U-shaped heat exchanger tube with a concavity formed into its return bend

Abstract

A heat exchanger tube includes a tube body that forms a hollow passageway and has a U-shaped tube section defining a return bend and a pair of straight tube sections. Respective ones of the straight tube sections are connected to the U-shaped section at respective connection locations and extend generally parallel to one another to define an internal space disposed between and among the U-shaped tube section and the straight tube sections connected to the U-shaped tube section. The U-shaped tube section has a concavity formed thereinto with the concavity defining a portion of the internal space. A heat exchanger serpentine tube includes a plurality of straight tube sections arranged in a plurality of generally parallel rows and disposed in a common plane and a plurality of U-shaped tube sections connected to the plurality of straight tube sections to form a serpentine configuration.

1 . A tube, comprising: 
 a tube body forming a hollow passageway and having a U-shaped tube section defining a return bend and a pair of straight tube sections with respective ones of the straight tube sections connected to the U-shaped section at respective connection locations and extending generally parallel to one another to define an internal space disposed between and among the U-shaped tube section and the straight tube sections connected to the U-shaped tube section, the U-shaped tube section having a concavity formed thereinto with the concavity defining a portion of the internal space.    
   
   
       2 . A tube according to  claim 1 , wherein the concavity extends continuously along the U-shaped tube section and terminates adjacent respective ones of the connection locations.  
   
   
       3 . A tube according to  claim 2 , wherein the concavity has a generally constant depth as the concavity extends continuously along the U-shaped tube section.  
   
   
       4 . A tube according to  claim 3 , wherein the concavity has a generally tapering depth that lessens commencing from the constant depth as the concavity terminates adjacent the respective connection locations.  
   
   
       5 . A tube according to  claim 1 , wherein the U-shaped tube section and the pair of straight tube sections are integrally constructed at the respective connection locations.  
   
   
       6 . A tube according to  claim 1 , wherein respective ones of the straight tube sections as viewed in cross-section have one of circular cross-sections, flattened circular cross-sections, elliptical cross-sections and flattened elliptical cross-sections.  
   
   
       7 . A tube according to  claim 1 , wherein the U-shaped tube section as viewed in cross-section is generally kidney-shaped.  
   
   
       8 . A tube according to  claim 1 , wherein the U-shaped tube section includes a main piece connected to the concavity as viewed in cross-section to define a continuous loop, the concavity forming an apex projecting into the hollow passageway and the main piece having a first imaginary reference point disposed diametric to the apex, a second imaginary reference point and a third imaginary reference point and wherein a first axis as viewed in cross-section extends through the apex and the first imaginary reference point dividing the U-shaped tube section generally symmetrically in half-sections with the apex and the first imaginary reference point being disposed apart from one another at a distance therebetween to define a height and a second axis as viewed in cross-section perpendicularly intersecting the first axis extends through the second imaginary reference point disposed on one of the half-sections and the third imaginary reference point disposed on a remaining one of the half-sections, the second and third imaginary reference points being disposed apart from one another at a widest distance therebetween to define a width.  
   
   
       9 . A tube according to  claim 8 , wherein a ratio of the height to the width is in a range of approximately 0.6 and 0.9.  
   
   
       10 . A tube according to  claim 1 , wherein at least one of the straight tube sections defines in cross-section a straight tube cross-sectional area of the hollow passageway and the U-shaped tube section defines in cross-section a U-shaped tube cross-sectional area of the hollow passageway, the U-shaped tube cross-sectional area being smaller than the straight tube cross-sectional area.  
   
   
       11 . A tube according to  claim 1 , wherein the U-shaped tube cross-sectional area is smaller than the straight tube cross-sectional area by an amount in a range of approximately 10% and 30%.  
   
