Heat exchanger for providing supercritical cooling of a working fluid in a transcritical cooling cycle

Abstract

A heat exchanger ( 10 ) preferably provides supercritical cooling to the refrigerant of a transcritical cooling system ( 12 ). The heat exchanger ( 10 ) includes a pair of elongated headers ( 20, 22 ) having longitudinal axes ( 24, 26 ) disposed substantially parallel to each other, a plurality of elongated tubes ( 28 ) spaced in side-by-side relation along the longitudinal axes ( 24, 26 ) of the headers ( 20, 22 ), and serpentine fins ( 30 ) extending between adjacent pairs of the tubes. Each of the tubes ( 28 ) has a first end ( 31 ) connected to the header ( 20 ) and a second end ( 32 ) connected to the other header ( 22 ) to the headers ( 20, 22 ). Each of the tubes ( 28 ) is folded upon itself to define at least two parallel legs ( 36 ) of the tubes ( 28 ) so that the refrigerant flows serially through at least two parallel fluid passes ( 38 ) from the header ( 20 ) to the header ( 22 ) Each of the tubes ( 28 ) has a flattened cross-section, and the parallel legs ( 36 ) of each of the tubes ( 28 ) are preferably spaced from each other, with the major dimension D of each of the parallel legs lying in a common plane. Preferably, each of the serpentine fins ( 30 ) has a transverse width W extending across the parallel legs ( 36 ) of the adjacent tubes ( 28 ). Each of the fins ( 30 ) includes a plurality of alternating tabs ( 40 ) and elongated separations ( 42 ) extending parallel to the parallel legs ( 36 ) and located between the parallel legs ( 36 ) of the adjacent tubes ( 28 ) to divide the width W of each fin ( 30 ) into two or more discrete fin elements ( 44 ) that are connected to each other by the tabs ( 40 ). Each of the fin elements ( 44 ) corresponds to and extends along one of the parallel legs ( 36 ) of each of the adjacent tubes ( 28 ).

I claim:  
     
         1 . A heat exchanger for providing supercritical cooling of a working fluid in a transcritical cooling cycle, the 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 flattened cross-section with a major dimension and a minor dimension, 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 being folded upon itself to define at least two parallel legs of the tube so that the working fluid flows serially through at least two parallel fluid passes from one of the headers to the other, the parallel legs of each of the tubes being spaced from each other with the major dimension of each of the parallel legs lying in a common plane that is substantially transverse to the longitudinal axes of the headers; and    serpentine fins extending between adjacent pairs of said tubes, each of the fins having a length extending parallel to the parallel legs of the adjacent tubes and a transverse width extending across the at least two parallel legs of the adjacent tubes, each of the fins including a plurality of alternating tabs and elongated separations extending parallel to the parallel legs, the tabs and separations located between the parallel legs of the adjacent tubes to divide the width of each fin into a plurality of discrete fin elements that are connected to each other by the tabs, each of the fin elements corresponding to and extending along one of the parallel legs of each of the adjacent tubes.    
     
     
         2 . The heat exchanger of  claim 1  wherein the major dimension of each of the tubes is no greater than 0.500 inch and the minor dimension is no greater than 0.100 inch.  
     
     
         3 . The heat exchanger of  claim 1  wherein the major dimension of each of the tubes is no greater than 0.320 inch and the minor dimension is no greater than 0.060 inch.  
     
     
         4 . The heat exchanger of  claim 1  wherein each of th e tubes is folded at least twice to define at least three parallel legs of the tube so that the working fluid flows serially through at least three parallel fluid passes from one of the headers to the other.  
     
     
         5 . The heat exchanger of  claim 1  wherein each of the fins have a fin height extending from one the tubes to an adjacent one of the tubes, parallel to the longitudinal axes of the headers, and the major dimension of the tubes is no greater than the fin height.  
     
     
         6 . 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.  
     
     
         7 . The heat exchanger of  claim 1  wherein said separations in said fins are slits that do not require removal of fin material when formed in the fins.  
     
     
         8 . The heat exchanger of  claim 1  wherein said separations in said fins are slots that do require removal of fin material when formed in the fins.  
     
     
         9 . The heat exchanger of  claim 1  wherein, for at least one of the fins in an unfolded state of the fin, said separations and said tabs have lengths extending parallel with the length of the fin, and the ratio of the lengths of the separations to the lengths of the tabs is in the range of 200 to 600.  
     
