperature heating mode of operation.
A further principal object of the present invention is to use existing off the shelf and proven components to provide a simple and durable heat pump with a reasonably good CG?P in the heating mode xhile operating at lo~rer ambient temperatures.
The forgoing objects are accomplished by a heat pump constructed in accordance with the present invention in which there is a first compressor for the heating and cooling mode of operation when the ambient air temperature is above a selected temperature and a second compressor, having operating characteristics different from said first compressor, for operating by itself and only in the heating mode when the ambient temperature is below that selected value and in which there is switching mesas causing the control system to switch from one to the other of said compressors at said selected value and ensuring only one compressor is active at any during operation of the heat pump.
There is particularly provided in accordance wi th the present invention an air-to-air heat pump comprising a first high temperature low volume ccmrpressor and a second low temperature high volume compressor connected in parallel with one another in the refrigerant circuit that includes an indoor coil, as out door coil and a reversing valve, means connecting said co~pressors in parallel in said refrigerant circuit and means causing switching the control system for the heat pump from one to the other of said compressors at a preselected outdoor temperature and ensuring only one of said compressors is active at any time during o~,neration of said heat pump. In most instances the preselected temperature will be approximately 20 degrees F(-6.5 degrees C) .
The switching can be in response to signals from an ambient air temperature sensor or a system pressure sensor that represents ie reflects the ambient temperature, for example a pressure transducer responsive to the refrigerant pressure on the outlet side of the outdoor coil.
ZIST OF DRXTi~INGS
The invention is illustrated, by way of example, in the accompanying drawing wherein:
Figure 1 is a s7rematic of an air-to-air heat g pump having a second lox temperature high volume compressor in accordance xith the present invention.
DESC~tIPTION OF PREFERRED EH~ODIMENT
Referring to the draxing there is illustrated an air-to-air best pu~ap comprising an indoor coil 10 and an outdoor coil 20 in a refrigerant closed loop circuit that includes an accumulator 50 and a reversing valve 60. In the cooling mode the indoor coil 10 is an evapora for and in the hea ting mode a condenser . The coil 10 has respective opposite ends IOA and IOB and the coil has respective opposite ends 20A aad 208.
There is a high temperature lox volume compressor that is efficient in the cooling mode but that efficiency, as is ~r~ell knoxa, drops off dramatically in 15 the besting mode as the ambient temperature drops and particularly as the temperature approaches and goes loxer than 20 degrees F.
In accordance xith the present invention there is an additional compressor 40 xhich is a lox temperature 20 high volume compressor aad it is sxitched into operation in place of compressor 30 xhen the ambient temperature drops below a preselected level normally aroouad the above mentioned 20 degrees F.
The system can be a conventional air-to-air heat pump system except for the additional compressor 40 in parallel with the conventional compressor and thus retro-fitting existing systeaus is relatively simple. A
larger indoor coil however may be required or at least desired because of the higher system BTU output provided by compressor 40 at the selected snitch over temperature. Additionally there is also a control system I30 to snitch the second compressor 40 into the operating control system and switch the first compressor 30 out of the control system when the ambient temperature reaches the preselected value.
The tvo compressors 30 and 40 have their suction side connected via refrigerant pipe A to the accumulator 50. The exhaust side of the compressors 30 and 40 is connected via respective one way flog control valves VZ
and V2 to the reversing valve 60 (which is a spool type) by refrigerant piping B. The valves YI and Y2 may be in the piping or alternatively incorporated in the respective compressors. A refrigerant pipe F connects the reversing valve 60 to the accumulator 50.
The compressors are turned on and off in the usual manner by signals from a the~ostat(not shown) in the 5 area being heated or cooled depending upon the demand to provide heating in the heating mode or cooling in the cooling mode as the case may be and connected to the control 130ie a demand for perfozmance by the heat pump.
The control system 130 brings the compressor 90 into a 10 ready state when the ambient temperature reaches the preselected value and such means may respond to signals from an outdoor temperature sensor 200 or alternatively a system pressure sensor 200A located on the side 20B of the outdoor coil 20. For purpose of illustration shown in solid line is the ambient temperature sensor 200 connected to the control means 130 and in dotted line, as an alternative, the pressure transducer 200A on the outlet side of the outdoor coil.
