CA1134157A - Means and method for independently controlling vapor compression cycle device evaporator superheat and thermal transfer capacity - Google Patents
Means and method for independently controlling vapor compression cycle device evaporator superheat and thermal transfer capacityInfo
- Publication number
- CA1134157A CA1134157A CA364,543A CA364543A CA1134157A CA 1134157 A CA1134157 A CA 1134157A CA 364543 A CA364543 A CA 364543A CA 1134157 A CA1134157 A CA 1134157A
- Authority
- CA
- Canada
- Prior art keywords
- evaporator
- superheat
- mixture
- vapor
- pressure 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.)
- Expired
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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
- F25B2600/00—Control issues
- F25B2600/21—Refrigerant outlet evaporator temperature
Landscapes
- Compression-Type Refrigeration Machines With Reversible Cycles (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A vapor compression cycle device with variable thermal capacity is provided with a means and a method for controlling device capacity modulation and evaporator superheat. Multi-component working fluid liquid flow from each of a pair of accumulators in a closed circuit device is regulatored either in response to sensed thermal demand or in response to sensed working fluid vapor superheat.
A vapor compression cycle device with variable thermal capacity is provided with a means and a method for controlling device capacity modulation and evaporator superheat. Multi-component working fluid liquid flow from each of a pair of accumulators in a closed circuit device is regulatored either in response to sensed thermal demand or in response to sensed working fluid vapor superheat.
Description
- 1~3~1S'7 This invention relates to vapor compression cycle devices and more particularly to a means and a method for controlling the modulation of both thermal capacity and evaporator superheat in such a device.
In a conventional vapor compression cycle device such as a heat pump a working fluid liquid is circulated through an expansion device into an evaporating heat exchanger where the working fluid absorbs heat. The heai vaporizes the working fluid liquid, and the resulting vapor is then circulated by a suitable compressor through a condensing heat exchanger where the vapor condenses inio a liquid as heat is given off. The cycle is then repeated as the workin~ fluid is recirculated through the system.
The quantity of heat required to vaporize the working fluid liquid is known as the heat of vaporization.
Additional heat absorpiton by the resulting working fluid vapor causes an increase in the vapor temperature above the temperature of vaporization. This increase in vapor temperature is defined as superheat.
In conventional vapor compression cycle devices it is desirable to control the amount of superheat in the device cycle to achieve optimum system performance. Typically this control of superheat is effected by regulating the flow rate of workingfluid liquid passing through the expansion de-vice to the evaporator.
A vapor compression cycle device should also include means to modulate the capacity of the device to absorb and deliver heat, herein referred to as device thermal capacity, in response to variable heating and cooling demands in order to maximize efficiency. A device of this type is disclosed in Canadian Application Serial Number 330,906, filed June 29, 1979, and assigned to the same ~13~15t7 assignee as the present application. The thermal capacity of this device i5 modulated by regulating the amount of a ~ ;
multi-component working fluid allowed to flow from a first accumulator through an evaporator to a second accumulator located at a compressor inlet. As described in the cited application, this results in a change in the molar flow rate through ~he compressor and thus a change in device ihermal capacity.
A device which includes means both for modulating device thermal capaciiy and for controlling the amount of evaporator superheai generated therein is disclosed in a -~
later filed Canadian application Serial No. 3C~ /~ Z
filed ~o~c~6~ c~ which is also assigned to the same assignee as the present invention. As in the earlier disclosed device described above, this latter device includes two accumulators. However, the second accumulator in the latter device is relocated intermediate two stages of an evaporating heat exchanger, and is adapted to decrease ~ :
the time required to switch the device from a high to a low capacity mode of operation. Additionally, the evaporator superheat of the latter device is controllable through reg-ulation of the amount of working fluid liquid allowed to flow from the second accumulator into the final evaporator stage.
The device disclosed in Canadian Application S.N.3~/~ thus includes means whereby both evaporator super-heat and device thermal capacity can be variably conlrolled.
However, optimal performance of this device can require the coordinated adjustment of a plurality of flow restricting devices in response to sensed conditions.
Accordingly, it is an object of this invention to provide a new and improved means for controlling the modulation ~3~S'7 of the thermal capacity of a vapor compression cycle device.
Another object of the present invention is to provide a new and improved means for controlling the evaporator superheat of such a device.
Still another object of the present invention is to provide a new and improved means and met~od for the control or a vapor compression cycle device thermal capacity and evaporator superheat.
