CA1198905A - Heat pump apparatus and method of operating the same - Google Patents
Heat pump apparatus and method of operating the sameInfo
- Publication number
- CA1198905A CA1198905A CA000437520A CA437520A CA1198905A CA 1198905 A CA1198905 A CA 1198905A CA 000437520 A CA000437520 A CA 000437520A CA 437520 A CA437520 A CA 437520A CA 1198905 A CA1198905 A CA 1198905A
- Authority
- CA
- Canada
- Prior art keywords
- refrigerant
- expansion device
- coil
- heat exchanger
- indoor
- 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
Links
Landscapes
- Compression-Type Refrigeration Machines With Reversible Cycles (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A single electrically operated expansion device 36 is provided in a heat pump system and is controlled in accordance with sensed temperatures at the indoor coil 18 by sensors 46, 48, 50 to operate the valve 36 as a subcool-ing valve to give flooded evaporator operation of the coil 22 in the heating mode, and to give superheat control of the coil 18 in the cooling mode.
A single electrically operated expansion device 36 is provided in a heat pump system and is controlled in accordance with sensed temperatures at the indoor coil 18 by sensors 46, 48, 50 to operate the valve 36 as a subcool-ing valve to give flooded evaporator operation of the coil 22 in the heating mode, and to give superheat control of the coil 18 in the cooling mode.
Description
HEAT PUMP APPARATUS AND METHOD
OF OPERATING THE SAME
GOVERNMENT CONTRACT
The Government has rights in this invention pursuant to Prime Contract No. W-7405-ENG-26 and Sub-contract No. 86X-24712-C awarded by the United States Department of ~nergy.
~ACKGROUND OF THE INVENTION
A refrigeration circuit in which the refrigerant exiting the evaporator is saturated vapor or contains small amo~mts of liauid has two important advantages over a system where the refrigerant exiting the evaporator is superheated. First, since the compressor is essentially a constant volume device, the refrigerant flow is maximized by ~xi~izing the density of the fluid entering the com-pressor. Since superheating the vapor reduces its density, it reduces the 10w of refrigerant. Second, since heat transfer coefficients in two-phase flow are higher than for single-phase flow, the utilization of the evaporator heat transfer surface is maximized by eliminating super heat. These advantages have been known for some years and have been availed of in the com~r~ial application of heat pump systems embodying the teachin~s of U.S. Patent 3,264,837. That system was designed to operate without superheat of the refrigerant exiting the evaporator in both the heating and cooling modes. In that system, as commercially a~ailable, refrigerant flow was basically s controlled by the use of a subcooling control valve, controlling in accordance with the temperature of the refrigerant exiting whichever coil was functioning as the condenser. The particular control valve commercially used required that the 10w through the valve be in the same direction in both heating and cooling modes and this accordingly required the use of an arrangement of our check valves, typically provided in the form of a manifold check valve assembly of the character described and claimed in U.S. Patent 3,299,661. Such assemblies are relatively expensive, impose additional refrigerant pressure drop, allow heat to be transferred from the hot liquid stream to the cold two-phase stream, and can leak or stick causing a loss in performance or failure of the system.
It is the aim of this invention to provide a heat pump system in which part or all of the check valves are eliminated, which utilizes a commercially available refrigerant expansion device adapted to control refrigerant flow in either direction through the device and which is controlled in different ways in the heating and cooling modes of operation of the system to provide advantages in both modes and in particular in a heat pump system designed especially for use in northern climates.
SUM~RY OF THE INVENTION
In accordance with the invention a heat pump system of the type which includes a suction line accumu~
lator and heat exchanger means is provided with a single refrigerant expansion device in the system, the expansion device being an electrically operated device located in a refrigerant line connected on one side of the expansion device to the outdoor coil, and connected on the other side of the expansion device at ~éast to the heat exchanger means. Means are provided to control the expansion device in the heating mode of operation of the heat pump to obtain a degree of subcooling of refrigerant passing through the indoor coil, which degree of subcooling coupled with further subcooling of the refrigerant in its passage -through the heat exchanger means, provides for flooded evaporator operation of the outdoor coil, and controlling the expansion device in a cooling mode of operation to pass refrigerant to the indoor coil at a rate to obtain a degree of superheat of refri~erant eY~iting the indoor coil.
