Double pipe for heat exchange

Abstract

A double pipe for heat exchange in which an inner pipe is inserted into an outer pipe to enable heat exchange among a fluid flowing through an inner flow path in the inner pipe and an outer flow path between the inner pipe and the outer pipe. In a straight pipe portion extending linearly in a pipe lengthwise direction, a pipe wall of the inner pipe has a plurality of convex portions in a circumferential direction so as to form a concave/convex cross-sectional shape, and in the pipe wall of the inner pipe, an inclined pipe wall portion whose convex portion extends spirally in the pipe lengthwise direction and a turbulence-generating pipe wall portion whose convex portion has a lead angle different from that of the inclined pipe wall portion are formed in series in the pipe lengthwise direction.

What is claimed is: 
     
         1 . A double pipe for heat exchange in which an inner pipe is inserted into an outer pipe to enable heat exchange among a heat medium flowing through an inner flow path in the inner pipe and an outer flow path between the inner pipe and the outer pipe, comprising:
 in a straight pipe portion extending linearly in a pipe lengthwise direction so as to constitute a heat exchange portion,   a pipe wall of the inner pipe having a plurality of convex portions in a circumferential direction so as to form a concave/convex cross-sectional shape, and   in the pipe wall of the inner pipe, an inclined pipe wall portion whose convex portion extends spirally in the pipe lengthwise direction and a turbulence-generating pipe wall portion whose convex portion has a lead angle different from that of the inclined pipe wall portion being formed in series in the pipe lengthwise direction.   
     
     
         2 . The double pipe for heat exchange according to  claim 1 , wherein the turbulence-generating pipe wall portion is shorter than the inclined pipe wall portion in the pipe lengthwise direction. 
     
     
         3 . The double pipe for heat exchange according to  claim 1 , wherein the turbulence-generating pipe wall portion includes a straight pipe wall portion whose convex portion extends linearly in the pipe lengthwise direction. 
     
     
         4 . The double pipe for heat exchange according to  claim 1 , wherein the inclined pipe wall portion and the turbulence-generating pipe wall portion in the pipe wall of the inner pipe have a constant cross-sectional shape across the entire length. 
     
     
         5 . The double pipe for heat exchange according to  claim 1 , wherein the convex portion of the inclined pipe wall portion extends spirally in the pipe lengthwise direction at a constant lead angle. 
     
     
         6 . The double pipe for heat exchange according to  claim 1 , wherein the inclined pipe wall portion is located on each side of the turbulence-generating pipe wall portion in the pipe lengthwise direction.