Heat exchanger tube and method of making

Abstract

A method of forming a tube for a heat exchanger includes advancing an expansion tool into a tube a first time and engaging the expansion tool with the tube to expand the tube diametrically at least partially along a length of the tube. The expansion tool is at least partially retracted from the tube. The expansion tool is advanced into the tube one or more subsequent times thereby engaging the expansion tool with the tube one or more subsequent times to further expand the tube at least partially along the length of the tube.

1 . A method of forming a tube for a heat exchanger comprising:
 advancing an expansion tool into a tube a first time;   engaging the expansion tool with the tube to expand the tube diametrically at least partially along a length of the tube;   at least partially retracting the expansion tool from the tube;   advancing the expansion tool into the tube one or more subsequent times; and   engaging the expansion tool with the tube one or more subsequent times to further expand the tube at least partially along the length of the tube.   
     
     
         2 . The method of  claim 1 , wherein advancing the expansion tool into the tube the first time comprises advancing the expansion tool along the entire length of the tube, thereby diametrically expanding the entire length of the tube. 
     
     
         3 . The method of  claim 1 , wherein engaging the expansion tool with the tube one or more subsequent times results in expansion of a tube end to receive a return bend. 
     
     
         4 . The method of  claim 1 , wherein engaging the expansion tool with the tube one or more subsequent times results in a flare of a tube end. 
     
     
         5 . The method of  claim 1 , wherein one or more subsequent times is one more time. 
     
     
         6 . The method of  claim 1 , wherein one or more subsequent times is two more times. 
     
     
         7 . A method of assembling a heat exchanger comprising:
 providing a plurality of fins;   locating one or more tubes in proximity to the plurality of fins;   advancing an expansion tool into the one or more tubes a first time;   engaging the expansion tool with the one or more tubes to expand the one or more tubes diametrically at least partially along a length of the one or more tubes resulting in an interference fit between the fins and the one or more tubes;   at least partially retracting the expansion tool from the one or more tubes;   advancing the expansion tool into the one or more tubes one or more subsequent times; and   engaging the expansion tool with the one or more tubes one or more subsequent times to further expand the one or more tubes at least partially along the length of the one or more tubes.   
     
     
         8 . The method of  claim 7 , wherein engaging the expansion tool with the one or more tubes one or more subsequent times results in expansion of a tube end of the one or more tubes to receive a return bend. 
     
     
         9 . The method of  claim 8 , further comprising:
 inserting the return bend into the tube end; and   securing the return bend to the tube end.   
     
     
         10 . The method of  claim 9 , wherein the return bend is secured to the tube end by brazing. 
     
     
         11 . The method of  claim 7 , wherein engaging the expansion tool with the one or more tubes tube one or more subsequent times results in a flare of a tube end. 
     
     
         12 . The method of  claim 11 , wherein the flare is configured to retain braze material when securing a return bend to the tube end. 
     
     
         13 . The method of  claim 7 , wherein one or more subsequent times is one more time. 
     
     
         14 . The method of  claim 7 , wherein one or more subsequent times is two more times.