The above and other objecis and advantages of the present invention are achieved through a means and a method for controlling the thermal capacity and evaporator superheat of a vapor compression cycle device employing a multi-component working fluid in which the amount of working fluid liquid allowed to flow from each of a pair of accum-ulators is controlled either in response to sensed thermal demand or to sensed working fluid vapor superheat.
For better understanding of the invention, reference may be made to the accompanying drawing wherein:
FIGURE 1 is a schematic illustration of a vapor compression cycle device constructed in accordance with an embodiment of the present invention; and FIGURE 2 is a view similar to that of Figure 1 illustrating a second embodiment of the present invention.
In the exemplary embodiments of the invention depicted in Figures 1 and 2 of the drawing a heat pump 10 is shown in a heating mode of operation. However, it is to be understood that the present invention is not limited to heat pump applications. Furthermorel it is also understood that the present invention can be operated in a cooling mode of operation.
The device 10 is a closed cycle device in which a ~. ; . ~ .
.
~3~15~
working fluid is circulated by a compressor 11 through a tube 12 to a condensing heat exchanger 13. ~fter trans-ferring its heat in the: condenser 13.'tQ the. household, the working fluid flows through a tube 14.to a high pressure accumulator 15. The accumulator .15 may be of a conventional ' ~
design or may be of a design such.'as disclosed in ': .
Çanadian Application Serial Number .331,333, filed. ~ ' ~uly 6, 1979, and assigned to the same assi~nee:as the present invention. The accumulator 15 is connected to an .
expansion valve 16 ~hich'controls the amount of the working fluid allowed to flow through a tube 17. to an evaporator assembly 18 where heat i.s absorbed by.the' fluid. ~he evap-orator assembly includes a low pres.sure:accumulator 19 connected iniermediate a first evaporaior stage 20 and a second evaporator stage 21. Thus, the working fluid entering the evaporator assembly 18 from the:tube 17.f.1Ows through:the first evaporator stage 20. to the low-pressure'accumulator 19 from which. it then flows through lines.-22 and.23.'.to the second evaporator stage 21. Tube 26 connects:thè.o.utlet side of the evaporator assembly 18 to the inl.et of the compressor : ' 11 to effect a closed system.
The working fluid circulated.in this closed system is a multi-component mixture of fluids.which'have different vapor pressures and which are mi.scibIe:over the operative range of the device 10. In the preferred embodiment of . the present inventi.on, the working:fluid is a multi-component fluorocarbon mixture. Such multi-component fluorocarbon mixtures can be selected for example from those disclosed in U.S. Patent No, 4,003,215 issued January 18, 1977, to John Roach.
The modulation of the. capacity of the device 10 is accomplished by altering the density of the working fluid , ~ . . . . .
:' '' . : ' i,. . : ... ;
~L~3~15~7 vapor at the inlet of the compressor 11. This effectively varies the` molar flow rate through the compressor, thereby affecting the capacity of the device 10 to absorb and deliver heat to an associated household, or its thermal capacity. The compressor inlet density is dependent upon the vapor pressure thereat which is in part a function of the composition of the working fluid liquid collected in the low pressure accumulator 19. Thus, if the composition of this liquid is enriched with a low boiling point component of the working fluid mixture, the thermal capacity of the device 10 is correspondingly increased. Conversely, a decrease in the concentration of the ~w boiling point component in theJ
liquid contained in the low pressure accumulator 19 will effect a decrease in the thermal capacity of the device.
The changing of the concentrations of the components of the liquid in the accumulator 19 is accomplished in part by adjusting the rate of flow from the accumulator 15. The high pressure accumulator 15 normally includes a higher concentration of the working fluid low boiling point component than.~does the liquid in the lo~ pressure accumulaior 19 due to equilibrium relationships between ihe working fluid vapor and liquid contained therein. Thus, to increase the capacity of the device 10 to transfer heat the valve 16 is adjusted to augment the flow from the accumulator 15 such that the liquid level in the low pressure accumulator 19 is raised and the composition thereof is enriched with the low boiling point component of the working fluid. This then causes an increase in the compressor inlet density, and thus increases the thermal capacity o the device.
In order to decrease device thermal capacity upon increased outdoor temperature and associated decreased household thermal demand, Ihe steps described above are . ~ - ; - - .
~3~
reversed. To thi:s end, ihe flow of ihe working fluid liquid from the accumulator 15 to the low pressure: accumu~ator 19 is restricted by adjusting the valve 16. The low boiling point component in the liquid contained in the low pressure accumulator 19 is slowly depleted through evaporation by means of heat transfer from the vapor interfacing therewith.
