Systems and methods for heat pump systems

Abstract

A heat pump heating, ventilation, and air conditioning (heat pump HVAC) system is operable to use a refrigerant to heat or cool an indoor space with a refrigerant circuit performing a reversible vapor compression cycle between an outdoor heat exchanger and an indoor heat exchanger. The heat pump HVAC system includes an ejector in fluid communication with the refrigerant circuit. The refrigerant circuit includes a first flow of refrigerant upstream from the outdoor heat exchanger and a second flow of refrigerant downstream from the outdoor heat exchanger; and the ejector is configurable to combine the first flow and the second flow into a combined flow, at least a portion of which is returned to the compressor.

What is claimed is: 
     
         1 . A heat pump heating, ventilation, and air conditioning (heat pump HVAC) system operable to use a refrigerant to heat or cool an indoor space and comprising:
 a compressor, an outdoor heat exchanger, an indoor heat exchanger, a first expansion device, and a four-way valve connected together as a refrigerant circuit, the four-way valve configurable to direct refrigerant flow through the first expansion device in a first direction in a cooling mode and in a second direction, opposite the first direction, in a heating mode;   an ejector in fluid communication with the refrigerant circuit; and   wherein when the heat pump HVAC system is in the heating mode:
 the refrigerant circuit comprises a first flow of refrigerant upstream from the outdoor heat exchanger and a second flow of refrigerant downstream from the outdoor heat exchanger; and 
 the ejector is configurable to combine the first flow and the second flow into a combined flow, at least a portion of which is returned to the compressor. 
   
     
     
         2 . The heat pump HVAC system of  claim 1 , wherein the first flow includes lower enthalpy than the second flow and the combined flow includes an enthalpy between the first flow and the second flow. 
     
     
         3 . The heat pump HVAC system of  claim 1 , wherein the refrigeration circuit further comprises:
 a separation tank configured to divide the combined flow into a liquid phase and a gas phase in the heating mode; and   a second expansion device configured to expand the liquid phase of the combined flow.   
     
     
         4 . The heat pump HVAC system of  claim 1 , wherein the refrigeration circuit further comprises an offset heat exchanger that receives the combined flow of refrigerant from the ejector when the refrigerant circuit is in the heating mode. 
     
     
         5 . The heat pump HVAC system of  claim 4 , wherein the refrigeration circuit further comprises a three-way valve configurable in the cooling mode to bypass the ejector by flowing the refrigerant between the offset heat exchanger and the outdoor heat exchanger. 
     
     
         6 . The heat pump HVAC system of  claim 4 , further comprising an outdoor fan that operates to produce an outdoor airflow through the offset heat exchanger and the outdoor heat exchanger. 
     
     
         7 . The heat pump HVAC system of  claim 6 , wherein the offset heat exchanger is in series with and upstream from the outdoor heat exchanger relative to the outdoor airflow, such that moisture is removed from the outdoor airflow by the offset heat exchanger and decrease the likelihood of frost forming on the outdoor heat exchanger. 
     
     
         8 . A method of operating a heat pump heating, ventilation, and air conditioning (heat pump HVAC) system operable to use a refrigerant to heat an indoor space in a heating mode or cool an indoor space in a cooling mode, the method comprising:
 compressing the refrigerant with a compressor;   flowing the refrigerant in a refrigerant circuit including an indoor heat exchanger, a first expansion device, and an outdoor heat exchanger, wherein the refrigerant flows through the first expansion device in a first direction in the cooling mode and in a second direction, opposite the first direction, in the heating mode;   flowing a first flow of refrigerant upstream from the outdoor heat exchanger in the heating mode;   flowing a second flow of refrigerant downstream from the outdoor heat exchanger in the heating mode;   combining the first flow and the second flow into a combined flow within an ejector in the heating mode; and   flowing at least a portion of the combined flow to the compressor in the heating mode.   
     
     
         9 . The method of  claim 8 , wherein combining of the first flow and the second flow results in the combined flow with an enthalpy between the first flow and the second flow. 
     
     
         10 . The method of  claim 8 , further comprising:
 separating a liquid phase of the refrigerant from the first flow of the refrigerant in a separation tank in the heating mode; and   flowing the liquid phase of the refrigerant through a second expansion device to expand the first flow in the heating mode.   
     
     
         11 . The method of  claim 8 , further comprising flowing the combined flow from the ejector through an offset heat exchanger in the heating mode. 
     
     
         12 . The method of  claim 11 , further comprising, flowing the refrigerant between the offset heat exchanger and the outdoor heat exchanger via a three-way valve to bypass flowing of refrigerant through the ejector in the cooling mode. 
     
     
         13 . The method of  claim 11 , further comprising operating an outdoor fan to flow an outdoor airflow through the offset heat exchanger and the outdoor heat exchanger. 
     
     
         14 . The method of  claim 11 , further comprising flowing the combined flow from the offset heat exchanger to the compressor in the heating mode and maintaining a first pressure of the refrigerant exiting the offset heat exchanger using the ejector, wherein a second pressure of the refrigerant exiting the outdoor heat exchanger is lower than the first pressure. 
     
     
         15 . A heat pump heating, ventilation, and air conditioning (heat pump HVAC) system operable to use a refrigerant to heat or cool an indoor space and comprising:
 a compressor, an outdoor heat exchanger, an indoor heat exchanger, a first expansion device, and a four-way valve connected together as a refrigerant circuit, the four-way valve configurable to direct the refrigerant flow through the first expansion device in a first direction in a cooling mode and in a second direction, opposite the first direction, in a heating mode;   an ejector in fluid communication with the refrigerant circuit; and   an internal heat exchanger thermally coupling a first flow of refrigerant upstream from the outdoor heat exchanger and a second flow of refrigerant downstream from the outdoor heat exchanger when in the heating mode.   
     
     
         16 . The heat pump HVAC system of  claim 15 , further comprising an offset heat exchanger configured to receive the refrigerant from the ejector in the heating mode. 
     
     
         17 . The heat pump HVAC system of  claim 16 , wherein the offset heat exchanger is configured to receive the refrigerant flow from the four-way valve in the cooling mode. 
     
     
         18 . The heat pump HVAC system of  claim 15 , wherein the refrigeration circuit further comprises a vapor line expansion device connected between the first flow of refrigerant and the compressor via a vapor injection line extending though the internal heat exchanger, wherein the internal heat exchanger is further configured to transfer heat between at least one of the first flow or the second flow and the vapor injection line in at least one of the heating or the cooling modes. 
     
     
         19 . The heat pump HVAC system of  claim 18 , wherein the internal heat exchanger is configured to transfer heat between both the first flow and the second flow and the vapor injection line. 
     
     
         20 . The heat pump HVAC system of  claim 18 , wherein the refrigeration circuit further comprises:
 a separation tank configured to divide the combined flow into a liquid phase and a gas phase in the heating mode; and   a second expansion device configured to expand the liquid phase of the combined flow.