Pressure containing heat transfer tube and method of making thereof

Abstract

A heat transfer tube and a method of forming a heat transfer tube with indents formed in the opposed walls. The indents may be cold welded or forge welded such that dimples or indentations meet in the middle of the tube. The bottom of a first indentation disposed on a first side of the tube is welded to the bottom of a second indentation formed in the opposite side of the tube.

1 . A heat transfer tube having a tube axis in the longitudinal direction, the tube comprising: 
 a first wall having an outer surface and an inner surface defining a first wall thickness therebetween, the first wall having a plurality of first indented portions formed along the outer surface of the first wall;    a second wall having an outer surface and an inner surface defining a second wall thickness therebetween, the second wall disposed in spaced apart relation to the first wall, the second wall having a plurality of second indented portions formed therein and disposed in registry with the first indented portions, the second indented portions disposed along the outer surface of the second wall;    a first end wall connecting the first wall to the second wall;    a second end wall disposed opposite from the first end wall and connecting the first end wall to the second end wall; and,    wherein each of the inner surfaces of the first and second walls located at the first and second indented portions are welded together to form a joint by cold welding.    
   
   
       2 . The heat transfer tube of  claim 1 , wherein the first and second indented portions are formed by stamping.  
   
   
       3 . The heat transfer tube of  claim 1 , wherein the first and second indented portions are formed by engagement of the outer surfaces of the tube with raised surfaces disposed on a roll.  
   
   
       4 . The heat transfer tube of  claim 1 , wherein an electrical current is passed through the tube during the cold welding.  
   
   
       5 . The heat transfer tube of  claim 1 , wherein the first and second indented portions have a shape selected from the group consisting of: elliptical, circular, oval, diamond, triangle, teardrop, double teardrop, and polyhedral.  
   
   
       6 . The heat transfer tube of  claim 1 , wherein the equivalent diameter is 0.5 to 30 mm.  
   
   
       7 . The heat transfer tube of  claim 1 , wherein the joint where welding occurs has an area of 0.5 mm 2  to 1,000 mm 2 .  
   
   
       8 . The heat transfer tube of  claim 1 , wherein the outer surface of the first wall defines a first wall area and the outer surface of each first indented portion defines a first indented portion area, the total of the first indented portion areas comprising 2-80% of the first wall area.  
   
   
       9 . The heat transfer tube of  claim 1 , wherein the joint has a thickness that varies from zero to about 180% of the first wall thickness.  
   
   
       10 . The heat transfer tube of  claim 1 , wherein the pitch is 2 mm to 1 inch in the direction of the tube axis.  
   
   
       11 . The heat transfer tube of  claim 1 , wherein the joint has a density of 0.1-100 joints per in 2 .  
   
   
       12 . The heat transfer tube of  claim 1 , wherein the first and second walls are curved.  
   
   
       13 . The heat transfer tube of  claim 1 , wherein the inner surfaces of the first and second indented portions are flat.  
   
   
       14 . The heat transfer tube of  claim 1 , wherein the inner surfaces of the first and second indented portions are curved.  
   
   
       15 . The heat transfer tube of  claim 1 , wherein the inner surfaces of the first and second indented portions are ridged.  
   
   
       16 . The heat transfer tube of  claim 1 , wherein the inner surface of the first indented portion has a complementary curved shape with respect to the inner surface of the second indented portion.  
   
   
       17 . The heat transfer tube of  claim 1 , wherein the inner surfaces of the first and second walls are substantially smooth.  
   
   
       18 . The heat transfer tube of  claim 1 , wherein the inner surfaces of the first and second walls are enhanced with fins.  
   
   
       19 . The heat transfer tube of  claim 1 , wherein the tube has regions disposed along the tube axis.  
   
   
       20 . The heat transfer tube of  claim 19 , wherein the joint density varies in successive regions in the direction of the tube axis.  
   
   
       21 . The heat transfer tube of  claim 19 , wherein the joint density increases in the successive regions along the direction of the tube axis.  
   
   
       22 . The heat transfer tube of  claim 19 , wherein the joint density decreases in the successive regions along the direction of the tube axis.  
   
   
       23 . The heat transfer tube of  claim 19 , wherein the joint density alternates in the successive regions in the direction of the tube axis between a first density and a second density which is greater than the first density.  
   
   
       24 . The heat transfer tube of  claim 19 , wherein the joint size increases in the successive regions in the direction of the tube axis.  
   
   
       25 . The heat transfer tube of  claim 19 , wherein the joint size decreases in the successive regions in the direction of the tube axis.  
   
   
       26 . The heat transfer tube of  claim 19 , wherein the joint size alternates in the successive regions between a first joint size and a second joint size, the second joint size being larger than the first joint size.  
   
   
       27 . The heat transfer tube of  claim 1 , wherein the tube is an internally enhanced copper tube.  
   
   
       28 . The heat transfer tube of  claim 21 , wherein the tube is roll formed and welded at a seam.  
   
   
       29 . The heat transfer tube of  claim 21 , wherein the tube is extruded.  
   
