Double-pipe heat exchanger and refrigeration cycle system

Abstract

In a double-pipe heat exchanger, a groove non-forming range is set as a non-groove surface in each of, in an inner surface of a heat transfer area increasing pipe, an inner surface of a part of the heat transfer area increasing pipe, which is held in close contact with an inner surface of an outer pipe, and a part of the inner surface of the outer pipe, which defines a second flow path in cooperation with an outer surface of the heat transfer area increasing pipe.

1 . A double-pipe heat exchanger, comprising:
 an outer pipe;   an inner pipe inserted to an inner side of the outer pipe, the inner pipe forming an annular region between the outer pipe and the inner pipe, and forming a first flow path in an inner side thereof; and   a heat transfer area increasing pipe arranged on the inner side of the outer pipe and an outer side of the inner pipe, the heat transfer area increasing pipe having projections and depressions in a radial direction, and forming a second flow path in the annular region,   wherein a non-groove surface is set in each of, in an inner surface of a part of the heat transfer area increasing pipe, which is held in close contact with an inner surface of the outer pipe, and a part of the inner surface of the outer pipe, which defines the second flow path in cooperation with an outer surface of the heat transfer area increasing pipe, and   wherein grooves are formed in at least a part or an entirety of a part excluding the non-groove surface from wall surface forming the second flow path.   
     
     
         2 . A double-pipe heat exchanger according to  claim 1 , wherein the non-groove surface is formed on each of a part of the inner surface of the outer pipe, which is held in close contact with the outer surface of the heat transfer area increasing pipe, a part of the outer surface of the heat transfer area increasing pipe, which is held in close contact with the inner surface of the outer pipe, a part of the outer surface of the inner pipe, which is held in close contact with the inner surface of the heat transfer area increasing pipe, and a part of the inner surface of the heat transfer area increasing pipe, which is held in close contact with the outer surface of the inner pipe. 
     
     
         3 . A double-pipe heat exchanger according to  claim 1 , wherein, after the grooves are formed in the heat transfer area increasing pipe, the heat transfer area increasing pipe is inserted to the annular region between the outer pipe and the inner pipe, and the outer pipe is reduced in diameter or the inner pipe is increased in diameter so that the heat transfer area increasing pipe is supported by the outer pipe and the inner pipe. 
     
     
         4 . A double-pipe heat exchanger according to  claim 1 , wherein the inner pipe and the outer pipe are brazed to the heat transfer area increasing pipe. 
     
     
         5 . A double-pipe heat exchanger according to  claim 4 , wherein the heat transfer area increasing pipe comprises a cladding material having a brazing material covered on a surface thereof. 
     
     
         6 . A refrigeration cycle system, comprising the double-pipe heat exchanger of  claim 1 ,
 wherein heat is exchanged between refrigerants in the double-pipe heat exchanger.   
     
     
         7 . A refrigeration cycle system, comprising the double-pipe heat exchanger of  claim 1 ,
 wherein heat is exchanged between a refrigerant and water or between a refrigerant and brine in the double-pipe heat exchanger.   
     
     
         8 . A double-pipe heat exchanger according to  claim 1 , wherein a groove forming candidate range comprises a part excluding the groove non-forming range from a part of the inner surface of the heat transfer area increasing pipe, which defines the second flow path in cooperation with an outer surface of the inner pipe, a part of the outer surface of the heat transfer area increasing pipe, which defines the second flow path in cooperation with the inner surface of the outer pipe, and a part of the outer surface of the inner pipe, which defines the second flow path in cooperation with the inner surface of the heat transfer area increasing pipe. 
     
     
         9 . A double-pipe heat exchanger according to  claim 1 , wherein grooves extend along a flow direction.