Method and System for Manufacturing Tube and Fin Heat Exchangers with Reduced Tube Diameter

Abstract

According to a preferred embodiment, an improved method and apparatus for manufacturing tube and fin heat exchangers that includes a step for reducing the outer diameter of stock tubing to a value well below nominal prior to bending the tubing into hairpins. The reduced diameter increases the stiffness of the resultant hairpins and allows for efficient lacing of the heat exchanger fins and end plates. The method uses pre-size rollers that are adjustable for reducing the diameter of the tubing.

1 . A method for manufacturing a tube and fin heat exchanger comprising the steps of:
 providing a supply of skin-hardened tubing;   cutting said tubing to plurality of predetermined lengths;   bending said plurality of predetermined lengths of tubing 180 degrees into hairpin tubes;   lacing said plurality of hairpin tubes through a plurality of apertures in a stack of fins sandwiched between first and second endplates; and   expanding the outer diameter of said laced hairpin tubes to create an interference fit between said hairpin tubes and said plurality of apertures.   
     
     
         2 . The method of  claim 1  wherein the step of providing a supply of skin-hardened tubing further comprises the steps of:
 providing a supply of non-skin-hardened tubing having a nominal outer diameter; and 
 reducing the outer diameter of said non-skin-hardened tubing to a value significantly smaller than said nominal outer diameter so as to produce said skin-hardened tubing from said non-skin-hardened tubing. 
 
     
     
         3 . The method of  claim 2  further comprising the step of:
 reducing the outer diameter of said non-skin-hardened tubing by at least about 3.8 percent so as to produce said skin-hardened tubing from said non-skin-hardened tubing.