Heat exchanger and folded tube used therein

Abstract

A folded, elongated tube ( 28 ) is provided for use in a heat exchanger ( 10, 11 ). The tube ( 28 ) has a flattened cross section with a minor dimension (d) and a major dimension (D). The tube ( 28 ) includes a pair of parallel tube runs ( 36 ), and a folded section ( 40 ) connecting the pair of tube runs ( 36 ). The major dimensions (D) of the tube runs ( 36 ) lie in a common plane. The folded section ( 40 ) includes a U-shaped bend ( 42 ), a first twist ( 44 ), and a second twist ( 46 ). The U-shaped bend ( 42 ) includes a straight section ( 48 ) extending between two curved sections ( 50, 52 ), and has its major dimension (D) extending substantially transverse to the major dimension (D) of the tube runs ( 36 ). The first twist ( 44 ) connects one of the tube runs ( 36 ) to the curved section ( 50 ), and the second twist ( 46 ) connects the other tube run ( 36 ) to the other curved section ( 52 ) of the U-shaped bend ( 42 ).

1 . A heat exchanger comprising: 
 a pair of elongated headers having longitudinal axes disposed substantially parallel to each other;    a plurality of elongated tubes spaced in side by side relation along the longitudinal axes of the headers, each of the tubes having a first end connected to one of the headers and a second end connected to the other header to transfer the working fluid between the headers, each of the tubes having a flattened cross section with a minor dimension and a major dimension, each of the tubes including a pair of parallel tube runs connected by a folded section of the tube, the major dimension of each of the tube runs extending substantially transverse to the longitudinal axes of the headers, the folded section of each of the tubes comprising 
 a U-shaped bend including a straight section of tube extending between two curved sections of tube, the bend having its major dimension extending substantially parallel to the longitudinal axes of the headers,  
 a first twist connecting one of the tube runs to one of the curved sections of the U-shaped bend, and  
 a second twist connecting the other tube run to the other curved section of the U-shaped bend; and  
   serpentine fins extending between adjacent pairs of said tubes.    
     
     
         2 . The heat exchanger of  claim 1  wherein for the major dimension of one of the tube runs of each tube lies in a common plane with the major dimension of the other tube run of the tube.  
     
     
         3 . The heat exchanger of  claim 1  wherein the straight section of each of the U-shaped bends extends transverse to the parallel legs.  
     
     
         4 . The heat exchanger of  claim 1  wherein each of the twists is a 90° twist.  
     
     
         5 . The heat exchanger of  claim 1  wherein each of the tubes further comprises: 
 a third tube run parallel to the pair of tube runs, the major dimension of the tube extending transverse to the longitudinal axes of the headers; and  
 a second folded section of tube connecting the third tube run to one of the other tube runs of the tube, the second folded section comprising 
 a second U-shaped bend including a straight section of tube extending between two curved sections of tube and having its major dimension extending substantially parallel to the longitudinal axes of the headers,  
 a third twist connecting the one of the other tube runs to one of the curved sections of the second U-shaped bend, and  
 a fourth twist connecting the third tube run to other curved section of the second U-shaped bend.  
 
 
     
     
         6 . The heat exchanger of  claim 1  wherein the straight section of each of the tubes has a length that at least doubles the minor dimension of the flattened tube cross section.  
     
     
         7 . The heat exchanger of  claim 1  wherein the parallel legs of each of the tubes are spaced from each other.  
     
     
         8 . The heat exchanger of  claim 1  wherein the major dimension of each of the tube ends extends parallel to the longitudinal axes of the headers at the location where the tube end is connected to the header.  
     
     
         9 . The heat exchanger of  claim 1  wherein one of the twists of each of the tubes is a left handed twist and the other twist of the tube is a right handed twist.  
     
     
         10 . The heat exchanger of  claim 1  wherein one of the twists of each of the tubes is a left handed twist and the other twist of the tube is a left handed twist.  
     
     
         11 . The heat exchanger of  claim 1  wherein one of the twists of each of the tubes is a right handed twist and the other twist of the tube is a right handed twist.  
     
     
         12 . A folded, elongated tube for use in a heat exchanger, the tube having a flattened cross section with a minor dimension and a major dimension, the tube comprising: 
 a pair of parallel tube runs, the major dimensions of the tube runs lying in a common plane; and    a folded section of tube connecting the pair of tube runs, the folded section comprising 
 a U-shaped bend including a straight section of tube extending between two curved sections of tube and having its major dimension extending substantially transverse to the major dimensions of the tube runs,  
 a first 90° twist connecting one of the tube runs to one of the curved sections of the U-shaped bend, and  
 a second 90° twist connecting the other tube run to the other curved section of the U-shaped bend.  
   
     
     
         13 . The tube of  claim 12  wherein the straight section of the tube has a length that at least doubles the minor dimension of the flattened tube cross section.  
     
     
         14 . The tube of  claim 12  wherein the straight section of the U-shaped bend extends transverse to the parallel legs.  
     
     
         15 . The tube of  claim 12  further comprising: 
 a third tube run parallel to the pair of tube runs, the major dimension of the tube run lying in the common plane; and  
 a second folded section of tube connecting the third tube run to one of the other tube runs, the second folded section comprising 
 a second U-shaped bend including a straight section of tube extending between two curved sections of tube and having its major dimension extending substantially transverse to the major dimensions of the tube runs,  
 a third 90° twist connecting the one of the other tube runs to one of the curved sections of the second U-shaped bend, and  
 a fourth 90° twist connecting the third tube run to other curved section of the second U-shaped bend.  
 
 
     
     
         16 . The tube of  claim 12  wherein the parallel legs are spaced from each other.  
     
     
         17 . The tube of  claim 12  wherein one of the twists is a left handed twist and the other twist is a right handed twist.  
     
     
         18 . The tube of  claim 12  wherein one of the twists is a left handed twist and the other twist is a left handed twist.  
     
     
         19 . The tube of  claim 1  wherein one of the twists is a right handed twist and the other twist is a right handed twist.