To accomplish a more rapid transition from a high to a low capacity mode of operation, the device 10 as illus-trated in Figures 1 and 2 includes tubes 23 and 24 and valve 25 which connect the liquid region of the accumulator 19 with the second evaporator stage 21. Thus, upon decreased thermal demand, the valve 25 is opened a predetermined amount to allow a portion of the liquid in the accumulator 19 to flow into ihe second evaporator .stage 21 along with the working fluid vapor flowi.ng through:the.tube.22. The mixture is therein vapor:i.zed prior. to entering the.compressor inlet through a tube 26.
In th.is manner, the time required to deplete the liquid level in the low pressure:.:accumulator 19, and thus to decrease th.e thermal capacity of the device 10, is sig-nificantly reduced.
Additionally,. th evaporator superheat of the device 10 is controlled by adjusting the valve 25.to augment or decrease the flow of working ~luid li:quid from the accumulator 17 to the second staye evaporator 21. More speci.fically, since the amount of heat transfer capabili~y available for transfer to the working fluid flowing through the second stage evaporator 21 is fixed for a given set of conditions, then the amount of fluid flowing therethrough accordingly governs the possible temperature rise therei.n. Thus the tempera~ure of the working fluid exiting the second stage evaporator 21, and hence evaporator superheat, i5 controllable ~3~ 5~7 by regulating the rate of working flu.id flow through the valve 25.
Means for controlling. the:thermal capacity and the evaporator superhea~ of the vapor compression cycle device 10 include superheat responsive actuation means 27 and thermal demand responsive actuation means 28. More specifically, as illustrated in Figures 1 and 2, actuation means 27 preferably includes a wetness sensing the`rmistor 29 and a valve actuator 30 connected in series to a voltage supply 31 by leads 32. The wetness sensing thermistor 29 controls voltage output to the valve actuator 30 causing.it to position the valve 16 such that a predetermined superheat condition in the suction line 26 of the compressor 11 is maintained. Actuation means of this type are commercially available from the Control Division of the Singer Company, Milwaukee, Wisconsin.
Although the thermistor 29 is depicted in Figures 1 and 2 positioned in the working fluid flow path after the second evaporator stage 21, ii is to be understood that the thermistor could be positioned earlier in the flow path to allow a higher degree of fluid superheat. In particular, the ~hermistor can be positioned to sense the vapor quality of . the working fluid at a predetermined point within the second evaporator stage, whereupon the fluid is heated a known amount in the portion of the evaporator following the thermi.stor to achieve a desired degree of fluid superheat at the inlet of the compressor 11.
Actuation means 28 includes a valve actuator 33 responsive to si.gnals transmitted from a thermal demand sensin~ controller 34. In the preferred embodiment of the invention the thermal demand sensing controller 34 is a ther-mostat, however, it is understood that other thermal demand sensing devices canb e substituted therefor~ Thermal demand ~3~ 7 responsive actuation means of thiS type are also commercially available from the above-noted Singer Co.
The embodiment of this invention illustrated in Figure 1, the method of modulating the thermal capacity of the device 10 ls initi:ated by a signal from the controller 34 corresponding to a sensed change in thermal demand. Upon a demand for increased device thermal capacity controller 34 signals valve actuator 33 to close valve 25 a predetermined amount, thereby decreasing the flow of working fluid liquid from the accumulator 19 through the heat exchanger 21. The decreased liquid flow results in an increased vapor superheat in the suction line 26 as sensed by the thermistor 29. Upon sensed increased vapor superheat the valve actuator 30 functions ~o open the cooperating valve 16 a predetermined amount, thereby augmeniing the working fluid flow from the accumulator 15 to the evaporator assembly 18. The re:sulting increase in the concentration of the low boiling point component of the working fluid mixture in the accumulator 19 causes an increase in the molar flow rate through the compressor 11, thereby increasing the thermal capacity of the device 10.
Conversely, upon a decrease in thermal demand, as sensed by the controller 34, the valve actuator 33 opens the valve 25 a predetermined amount to permit more li~uid working fluid to flow from the accumulator 19. This increased flow of liquid causes a decrease of superheat in the working fluid vapor exiting the second evaporator stage 21, thereby causing the closing of the valve 16 the the actuator 30. This leads to a gradual depletion of working fluid liquid in the accumulator 19 and a ~radual increase in liquid level in the accumulator 15. The thermal capacity of the device 10 thusly makes a gradual transition to a ~ower level of operation.
A variation on this first embodiment of the invention ~3~5'7 is illustrated in Figure 2 of the dra~ing. In this embodiment the valve 16 is controlled by the thermal demand responsive actuation means 28, and valve 25 is controlled by the superheat responsive actuation means 27. Upon a sensed in-crease in thermal demand the controller 34 transmits a signal causing the valve actuator 33 to open the valve 16.
