Expansion system and heat pump incorporating the same

Abstract

A heat pump includes a refrigeration circuit. The heat pump includes a compressor configured to move refrigerant through the refrigeration circuit. The heat pump includes an expansion system fluidly coupled with the refrigeration circuit via a first valve. The heat pump includes control circuitry configured to control the first valve to selectively provide fluid communication of the refrigerant between the refrigeration circuit and the expansion system.

What is claimed is: 
     
         1 . A heat pump, comprising:
 a refrigeration circuit;   a compressor configured to move refrigerant through the refrigeration circuit;   an expansion system fluidly coupled with the refrigeration circuit via a first valve; and   control circuitry configured to control the first valve to selectively provide fluid communication of the refrigerant between the refrigeration circuit and the expansion system.   
     
     
         2 . The heat pump of  claim 1 , wherein the expansion system includes an expansion tank configured to store the refrigerant. 
     
     
         3 . The heat pump of  claim 2 , wherein the first valve fluidly interposes the refrigeration circuit and the expansion tank. 
     
     
         4 . The heat pump of  claim 1 , further comprising:
 a sensor configured to detect a condition of the refrigeration circuit, wherein the control circuitry is configured to control the first valve in response to the condition of the refrigeration circuit.   
     
     
         5 . The heat pump of  claim 4 , wherein the condition includes a pressure of the refrigeration circuit. 
     
     
         6 . The heat pump of  claim 5 , wherein the control circuitry is configured to communicate a signal to close the first valve when the pressure is below a pressure threshold. 
     
     
         7 . The heat pump of  claim 6 , wherein the control circuitry is configured to control the first valve to open when the pressure is at or above the pressure threshold. 
     
     
         8 . The heat pump of  claim 5 , further comprising:
 a second valve in series with the first valve via an interposing conduit in fluid communication with the refrigeration circuit.   
     
     
         9 . The heat pump of  claim 8 , wherein the second valve is normally open. 
     
     
         10 . The heat pump of  claim 9 , wherein the control circuitry is configured to:
 control the first valve and the second valve based on the pressure of the refrigeration circuit.   
     
     
         11 . The heat pump of  claim 8 , wherein the first valve is fluidly coupled with the refrigeration circuit upstream of the compressor. 
     
     
         12 . The heat pump of  claim 1 , further comprising:
 a gas cooler heat exchanger for transferring heat from the refrigerant to a water supply.   
     
     
         13 . The heat pump of  claim 12 , wherein the refrigerant is carbon dioxide. 
     
     
         14 . The heat pump of  claim 1 , wherein the first valve is normally open. 
     
     
         15 . A method for operating a heat pump having an expansion system, comprising:
 closing a suction valve upstream of the expansion system;   operating a compressor of a refrigeration circuit to draw refrigerant from the expansion system through a control valve;   opening the suction valve based on a pressure of the refrigeration circuit; and   closing fluid communication between the refrigeration circuit and the expansion system.   
     
     
         16 . The method of  claim 15 , wherein opening the suction valve is based further on the pressure of the refrigeration circuit being below a pressure threshold. 
     
     
         17 . The method of  claim 15 , further comprising:
 closing an expansion valve downstream of the compressor when the suction valve is closed.   
     
     
         18 . The method of  claim 15 , further comprising:
 in response to the pressure being below a pressure threshold, closing the control valve, deactivating the compressor, and opening the suction valve.   
     
     
         19 . A heat pump water heater, comprising:
 a refrigeration circuit;   carbon-dioxide refrigerant disposed in the refrigeration circuit;   an expansion tank configured to store the carbon-dioxide refrigerant in response to pressure of the refrigeration circuit exceeding a pressure threshold; and   a normally-open expansion circuit fluidly interposing the refrigeration circuit and the expansion tank.   
     
     
         20 . The heat pump water heater of  claim 19 , further comprising:
 a compressor configured to pressurize the refrigerant carbon-dioxide, wherein the normally-open expansion circuit is coupled with the refrigeration circuit upstream of the compressor.