   
       12 . A serpentine tube, comprising: 
 a serpentine tube body having a plurality of straight tube sections and a plurality of U-shaped tube sections, the plurality of straight tube sections arranged in a plurality of generally parallel rows and disposed in a common plane, the plurality of U-shaped tube sections connected to the plurality of straight tube sections in a manner such that a respective one of the U-shaped tube sections defining a return bend connects sequential ones of the plurality of straight tube sections to form a serpentine configuration, each of the sequential ones of straight tube sections connected to a respective one of the U-shaped sections defines an internal space disposed between and among the respective U-shaped tube section and the sequential ones of the straight tube sections, each one of the U-shaped tube sections having a concavity formed thereinto with the concavity defining a portion of the internal space.    
   
   
       13 . A serpentine tube according to  claim 12 , wherein each U-shaped tube section and sequential ones of the straight tube sections are connected at respective connection locations.  
   
   
       14 . A serpentine tube according to  claim 12 , wherein the concavity extends continuously along each one of the U-shaped tube sections and terminates adjacent the sequential ones of the straight tube sections at the respective connection locations.  
   
   
       15 . A serpentine tube according to  claim 12 , wherein each concavity has a generally constant depth as the concavity extends continuously along the U-shaped tube section.  
   
   
       16 . A serpentine tube according to  claim 15 , wherein each concavity has a generally tapering depth that lessens commencing from the constant depth as the concavity terminates adjacent the respective connection locations.  
   
   
       17 . A serpentine tube according to  claim 12 , wherein each one of the U-shaped sections as viewed in cross-section is generally kidney-shaped.  
   
   
       18 . A serpentine tube according to  claim 12 , wherein each one of the straight tube sections defines in cross-section a straight tube cross-sectional area and each one of the U-shaped tubes define in cross-section a U-shaped tube cross-sectional area, respective ones of the U-shaped tube cross-sectional areas being smaller than respective ones of the straight tube cross-sectional areas.  
   
   
       19 . A serpentine tube according to  claim 18 , wherein each of the U-shaped tube cross-sectional areas is smaller than each of the straight tube cross-sectional areas by an amount in a range of approximately 10% and 30%.  
   
   
       20 . A heat exchanger, comprising: 
 an inlet header;    an inlet connection connected to the inlet header;    an outlet header;    an outlet connection connected to the outlet header; and    a plurality of serpentine tube bodies, each serpentine tube body having a plurality of straight tube sections and a plurality of U-shaped tube sections, the plurality of straight tube sections arranged in a plurality of generally parallel rows and disposed in a common plane, the plurality of U-shaped tube sections connected to the plurality of straight tube sections in a manner such that a respective one of the U-shaped tube sections defining a return bend connects sequential ones of the plurality of straight tube sections to form a serpentine configuration, each of the sequential ones of straight tube sections connected to a respective one of the U-shaped sections defines an internal space disposed between and among the respective U-shaped tube section and the sequential ones of the straight tube sections, each one of the U-shaped tube sections having a concavity formed thereinto with the concavity defining a portion of the internal space, the plurality of serpentine tube bodies interconnecting the inlet and outlet headers.    
   
   
       21 . A method of forming a straight tube into a U-shaped tube having a U-shaped section defining a return bend and a pair of straight tube sections with respective ones of the straight tube sections extending generally parallel to one another to define an internal space disposed between and among the U-shaped tube section and the straight tube sections connected to the U-shaped tube section with the U-shaped tube section having a concavity formed thereinto, the concavity defining a portion of the internal space, the method comprising the steps of: 
 providing a cylindrically-shaped bend die having a pair of grooves extending into and circumferentially about an outer circumferential surface of the bend die with a protuberance configured as a ring and disposed between the pair of grooves and projecting outwardly relative to the pair of grooves; and    bending the straight tube about the bend die at a selected angle in an approximate range of 170° and 190° in a manner to form the U-shaped tube having the U-shaped tube section defining the return bend and the pair of straight tube sections with the U-shaped tube section having the concavity formed thereinto with the concavity defining a portion of the internal space.