This results in an increased flow of working fluid liquid from the accumulator 15 to the evaporator assembly 18, thereby increasing the concentration of the low boiling point component of the working fluid in the liquid contained in the accumulator 22 and causing an increase in the thermal capacity of the device 10. During this process the valve 25 is independently controlled by the actuation means 27 to meter out the amount of liquid required to maintain a predetermined degree of superheat at the exii of ihe evaporator assembly 18.
Upon a sensed need to decrease device thermal capacity the process is reversed wherein valve 16 is closed a predetermined amount resulting in less working fluid li~uid entering the accumulator 19. This leads to a gradual depletion of the liquid in the accumulator 19 and a decrease in device thermal capacity. As in the preceding case the valve 25 is again independently controlled to maintain a predetermined degree of superheat at the exit of the evaporator assembly 18.
The above-described embodiments of this invention are inlended to be examplative only and not limiting and it will be appreciaied from the foregoing by those skilled in the art that many substitutions, alternations and changes may be made to the described structure and method without department from the spirit or scope of the invention.
_g_
In a conventional vapor compression cycle device such as a heat pump a working fluid liquid is circulated through an expansion device into an evaporating heat exchanger where the working fluid absorbs heat. The heai vaporizes the working fluid liquid, and the resulting vapor is then circulated by a suitable compressor through a condensing heat exchanger where the vapor condenses inio a liquid as heat is given off. The cycle is then repeated as the workin~ fluid is recirculated through the system.
The quantity of heat required to vaporize the working fluid liquid is known as the heat of vaporization.
Additional heat absorpiton by the resulting working fluid vapor causes an increase in the vapor temperature above the temperature of vaporization. This increase in vapor temperature is defined as superheat.
In conventional vapor compression cycle devices it is desirable to control the amount of superheat in the device cycle to achieve optimum system performance. Typically this control of superheat is effected by regulating the flow rate of workingfluid liquid passing through the expansion de-vice to the evaporator.
A vapor compression cycle device should also include means to modulate the capacity of the device to absorb and deliver heat, herein referred to as device thermal capacity, in response to variable heating and cooling demands in order to maximize efficiency. A device of this type is disclosed in Canadian Application Serial Number 330,906, filed June 29, 1979, and assigned to the same ~13~15t7 assignee as the present application. The thermal capacity of this device i5 modulated by regulating the amount of a ~ ;
multi-component working fluid allowed to flow from a first accumulator through an evaporator to a second accumulator located at a compressor inlet. As described in the cited application, this results in a change in the molar flow rate through ~he compressor and thus a change in device ihermal capacity.
A device which includes means both for modulating device thermal capaciiy and for controlling the amount of evaporator superheai generated therein is disclosed in a -~
later filed Canadian application Serial No. 3C~ /~ Z
filed ~o~c~6~ c~ which is also assigned to the same assignee as the present invention. As in the earlier disclosed device described above, this latter device includes two accumulators. However, the second accumulator in the latter device is relocated intermediate two stages of an evaporating heat exchanger, and is adapted to decrease ~ :
the time required to switch the device from a high to a low capacity mode of operation. Additionally, the evaporator superheat of the latter device is controllable through reg-ulation of the amount of working fluid liquid allowed to flow from the second accumulator into the final evaporator stage.
The device disclosed in Canadian Application S.N.3~/~ thus includes means whereby both evaporator super-heat and device thermal capacity can be variably conlrolled.
However, optimal performance of this device can require the coordinated adjustment of a plurality of flow restricting devices in response to sensed conditions.
Accordingly, it is an object of this invention to provide a new and improved means for controlling the modulation ~3~S'7 of the thermal capacity of a vapor compression cycle device.
Another object of the present invention is to provide a new and improved means for controlling the evaporator superheat of such a device.
Still another object of the present invention is to provide a new and improved means and met~od for the control or a vapor compression cycle device thermal capacity and evaporator superheat.
The above and other objecis and advantages of the present invention are achieved through a means and a method for controlling the thermal capacity and evaporator superheat of a vapor compression cycle device employing a multi-component working fluid in which the amount of working fluid liquid allowed to flow from each of a pair of accum-ulators is controlled either in response to sensed thermal demand or to sensed working fluid vapor superheat.
For better understanding of the invention, reference may be made to the accompanying drawing wherein:
FIGURE 1 is a schematic illustration of a vapor compression cycle device constructed in accordance with an embodiment of the present invention; and FIGURE 2 is a view similar to that of Figure 1 illustrating a second embodiment of the present invention.
