Multi-layered heat transfer tube, manufacturing method of multi-layered heat transfer tube, and forming device used in the manufacturing method

Abstract

A multi-layered heat transfer tube for use in a carburetor for a liquefied gas, comprising an inner tube which is equipped with a passage through which a liquefied gas can pass and an outer tube which covers the outer peripheral surface of the inner tube, wherein each of the inner tube and the outer tube has multiple fins that extend in the direction of the length of the multi-layered heat transfer tube and are arranged along the direction of the circumference of the multi-layered heat transfer tube, at least the outer tube is composed of a fully dense material, and the outer tube covers the entire outer surface of the inner tube and is bound to the inner tube via a metallic bond.

1 - 6 . (canceled) 
     
     
         7 . A multi-layered heat transfer tube used in a liquefied gas vaporizer, comprising:
 an inner tube having a flow path through which liquefied gas flows; and   an outer tube covering the outer peripheral surface of the inner tube,   wherein the inner tube and the outer tube have a plurality of fins extending in the longitudinal direction of the multi-layered heat transfer tube and arranged in the circumferential direction of the multi-layered heat transfer tube,   at least the outer tube is formed of a fully dense material, and   the outer tube covers the entire outer surface of the inner tube and is metallically bonded to the inner tube.   
     
     
         8 . The multi-layered heat transfer tube according to  claim 7 , wherein the outer tube is formed so as to have a thickness that is largest at the apex portions of the plurality of fins and is smallest at valley portions, and
 the thickness continuously changes from the apex portions of the fins toward the valley portions.   
     
     
         9 . The multi-layered heat transfer tube according to  claim 7 , wherein the outer tube is formed so as to have a thickness that is substantially constant throughout the length from one end to the other end of the multi-layered heat transfer tube. 
     
     
         10 . The multi-layered heat transfer tube according to  claim 9 , wherein the inner tube is formed of aluminum, and
 the outer tube is formed of an alloy of aluminum and zinc.   
     
     
         11 . The A manufacturing method of the multi-layered heat transfer tube according to  claim 7 , comprising:
 preparing a multi-layered tube material including an inner tube material that is a metal original material for forming the inner tube and an outer tube material that is a metal original material for forming the outer tube and that surrounds the inner tube material; and   extruding or drawing the multi-layered tube material through a forming device under a predetermined hydrostatic pressure environment.   
     
     
         12 . The A forming device for manufacturing the multi-layered heat transfer tube according to  claim 7 , the forming device comprising:
 an approach portion in which an insertion hole is formed into which a multi-layered tube material is inserted, the multi-layered tube material including an inner tube material that is a metal original material for forming the inner tube and an outer tube material that is a metal original material for forming the outer tube and that surrounds the inner tube material,   wherein the approach portion has an approach surface that forms at least part of the insertion hole and that is inclined at a predetermined angle with respect to the insertion direction of the multi-layered tube material,   the exit side portion of the insertion hole has a shape corresponding to the sectional shape of the multi-layered heat transfer tube,   the approach surface is such that the opening on the entrance side of the insertion hole is substantially circular, and the sectional shape perpendicular to the insertion direction continuously changes from the opening on the entrance side toward the exit side portion of the insertion hole, and   the area of the opening on the exit side is smaller than the area of the opening on the entrance side.