The Indoor coil end 10A and outdoor coil end 20A
are connected via respective refrigerant lines C and D
to the reversing valve 60 and the other respective ends ZOB and 20B are interconnected via refrigerant line E in which there are expansion valves 90 and 95. Valves 90 and 95 are conventional in the art as well as by pass one way flow control valves 91 and 96 associated respectively therewith. Completing the closed loop of the refrigerant circuit is a refrigerant line F
connected at one end to the reversing valve 60 and at the other end to the accumulator 50. One refinement in the system is a sub-cooling coil 100 in the refrigerant line E and this coil is located in the accumulator. The heat exchanger coil I00 is optional but it helps speed up defrosting of the outdoor coil 20 and provide some sub-cooling.
The sys tem when opera ting in the hen ting mode autcmiatically switches to a defrost mode at selected time intervals(usually ~45 or 90 minutes depending upon the timer setting) to defrost the outdoor coil as is conventional in the art. In the defrost mode the reversing valve switches to the cooling mode, the compressor is rW ng and the outdoor fan shuts off. The defrost mode continues until tezminated by the timer time lapse or by the coil thermostat and the heat cycle then continues. The heat exchanger coil 100 speeds up the defrost cycle.
The compressors 30 and 40 share a common oil sump via conduit I25.
Another refinement to the system is a liquid injection system comprising a temperature sensor 140 associated with the refrigerant line B, a metering device 141 connected at one end to refrigerant pipe F
and a t the o flier end to refri geran t pipe E ( be txeen coi 1 100 and expansion valve 95) through a solenoid actuated, normally closed, valve 142.
The liquid injection system serves as a de-super-heater for the suction and discharge gas and provides liquid line sub-cooling. When the temperature of the refrigerant in the exhaust line B becomes too high the sensor 140(for example a thermo-disc sensor) signals the solenoid to open the normally closed valve 142 alloying liquid refrigerant through the metering device( ie a capillary tube, restrictor etc). The liquid discharges into the accumulator and evaporates therein sub-cooling the liquid line heat exchanger 100 in the acc~rulator.
The refrigerant vapours produced in the accumulator de-superheats the suction gas and thus the gas exiting the compressor is cooler. The sub-cooled liquid line improves the heat pump capacity. The cooler compression discharge gas extends the life of the compressor. The added vapour produced in the accu~aulator increases system heating capacity.
Refrigerants considered suitable are R-22. R-502, R-410 (AZ-20) , R-408, BP80, and R-404 or any low temperature refrigerant.
By way of example using a low temperature compressor model AH2511K from Tecumseh products Company of Tecumseh Michigan as the low temperature co~pressor 40 and refrigerant 404 one might expect a COP with a IO
degree F delta T outdoor evaporator as follows:
Evap orator Temp Bestinct Produced COP
(Evap + Compressor i~a t ts) +Z0 degrees F 32,628 BTU 2.58 0 degrees F 15,300BTU 2.48 -10 degrees F 11,300 BTU 2.32 -20 degrees F 8,300 BTU 2.17 -40 degrees F 4,080 BTU 1.92 At +20 degrees F ambient before the switch over the heat produced Would have been about 13,000 BTD. As mentioned in the forgroing because of the higher output at the switch over ie 32,000+ BTD it is atesirable to have a larger indoor coil.
The ambient temperature at Which switch over from one to the other compressor takes place can be chosen to suit the system and operating conditions at hand.
In the heating mode of operation the compressed refrigerant, from compressor 30 When the ambient temperature i.s above the preselected value, and from compressor 90 When the temperature is at or below that selected value, flows through refrigerant line B and is directed by the reversing valve 60 to one end of the indoor coil 10 then via bypass valve 91 to the coil 100, then the expansion valve 95 to one end of the outdoor coil 2D and from the other end of that coil through line D to the reversing valve 60. The reversing valve 60 directs the refrigerant into the accumulator 50 via refrigerant line F. The suction side of the respective compressors 30 and ~!0 is connected to the accumulator via refrigerant line A. The control 130 responds to signals from a room thesmostat(not shoxn) demanding operation of the heat pump to provide heat from the indoor coil 10. A signal from the unit 200 or the unit 200A as the case maybe determines, in response to 5 ambient air temperature, whether compressor 30 operates or whether compressor 40 operates.