In the exemplary embodiments of the invention depicted in Figures 1 and 2 of the drawing a heat pump 10 is shown in a heating mode of operation. However, it is to be understood that the present invention is not limited to heat pump applications. Furthermorel it is also understood that the present invention can be operated in a cooling mode of operation.
The device 10 is a closed cycle device in which a ~. ; . ~ .
.
~3~15~
working fluid is circulated by a compressor 11 through a tube 12 to a condensing heat exchanger 13. ~fter trans-ferring its heat in the: condenser 13.'tQ the. household, the working fluid flows through a tube 14.to a high pressure accumulator 15. The accumulator .15 may be of a conventional ' ~
design or may be of a design such.'as disclosed in ': .
Çanadian Application Serial Number .331,333, filed. ~ ' ~uly 6, 1979, and assigned to the same assi~nee:as the present invention. The accumulator 15 is connected to an .
expansion valve 16 ~hich'controls the amount of the working fluid allowed to flow through a tube 17. to an evaporator assembly 18 where heat i.s absorbed by.the' fluid. ~he evap-orator assembly includes a low pres.sure:accumulator 19 connected iniermediate a first evaporaior stage 20 and a second evaporator stage 21. Thus, the working fluid entering the evaporator assembly 18 from the:tube 17.f.1Ows through:the first evaporator stage 20. to the low-pressure'accumulator 19 from which. it then flows through lines.-22 and.23.'.to the second evaporator stage 21. Tube 26 connects:thè.o.utlet side of the evaporator assembly 18 to the inl.et of the compressor : ' 11 to effect a closed system.
The working fluid circulated.in this closed system is a multi-component mixture of fluids.which'have different vapor pressures and which are mi.scibIe:over the operative range of the device 10. In the preferred embodiment of . the present inventi.on, the working:fluid is a multi-component fluorocarbon mixture. Such multi-component fluorocarbon mixtures can be selected for example from those disclosed in U.S. Patent No, 4,003,215 issued January 18, 1977, to John Roach.
The modulation of the. capacity of the device 10 is accomplished by altering the density of the working fluid , ~ . . . . .
:' '' . : ' i,. . : ... ;
~L~3~15~7 vapor at the inlet of the compressor 11. This effectively varies the` molar flow rate through the compressor, thereby affecting the capacity of the device 10 to absorb and deliver heat to an associated household, or its thermal capacity. The compressor inlet density is dependent upon the vapor pressure thereat which is in part a function of the composition of the working fluid liquid collected in the low pressure accumulator 19. Thus, if the composition of this liquid is enriched with a low boiling point component of the working fluid mixture, the thermal capacity of the device 10 is correspondingly increased. Conversely, a decrease in the concentration of the ~w boiling point component in theJ
liquid contained in the low pressure accumulator 19 will effect a decrease in the thermal capacity of the device.
The changing of the concentrations of the components of the liquid in the accumulator 19 is accomplished in part by adjusting the rate of flow from the accumulator 15. The high pressure accumulator 15 normally includes a higher concentration of the working fluid low boiling point component than.~does the liquid in the lo~ pressure accumulaior 19 due to equilibrium relationships between ihe working fluid vapor and liquid contained therein. Thus, to increase the capacity of the device 10 to transfer heat the valve 16 is adjusted to augment the flow from the accumulator 15 such that the liquid level in the low pressure accumulator 19 is raised and the composition thereof is enriched with the low boiling point component of the working fluid. This then causes an increase in the compressor inlet density, and thus increases the thermal capacity o the device.
In order to decrease device thermal capacity upon increased outdoor temperature and associated decreased household thermal demand, Ihe steps described above are . ~ - ; - - .
~3~
reversed. To thi:s end, ihe flow of ihe working fluid liquid from the accumulator 15 to the low pressure: accumu~ator 19 is restricted by adjusting the valve 16. The low boiling point component in the liquid contained in the low pressure accumulator 19 is slowly depleted through evaporation by means of heat transfer from the vapor interfacing therewith.
To accomplish a more rapid transition from a high to a low capacity mode of operation, the device 10 as illus-trated in Figures 1 and 2 includes tubes 23 and 24 and valve 25 which connect the liquid region of the accumulator 19 with the second evaporator stage 21. Thus, upon decreased thermal demand, the valve 25 is opened a predetermined amount to allow a portion of the liquid in the accumulator 19 to flow into ihe second evaporator .stage 21 along with the working fluid vapor flowi.ng through:the.tube.22. The mixture is therein vapor:i.zed prior. to entering the.compressor inlet through a tube 26.