     
         10 . The heat exchanger of  claim 1  wherein at least one of the tubes is a multi-port tube having a hydraulic diameter in the range of 0.015 inch to 0.040 inch.  
     
     
         11 . A heat exchanger for providing supercritical cooling of a working fluid in a transcritical cooling cycle, the 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 flattened cross-section with a major dimension and a minor dimension, 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 being folded upon itself to define at least two parallel legs of the tube so that the working fluid flows serially through at least two parallel fluid passes from one of the headers to the other, the parallel legs of each of the tubes having their major dimensions lying in a common plane that is substantially transverse to the longitudinal axes of the headers; and    serpentine fins extending between adjacent pairs of said tubes, each of the fins having a length extending parallel to the parallel legs of the adjacent tubes and a transverse width extending across the at least two parallel legs of the adjacent tubes, each of the fins including a plurality of alternating tabs and elongated separations extending parallel to the parallel legs, the tabs and separations located between the parallel legs of each of the adjacent tubes to divide the width of each fin into a plurality of discrete fin elements that are connected to each other by the tabs, each of the fin elements corresponding to and extending along one of the parallel legs of each of the adjacent tubes.    
     
     
         12 . The heat exchanger of  claim 11  wherein the major dimension of each of the tubes is no greater than 0.500 inch and the minor dimension is no greater than 0.100 inch.  
     
     
         13 . The heat exchanger of  claim 11  wherein the major dimension of each of the tubes is no greater than 0.320 inch and the minor dimension is no greater than 0.060 inch.  
     
     
         14 . The heat exchanger of  claim 11  wherein each of the tubes is folded at least twice to define at least three parallel legs of the tube so that the working fluid flows serially through at least three parallel fluid passes from one of the headers to the other.  
     
     
         15 . The heat exchanger of  claim 11  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.  
     
     
         16 . The heat exchanger of  claim 11  wherein said separations in said fins are slits that do not require removal of fin material when formed in the fins.  
     
     
         17 . The heat exchanger of  claim 11  wherein, for at least one of the fins in an unfolded state of the fin, said separations and said tabs have lengths extending parallel with the length of the fin, and the ratio fo the lengths of the separations to the lengths of the tabs is in the range of 200 to 600.  
     
     
         18 . A heat exchanger for providing supercritical cooling of a working fluid in a transcritical cooling cycle, the 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 flattened cross-section with a major dimension and a minor dimension, the major dimension of each of the tubes being no greater than 0.500 inch and the minor dimension being no greater than 0.100 inch, 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 being folded upon itself to define at least two parallel legs of the tube so that the working fluid flows serially through at least two parallel fluid passes from one of the headers to the other, the parallel legs of each of the tubes having their major dimensions lying in a common plane that is substantially transverse to the longitudinal axes of the headers; and    serpentine fins extending between adjacent pairs of said tubes, each of the fins having a length extending parallel to the parallel legs of the adjacent tubes.    
     
     
         19 . A heat exchanger for providing supercritical cooling of a working fluid in a transcritical cooling cycle, the 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 flattened cross-section with a major dimension and a minor dimension, 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 being folded upon itself at least twice to define at least three parallel legs of the tube so that the working fluid flows serially through at least three parallel fluid passes from one of the headers to the other, the parallel legs of each of the tubes having their major dimensions lying in a common plane that is substantially transverse to the longitudinal axes of the headers; and    serpentine fins extending between adjacent pairs of said tubes, each of the fins having a length extending parallel to the parallel legs of the adjacent tubes.    
     
     
         20 . A heat exchanger for providing supercritical cooling of a working fluid in a transcritical cooling cycle, the 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 flattened cross-section with a major dimension and a minor dimension, each of the tubes being a multi-port tube with a hydraulic diameter in the range of 0.015 inch to 0.040 inch, 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 being folded upon itself to define at least two parallel legs of the tube so that the working fluid flows serially through at least two parallel fluid passes from one of the headers to the other, the parallel legs of each of the tubes having their major dimensions lying in a common plane that is substantially transverse to the longitudinal axes of the headers; and    serpentine fins extending between adjacent pairs of said tubes, each of the fins having a length extending parallel to the parallel legs of the adjacent tubes.