Stated in another manner, the heat pump system of the invention functions to provide subcool control of the refrigerant iIl the hea-ting mode to give flooded evapor-ator operation, and functions to provide superheated control in the cooling mode Various advantages are available from a system of this character, which advantages will be noted later herein.
BRIEF DESCRIPTION OE THE DRAWING
Figure 1 is a schematic diagram of one form of heat pump system according to the invention; and Figure 2 is a schematic diagram of another form of the heat pump system of the invention.
DESCRIPTION OE THE PREFERRED EMBODIMENTS
Most of the basic elements shown in both Figures l and 2 are the same, and to the extent they are, the same reference numerals are applied to both figures. In both figures, the solid line directional arrows indicate the direction of refrigerant flow in the heating mode of operation, while the dash line arrows indicate the direc-tion of flow in the cooling mode of operation.
In the Figures, the re~rigerant compressor lO
pumps hot gaseous refrigerant through discharge line 12 to a conventional reversing valve 14 which, according to its positioning, directs the hot gas either through line 16 to the indoor coil 18 or, alternatively, through the line 20 to the outdoor coil 22.
Referring now to Figure l alone, and assuming the heat pump is operating in a heating mode, the refrig-erant leaving the indoor coil 18 passes through line 24,line 25, through a heat exchanger element 26 physically located in a suction line accumulator 28, through line 30 containing a check valve 32, through line 34 to the elec-trically controlled refrigerant expansion device 36 and line 38 to the outdoor coil 22. From the outdoor coil the refrigerant passes back through line 20 to the reversing 5 valve 14 which, in the heating mode position, directs the returning suction gas through line 40 to the suction line accumulator 28. Suction gas returns to the compressor 10 from the accumulator 28 through line 42.
In the cooling mode of operation the refrigerant 10 flow is from the compressor 10 through the discharge line 12, reversing valve 14 positioned to pass refrigerant to line 20 leading to the outdoor coil 22, then line 38 to the expansion valve 36, line 34 through the check valve 44, llne 24, indoor coil 18, line 16 to the reversing 15 valve 14 and then through line 40 to the suction accumula-tor 28, and back to the compressor 10 through line 42. It will be noted that in the heating mode of operation the check valve 44 compells the refrigerant to pass through the heat exchanger 26, while in the cooling mode of opera-20 tion the check valve 32 compels the refrigerant to bypassthe heat exchanger 26.
The refrigerant flow paths for the Figure 2 system in both the heating and cooling modes of operation are very similar except that while in the Figure 1 arrange-25 ment the heat exchanger 26 is bypassed in the coolingmode, in the Figure 2 arrangement the heat exchanger 26 has refrigerant flow therethrough in both the heating and cooling modes.
In contrasting the systems of Figures 1 and 2, 30 Figure 1 is advantageous in the cooling mode in that there is no heat transfer between the suction gas and the accumu-lator 28 and the refrigerant flowing to the indoor coil 18 from the expansion device 36, but is disadvantageous in that it includes the t~o check valves 32 and 44 which 35 impose some additional pressure drop, add to the cost of the system and sometimes are susceptible to leaking or sticking. The disadvantage of the Figure 2 system is that the heat exchanger 26 functions in the cooling mode as well as the heating mode, and in the cooling mode there will typically be some small degree of heat transfer which will penalize cooling performance slightly.
It will be seen that in both systems a single refrigerant expansion device 36 is used, which is electri-cally operated and may be a commercially available valve such as the No. 625 available from the Singer Company. It will also be seen that it is located in a refrigerant line which includes the part 38 connected to the outdoor coil, and the part 34 on the other side of the valve 36 which is connected at least to the heat exchanger 26 through line 30 in Figure 2, and through line 30 in check valve 32 in Figure 1, and as well as connected to the second check valve 44 in Figure 1.
The difference in control of the refrigerant flow by the expansion device 36 in accordance with the cooling or heating mode of operation is a very important aspect of the invention. The temperature of the indoor coil at a central or representative location is sensed by the sensor 46. Another sensor 48 located at or adjacent the exit end of the coil ~when the coil is operating in a cooling mode) senses superheat temperature of the refriger-ant leaving the coil. Another sensor 50 at or adjacent the other ~nd of the coil which end of the coil is the end through which refrigerant exits when the indoor coil is functioning as a condenser, is used to sense the degree of subcooling occurring in the coil. These three sensors are connected through lines 52, 54 and 56, respectively, to the controller 58 which in turn is connected by electric line means 60 to provide the electrical signal to the electric expansion valve 36.
