Serpentine heat exchanger

Abstract

A serpentine heat exchanger includes a tube formed by bonding two press-molded tube sheets and folded back in a serpentine shape, and a corrugated fin arranged in a space enclosed by the tube that is folded-back. An inside of a folded-back portion of the tube includes a plurality of protrusions at a distance from one another, the protrusions protruding from one tube sheet and contacting the other tube sheet.

1 . A serpentine heat exchanger comprising:
 a tube formed by bonding two press-molded tube sheets and folded back in a serpentine shape; and   a fin arranged in a space enclosed by the tube that is folded-back, wherein   an inside of a folded-back portion of the tube includes a plurality of protrusions at a distance from one another, the protrusions protruding from a first tube sheet and contacting a second tube sheet.   
     
     
         2 . The serpentine heat exchanger according to  claim 1 , wherein
 an inside of a straight portion of the tube also includes the protrusions.   
     
     
         3 . The serpentine heat exchanger according to  claim 1 , wherein
 the protrusion is butted on another protrusion protruding from the second tube sheet.   
     
     
         4 . The serpentine heat exchanger according to  claim 1 , wherein
 the protrusions are formed only on the first tube sheet.   
     
     
         5 . The serpentine heat exchanger according to  claim 1 , wherein
 the protrusions are arranged in a staggered pattern.   
     
     
         6 . The serpentine heat exchanger according to  claim 1 , wherein
 the protrusion has a truncated conical shape, a cylindrical shape, or a prism shape.   
     
     
         7 . The serpentine heat exchanger according to  claim 1 , wherein
 the first tube sheet and the second tube sheet are swaged together on both sides in the folded-back portion of the tube.