In th.is manner, the time required to deplete the liquid level in the low pressure:.:accumulator 19, and thus to decrease th.e thermal capacity of the device 10, is sig-nificantly reduced.
Additionally,. th evaporator superheat of the device 10 is controlled by adjusting the valve 25.to augment or decrease the flow of working ~luid li:quid from the accumulator 17 to the second staye evaporator 21. More speci.fically, since the amount of heat transfer capabili~y available for transfer to the working fluid flowing through the second stage evaporator 21 is fixed for a given set of conditions, then the amount of fluid flowing therethrough accordingly governs the possible temperature rise therei.n. Thus the tempera~ure of the working fluid exiting the second stage evaporator 21, and hence evaporator superheat, i5 controllable ~3~ 5~7 by regulating the rate of working flu.id flow through the valve 25.
Means for controlling. the:thermal capacity and the evaporator superhea~ of the vapor compression cycle device 10 include superheat responsive actuation means 27 and thermal demand responsive actuation means 28. More specifically, as illustrated in Figures 1 and 2, actuation means 27 preferably includes a wetness sensing the`rmistor 29 and a valve actuator 30 connected in series to a voltage supply 31 by leads 32. The wetness sensing thermistor 29 controls voltage output to the valve actuator 30 causing.it to position the valve 16 such that a predetermined superheat condition in the suction line 26 of the compressor 11 is maintained. Actuation means of this type are commercially available from the Control Division of the Singer Company, Milwaukee, Wisconsin.
Although the thermistor 29 is depicted in Figures 1 and 2 positioned in the working fluid flow path after the second evaporator stage 21, ii is to be understood that the thermistor could be positioned earlier in the flow path to allow a higher degree of fluid superheat. In particular, the ~hermistor can be positioned to sense the vapor quality of . the working fluid at a predetermined point within the second evaporator stage, whereupon the fluid is heated a known amount in the portion of the evaporator following the thermi.stor to achieve a desired degree of fluid superheat at the inlet of the compressor 11.
Actuation means 28 includes a valve actuator 33 responsive to si.gnals transmitted from a thermal demand sensin~ controller 34. In the preferred embodiment of the invention the thermal demand sensing controller 34 is a ther-mostat, however, it is understood that other thermal demand sensing devices canb e substituted therefor~ Thermal demand ~3~ 7 responsive actuation means of thiS type are also commercially available from the above-noted Singer Co.
The embodiment of this invention illustrated in Figure 1, the method of modulating the thermal capacity of the device 10 ls initi:ated by a signal from the controller 34 corresponding to a sensed change in thermal demand. Upon a demand for increased device thermal capacity controller 34 signals valve actuator 33 to close valve 25 a predetermined amount, thereby decreasing the flow of working fluid liquid from the accumulator 19 through the heat exchanger 21. The decreased liquid flow results in an increased vapor superheat in the suction line 26 as sensed by the thermistor 29. Upon sensed increased vapor superheat the valve actuator 30 functions ~o open the cooperating valve 16 a predetermined amount, thereby augmeniing the working fluid flow from the accumulator 15 to the evaporator assembly 18. The re:sulting increase in the concentration of the low boiling point component of the working fluid mixture in the accumulator 19 causes an increase in the molar flow rate through the compressor 11, thereby increasing the thermal capacity of the device 10.
Conversely, upon a decrease in thermal demand, as sensed by the controller 34, the valve actuator 33 opens the valve 25 a predetermined amount to permit more li~uid working fluid to flow from the accumulator 19. This increased flow of liquid causes a decrease of superheat in the working fluid vapor exiting the second evaporator stage 21, thereby causing the closing of the valve 16 the the actuator 30. This leads to a gradual depletion of working fluid liquid in the accumulator 19 and a ~radual increase in liquid level in the accumulator 15. The thermal capacity of the device 10 thusly makes a gradual transition to a ~ower level of operation.
A variation on this first embodiment of the invention ~3~5'7 is illustrated in Figure 2 of the dra~ing. In this embodiment the valve 16 is controlled by the thermal demand responsive actuation means 28, and valve 25 is controlled by the superheat responsive actuation means 27. Upon a sensed in-crease in thermal demand the controller 34 transmits a signal causing the valve actuator 33 to open the valve 16.
