Double Pipe Heat Exchanger and Method of Manufacturing the Same

Abstract

A double pipe heat exchanger that can be produced easily and can be used as a part of piping by bending the whole body, wherein an inner pipe is configured so that: a plurality of balloon-shaped bulges communicating with one another and extending from the center toward the radial directions in a cross section orthogonal to the axis line thereof may be formed; the outer circumference of the bulges may be bent into the shape of waves in an axial cross section; and the top portions of the waves may touch the inner surface of an outer pipe. Then in the state, the whole body including the inner pipe and the outer pipe is bent by applying external force.

1 . A double pipe heat exchanger wherein:
 an outer pipe is fitted outside an inner pipe;   in a cross section orthogonal to the axis line of the inner pipe, the inner pipe has a plurality of balloon-shaped bulges communicating with one another and extending in the radial directions from the center, and the width of each of the bulges is the largest at an intermediate portion between the center and the outside of the inner pipe in a radial direction and gradually decreases toward both the sides of the bulge in the radial direction;   a plurality of grooves is formed on the outer surface side at the center portion of the inner pipe in the manner of extending in an axial direction thereof;   the outer circumference of each of the bulges is bent into the shape of waves in an axial cross-section;   each top portion of the wave touches the inner surface of the outer pipe at the outermost end of the bulges in the radial directions in the cross section;   the axis lines of the outer pipe and the inner pipe are bent in the state where the outer pipe is fitted outside the inner pipe;   a first fluid flows in the inner pipe; and   a second fluid flows between the inner pipe and the outer pipe.   
   
   
       2 . The double pipe heat exchanger according to  claim 1 , wherein only the center portions of the end edges of said balloon-shaped bulges on the outside in the radial directions touch the inner surface of said outer pipe. 
   
   
       3 . The double pipe heat exchanger according to  claim 1  or  2  in combination with an exhaust gas system of a vehicle internal combustion engine, wherein:
 opening rims at both the ends of the inner pipe in the axial direction are connected and fixed to the inner surface of the outer pipe all around the rims;   a pair of ports for the first fluid is provided on the outer surface at both the ends of the outer pipe;   flanges for connection are protrusively attached to both the ends of the outer pipe; and   wherein the exhaust gas of the engine flows as the first fluid and cooling water flows as the second fluid whereby the heat exchanger functions as an EGR cooler.   
   
   
       4 . The double pipe heat exchanger according to  claim 1  or  2  in combination with a lubricating oil circulation system of a vehicle internal combustion engine, wherein:
 opening rims at both the ends of the inner pipe in the axial direction are connected and fixed to the inner surface of the outer pipe all around the rims;   a pair of ports for the first fluid is provided on the outer surface at both the ends of the outer pipe;   flanges for connection are protrusively attached to both the ends of the outer pipe; and   wherein one of the first fluid and the second fluid is cooling water and the other is an oil whereby the heat exchanger functions as an oil cooler.   
   
   
       5 . The double pipe heat exchanger according to  claim 1  or  2 , wherein the balloon-shaped bulges are three in number and, in an axial cross-section of said inner pipe:
 the three balloon-shaped bulges communicate with one another in the center; and   the whole appearance of the inner pipe is formed into the shape of a three-leaf clover.   
   
   
       6 . A method for producing a double pipe heat exchanger according to  claim 1  or  2 , comprising:
 inserting the inner pipe into the outer pipe and bringing the top portions of the waves of the bulges of the inner pipe into contact with the inner surface of the outer pipe while keeping each of the axis lines straight;   welding only the opening rims at both the ends of the inner pipe in the axial direction to the outer pipe; and   successively applying external force to the inner pipe and the outer pipe and bending the whole body so as to bend the axis lines of the pipes.