Heat pump with microchannel heat exchangers as both outdoor and reheat exchangers

Abstract

A heat pump refrigerant system has a compressor for delivering a compressed refrigerant to a reversing refrigerant flow control device. The reversing refrigerant flow control device selectively delivers refrigerant to an outdoor heat exchanger in a cooling mode of operation, and to an indoor heat exchanger in a heating mode of operation. Refrigerant from an outdoor heat exchanger passes through an expansion device to an indoor heat exchanger in a cooling mode, and from the indoor heat exchanger through an expansion device and to the outdoor heat exchanger in a heating mode. A reheat circuit includes a reheat heat exchanger positioned to be in the path of air delivered over the indoor heat exchanger and into an environment to be conditioned. The reheat heat exchanger and outdoor heat exchanger both are provided by microchannel heat exchangers. The reheat circuit is utilized to minimize or prevent refrigerant charge migration while operating at a wide spectrum of environmental conditions or switching between modes of operation.

1 . A heat pump refrigerant system comprising:
 a compressor for delivering a compressed refrigerant to a reversing refrigerant flow control device, said reversing refrigerant flow control device selectively delivering the refrigerant to an outdoor heat exchanger in a cooling mode, and to an indoor heat exchanger in a heating mode, refrigerant from said outdoor heat exchanger passing through an expansion device and to said indoor heat exchanger in a cooling mode, and from said indoor heat exchanger through an expansion device and to said outdoor heat exchanger in a heating mode;   a reheat circuit including a reheat heat exchanger positioned to be in the path of air delivered over said indoor heat exchanger and into an environment to be conditioned; and   said reheat heat exchanger and said outdoor heat exchanger both being provided by microchannel heat exchangers.   
     
     
         2 . The heat pump refrigerant system as set forth in  claim 1 , wherein said reheat circuit is utilized to minimize or prevent refrigerant charge migration. 
     
     
         3 . The heat pump refrigerant system as set forth in  claim 1 , wherein said reheat circuit taps refrigerant from a location intermediate said outdoor heat exchanger and said expansion device. 
     
     
         4 . The heat pump refrigerant system as set forth in  claim 1 , wherein said reheat circuit taps refrigerant from a location intermediate said compressor and said outdoor heat exchanger. 
     
     
         5 . The heat pump refrigerant system as set forth in  claim 1 , wherein said reheat circuit includes a refrigerant flow control device controlled with at least one of modulation and pulsation techniques to vary the amount of refrigerant that is tapped into the reheat circuit. 
     
     
         6 . The heat pump refrigerant system as set forth in  claim 1 , wherein said heat pump refrigerant system is a multi-circuit refrigerant system with a plurality of said compressors delivering refrigerant through a plurality of said reversing refrigerant flow control devices. 
     
     
         7 . The heat pump refrigerant system as set forth in  claim 6 , wherein the amount of refrigerant tapped into the reheat circuit is selectively controlled at part-load and full-load conditions to minimize or prevent refrigerant charge migration. 
     
     
         8 . The heat pump refrigerant system as set forth in  claim 1 , wherein said microchannel heat exchangers include a plurality of tube banks that route the refrigerant in parallel paths and in opposed directions. 
     
     
         9 . The heat pump refrigerant system as set forth in  claim 1 , wherein each of said microchannel heat exchangers include tubes with a plurality of separate refrigerant channels which extend parallel to each other and have a hydraulic diameter of less than 5 mm, and preferably less than 3 mm. 
     
     
         10 . The heat pump refrigerant system as set forth in  claim 1 , wherein a bypass is provided around said outdoor heat exchanger to selectively bypass at least a portion of refrigerant around said outdoor heat exchanger. 
     
     
         11 . The heat pump refrigerant system as set forth in  claim 1 , wherein said indoor heat exchanger is also a microchannel heat exchanger. 
     
     
         12 . A method of operating a heat pump refrigerant system comprising the steps of:
 (a) delivering a compressed refrigerant to a reversing refrigerant flow control device, said reversing refrigerant flow control device selectively delivering the refrigerant to an outdoor heat exchanger in a cooling mode, and to an indoor heat exchanger in a heating mode, refrigerant from said outdoor heat exchanger passing through an expansion device and to said indoor heat exchanger in a cooling mode, and from said indoor heat exchanger through an expansion device and to said outdoor heat exchanger in a heating mode;   (b) a reheat circuit including a reheat heat exchanger positioned to be in the path of air delivered over said indoor heat exchanger and into an environment to be conditioned;   (c) said reheat heat exchanger and said outdoor heat exchanger both being provided by microchannel heat exchangers;   (d) communicating refrigerant to said reheat heat exchanger when the heat pump is a heating mode.   
     
     
         13 . The method of operating a heat pump refrigerant system as set forth in  claim 12 , wherein said reheat circuit is utilized to minimize or prevent refrigerant charge migration. 
     
     
         14 . The method as set forth in  claim 12 , including the step of bypassing refrigerant around said outdoor heat exchanger when the heating mode is actuated. 
     
     
         15 . The method as set forth in  claim 12 , wherein said heat pump refrigerant system is a multi-circuit system and the amount of refrigerant tapped into the reheat circuit is selectively controlled at part-load and full-load conditions to minimize or prevent refrigerant charge migration.