Low ambient temperature heat pump water heater systems, heat exchangers, and methods thereto

Abstract

Systems and methods for a heat pump water heater can include a heat pump water heater system having an evaporator, a condenser, a vapor injection line, a compressor, and a multi-fluid heat exchanger. The vapor injection line can include an expansion valve to transition refrigerant received from the condenser at a first pressure to a second pressure. The compressor can be configured to circulate refrigerant through the condenser, the multi-fluid heat exchanger, the vapor injection line, and the evaporator. The multi-fluid heat exchanger can be configured to receive refrigerant at a first pressure from the condenser, refrigerant at a second pressure from the vapor injection line, and water. The multi-fluid heat exchanger can further facilitate heat transfer between the refrigerants at the first and second pressures and the water to preheat the water before the water is passed through the condenser.

What is claimed is: 
     
         1 . A heat pump water heater system comprising:
 a condenser configured to provide a first refrigerant at a first pressure;   a vapor injection path comprising an expansion valve and configured to receive the first refrigerant at the first pressure from the condenser, the expansion valve configured to transition the first refrigerant at the first pressure to a second refrigerant at a second pressure; and   
       a three-fluid economizer comprising: 
       a first passage configured to allow the first refrigerant at the first pressure to pass through the economizer; 
       a second passage configured to allow the second refrigerant at the second pressure to pass through the economizer; and 
       a third passage configured to allow water to pass through the economizer, wherein the three-fluid economizer is configured to facilitate heat exchange between the first refrigerant, the second refrigerant, and the water. 
     
     
         2 . The heat pump water heater system of  claim 1 , wherein the condenser is a refrigerant-to-water condenser. 
     
     
         3 . The heat pump water heater system of  claim 1 , wherein, when the refrigerant at the second pressure passes through the economizer, the refrigerant at the second pressure is transitioned into a superheated vapor by receiving heat from the refrigerant at the first pressure. 
     
     
         4 . The heat pump water heater system of  claim 1 , wherein the water is configured to first pass through the economizer and then through the condenser, the economizer being configured to preheat the water. 
     
     
         5 . The heat pump water heater system of  claim 1 , wherein a first portion of water that is output from the economizer is recirculated through the condenser. 
     
     
         6 . The heat pump water heater system of  claim 5 , wherein a second portion of the water that is output from the economizer bypasses the condenser. 
     
     
         7 . The heat pump water heater system of  claim 1 , wherein the economizer is configured to pass the first refrigerant and the second refrigerant in counterflow directions therethrough. 
     
     
         8 . The heat pump water heater system of  claim 1 , wherein the first pressure is greater than the second pressure. 
     
     
         9 . The heat pump water heater system of  claim 1 , wherein the refrigerant at the first pressure heats both the refrigerant at the second pressure and the water. 
     
     
         10 . The heat pump water heater system of  claim 1 , wherein the first passage is a first microchannel tube and the second passage is a second microchannel tube. 
     
     
         11 . A heat pump water heater system comprising:
 a condenser configured to provide a first refrigerant at a first pressure, wherein the condenser is a refrigerant-to-water condenser;   a vapor injection path comprising an expansion valve and configured to receive the first refrigerant at the first pressure from the condenser, the expansion valve configured to transition the first refrigerant at the first pressure to a second refrigerant at a second pressure; and   
       a three-fluid economizer comprising: 
       a first passage configured to allow the first refrigerant at the first pressure to pass through the economizer; 
       a second passage configured to allow the second refrigerant at the second pressure to pass through the economizer; and 
       a third passage configured to allow water to pass through the economizer. 
     
     
         12 . The heat pump water heater system of  claim 11 , wherein the three-fluid economizer is configured to facilitate heat exchange between the first refrigerant, the second refrigerant, and the water. 
     
     
         13 . The heat pump water heater system of  claim 11 , wherein, when the refrigerant at the second pressure passes through the economizer, the refrigerant at the second pressure is transitioned into a superheated vapor by receiving heat from the refrigerant at the first pressure. 
     
     
         14 . The heat pump water heater system of  claim 11 , wherein the water is configured to first pass through the economizer and then through the condenser, the economizer being configured to preheat the water. 
     
     
         15 . The heat pump water heater system of  claim 11 , wherein a first portion of water that is output from the economizer is recirculated through the condenser. 
     
     
         16 . The heat pump water heater system of  claim 15 , wherein a second portion of the water that is output from the economizer bypasses the condenser. 
     
     
         17 . The heat pump water heater system of  claim 11 , wherein the economizer is configured to pass the first refrigerant and the second refrigerant in counterflow directions therethrough. 
     
     
         18 . The heat pump water heater system of  claim 11 , wherein the first pressure is greater than the second pressure. 
     
     
         19 . The heat pump water heater system of  claim 11 , wherein the refrigerant at the first pressure heats both the refrigerant at the second pressure and the water. 
     
     
         20 . The heat pump water heater system of  claim 11 , wherein the first passage is a first microchannel tube and the second passage is a second microchannel tube.