Heat exchanger, and method for transferring heat

Abstract

A heat exchanger is provided to efficiently transfer heat between air and a flow of refrigerant in a reversing air-sourced heat pump system. When the system is operating in heat pump mode, a flow of air is directed through the heat exchanger and is heated by the refrigerant. A portion of the flow of air is prevented from being heated by the refrigerant in a first section of the heat exchanger, and is used to sub-cool the refrigerant in another section of the heat exchanger after the remaining air has been heated by the refrigerant. The same heat exchanger can be used to cool a flow of air using expanded refrigerant when the system is operating in an air conditioning (cooling) mode.

We claim: 
     
         1 . A heat exchanger to transfer heat between a refrigerant and air, comprising:
 a refrigerant flow path extending between a first refrigerant port and a second refrigerant port;   a first section, a second section, and a third section of the heat exchanger arranged sequentially along the refrigerant flow path, the first section arranged between the first refrigerant port and the second section, the third section arranged between the second refrigerant port and the second section; and   first and second parallel arranged air flow paths extending through the heat exchanger, the first airflow path extending sequentially through the first section and the third section and bypassing the second section, the second airflow path extending through the second section and bypassing the first section and the third section, wherein heat transfer between the refrigerant and air is substantially inhibited in the first section of the heat exchanger,   wherein the second refrigerant port is operatively coupled to an expansion device to receive cooled refrigerant therefrom when the heat exchanger is operated in an air conditioning mode.   
     
     
         2 . The heat exchanger of  claim 1 , wherein the refrigerant flow path comprises at least two passes through the second section, refrigerant flowing through said at least two passes in a countercurrent flow heat transfer relationship to the air when the heat exchanger is operated in the air conditioning mode. 
     
     
         3 . The heat exchanger of  claim 1  further comprising a plurality of extended surface features arranged along the first and second air flow paths to promote heat transfer between the air and the refrigerant. 
     
     
         4 . The heat exchanger of  claim 3 , wherein the spacing density of the extended surface features in the first section is substantially lower than the spacing density of the extended surface features in the second and third sections. 
     
     
         5 . The heat exchanger of  claim 3 , wherein the first section is substantially absent of said extended surface features. 
     
     
         6 . The heat exchanger of  claim 1 , further comprising a plurality of flattened tubes to define the refrigerant flow path in one or more of the first, second, and third sections of the heat exchanger. 
     
     
         7 . The heat exchanger of  claim 7 , wherein the refrigerant flow path comprises at least two passes through the second section, the plurality of flattened tubes includes a first plurality of flattened tubes defining one of the at least two passes, and the plurality of flattened tubes includes a second plurality of flattened tubes defining another one of the at least two passes. 
     
     
         8 . The heat exchanger of  claim 7 , wherein the first plurality of flattened tubes further defines the refrigerant flow path in the third section of the heat exchanger. 
     
     
         9 . The heat exchanger of  claim 8 , wherein the second plurality of flattened tubes further defines the refrigerant flow path in the first section of the heat exchanger. 
     
     
         10 . A method of removing heat from refrigerant, comprising:
 separating a flow of air into a first portion and a second portion;   transferring a first quantity of heat between the refrigerant and the first portion of the air while simultaneously inhibiting transfer of heat between the refrigerant and the second portion of the air;   transferring a second quantity of heat between the refrigerant and the first portion of the air after the first quantity of heat has been transferred to the first portion of the air;   transferring a third quantity of heat between the refrigerant and the second portion of the air after the first and second quantities of heat have been transferred; and   recombining the first and second portions to provide an air flow with a changed temperature.   
     
     
         11 . The method of  claim 10 , wherein transferring the first and second quantities of heat desuperheats and condenses the refrigerant. 
     
     
         12 . The method of  claim 10 , wherein transferring the third quantity of heat subcools the refrigerant. 
     
     
         13 . The method of  claim 10 , further comprising passing the air and the refrigerant through a heat exchanger to transfer the first, second, and third quantities of heat. 
     
     
         14 . The method of  claim 15 , further comprising:
 passing the refrigerant through a section of the heat exchanger prior to transferring either of the first and second quantities of heat from the refrigerant; and   passing the second portion of the air through said section of the heat exchanger prior to transferring the third quantity of heat to the second portion of the air, wherein the temperature of the second portion of the air is substantially unchanged as it passes through said section of the heat exchanger.   
     
     
         15 . The method of  claim 10 , further comprising moving refrigerant in a counterflow with respect to the first and second portions of air. 
     
     
         16 . The method of  claim 10 , further comprising moving refrigerant in concurrent flow with respect to the first and second portions of air.