In the cooling mode the indoor coil 18 functions as an evaporator and the temperature difference between the refrigerant exiting the coil as measured by sensor 48, and the saturation temperature as measured by sensor 46 is measured and the two temperatures compared to the set poin~ in the controller 58. This signal is then fed back to the expansion device 36 to control the flow of refrigerant to the indoor coil to obtain the proper flow for conditions.
In the heating mode the temperatures at 46 and 50 are measured and the difference compared to the set point to obtain the proper refrigerant flow for the partic-ular conditions. The degree of superheat, and subcooling giving best performance in accordance with outdoor ambient temperature can also be controlled in the systems by the provision of an outdoor ambient temperature sensor as indicated at 62 and fed into the controller 58 through line 64. Thus in the heating mode of operation the valve 36 functions as a subcooling control valve which operates to obtain the degree of subcooling of refrigerant exiting the indoor coil 18. This degree of subcooling coupled with the further subcooling of the refrigerant in its passage through the heat exchanger 26 where it is in heat a~c~ ~ r. relation with the cold suction gas, provides for flooded evaporator operation of the outdoor coil 22. In the cooling mode of operation, the indoor coil 18 functions as the evaporator and the control of the refrigerant flow through the valve 36 is that giving a rate to ohtain the proper degree of superheat of the refrigerant exiting the indoor coil.
It is noted that the basic operation of the system in the heating mode, as distinguished from differ-ences in parts of the systems, is essentially the same as that of commercial devices based upon the concepts of U.S.
30 Patent 3,264,837. The operation of the systems in a cooling mode is ~uite different from the concepts of that patent with respect to its operation in the cooling mode.
Among the advantages of the system and method of operation, in which the subcool control and flooded evap-orator i5 used in the heating mode and the superheat control is used in the cooling mode, is that all of the control sensors may be located at the indoor coil 18. The system may be provided with no check valves or, alter-native.ly, with a reduced number of check valves as con-trasted to the commercial devices based upon U.S. Patent 3,264,837. The system is adapted to using the conven-tionally available suction accumulator with the built-in heat exchanger. Another important advantage of the system is it is adapted to be charged when it i5 set up for operation in the cooling mode so that it is much easier to obtain a proper charge of refrigerant. This is in contrast to those commercial devices based upon U.S. Patent 3,264,837, for which were ound to present substantial difficulty to typical service people in determining when they were properly charged. Those prior art devices are rather insensitive to excess charge, but undercharging results in a precipitous loss in performance. The primary difficulty is that the charging method is more dificult, and is unfamiliar to many service people.
OF OPERATING THE SAME
GOVERNMENT CONTRACT
The Government has rights in this invention pursuant to Prime Contract No. W-7405-ENG-26 and Sub-contract No. 86X-24712-C awarded by the United States Department of ~nergy.
~ACKGROUND OF THE INVENTION
A refrigeration circuit in which the refrigerant exiting the evaporator is saturated vapor or contains small amo~mts of liauid has two important advantages over a system where the refrigerant exiting the evaporator is superheated. First, since the compressor is essentially a constant volume device, the refrigerant flow is maximized by ~xi~izing the density of the fluid entering the com-pressor. Since superheating the vapor reduces its density, it reduces the 10w of refrigerant. Second, since heat transfer coefficients in two-phase flow are higher than for single-phase flow, the utilization of the evaporator heat transfer surface is maximized by eliminating super heat. These advantages have been known for some years and have been availed of in the com~r~ial application of heat pump systems embodying the teachin~s of U.S. Patent 3,264,837. That system was designed to operate without superheat of the refrigerant exiting the evaporator in both the heating and cooling modes. In that system, as commercially a~ailable, refrigerant flow was basically s controlled by the use of a subcooling control valve, controlling in accordance with the temperature of the refrigerant exiting whichever coil was functioning as the condenser. The particular control valve commercially used required that the 10w through the valve be in the same direction in both heating and cooling modes and this accordingly required the use of an arrangement of our check valves, typically provided in the form of a manifold check valve assembly of the character described and claimed in U.S. Patent 3,299,661. Such assemblies are relatively expensive, impose additional refrigerant pressure drop, allow heat to be transferred from the hot liquid stream to the cold two-phase stream, and can leak or stick causing a loss in performance or failure of the system.
