Multi-Temperature Level Heat Pump Water Heaters (HPWH)

Abstract

A heat pump water heater system includes a water source providing water at a water source temperature to inlet water line(s). The system includes heat pump (“HP”) circuits that involve a heat exchanger, such as an upper HP circuit and a lower HP circuit or a main HP circuit and an auxiliary refrigerant line. The heat exchanger thermally connects the HP circuits and/or auxiliary refrigerant line to facilitate heat exchange between refrigerants flowing therethrough to allow the HP circuits to operate with different pressure differentials, improving efficiency. Heat is also be exchanged to water tanks thermally coupled to the inlet water line(s) and various HP circuit components such that outlet water lines can deliver water at a first temperature, a second temperature, or at an intermediate temperature between the two by mixing water from one or more tanks and/or inlet water lines.

What is claimed is: 
     
         1 . A heat pump water heater (“HPWH”) system comprising:
 at least one water source providing water at a water source temperature to a first inlet water line, a second inlet water line, and a third inlet water line; 
 an upper HP circuit comprising a condenser thermally coupled to a first water tank in fluid communication with the first inlet water line, an upper expansion device, a heat exchanger, an upper compressor, and a first refrigerant flowing therethrough; 
 a lower HP circuit, fluidly isolated from the upper HP circuit, comprising the heat exchanger thermally coupled to a second water tank in fluid communication with the second inlet water line, a lower expansion device, an evaporator, a lower compressor, and a second refrigerant flowing therethrough, wherein the heat exchanger thermally couples the fluidly isolated upper HP circuit to the lower HP circuit to facilitate heat exchange between the first refrigerant and the second refrigerant within the heat exchanger such that the heat exchange reduces a temperature lift needed by each of the upper HP circuit and the lower HP circuit thereby allowing the upper HP circuit and the lower HP circuit to operate at different pressure differentials; and 
 at least two outlet water lines configured to deliver at least one of (i) water at a first temperature level from the first water tank, (ii) water at a second temperature level from the second water tank, and (iii) water at an intermediate temperature between the first temperature level and the second temperature level by mixing water from at least two of the first water tank, the second water tank, and the third inlet water line. 
 
     
     
         2 . The HPWH system of  claim 1 , wherein the first water tank is configured to store water at the first temperature level, and wherein the first temperature level is a higher temperature level than both the second temperature level and the water source temperature. 
     
     
         3 . The HPWH system of  claim 2 , wherein the second water tank is configured to store water at the second temperature level, and wherein the second temperature level a lower temperature level than the first temperature level and a higher temperature than the water source temperature. 
     
     
         4 . The HPWH system of  claim 1 , further comprising a fan that is associated with the evaporator and is operable to move air over the evaporator. 
     
     
         5 . The HPWH system of  claim 1 , wherein the third water inlet line is thermally coupled to the evaporator. 
     
     
         6 . The HPWH system of  claim 1 , further comprising a third water tank in fluid communication with the third water inlet line, wherein the third water tank is thermally coupled to the evaporator and configured to store water at the water source temperature. 
     
     
         7 . The HPWH system of  claim 1 , wherein the first refrigerant and the second refrigerant are different refrigerants. 
     
     
         8 . The HPWH system of  claim 1 , wherein the first refrigerant and the second refrigerant are the same refrigerant. 
     
     
         9 . The HPWH system of  claim 1 , wherein at least one of the upper compressor and the lower compressor is one of a fixed speed compressor, two-stage compressor, tandemized compressor, or a variable speed compressor. 
     
     
         10 . The HPWH system of  claim 1 , wherein the upper compressor is a variable speed compressor that is configured to maintain the first refrigerant in the upper HP circuit at a first refrigerant temperature. 
     
     
         11 . The HPWH system of  claim 1 , wherein at least one of an upper pump of the upper HP circuit and a lower pump of the lower HP circuit is a variable speed water pump. 
     
