Concentric Tube Heat Exchanger and Method

Abstract

A heat exchanger comprises an outer tube and an inner tube. The outer tube has an annular wall and ribs. The ribs extend radially inward from the annular wall. Some of the ribs extend clockwise as they extend toward the centroid and some other of the ribs extend counter-clockwise as they extend toward the centroid. The annular wall of the inner tube has an outer surface that is in contact with the ribs of the outer tube. The outer tube and the inner tube collectively define a plurality of outer fluid passageways bound by the annular walls of the outer and inner tubes and the ribs of the outer tube. A method of assembly for terminating the outer tube of a concentric tube heat exchanger is also described.

What is claimed is: 
     
         1 . A heat exchanger comprising:
 an outer tube having an annular wall, ribs, and a transverse cross-section, the cross-section of the outer tube having a centroid, the outer tube extending along a longitudinal path, the ribs extending toward the centroid from the annular wall of the outer tube, some of the ribs extending clockwise as they extend toward the centroid and some other of the ribs extending counter-clockwise as they extend toward the centroid; and   an inner tube having an annular wall, the outer tube encircling the inner tube, the annular wall of the inner tube having an outer surface, the outer surface being in contact with at least some of the ribs of the outer tube, the inner tube encircling an inner fluid passageway that extends along the longitudinal path, the outer tube and the inner tube collectively defining a plurality of outer fluid passageways bound by the annular walls of the outer and inner tubes and the ribs of the outer tube, the outer fluid passageways extending along the longitudinal path.   
     
     
         2 . A heat exchanger in accordance with  claim 1  wherein the ribs of the outer tube consist only of the ribs that extend clockwise and the ribs that extend counter-clockwise, and the ribs that extend clockwise alternate with the ribs that extend counter-clockwise. 
     
     
         3 . A heat exchanger in accordance with  claim 1  wherein the inner tube comprises ribs, the ribs extending toward the centroid from the annular wall of the inner tube. 
     
     
         4 . A heat exchanger in accordance with  claim 3  wherein the ribs of the inner tube spiral about the longitudinal path. 
     
     
         5 . A heat exchanger in accordance with  claim 1  wherein the outer tube comprises a longitudinal end and the heat exchanger further comprises an end fitting connected to the longitudinal end, the end fitting having a primary opening through which the inner tube extends, the end fitting having a secondary opening that is in fluid communication with the outer fluid passageways. 
     
     
         6 . A heat exchanger in accordance with  claim 1  wherein the longitudinal path is linear, the ribs of the outer tube extend parallel to the longitudinal path, and the annular walls of the inner and outer tubes are cylindrical. 
     
     
         7 . A heat exchanger comprising:
 an outer tube having an annular wall, ribs, and a transverse cross-section, the cross-section of the outer tube having a centroid, the outer tube extending along a longitudinal path, the ribs extending toward the centroid from the annular wall of the outer tube, the annular wall of the outer tube having a longitudinal end, an enlarged region, and an opening, the opening extending through the annular wall of the outer tube within the enlarged region; and   an inner tube having an annular wall, the outer tube encircling the inner tube, the annular wall of the inner tube having an outer surface, the outer surface being in contact with at least some of the ribs of the outer tube, the inner tube encircling an inner fluid passageway that extends along the longitudinal path, the outer tube and the inner tube collectively defining a plurality of outer fluid passageways bound by the annular walls of the outer and inner tubes and the ribs of the outer tube, the outer fluid passageways extending along the longitudinal path and being in fluid communication with the opening of the outer tube, the annular wall of the outer tube being annularly sealed to the annular wall of the inner tube at the longitudinal end.   
     
     
         8 . A heat exchanger in accordance with  claim 7  wherein the inner tube extends through and beyond the longitudinal end of the annular wall of the outer tube. 
     
     
         9 . A heat exchanger in accordance with  claim 7  wherein the ribs extend within the enlarged region of the outer tube and are spaced radially from the outer surface of the annular wall of the inner tube within the enlarged region. 
     
     
         10 . A heat exchanger in accordance with  claim 7  wherein some of the ribs extend clockwise as they extend toward the centroid and some other of the ribs extend counter-clockwise as they extend toward the centroid. 
     
     
         11 . A heat exchanger in accordance with  claim 7  wherein the inner tube comprises ribs that extend toward the centroid from the annular wall of the inner tube. 
     
     
         12 . A heat exchanger in accordance with  claim 11  wherein the ribs of the inner tube spiral about the longitudinal path. 
     
     
         13 . A heat exchanger in accordance with  claim 7  wherein the annular wall of the outer tube is annularly sealed to the annular wall of the inner tube via solder, a braze, or a weld. 
     
     
         14 . A heat exchanger in accordance with  claim 7  further comprising an outlet tube extending external to the outer tube and connected to the opening of the outer tube, the outlet tube having an internal passageway that is in fluid communication with the outer fluid passageways. 
     
     
         15 . A heat exchanger in accordance with  claim 7  wherein the annular wall of the outer tube comprises a crimped region adjacent the longitudinal end of the annular wall of the outer tube and is annularly sealed to annular wall of the inner tube via solder, a braze, or a weld at the crimped region. 
     
     
         16 . A method of forming a heat exchanger comprising:
 expanding an outer tube, the outer tube having an annular wall, ribs, and a transverse cross-section, the cross-section of the outer tube having a centroid, the outer tube extending along a longitudinal path, the ribs extending toward the centroid from the annular wall of the outer tube, the annular wall of the outer tube having a longitudinal end and the expanding of the outer tube causing the annular wall of the outer tube to radially expand and defining an enlarged region of the outer tube;   forming an opening through the annular wall of the outer tube within the enlarged region;   inserting an inner tube into the outer tube in a manner such that the inner tube extends through the longitudinal end of the outer tube, the inner tube having an annular wall that encircles an inner fluid passageway that extends along the longitudinal path, the insertion causing the annular wall of the inner tube to be in contact with at least some of the ribs of the outer tube in a manner defining a plurality of outer fluid passageways bound by the annular walls of the outer and inner tubes and the ribs of the outer tube and in manner such that the outer fluid passageways are in fluid communication with the opening of the outer tube; and   annularly sealing the longitudinal end of the annular wall of the outer tube to the annular wall of the inner tube.   
     
     
         17 . A method in accordance with  claim 16  wherein the enlarged region of the outer tube comprises portions of the ribs and the expanding of the outer tube occurs in a manner that causes the ribs of the outer tube to radially move away from the centroid within the enlarged region. 
     
     
         18 . A method in accordance with  claim 16  wherein the method further comprises crimping the annular wall of the outer tube adjacent the longitudinal end of the annular wall of the outer tube. 
     
     
         19 . A method in accordance with  claim 18  wherein the sealing of the longitudinal end of the annular wall of the outer tube to the annular wall of the inner tube comprises soldering, brazing, or welding. 
     
     
         20 . A method in accordance with  claim 16  wherein the method further comprises connecting an outlet tube to the opening of the outer tube, the outlet tube has an internal passageway and extends external to the outer tube, and the connecting of the outlet tube occurs in a manner such that the internal passageway of the outlet tube is in fluid communication with the outer fluid passageways.