It is the aim of this invention to provide a heat pump system in which part or all of the check valves are eliminated, which utilizes a commercially available refrigerant expansion device adapted to control refrigerant flow in either direction through the device and which is controlled in different ways in the heating and cooling modes of operation of the system to provide advantages in both modes and in particular in a heat pump system designed especially for use in northern climates.
SUM~RY OF THE INVENTION
In accordance with the invention a heat pump system of the type which includes a suction line accumu~
lator and heat exchanger means is provided with a single refrigerant expansion device in the system, the expansion device being an electrically operated device located in a refrigerant line connected on one side of the expansion device to the outdoor coil, and connected on the other side of the expansion device at ~éast to the heat exchanger means. Means are provided to control the expansion device in the heating mode of operation of the heat pump to obtain a degree of subcooling of refrigerant passing through the indoor coil, which degree of subcooling coupled with further subcooling of the refrigerant in its passage -through the heat exchanger means, provides for flooded evaporator operation of the outdoor coil, and controlling the expansion device in a cooling mode of operation to pass refrigerant to the indoor coil at a rate to obtain a degree of superheat of refri~erant eY~iting the indoor coil.
Stated in another manner, the heat pump system of the invention functions to provide subcool control of the refrigerant iIl the hea-ting mode to give flooded evapor-ator operation, and functions to provide superheated control in the cooling mode Various advantages are available from a system of this character, which advantages will be noted later herein.
BRIEF DESCRIPTION OE THE DRAWING
Figure 1 is a schematic diagram of one form of heat pump system according to the invention; and Figure 2 is a schematic diagram of another form of the heat pump system of the invention.
DESCRIPTION OE THE PREFERRED EMBODIMENTS
Most of the basic elements shown in both Figures l and 2 are the same, and to the extent they are, the same reference numerals are applied to both figures. In both figures, the solid line directional arrows indicate the direction of refrigerant flow in the heating mode of operation, while the dash line arrows indicate the direc-tion of flow in the cooling mode of operation.
In the Figures, the re~rigerant compressor lO
pumps hot gaseous refrigerant through discharge line 12 to a conventional reversing valve 14 which, according to its positioning, directs the hot gas either through line 16 to the indoor coil 18 or, alternatively, through the line 20 to the outdoor coil 22.
Referring now to Figure l alone, and assuming the heat pump is operating in a heating mode, the refrig-erant leaving the indoor coil 18 passes through line 24,line 25, through a heat exchanger element 26 physically located in a suction line accumulator 28, through line 30 containing a check valve 32, through line 34 to the elec-trically controlled refrigerant expansion device 36 and line 38 to the outdoor coil 22. From the outdoor coil the refrigerant passes back through line 20 to the reversing 5 valve 14 which, in the heating mode position, directs the returning suction gas through line 40 to the suction line accumulator 28. Suction gas returns to the compressor 10 from the accumulator 28 through line 42.
In the cooling mode of operation the refrigerant 10 flow is from the compressor 10 through the discharge line 12, reversing valve 14 positioned to pass refrigerant to line 20 leading to the outdoor coil 22, then line 38 to the expansion valve 36, line 34 through the check valve 44, llne 24, indoor coil 18, line 16 to the reversing 15 valve 14 and then through line 40 to the suction accumula-tor 28, and back to the compressor 10 through line 42. It will be noted that in the heating mode of operation the check valve 44 compells the refrigerant to pass through the heat exchanger 26, while in the cooling mode of opera-20 tion the check valve 32 compels the refrigerant to bypassthe heat exchanger 26.
The refrigerant flow paths for the Figure 2 system in both the heating and cooling modes of operation are very similar except that while in the Figure 1 arrange-25 ment the heat exchanger 26 is bypassed in the coolingmode, in the Figure 2 arrangement the heat exchanger 26 has refrigerant flow therethrough in both the heating and cooling modes.
In contrasting the systems of Figures 1 and 2, 30 Figure 1 is advantageous in the cooling mode in that there is no heat transfer between the suction gas and the accumu-lator 28 and the refrigerant flowing to the indoor coil 18 from the expansion device 36, but is disadvantageous in that it includes the t~o check valves 32 and 44 which 35 impose some additional pressure drop, add to the cost of the system and sometimes are susceptible to leaking or sticking. The disadvantage of the Figure 2 system is that the heat exchanger 26 functions in the cooling mode as well as the heating mode, and in the cooling mode there will typically be some small degree of heat transfer which will penalize cooling performance slightly.