In the cooling mode of operation the compressed refrigerant from compressor 30 is directed by the reversing valve 60 to the outdoor coil 20 via 10 refrigerant line D. The refrigerant flows through bypass valve 96 to the coil 100 and through the expansion valve 90 to the indoor coil 10 and then to the reversing valve. The reversing valve directs the refrigerant to the accumulator 50 via refrigerant line F. From the 15 accumulator 50 the refrigerant enters the suction side of the compressor via refrigerant line A.
In each of the heating and cooling modes of operation refrigerant caa be injected into the accumulator by the injector 141 in response to a signal from the temperature sensor 140.
5,582,022 issued Dec.10,1996 to A D 8einrichs;
x,100,763 issued July 18,1978 to 8 M Brody;
5 5,211,031 issued may 18, 1993 to A Murayama et al;
and 4,528,823 issued July 16,1985 to T Mochizuki et el.
SU~.RY OF INVENTION
An object of the present invention is to provide an air-to-air heat pump that has an improved efficiency in the hea ting mode .
A principal object of the present invention is to provide a relatively inexpensive but effective means of improving the COP of an air-to-air heat pump in the heating mode of operation at lower ambient temperatures.
A further object of the present invention is to provide a simple retro-fit to existing air-to-air heat pumps to improve their COP in the low ambient temperature heating mode of operation.
A further principal object of the present invention is to use existing off the shelf and proven components to provide a simple and durable heat pump with a reasonably good CG?P in the heating mode xhile operating at lo~rer ambient temperatures.
The forgoing objects are accomplished by a heat pump constructed in accordance with the present invention in which there is a first compressor for the heating and cooling mode of operation when the ambient air temperature is above a selected temperature and a second compressor, having operating characteristics different from said first compressor, for operating by itself and only in the heating mode when the ambient temperature is below that selected value and in which there is switching mesas causing the control system to switch from one to the other of said compressors at said selected value and ensuring only one compressor is active at any during operation of the heat pump.
There is particularly provided in accordance wi th the present invention an air-to-air heat pump comprising a first high temperature low volume ccmrpressor and a second low temperature high volume compressor connected in parallel with one another in the refrigerant circuit that includes an indoor coil, as out door coil and a reversing valve, means connecting said co~pressors in parallel in said refrigerant circuit and means causing switching the control system for the heat pump from one to the other of said compressors at a preselected outdoor temperature and ensuring only one of said compressors is active at any time during o~,neration of said heat pump. In most instances the preselected temperature will be approximately 20 degrees F(-6.5 degrees C) .
The switching can be in response to signals from an ambient air temperature sensor or a system pressure sensor that represents ie reflects the ambient temperature, for example a pressure transducer responsive to the refrigerant pressure on the outlet side of the outdoor coil.
ZIST OF DRXTi~INGS
The invention is illustrated, by way of example, in the accompanying drawing wherein:
Figure 1 is a s7rematic of an air-to-air heat g pump having a second lox temperature high volume compressor in accordance xith the present invention.
DESC~tIPTION OF PREFERRED EH~ODIMENT
Referring to the draxing there is illustrated an air-to-air best pu~ap comprising an indoor coil 10 and an outdoor coil 20 in a refrigerant closed loop circuit that includes an accumulator 50 and a reversing valve 60. In the cooling mode the indoor coil 10 is an evapora for and in the hea ting mode a condenser . The coil 10 has respective opposite ends IOA and IOB and the coil has respective opposite ends 20A aad 208.
There is a high temperature lox volume compressor that is efficient in the cooling mode but that efficiency, as is ~r~ell knoxa, drops off dramatically in 15 the besting mode as the ambient temperature drops and particularly as the temperature approaches and goes loxer than 20 degrees F.
In accordance xith the present invention there is an additional compressor 40 xhich is a lox temperature 20 high volume compressor aad it is sxitched into operation in place of compressor 30 xhen the ambient temperature drops below a preselected level normally aroouad the above mentioned 20 degrees F.
The system can be a conventional air-to-air heat pump system except for the additional compressor 40 in parallel with the conventional compressor and thus retro-fitting existing systeaus is relatively simple. A
larger indoor coil however may be required or at least desired because of the higher system BTU output provided by compressor 40 at the selected snitch over temperature. Additionally there is also a control system I30 to snitch the second compressor 40 into the operating control system and switch the first compressor 30 out of the control system when the ambient temperature reaches the preselected value.