     
         12 . A heat pump water heater (“HPWH”) system comprising:
 at least one water source providing water at a water source temperature to a first inlet water line, a second inlet water line, and a third inlet water line; 
 a main HP circuit comprising a condenser thermally coupled to a first water tank in fluid communication with the first inlet water line, a heat exchanger thermally coupled to a second water tank in fluid communication with the second inlet water line, an expansion device, an evaporator, a compressor, and a refrigerant flowing therethrough; 
 a vapor injection system extending along an auxiliary refrigerant line that extends between the condenser and the compressor and passes through the heat exchanger of the main HP circuit, the vapor injection system comprising a vapor injection device, wherein the heat exchanger thermally couples the main HP circuit to the vapor injection system extending along an auxiliary refrigerant line, the vapor injection system is configured to receive a portion of refrigerant diverted from the main HP circuit to the auxiliary refrigerant line as auxiliary flow while the remaining portion of refrigerant continues through the main HP circuit as a main flow thereby cooling the auxiliary flow more than the main flow to facilitate heat exchange between the main flow and the auxiliary flow within the heat exchanger; and 
 at least two outlet water lines configured to deliver at least one of (i) water at a first temperature level from the first water tank, (ii) water at a second temperature level from the second water tank, and (iii) water at an intermediate temperature between the first temperature level and the second temperature level by mixing water from at least two of the first water tank, the second water tank, and the third inlet water line. 
 
     
     
         13 . The HPWH system of  claim 12 , wherein the heat exchanger thermally connected the main flow and the auxiliary flow is configured to exchange heat between the main flow and the auxiliary flow to cool the main flow and evaporate the auxiliary flow, and wherein the evaporated auxiliary flow is directable into the compressor to improve the performance of the compressor as compared to not using the auxiliary flow and the vapor injection system. 
     
     
         14 . The HPWH system of  claim 12 , wherein the third inlet water line is thermally coupled to the evaporator  130 . 
     
     
         15 . The HPWH system of  claim 12 , further comprising a third water tank in fluid communication with the third inlet water line, the third water tank is thermally coupled to the evaporator and is configured to store water at the water source temperature. 
     
     
         16 . The HPWH system of  claim 12 , wherein the vapor injection device is one of (i) a single vapor injected compressor, (ii) a variable speed compressor, and (iii) two compressors connected in series. 
     
     
         17 . The HPWH system of  claim 12 , wherein the heat exchanger is one of a flash tank or an economizer heat exchanger. 
     
     
         18 . A method of heating water comprising:
 flowing water along a fist inlet water line from a water source to a first water tank that is thermally coupled to a condenser of a first HP circuit of a heat pump water heater;   flowing water from a second inlet water line from the water source to a second water tank that is thermally coupled to a heat exchanger of the first HP circuit and at least one of a second HP circuit or an auxiliary refrigerant line of the HPWH;   circulating a first refrigerant flow through the first HP circuit;   circulating a second refrigerant flow through at least one of the second HP circuit or the auxiliary refrigerant line;   exchanging heat between the first refrigerant flow and the second refrigerant flow via the heat exchanger to adjust the temperature of the water in one or more of the second water tank and the first water tank;   controlling a valve arrangement associated with the first water tank, the second water tank, and the water source to direct flow from at least one of the first water tank, the second water tank, or the water source towards a water outlet at a desired outlet temperature.   
     
     
         19 . The method of  claim 18 , wherein the first HP circuit includes a condenser, an upper expansion device, a heat exchanger, and an upper compressor, wherein the second HP circuit includes the heat exchanger, a lower expansion device, an evaporator, and a lower compressor, and wherein the heat exchanger thermally couples the first HP circuit to the second HP circuit. 
     
     
         20 . The method of  claim 18 , wherein the first HP circuit includes a condenser, a heat exchanger, an expansion device, an evaporator, and a compressor, and wherein the auxiliary refrigerant line extends between the condenser and the compressor of the first HP circuit and includes a vapor injection system positioned along the auxiliary refrigerant line between the condenser and the compressor. 
     
     
         21 . The method of  claim 20 , wherein the auxiliary refrigerant line, which is thermally coupled to the heat exchanger and the second water tank, is in fluid communication with the vapor injection system and the compressor, and is configured to receive the second refrigerant flow as an auxiliary flow such that (i) the auxiliary flow is cooled by the vapor injection system positioned along the auxiliary refrigerant line, (ii) the auxiliary flow is evaporated at the heat exchanger while exchanging heat with the first refrigerant flow, and (iii) the evaporated auxiliary flow is provided to the compressor to improve performance of the compressor as compared to not using the evaporated auxiliary flow. 
     
     
         22 . The method of  claim 18 , wherein providing water at a desired outlet temperature includes at least one of (i) providing water solely from the first water tank at a first temperature, (ii) providing water solely from the second water tank at a second temperature, lower than the first temperature, (iii) providing water solely from the water source at a water source temperature, lower than the second temperature (iv) providing water at a first intermediate temperature by mixing water from the water source and at least one of the first water tank or the second water tank (v) providing water a second intermediate temperature by mixing water from the first water tank and the second water tank.