It will be seen that in both systems a single refrigerant expansion device 36 is used, which is electri-cally operated and may be a commercially available valve such as the No. 625 available from the Singer Company. It will also be seen that it is located in a refrigerant line which includes the part 38 connected to the outdoor coil, and the part 34 on the other side of the valve 36 which is connected at least to the heat exchanger 26 through line 30 in Figure 2, and through line 30 in check valve 32 in Figure 1, and as well as connected to the second check valve 44 in Figure 1.
The difference in control of the refrigerant flow by the expansion device 36 in accordance with the cooling or heating mode of operation is a very important aspect of the invention. The temperature of the indoor coil at a central or representative location is sensed by the sensor 46. Another sensor 48 located at or adjacent the exit end of the coil ~when the coil is operating in a cooling mode) senses superheat temperature of the refriger-ant leaving the coil. Another sensor 50 at or adjacent the other ~nd of the coil which end of the coil is the end through which refrigerant exits when the indoor coil is functioning as a condenser, is used to sense the degree of subcooling occurring in the coil. These three sensors are connected through lines 52, 54 and 56, respectively, to the controller 58 which in turn is connected by electric line means 60 to provide the electrical signal to the electric expansion valve 36.
In the cooling mode the indoor coil 18 functions as an evaporator and the temperature difference between the refrigerant exiting the coil as measured by sensor 48, and the saturation temperature as measured by sensor 46 is measured and the two temperatures compared to the set poin~ in the controller 58. This signal is then fed back to the expansion device 36 to control the flow of refrigerant to the indoor coil to obtain the proper flow for conditions.
In the heating mode the temperatures at 46 and 50 are measured and the difference compared to the set point to obtain the proper refrigerant flow for the partic-ular conditions. The degree of superheat, and subcooling giving best performance in accordance with outdoor ambient temperature can also be controlled in the systems by the provision of an outdoor ambient temperature sensor as indicated at 62 and fed into the controller 58 through line 64. Thus in the heating mode of operation the valve 36 functions as a subcooling control valve which operates to obtain the degree of subcooling of refrigerant exiting the indoor coil 18. This degree of subcooling coupled with the further subcooling of the refrigerant in its passage through the heat exchanger 26 where it is in heat a~c~ ~ r. relation with the cold suction gas, provides for flooded evaporator operation of the outdoor coil 22. In the cooling mode of operation, the indoor coil 18 functions as the evaporator and the control of the refrigerant flow through the valve 36 is that giving a rate to ohtain the proper degree of superheat of the refrigerant exiting the indoor coil.
It is noted that the basic operation of the system in the heating mode, as distinguished from differ-ences in parts of the systems, is essentially the same as that of commercial devices based upon the concepts of U.S.
30 Patent 3,264,837. The operation of the systems in a cooling mode is ~uite different from the concepts of that patent with respect to its operation in the cooling mode.
Among the advantages of the system and method of operation, in which the subcool control and flooded evap-orator i5 used in the heating mode and the superheat control is used in the cooling mode, is that all of the control sensors may be located at the indoor coil 18. The system may be provided with no check valves or, alter-native.ly, with a reduced number of check valves as con-trasted to the commercial devices based upon U.S. Patent 3,264,837. The system is adapted to using the conven-tionally available suction accumulator with the built-in heat exchanger. Another important advantage of the system is it is adapted to be charged when it i5 set up for operation in the cooling mode so that it is much easier to obtain a proper charge of refrigerant. This is in contrast to those commercial devices based upon U.S. Patent 3,264,837, for which were ound to present substantial difficulty to typical service people in determining when they were properly charged. Those prior art devices are rather insensitive to excess charge, but undercharging results in a precipitous loss in performance. The primary difficulty is that the charging method is more dificult, and is unfamiliar to many service people.
