Heat pump, systems, and methods for operating the same

Abstract

A heat pump, heat pump system, and method for operating the same is provided. The heat pump preferably operates using a supercritical working fluid, from which heat is extracted through a multi-stage heat exchanger. Heat is extracted from the working fluid to supply at least two heat sinks, such as a hot water system or space heating system of a building and a working fluid re-heater or economizer. The configuration of the multi-stage heat sinks facilitates the heat pump to serve as a drop-in replacement for traditional fossil-fuel powered boilers or the like and to provide heat at temperatures typically provided by these traditional systems, eliminating the need for excess or replacement infrastructure when retrofitting or upgrading existing installations. The working fluid is expanded twice to limit flashing of the working fluid during expansion and to facilitate recirculation of such gases without damaging components of the system.

What is claimed is: 
     
         1 . A heat pump circuit, comprising:
 a compressor for compressing a working fluid;   an expansion stage for expanding the working fluid;   a first heat exchanger arranged downstream of the compressor and upstream of the expansion stage, wherein the first heat exchanger is configured to exchange heat between the working fluid and a first heat sink;   a second heat exchanger arranged downstream of the first heat exchanger and upstream of the expansion stage, wherein the second heat exchanger is configured exchange heat with the working fluid after the working fluid exits an evaporation stage but before the working fluid re-enters the compressor; and   the evaporation stage arranged downstream of the expansion stage, wherein the evaporation stage is configured to exchange heat between the working fluid and ambient air.   
     
     
         2 . The heat pump according to  claim 1 , wherein the first heat sink is a hot water system of a building. 
     
     
         3 . The heat pump according to  claim 1 , wherein the first heat sink is a space heating system of the building. 
     
     
         4 . The heat pump according to  claim 1 , wherein the expansion stage comprises a first expansion valve, a second expansion valve, and a liquid receiver therebetween. 
     
     
         5 . The heat pump according to the  claim 4 , further comprising a bypass line and a pressure valve via which gaseous subcritical working fluid may be vented from the liquid receiver to a suction line of the compressor. 
     
     
         6 . The heat pump according to  claim 4 , wherein the first and second expansion valves are independently controlled. 
     
     
         7 . The heat pump according to  claim 1 , wherein the evaporation stage comprises a first evaporator and a fan which is configured to force the ambient air over the at least one evaporator. 
     
     
         8 . The heat pump according to  claim 1 , further comprising an accumulator arranged downstream of the evaporation stage for holding the working fluid in a gaseous form. 
     
     
         9 . The heat pump according to  claim 1 , further comprising an oil system for providing a lubricant to the compressor. 
     
     
         10 . The heat pump according to  claim 9 , wherein the oil system comprises an oil separator arranged downstream of the compressor and upstream of the first heat exchanger. 
     
     
         11 . The heat pump according to  claim 10 , wherein the oil system further comprises an oil reservoir, and
 wherein the lubricant passes from the oil separator to the oil reservoir via an oil valve which is configured to open when lubricant is detected in the oil separator.   
     
     
         12 . The heat pump according to  claim 11 , wherein a pressure in the oil reservoir is maintained, via control of an oil pressure valve that is in fluidic connection with the oil reservoir, to be greater than an inlet pressure of the compressor. 
     
     
         13 . The heat pump according to  claim 1 , further comprising at least a third heat exchanger arranged downstream of the compressor and upstream of the expansion stage. 
     
     
         14 . A heat pump system comprising:
 the heat pump according to  claim 1 ; and   a controller, the controller comprising at least one processor,   wherein the controller is configured to adjust a speed of the compressor and a state of the expansion stage to set an operating point of the heat pump.   
     
     
         15 . The heat pump system according to  claim 14 , further comprising a hot coolant loop for circulating an intermediate coolant,
 wherein the hot coolant loop is fluidically separate from a transcritical loop which circulates the working fluid, and   wherein the hot coolant loop exchanges heat between the first heat exchanger and the first heat sink.   
     
     
         16 . The heat pump according to  claim 1 , wherein the working fluid is carbon dioxide. 
     
     
         17 . The heat pump system according to  claim 16 , wherein the intermediate coolant is a water-glycol mixture. 
     
     
         18 . A method for operating a heat pump, comprising the steps of:
 compressing a working fluid in a compressor;   exchanging heat between the working fluid and a first heat sink via a first heat exchanger, the first heat exchanger arranged downstream of the compressor and upstream of an expansion stage;   exchanging heat between the working fluid in a supercritical state and the working fluid in a subcritical state via a second heat exchanger, the second heat exchanger arranged downstream of the first heat exchanger and upstream of the expansion stage;   expanding the working fluid in the expansion stage; and   evaporating the working fluid in an evaporation stage by exchanging heat between the working fluid and ambient air.