The tvo compressors 30 and 40 have their suction side connected via refrigerant pipe A to the accumulator 50. The exhaust side of the compressors 30 and 40 is connected via respective one way flog control valves VZ
and V2 to the reversing valve 60 (which is a spool type) by refrigerant piping B. The valves YI and Y2 may be in the piping or alternatively incorporated in the respective compressors. A refrigerant pipe F connects the reversing valve 60 to the accumulator 50.
The compressors are turned on and off in the usual manner by signals from a the~ostat(not shown) in the 5 area being heated or cooled depending upon the demand to provide heating in the heating mode or cooling in the cooling mode as the case may be and connected to the control 130ie a demand for perfozmance by the heat pump.
The control system 130 brings the compressor 90 into a 10 ready state when the ambient temperature reaches the preselected value and such means may respond to signals from an outdoor temperature sensor 200 or alternatively a system pressure sensor 200A located on the side 20B of the outdoor coil 20. For purpose of illustration shown in solid line is the ambient temperature sensor 200 connected to the control means 130 and in dotted line, as an alternative, the pressure transducer 200A on the outlet side of the outdoor coil.
The Indoor coil end 10A and outdoor coil end 20A
are connected via respective refrigerant lines C and D
to the reversing valve 60 and the other respective ends ZOB and 20B are interconnected via refrigerant line E in which there are expansion valves 90 and 95. Valves 90 and 95 are conventional in the art as well as by pass one way flow control valves 91 and 96 associated respectively therewith. Completing the closed loop of the refrigerant circuit is a refrigerant line F
connected at one end to the reversing valve 60 and at the other end to the accumulator 50. One refinement in the system is a sub-cooling coil 100 in the refrigerant line E and this coil is located in the accumulator. The heat exchanger coil I00 is optional but it helps speed up defrosting of the outdoor coil 20 and provide some sub-cooling.
The sys tem when opera ting in the hen ting mode autcmiatically switches to a defrost mode at selected time intervals(usually ~45 or 90 minutes depending upon the timer setting) to defrost the outdoor coil as is conventional in the art. In the defrost mode the reversing valve switches to the cooling mode, the compressor is rW ng and the outdoor fan shuts off. The defrost mode continues until tezminated by the timer time lapse or by the coil thermostat and the heat cycle then continues. The heat exchanger coil 100 speeds up the defrost cycle.
The compressors 30 and 40 share a common oil sump via conduit I25.
Another refinement to the system is a liquid injection system comprising a temperature sensor 140 associated with the refrigerant line B, a metering device 141 connected at one end to refrigerant pipe F
and a t the o flier end to refri geran t pipe E ( be txeen coi 1 100 and expansion valve 95) through a solenoid actuated, normally closed, valve 142.
The liquid injection system serves as a de-super-heater for the suction and discharge gas and provides liquid line sub-cooling. When the temperature of the refrigerant in the exhaust line B becomes too high the sensor 140(for example a thermo-disc sensor) signals the solenoid to open the normally closed valve 142 alloying liquid refrigerant through the metering device( ie a capillary tube, restrictor etc). The liquid discharges into the accumulator and evaporates therein sub-cooling the liquid line heat exchanger 100 in the acc~rulator.
The refrigerant vapours produced in the accumulator de-superheats the suction gas and thus the gas exiting the compressor is cooler. The sub-cooled liquid line improves the heat pump capacity. The cooler compression discharge gas extends the life of the compressor. The added vapour produced in the accu~aulator increases system heating capacity.
Refrigerants considered suitable are R-22. R-502, R-410 (AZ-20) , R-408, BP80, and R-404 or any low temperature refrigerant.
By way of example using a low temperature compressor model AH2511K from Tecumseh products Company of Tecumseh Michigan as the low temperature co~pressor 40 and refrigerant 404 one might expect a COP with a IO
degree F delta T outdoor evaporator as follows:
Evap orator Temp Bestinct Produced COP
(Evap + Compressor i~a t ts) +Z0 degrees F 32,628 BTU 2.58 0 degrees F 15,300BTU 2.48 -10 degrees F 11,300 BTU 2.32 -20 degrees F 8,300 BTU 2.17 -40 degrees F 4,080 BTU 1.92 At +20 degrees F ambient before the switch over the heat produced Would have been about 13,000 BTD. As mentioned in the forgroing because of the higher output at the switch over ie 32,000+ BTD it is atesirable to have a larger indoor coil.