This results in an increased flow of working fluid liquid from the accumulator 15 to the evaporator assembly 18, thereby increasing the concentration of the low boiling point component of the working fluid in the liquid contained in the accumulator 22 and causing an increase in the thermal capacity of the device 10. During this process the valve 25 is independently controlled by the actuation means 27 to meter out the amount of liquid required to maintain a predetermined degree of superheat at the exii of ihe evaporator assembly 18.
Upon a sensed need to decrease device thermal capacity the process is reversed wherein valve 16 is closed a predetermined amount resulting in less working fluid li~uid entering the accumulator 19. This leads to a gradual depletion of the liquid in the accumulator 19 and a decrease in device thermal capacity. As in the preceding case the valve 25 is again independently controlled to maintain a predetermined degree of superheat at the exit of the evaporator assembly 18.
The above-described embodiments of this invention are inlended to be examplative only and not limiting and it will be appreciaied from the foregoing by those skilled in the art that many substitutions, alternations and changes may be made to the described structure and method without department from the spirit or scope of the invention.
_g_
Claims (11)
1. A method for controlling the capacity and evaporator superheat of a vapor compression cycle device comprising the steps of:
compressing vapor of a miscible multicomponent working fluid mixture comprising at least two refrigerants having different boiling points, circulating the mixture vapor through a condensing heat exchanger, circulating mixture from the condensing heat exchanger to a high pressure accumulator, circulating a controlled amount of the mixture from the high pressure accumulator to a first evaporator stage in response to a sensed household thermal demand, circulating mixture from the first evaporator stage to a low pressure accumulator, controlling the circulation of the mixture from the low pressure accumulator to a second evaporator stage in response to the degree of mixture vapor superheat sensed at a point intermediate the second evaporator stage inlet and a compressor, and circulating the mixture exiting from the second evaporator stage to the compressor.
compressing vapor of a miscible multicomponent working fluid mixture comprising at least two refrigerants having different boiling points, circulating the mixture vapor through a condensing heat exchanger, circulating mixture from the condensing heat exchanger to a high pressure accumulator, circulating a controlled amount of the mixture from the high pressure accumulator to a first evaporator stage in response to a sensed household thermal demand, circulating mixture from the first evaporator stage to a low pressure accumulator, controlling the circulation of the mixture from the low pressure accumulator to a second evaporator stage in response to the degree of mixture vapor superheat sensed at a point intermediate the second evaporator stage inlet and a compressor, and circulating the mixture exiting from the second evaporator stage to the compressor.
2. A method for controlling vapor compression cycle device capacity and evaporator superheat as in claim 1 wherein the amount of the mixture allowed to circulate from the high pressure accumulator to the first evaporator stage is increased with increasing household thermal demand.
3. A method for controlling vapor compression cycle device capacity and evaporator superheat as in claim 1 or 2 wherein the amount of the mixture allowed to circulate from the low pressure accumulator to the second evaporator stage is increased a predetermined amount corresponding to sensed increases in mixture vapor superheat.
4. A method for controlling vapor compression cycle device capacity and evaporator superheat comprising the following steps:
compressing vapor of a miscible multicomponent working fluid mixture comprising at least two refrigerants having differ-ent boiling points, circulating mixture vapor to a condensing heat exchanger, circulating the mixture liquid from the condensing heat exchanger to a high pressure accumulator, controlling the circulation of the mixture from the high pressure accumulator to a first evaporator stage in response to the degree of mixture vapor superheat sensed at a point in the device intermediate the inlet of a second evaporator stage and a compressor, circulating the mixture from the first evaporator stage to a low pressure accumulator, controlling the circulation of the mixture from the low pressure accumulator to the second evaporator stage in response to sensed household thermal demand, and circulating the mixture from the second evaporator stage to the compressor.
compressing vapor of a miscible multicomponent working fluid mixture comprising at least two refrigerants having differ-ent boiling points, circulating mixture vapor to a condensing heat exchanger, circulating the mixture liquid from the condensing heat exchanger to a high pressure accumulator, controlling the circulation of the mixture from the high pressure accumulator to a first evaporator stage in response to the degree of mixture vapor superheat sensed at a point in the device intermediate the inlet of a second evaporator stage and a compressor, circulating the mixture from the first evaporator stage to a low pressure accumulator, controlling the circulation of the mixture from the low pressure accumulator to the second evaporator stage in response to sensed household thermal demand, and circulating the mixture from the second evaporator stage to the compressor.
5. A method for controlling vapor compression cycle device capacity and evaporator superheat as in claim 4 wherein said circulation of mixture from the high pressure accumulator to the first evaporator stage is increased a predetermined amount corresponding to sensed increases in mixture vapor superheat.