Claims (4)
1. A heat pump system operable in either a heating mode or a cooling mode and of the type including a compressor, reversing valve, indoor and outdoor coils, a suction line accumulator including heat exchanger means therein, and refrigerant line means connecting the elements, and having the improvement comprising:
a single refrigerant expansion device in said system, and said device being an electrically operated expansion device located in a refrigerant line connected on one side of the expansion device to said outdoor coil and connected on the other side of said expansion device at least to said heat exchanger means to evaporate refrigerant in, and maintain a proper liquid level in, said accumulator;
means controlling said expansion device in a heating mode of operation of said system to obtain a degree of sub-cooling of refrigerant exiting said indoor coil which, coupled with further subcooling of refrigerant in its passage through said heat exchanger means, provides for flooded evaporator operation of said outdoor coil, and controlling said expansion device in a cooling mode of operation to pass refrigerant to said indoor coil at a rate to obtain a degree of superheat of refrigerant exiting said indoor coil.
a single refrigerant expansion device in said system, and said device being an electrically operated expansion device located in a refrigerant line connected on one side of the expansion device to said outdoor coil and connected on the other side of said expansion device at least to said heat exchanger means to evaporate refrigerant in, and maintain a proper liquid level in, said accumulator;
means controlling said expansion device in a heating mode of operation of said system to obtain a degree of sub-cooling of refrigerant exiting said indoor coil which, coupled with further subcooling of refrigerant in its passage through said heat exchanger means, provides for flooded evaporator operation of said outdoor coil, and controlling said expansion device in a cooling mode of operation to pass refrigerant to said indoor coil at a rate to obtain a degree of superheat of refrigerant exiting said indoor coil.
2. A heat pump system according to claim 1 wherein:
said refrigerant line connection on said other side of said expansion device is solely to said heat exchanger means.
said refrigerant line connection on said other side of said expansion device is solely to said heat exchanger means.
3. The heat pump system according to claim 1 wherein:
said refrigerant line connection on said other side of said expansion device is to said heat exchanger means through a first check valve permitting flow in the heating mode only from said heat exchanger to said expan-sion device, and is also to said indoor coil through a second check valve permitting flow in the cooling mode only from said expansion device to said indoor coil.
said refrigerant line connection on said other side of said expansion device is to said heat exchanger means through a first check valve permitting flow in the heating mode only from said heat exchanger to said expan-sion device, and is also to said indoor coil through a second check valve permitting flow in the cooling mode only from said expansion device to said indoor coil.
4. The method of operating a heat pump system operable in either a heating mode or a cooling mode and of the type including a compressor, reversing valve, indoor and outdoor coils, a suction line accumulator with heat exchanger means therein, refrigerant line means connecting the elements, and a single refrigerant expansion device in said system, said device being an electrically operated expansion device located in a refrigerant line connected on one side of said expansion device to said outdoor coil and connected on the other side of said expansion device at least to said heat exchanger means to evaporate refrigerant in, and maintain a proper liquid level in, said accumulator, comprising:
controlling the flow of refrigerant through said expansion device in the heating mode of said system to obtain a degree of subcooling of refrigerant exiting said indoor coil which coupled with further subcooling of refrigerant in its passage through said heat exchanger means, provides for flooded evaporated operation of said outdoor coil and controlling said expansion device in a cooling mode of operation to pass refrigerant to said indoor coil at a rate to obtain a degree of superheat of refrigerant exiting said indoor coil.
controlling the flow of refrigerant through said expansion device in the heating mode of said system to obtain a degree of subcooling of refrigerant exiting said indoor coil which coupled with further subcooling of refrigerant in its passage through said heat exchanger means, provides for flooded evaporated operation of said outdoor coil and controlling said expansion device in a cooling mode of operation to pass refrigerant to said indoor coil at a rate to obtain a degree of superheat of refrigerant exiting said indoor coil.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US46216283A | 1983-01-31 | 1983-01-31 | |
| US462,162 | 1983-01-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1198905A true CA1198905A (en) | 1986-01-07 |
Family
ID=23835380
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000437520A Expired CA1198905A (en) | 1983-01-31 | 1983-09-26 | Heat pump apparatus and method of operating the same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1198905A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105972717A (en) * | 2016-05-11 | 2016-09-28 | 珠海格力电器股份有限公司 | Multi-split air conditioning system and control method thereof |
-
1983
- 1983-09-26 CA CA000437520A patent/CA1198905A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105972717A (en) * | 2016-05-11 | 2016-09-28 | 珠海格力电器股份有限公司 | Multi-split air conditioning system and control method thereof |
| CN105972717B (en) * | 2016-05-11 | 2018-11-02 | 珠海格力电器股份有限公司 | Multi-split air conditioning system and control method thereof |
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| MKEX | Expiry |