The ambient temperature at Which switch over from one to the other compressor takes place can be chosen to suit the system and operating conditions at hand.
In the heating mode of operation the compressed refrigerant, from compressor 30 When the ambient temperature i.s above the preselected value, and from compressor 90 When the temperature is at or below that selected value, flows through refrigerant line B and is directed by the reversing valve 60 to one end of the indoor coil 10 then via bypass valve 91 to the coil 100, then the expansion valve 95 to one end of the outdoor coil 2D and from the other end of that coil through line D to the reversing valve 60. The reversing valve 60 directs the refrigerant into the accumulator 50 via refrigerant line F. The suction side of the respective compressors 30 and ~!0 is connected to the accumulator via refrigerant line A. The control 130 responds to signals from a room thesmostat(not shoxn) demanding operation of the heat pump to provide heat from the indoor coil 10. A signal from the unit 200 or the unit 200A as the case maybe determines, in response to 5 ambient air temperature, whether compressor 30 operates or whether compressor 40 operates.
In the cooling mode of operation the compressed refrigerant from compressor 30 is directed by the reversing valve 60 to the outdoor coil 20 via 10 refrigerant line D. The refrigerant flows through bypass valve 96 to the coil 100 and through the expansion valve 90 to the indoor coil 10 and then to the reversing valve. The reversing valve directs the refrigerant to the accumulator 50 via refrigerant line F. From the 15 accumulator 50 the refrigerant enters the suction side of the compressor via refrigerant line A.
In each of the heating and cooling modes of operation refrigerant caa be injected into the accumulator by the injector 141 in response to a signal from the temperature sensor 140.
Claims (12)
1. An air-to-air heat pump comprising a first high temperature low volume compressor, refrigerant piping means connecting said compressor to a condenser, an evaporator, an expansion valve and a reversing valve in a known refrigerant closed loop circuit providing an operative heating and cooling system, said reversing valve being operative to switch the heat pump from one mode to the other selected from a cooling mode and a heating mode, a control system for said heat pump responsive to a demand for performance by said heat pump, a second low temperature high volume compressor, refrigerant piping means connecting said first and second compressors in parallel and means, responsive to a selected ambient temperature, operative to switch said second compressor into said control system for operation by itself when the ambient temperature is below said selected value.
2. An air-to-air heat pump comprising refrigerant piping means connecting an evaporator coil, a condenser coil, an expansion valve, a reversing valve and refrigerant compressor means in a closed loop refrigerant circuit, said compressor means comprising a first, high temperature low volume, compressor operative in the heating and cooling mode of the heat pump and a second, low temperature high volume, compressor operative only in the heating mode below a selected ambient air temperature and control means isolating said first compressor from the operating control system for said heat pump at said ambient air temperature and switching said second compressor into said control system.
3. An air-to-air heat pump as defined in claims 1 or 2 wherein said selected temperature is approximately 20 degrees F.
4. Aa air-to-air best pump as defined in claims 1, 2, or 3 wherein said second compressor is a scroll type compressor.
5. An air-to-air heat pump as defined in claim 1 including an accumulator and refrigerant piping means connecting a suction side of said compressors to said accumulator, connecting an output side of the compressors to the reversing valve through respective ones of a pair of reversing valves and connecting said reversing valve to said accumulator.
6. An air-to-air heat pump as defined in claim 2 including as accumulator and refrigerant piping means connecting a suction side of said compressors to said accumulator, connecting an output side of the compressors to the reversing valve through respective ones of a pair of reversing valves and connecting said reversing valve to said accumulator.
7. An air-to-air heat pump as defined in claims 5 or 6 including a coil, for refrigerant, located in said accumulator and wherein said coil is in series in refrigerant piping means interconnecting one end of the respective coils of the condenser and evaporator.
8. An air-to-air heat pump as defined in claims 5 or 6 including injector means having an input side thereof connected by way of a normally closed solenoid operated valve to the outdoor coil through an expansion valve and an output side connected to said accumulator.
9. An air-to-air heat pump as defined in claims 5 or 6 including a coil, for refrigerant, located in said accumulator and wherein said coil is in series in refrigerant piping means interconnecting one end of the respective coils of the condenser and evaporator and injector means having as input side thereof connected by way of a normally closed solenoid operated valve to the outdoor coil through an expansion valve and an output side connected to said accumulator.