6. A method for controlling vapor compression cycle device capacity and evaporator superheat as in claim 4 or 5 wherein said circulation of the mixture from the low pressure accumulator to the second evaporator stage is decreased with increasing household thermal demand.
7. In a vapor compression cycle device having a miscible multicomponent working fluid comprising at least two refrigerants with different boiling points which is circulated by a compressor through a condensing heat exchanger to a high pressure accumulator, an evaporator assembly connected at its inlet to said high pressure accumulator through a first flow restricting device and connected at its exhaust to said compressor, said evaporator assembly including a low pressure accumulator connected intermediate a first evaporator stage and a second evaporator stage with said connection to said second evaporator stage including a second flow restricting device, a means for controlling the capacity and the evaporator superheat of said vapor compression cycle device comprising:
a first actuation assembly including means for sensing working fluid vapor superheat at a point in the device intermediate said second low restricting device and said compressor and an actuating means in cooperative engagement with said first flow restricting device for regulating the amount of working fluid flowing through said first flow restricting device in response to a signal from said vapor superheat sensing means; and a second actuation assembly including a thermal demand sensing means and an actuating means in cooperative engagement with said second flow restricting device for regulating the amount of working fluid flowing through said flow restricting device in response to a signal from said demand sensing means.
a first actuation assembly including means for sensing working fluid vapor superheat at a point in the device intermediate said second low restricting device and said compressor and an actuating means in cooperative engagement with said first flow restricting device for regulating the amount of working fluid flowing through said first flow restricting device in response to a signal from said vapor superheat sensing means; and a second actuation assembly including a thermal demand sensing means and an actuating means in cooperative engagement with said second flow restricting device for regulating the amount of working fluid flowing through said flow restricting device in response to a signal from said demand sensing means.
8. In a vapor compression cycle device having miscible multicomponent working fluid comprising at least two refrigerants with different boiling points which is circulated by a compressor through a condensing heat exchanger to a high pressure accumula-tor, an evaporator assembly connected at its inlet to said high pressure accumulator through a first flow restricting device and connected at its exhaust to said compressor, said evaporator assembly including a low pressure accumulator connected inter-mediate a first evaporator stage and a second evaporator stage with said connection to said second evaporator stage including .DELTA.
a second flow restricting device, a means for controlling the capacity and the evaporator superheat of said vapor compression cycle device comprising:
a first actuation assembly including means for sensing working fluid vapor superheat at a point in the device inter-mediate said second flow restricting device and said compressor and an actuating means in cooperative engagement with said second flow restricting device for regulating the amount of working fluid flowing through said second flow restricting device in response to a signal from said vapor superheat sensing means; and a second actuation assembly including a thermal demand sensing means and an actuating means in cooperative engagement with said first flow restricting device for regulating the amount of working fluid flowing through said first flow restricting device in response to a signal from said demand sensing means.
a second flow restricting device, a means for controlling the capacity and the evaporator superheat of said vapor compression cycle device comprising:
a first actuation assembly including means for sensing working fluid vapor superheat at a point in the device inter-mediate said second flow restricting device and said compressor and an actuating means in cooperative engagement with said second flow restricting device for regulating the amount of working fluid flowing through said second flow restricting device in response to a signal from said vapor superheat sensing means; and a second actuation assembly including a thermal demand sensing means and an actuating means in cooperative engagement with said first flow restricting device for regulating the amount of working fluid flowing through said first flow restricting device in response to a signal from said demand sensing means.
9. A means for controlling vapor compression cycle device capacity and evaporator superheat as in claim 7 or 8 wherein said vapor superheat sensing means is a thermistor.
10. A means for controlling vapor compression cycle device capacity and evaporator superheat as in claim 7 or 8 wherein said vapor superheat sensing means is disposed inter-mediate said second evaporator stage inlet and said compressor inlet.
11. A means for controlling vapor compression cycle
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA364,543A CA1134157A (en) | 1980-11-13 | 1980-11-13 | Means and method for independently controlling vapor compression cycle device evaporator superheat and thermal transfer capacity |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA364,543A CA1134157A (en) | 1980-11-13 | 1980-11-13 | Means and method for independently controlling vapor compression cycle device evaporator superheat and thermal transfer capacity |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1134157A true CA1134157A (en) | 1982-10-26 |
Family
ID=4118431
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA364,543A Expired CA1134157A (en) | 1980-11-13 | 1980-11-13 | Means and method for independently controlling vapor compression cycle device evaporator superheat and thermal transfer capacity |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1134157A (en) |
-
1980
- 1980-11-13 CA CA364,543A patent/CA1134157A/en not_active Expired
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