   
       30 . The heat transfer tube of  claim 21 , wherein the tube is initially formed with a round cross-section and then flattened by a press.  
   
   
       31 . A method of forming a heat transfer tube, the method comprising: 
 forming a tube having a first wall with an outer surface and an inner surface defining a first wall thickness therebetween, a second wall having an outer surface and an inner surface defining a second wall thickness therebetween, the second wall disposed in spaced apart relation to the first wall, a first end wall connecting the first wall to the second wall, a second end wall disposed opposite from the first end wall and connecting the first end wall to the second end wall; and,    forming a plurality of first indented portions in the first wall and a plurality of second indented portions in the second wall such that the inner surfaces of the first and second walls at the first and second indented portions are cold welded together to form a joint.    
   
   
       32 . A heat transfer tube having a tube axis in the longitudinal direction, the tube comprising: 
 a first wall having an outer surface and an inner surface defining a first wall thickness therebetween, the first wall having a plurality of first indented portions formed along the outer surface of the first wall;    a second wall having an outer surface and an inner surface defining a second wall thickness therebetween, the second wall disposed in spaced apart relation to the first wall, the second wall having a plurality of second indented portions formed therein and disposed in registry with the first indented portions, the second indented portions disposed along the outer surface of the second wall;    a first end wall connecting the first wall to the second wall;    a second end wall disposed opposite from the first end wall and connecting the first end wall to the second end wall; and,    wherein each of the inner surfaces of the first and second walls located at the first and second indented portions are welded together to form a joint by forge welding.    
   
   
       33 . The heat transfer tube of  claim 32 , wherein the first and second indented portions have a shape selected from the group consisting of: elliptical, circular, oval, diamond, triangle, teardrop, double teardrop, and polyhedral.  
   
   
       34 . The heat transfer tube of  claim 32 , wherein the equivalent diameter is 0.5 to 30 mm.  
   
   
       35 . The heat transfer tube of  claim 32 , wherein the joint where welding occurs has an area of 0.5 mm 2  to 1,000 mm 2 .  
   
   
       36 . The heat transfer tube of  claim 32 , wherein the outer surface of the first wall defines a first wall area and the outer surface of each first indented portion defines a first indented portion area, the total of the first indented portion areas comprising 2-80% of the first wall area.  
   
   
       37 . The heat transfer tube of  claim 32 , wherein the joint has a thickness that varies from zero to about 180% of the first wall thickness.  
   
   
       38 . The heat transfer tube of  claim 32 , wherein the pitch is 2 mm to 1 inch in the direction of the tube axis.  
   
   
       39 . The heat transfer tube of  claim 32 , wherein the joint has a density of 0.1-100 joints per in 2 .  
   
   
       40 . The heat transfer tube of  claim 32 , wherein the first and second walls are curved.  
   
   
       41 . The heat transfer tube of  claim 32 , wherein the inner surfaces of the first and second indented portions are flat.  
   
   
       42 . The heat transfer tube of  claim 32 , wherein the inner surfaces of the first and second indented portions are curved.  
   
   
       43 . The heat transfer tube of  claim 32 , wherein the inner surfaces of the first and second indented portions are ridged.  
   
   
       44 . The heat transfer tube of  claim 32 , wherein the inner surface of the first indented portion has a complementary curved shape with respect to the inner surface of the second indented portion.  
   
   
       45 . The heat transfer tube of  claim 32 , wherein the inner surfaces of the first and second walls are substantially smooth.  
   
   
       46 . The heat transfer tube of  claim 32 , wherein the inner surfaces of the first and second walls are enhanced with fins.  
   
   
       47 . The heat transfer tube of  claim 32 , wherein the tube has regions disposed along the tube axis.  
   
   
       48 . The heat transfer tube of  claim 47 , wherein the joint density varies in successive regions in the direction of the tube axis.  
   
   
       49 . The heat transfer tube of  claim 47 , wherein the joint density increases in the successive regions along the direction of the tube axis.  
   
   
       50 . The heat transfer tube of  claim 47 , wherein the joint density decreases in the successive regions along the direction of the tube axis.  
   
   
       51 . The heat transfer tube of  claim 47 , wherein the joint density alternates in the successive regions in the direction of the tube axis between a first density and a second density which is greater than the first density.  
   
   
       52 . The heat transfer tube of  claim 47 , wherein the joint size increases in the successive regions in the direction of the tube axis.  
   
   
       53 . The heat transfer tube of  claim 47 , wherein the joint size decreases in the successive regions in the direction of the tube axis.  
   
   
       54 . The heat transfer tube of  claim 47 , wherein the joint size alternates in the successive regions between a first joint size and a second joint size, the second joint size being larger than the first joint size.  
   
   
       55 . The heat transfer tube of  claim 32 , wherein the tube is an internally enhanced copper tube.  
   
   
       56 . The heat transfer tube of  claim 32 , wherein the tube is roll formed and welded at a seam.  
   
   
       57 . The heat transfer tube of  claim 32 , wherein the tube is extruded.  
   
   
       58 . The heat transfer tube of  claim 32 , wherein the tube is initially formed with a round cross-section and then flattened by a press.