10. An air-to-air heat pump comprising an indoor coil, an outdoor coil, a first and a second compressor each having a suction side and an output side, an accumulator, a reversing valve, first refrigerant conduit means connecting the output side of the compressors to said reversing valve, second refrigerant conduit means connecting the suction side of said compressors to said accumulator, third refrigerant conduit means connecting said reversing valve to said accumulator, forth and fifth refrigerant conduit means connecting said reversing valve to one side of the respective indoor and outdoor coils and a sixth refrigerant conduit means interconnecting the other side of said indoor and outdoor coils, expansion valve means serially connected in said sixth conduit means, said first compressor means comprising a high temperature low volume, compressor operative in the heating and cooling mode of operation of the heat pump and the second compressor being a low temperature high volume compressor operative only in the heating mode below a selected ambient air temperature and control means for said best pump having an input signal from means responsive to the ambient air temperature isolating said first compressor from the operating control system for said best pump at said selected ambient air temperature and switching said second compressor into said control system for operation until the ambient temperature exceeds said selected value.
11. An air-to-air heat pump as defined in claim 10 wherein said expansion valve means comprises a pair of expansion valves in series and each bypassed by a one way flow control valve and wherein the direction of flow is toward one another.
12. An air-to-air heat pump comprising a first and second pair of compressors each having a suction side and an exhaust side, said first compressor being a high temperature low volume compressor and said second compressor being a low temperature high volume compressor, an indoor coil and an outdoor coil each having respective opposite ends, a reversing valve, a first refrigerant conduit means connecting the exhaust side of said compressors to said reversing valve, a second and third refrigerant conduit means connecting a first end of the respective indoor and outdoor coils to said reversing valve, a fourth refrigerant conduit means interconnecting said second ends of the respective indoor and outdoor coils, a first and a second pair of one way flow control valves bypassing respective ones of the expansion valves and a fifth refrigerant conduit means connecting said reversing valve to the suction side of the compressors via an accumulator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2312175 CA2312175A1 (en) | 2000-06-23 | 2000-06-23 | Improved air-to-air heat pump |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2312175 CA2312175A1 (en) | 2000-06-23 | 2000-06-23 | Improved air-to-air heat pump |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2312175A1 true CA2312175A1 (en) | 2001-12-23 |
Family
ID=4166546
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2312175 Abandoned CA2312175A1 (en) | 2000-06-23 | 2000-06-23 | Improved air-to-air heat pump |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2312175A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010085593A3 (en) * | 2009-01-23 | 2010-11-18 | Bitzer Kuhlmaschinenbau Gmbh | Scroll compressors with different volume indexes and systems and methods for same |
| US9551335B2 (en) | 2011-10-07 | 2017-01-24 | Danfoss A/S | Method of coordinating operation of compressors |
| WO2023118777A1 (en) * | 2021-12-22 | 2023-06-29 | Dyson Technology Limited | A refrigeration system |
-
2000
- 2000-06-23 CA CA 2312175 patent/CA2312175A1/en not_active Abandoned
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010085593A3 (en) * | 2009-01-23 | 2010-11-18 | Bitzer Kuhlmaschinenbau Gmbh | Scroll compressors with different volume indexes and systems and methods for same |
| CN102326000B (en) * | 2009-01-23 | 2014-03-12 | 比策尔制冷机械制造有限公司 | Scroll compressors with different volume indexes and systems and methods for same |
| EP2389516A4 (en) * | 2009-01-23 | 2016-01-06 | Bitzer Kuehlmaschinenbau Gmbh | Scroll compressors with different volume indexes and systems and methods for same |
| US11635243B2 (en) | 2009-01-23 | 2023-04-25 | Bitzer Kuehlmaschinenbau Gmbh | Scroll compressors with different volume indexes and systems and methods for same |
| US9551335B2 (en) | 2011-10-07 | 2017-01-24 | Danfoss A/S | Method of coordinating operation of compressors |
| WO2023118777A1 (en) * | 2021-12-22 | 2023-06-29 | Dyson Technology Limited | A refrigeration system |
| GB2614245A (en) * | 2021-12-22 | 2023-07-05 | Dyson Technology Ltd | A refrigeration system |
| GB2614245B (en) * | 2021-12-22 | 2024-09-04 | Dyson Technology Ltd | A refrigeration system |
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