Multi-circuit climate control systems

Abstract

An embodiment of a heat pump for conditioning an interior space includes a thermal fluid circuit. In addition, the heat pump includes an outdoor unit including a refrigerant circuit, a first heat exchanger to exchange heat between a refrigerant of the refrigerant circuit and a thermal fluid of the thermal fluid circuit, and a second heat exchanger to exchange heat between the refrigerant and an outdoor environment. The second heat exchanger having a larger refrigerant volume than the first heat exchanger. In addition, the outdoor unit includes a charge compensator to receive excess refrigerant therein when the heat pump operates in a heating mode and to discharge the excess refrigerant to the refrigerant circuit when the heat pump operates in a cooling mode. The heat pump includes an air handler having a third heat exchanger to exchange heat between the thermal fluid circuit and an airflow for the interior space.

What is claimed is: 
     
         1 . A heat pump for conditioning an interior space, the heat pump comprising:
 a thermal fluid circuit that is configured to circulate a thermal fluid;   an outdoor unit comprising:
 a refrigerant circuit that is configured to circulate a refrigerant to cool the thermal fluid during a cooling mode of the heat pump and to heat the thermal fluid during a heating mode of the heat pump; 
 a first heat exchanger positioned along the refrigerant circuit that is configured to exchange heat between the refrigerant and the thermal fluid; 
 a second heat exchanger positioned along the refrigerant circuit that is configured to exchange heat between the refrigerant of the refrigerant circuit and an outdoor environment surrounding the outdoor unit, wherein a refrigerant volume of the second heat exchanger is larger than a refrigerant volume of the first heat exchanger; and 
 a charge compensator positioned along the refrigerant circuit that is configured to receive excess refrigerant therein when the heat pump operates in the heating mode and configured to discharge the excess refrigerant into the refrigerant circuit when the heat pump operates in the cooling mode; and 
   an air handler having a third heat exchanger that is configured to exchange heat between the thermal fluid circuit and an airflow for the interior space.   
     
     
         2 . The heat pump of  claim 1 , wherein the refrigerant volume of the second heat exchanger is two to ten times greater than the refrigerant volume of the first heat exchanger. 
     
     
         3 . The heat pump of  claim 2 , wherein the refrigerant is a flammable refrigerant. 
     
     
         4 . The heat pump of  claim 3 , wherein the refrigerant comprises propane. 
     
     
         5 . The heat pump of  claim 2 , wherein the thermal fluid comprises an aqueous fluid. 
     
     
         6 . The heat pump of  claim 5 , further comprising a fourth heat exchanger positioned along the refrigerant circuit that is configured to exchange heat between the refrigerant and a hot water supply for the interior space. 
     
     
         7 . The heat pump of  claim 1 , wherein the refrigerant circuit comprises a vapor compression circuit in which the refrigerant is configured to undergo phase change during circulation, and wherein the outdoor unit further comprises:
 a compressor that is configured to pressurize the refrigerant along the refrigerant circuit; and   a switchover valve that is actuatable to selectively flow the refrigerant in a first direction along the refrigerant circuit during the cooling mode, and to flow the refrigerant in a second direction along the refrigerant circuit during the heating mode.   
     
     
         8 . The heat pump of  claim 7 , further comprising a pump positioned along the thermal fluid circuit that is configured to pressurize the thermal fluid. 
     
     
         9 . The heat pump of  claim 7 , wherein the charge compensator is positioned along the refrigerant circuit such that:
 during the heating mode, the charge compensator is connected in series between the first heat exchanger and the second heat exchanger; and   during the cooling mode, the charge compensator is connected in parallel with the second heat exchanger, upstream of the first heat exchanger.   
     
     
         10 . A method of operating a heat pump to condition an interior space, the method comprising:
 (a) circulating a refrigerant along a refrigerant circuit defined in an outdoor unit of the heat pump in a first direction to transfer heat from a thermal fluid flowing along a thermal fluid circuit to the refrigerant via a first heat exchanger and to transfer heat from the refrigerant to an ambient environment via a second heat exchanger, wherein the refrigerant circuit is a vapor compression circuit, wherein the refrigerant is a flammable refrigerant, and wherein the second heat exchanger has a larger refrigerant volume than the first heat exchanger;   (b) circulating the refrigerant along the refrigerant circuit in a second direction to transfer heat from the ambient environment to the refrigerant via the second heat exchanger and to transfer heat from the refrigerant to the thermal fluid via the first heat exchanger;   (c) circulating the thermal fluid substantially in a liquid phase between the first heat exchanger and a third heat exchanger during (a) and (b) to transfer heat between the thermal fluid and the interior space;   (d) collecting excess refrigerant from the refrigerant circuit in a charge compensator in fluid communication with the refrigerant circuit during (b); and   (e) discharging the excess refrigerant from the charge compensator to the refrigerant circuit during (a).   
     
