Round metal pipe, heat exchanger provided with same, pipe bender, and method for bend-processing round metal pipe

Abstract

A round metal pipe 1 including a bend portion 10 is configured such that on an axial direction cross-section of the bend portion 10, an outer half portion 11b of a peripheral wall portion 11 of the bend portion 10 has an outwardly projecting, non-circular arc shape in which a central portion in a y direction, which is orthogonal to a bend radius direction x of the bend portion 10, forms an outermost peripheral portion 13, and a distance Lb from respective intermediate portions 15 between the outermost peripheral portion 13 and a pair of proximal end portions 14 of the outer half portion 11b to a pipe center O is shorter than a distance La from the outermost peripheral portion 13 to the pipe center O. Thus, advantages such as suppressing reductions in the sectional area and minimum inside width of the bend portion 10 and reducing flow path resistance can be obtained, and the round metal pipe 1 can be manufactured easily and appropriately.

1 . A round metal pipe including a bend portion, wherein,
 on an axial direction cross-section of the bend portion, an outer half portion of a peripheral wall portion of the bend portion has an outwardly projecting, non-circular arc shape in which a central portion in an orthogonal direction to a bend radius direction of the bend portion forms an outermost peripheral portion, and a distance from respective intermediate portions between the outermost peripheral portion and a pair of proximal end portions of the outer half portion to a pipe center is shorter than a distance from the outermost peripheral portion to the pipe center.   
     
     
         2 . The round metal pipe according to  claim 1 , wherein,
 on the axial direction cross-section of the bend portion, an inner half portion of the peripheral wall portion of the bend portion has either a semicircular arc shape or a shape that is closer to a semicircular arc shape than the outer half portion.   
     
     
         3 . The round metal pipe according to  claim 1 , wherein,
 on the axial direction cross-section of the bend portion, the outermost peripheral portion and the intermediate portions of the outer half portion are respectively formed in either an outwardly projecting curved shape or a straight shape such that no inwardly depressed parts are provided on the outer half portion.   
     
     
         4 . A heat exchanger comprising a heat transfer pipe, wherein
 the heat transfer pipe is constructed using the round metal pipe according to  claim 1 .   
     
     
         5 . The heat exchanger according to  claim 4 , wherein
 the heat transfer pipe is a meandering heat transfer pipe in which a plurality of bend portions are provided as the bend portion and a plurality of straight pipe body portions arranged via intervals in a direction intersecting an axial length direction are connected in series via the plurality of bend portions.   
     
     
         6 . A pipe bender comprising:
 a rolling block having a first pipe insertion recess, into which a bending direction inner surface side of a round metal pipe is to be inserted, formed in an outer peripheral surface thereof; and   a pressure die having a second pipe insertion recess, into which a bending direction outer surface side of the round metal pipe is to be inserted, formed in a side face thereof, wherein   a bend portion is formable on the round metal pipe by clamping the round metal pipe between respective inner surfaces of the first and second pipe insertion recesses, and   the second pipe insertion recess has a non-semicircular cross-section on which a central portion in an opening width direction of the second pipe insertion recess forms a deepest portion, and a distance from respective intermediate portions between the deepest portion and a pair of edge portions of the second pipe insertion recess to a center between the pair of edge portions is shorter than a distance from the deepest portion to the center.   
     
     
         7 . The pipe bender according to  claim 6 , wherein
 the first pipe insertion recess is formed to have either a semicircular sectional shape or a sectional shape that is closer to a semicircular shape than the second pipe insertion recess.   
     
     
         8 . The pipe bender according to  claim 6 , wherein
 the deepest portion and the intermediate portions of the second pipe insertion recess are formed to have either a recessed, curved sectional shape or a straight sectional shape such that no projecting parts are provided on the second pipe insertion recess.   
     
     
         9 . A method for bend-processing a round metal pipe, comprising the step of:
 using a pipe bender including a rolling block having a first pipe insertion recess formed in an outer peripheral surface thereof and a pressure die having a second pipe insertion recess formed in a side face thereof to bend the round metal pipe by clamping the round metal pipe between respective inner surfaces of the first and second pipe insertion recesses, wherein   the pipe bender according to  claim 6  is used as the pipe bender.