Heat Exchanger Tubes, and Method for Producing Heat Exchanger Tubes

Abstract

A method for producing heat exchanger tubes involves applying a surface coating to the tube through which a fluid medium flows and which has a number of cooling fins arranged on an outer wall. The method comprises applying a surface coating to an inner wall and the outer wall of the tube, the inner wall and the outer wall comprised of structural steel, the surface coating comprising copper, nickel, cobalt, chromium, a nickel alloy, a chromium alloy, a copper alloy, a cobalt alloy or stainless steel. The method further comprises soldering the number of cooling fins to the outer wall. The surface coating is configured to facilitate direct soldering of the number of cooling fins to the outer wall of the tube and to provide the inner wall with corrosion resistance to the fluid medium in the tube.

1 . A method for producing heat exchanger tubes comprising a tube through which a medium flows and which has a number of cooling fins arranged on an outer wall, the method comprising:
 applying a surface coating to an inner wall and the outer wall of the tube, the inner wall and the outer wall comprised of structural steel, the surface coating comprising copper, nickel, cobalt, chromium, a nickel alloy, a chromium alloy, a copper alloy, a cobalt alloy or stainless steel, and   soldering the number of cooling fins to the outer wall,   wherein the surface coating is configured to provide the inner wall with corrosion resistance to fluid in the tube.   
   
   
       2 . The method as claimed in  claim 1 , wherein the surface coating is in the form of a cladding or plating. 
   
   
       3 . The method as claimed in  claim 1 , wherein the surface coating is applied to the inner wall and to the outer wall—comprising the same material—in one working operation. 
   
   
       4 . The method as claimed in  claim 3 , wherein the tube is produced by providing both sides of a sheet-metal strip of structural steel with the surface coating, shaping said strip to form a flat tube, and welding said strip, wherein a weld seam which is produced remains free from an iron/aluminum interlayer. 
   
   
       5 . The method as claimed in  claim 1  wherein the number of cooling fins are comprised of aluminum, of an aluminum alloy, of steel, of clad steel or of alloyed steel, wherein the soldering process is carried out in such a way that a joint between the cooling fins and the surface-coated tube is free from a continuous iron/aluminum interlayer as far as the tube wall, and wherein the surface coating facilitates the soldering the number of cooling fins to the outer wall. 
   
   
       6 . The method as claimed in  claim 1 , wherein an interlayer which is formed during the soldering process is rendered ductile by adding boron. 
   
   
       7 . A heat exchanger tube comprising:
 a tube configured to allow a fluid medium to flow through it, the tube including an inner wall and an outer wall comprised of structural steel;   a number of cooling fins soldered to the tube; and   a surface coating of copper, nickel, cobalt, chromium, a nickel alloy, a chromium alloy, a copper alloy or stainless steel provided on the inner wall and the outer wall of the tube, the surface coating configured to facilitate direct soldering of the number of cooling fins to the outer wall of the tube and for providing the inner wall with corrosion resistance to the fluid medium in the tube.   
   
   
       8 . The heat exchanger tube as claimed in  claim 7 , wherein the surface coating, in the form of a cladding or plating, comprises the same material on the inner wall and on the outer wall.