     
         11 . The method of  claim 10 , further comprising:
 (f) transferring heat from the refrigerant to a hot water supply for the interior space by use of a fourth heat exchanger that is thermally coupled to the refrigerant circuit.   
     
     
         12 . The method of  claim 10 , wherein (d) comprises flowing the refrigerant from the first heat exchanger, through the charge compensator, and then through the second heat exchanger to collect the excess refrigerant in the charge compensator. 
     
     
         13 . The method of  claim 12 , wherein (e) further comprises:
 (e1) merging refrigerant flowing out of the charge compensator with refrigerant discharged from the second heat exchanger to form a combined refrigerant flow; and   (e2) expanding the combined refrigerant flow upstream of the first heat exchanger.   
     
     
         14 . A heat pump for conditioning an interior space, the heat pump comprising:
 a thermal fluid circuit including a pump that is configured to circulate an aqueous fluid such that the aqueous fluid is maintained in a substantially liquid phase;   an outdoor unit comprising:
 a vapor compression circuit contained in the outdoor unit that is configured to circulate a refrigerant, wherein the refrigerant comprises a flammable refrigerant; 
 a compressor positioned along the vapor compression circuit that is configured to compress the refrigerant; 
 a first heat exchanger positioned along the vapor compression circuit and the thermal fluid circuit that is configured to exchange heat between the refrigerant and the aqueous fluid; 
 a switchover valve that is configured to selectively circulate the refrigerant in a first direction to cool the aqueous fluid via the first heat exchanger and to circulate the refrigerant in a second direction to heat the aqueous fluid via the first heat exchanger; 
 a second heat exchanger positioned along the vapor compression circuit that is configured to exchange heat between the refrigerant and an outdoor environment surrounding the outdoor unit, wherein a refrigerant volume of the second heat exchanger is larger than a refrigerant volume of the first heat exchanger; and 
 a charge compensator positioned along the vapor compression circuit and configured to remove a volume of refrigerant from the vapor compression circuit when the refrigerant flows in the second direction and to permit a full volume of refrigerant in the vapor compression circuit when the refrigerant flows in the first direction; and 
   an air handler having a third heat exchanger that is positioned along the thermal fluid circuit and configured to exchange heat between the thermal fluid circuit and an airflow for the interior space.   
     
     
         15 . The heat pump of  claim 14 , wherein the charge compensator is positioned along the vapor compression circuit such that when the refrigerant circulates in the second direction, the charge compensator is connected in series between the first heat exchanger and the second heat exchanger along the vapor compression circuit. 
     
     
         16 . The heat pump of  claim 15 , wherein the charge compensator is positioned along the vapor compression circuit such when the refrigerant circulates in the first direction, the charge compensator is connected in parallel with the second heat exchanger, upstream of the first heat exchanger along the vapor compression circuit. 
     
     
         17 . The heat pump of  claim 16 , further comprising:
 a first expansion device and a second expansion device positioned along a liquid line of the vapor compression circuit that extends between the first heat exchanger and the second heat exchanger, wherein the first expansion device is positioned along the liquid line between the second expansion device and the first heat exchanger; and   a bypass line that extends from a first point along the liquid line that is between the first expansion device and the first heat exchanger to a second point along the liquid line that is between the first expansion device and the second expansion device,   wherein the charge compensator is positioned along the bypass line.   
     
     
         18 . The heat pump of  claim 17 , further comprising:
 a first check valve positioned along the liquid line between the second point and the first expansion device, the first check valve being configured to allow refrigerant flow along the liquid line from the second expansion device to the first expansion device and to prevent refrigerant flow along the liquid line from the first expansion device to the second expansion device; and   a second check valve positioned along the bypass line between the charge compensator and the second point, the second check valve being configured to allow refrigerant flow along the bypass line from the charge compensator to the second point and to prevent refrigerant flow along the bypass line from the second point to the charge compensator.   
     
     
         19 . The heat pump of  claim 18 , wherein the refrigerant volume of the second heat exchanger is two to ten times greater than the refrigerant volume of the first heat exchanger. 
     
     
         20 . The heat pump of  claim 19 , further comprising a fourth heat exchanger positioned along the vapor compression circuit that is configured to exchange heat between the refrigerant and a hot water supply for the interior space.