Flat heat transfer tube, manufacturing method of cross fin tube type heat exchanger having the same, and cross fin tube type heat exchanger manufactured by the same manufacturing method

Patent metadata

Field	Value
Publication number	US-9733025-B2
Application number	US-201214439767-A
Country	US
Kind code	B2
Filing date	Nov 13, 2012
Priority date	Nov 13, 2012
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

A flat heat transfer tube is used for a cross fin tube type heat exchanger including the flat heat transfer tube having a bending portion and a plurality of holes extending in a direction parallel with an axis direction of the flat heat transfer tube, and a plurality of plate fins bonded by welding to the flat heat transfer tube, wherein an interval between an outer surface of the flat heat transfer tube and an inner surface of the hole of a portion which is curved with a small curvature during bending is larger than an interval between an outer surface of the flat heat transfer tube and an inner surface of the hole of a portion which is curved with a large curvature during bending in a cross section of a portion of the flat heat transfer tube which corresponds to the bending portion before bending.

First claim

The invention claimed is:

1. A flat heat transfer tube used for a cross fin tube type heat exchanger including the flat heat transfer tube having a bending portion and a plurality of holes extending through in a direction parallel with an axial direction of the flat heat transfer tube, and a plurality of plate fins bonded by welding to the flat heat transfer tube, wherein
an interval between an outer surface of the flat heat transfer tube and an inner surface of at least one of the plurality of holes of a portion that is curved with a small curvature during bending is larger than an interval between an outer surface of the flat heat transfer tube and an inner surface of at least one of the plurality of holes of a portion that is curved with a large curvature during bending, wherein the intervals are measured in a radial direction of the curvatures and in a cross-sectional plane that extends through a portion of the flat heat transfer tube that corresponds to the bending portion before bending, and
an interval (t) of a portion that is curved with the smallest curvature during bending is determined based on a minimum interval (t 0 ) that is required after bending, an elongation rate (a), and a change rate (σ ratio ) of the tensile strength between before and after welding calculated by dividing a tensile strength after welding by a tensile strength before welding, and the elongation rate (a), a length (L) in a direction in which the curvature varies during bending of a length in a long diameter direction and a length in a short diameter direction of the cross section, and a radius of curvature (r) of a portion that is curved with the largest curvature during bending have a relationship of the following equation:

[

Math
.

⁢
1

]

a
=

r
+
L

r
+

L
/
2

.

2. The flat heat transfer tube of claim 1 , wherein the interval (t) of the portion that is curved with the smallest curvature during bending, the minimum interval (t 0 ), and the elongation rate (a) have a relationship of the following equation:
[Math. 2]
t=t 0× a.

3. The flat heat transfer tube of claim 1 , wherein the interval (t) of the portion that is curved with the smallest curvature during bending, the minimum interval (t 0 ), the elongation rate (a), and the change rate (σ ratio ) have a relationship of the following equation:

[

Math
.

⁢
3

]

t
=

t
⁢

⁢
0
×
a
×

1

σ
ratio

.

4. The flat heat transfer tube of claim 1 , wherein a size of one of the plurality of holes in the cross section of the portion that is curved with the small curvature during bending is smaller than a size of one of the plurality of holes in the cross section of the portion that is curved with the large curvature during bending.

5. The flat heat transfer tube of claim 1 , wherein an interval between adjacent holes in the cross section of a portion that is curved with the small curvature during bending is larger than an interval between adjacent holes in the cross section of a portion that is curved with the large curvature during bending.

6. A manufacturing method of a cross fin tube type heat exchanger including the flat heat transfer tube having a bending portion and a plurality of holes extending through in a direction parallel with an axis direction of the flat heat transfer tube, and a plurality of plate fins bonded by welding to the flat heat transfer tube, comprising:
forming the holes in the flat heat transfer tube so that an interval between an outer surface of the flat heat transfer tube and an inner surface of at least one of the plurality of holes of a portion that is curved with a small curvature during bending is larger than an interval between an outer surface of the flat heat transfer tube and the inner surface of at least one of the plurality of holes of a portion that is curved with a large curvature during bending wherein the intervals are measured in a radial direction of the curvatures and in a cross-sectional plane that extends through a portion of the flat heat transfer tube that corresponds to the bending portion before bending;
welding the plate fins to the flat heat transfer tube in a state in which one end of the flat heat transfer tube in the long diameter direction protrudes; and
bending the flat heat transfer tube that is welded to the plate fins while a jig is pressed against the one end thereof,
wherein an interval (t) of a portion that is curved with the smallest curvature during bending is determined based on a minimum interval (t 0 ) that is required after bending, an elongation rate (a), and a change rate (σ ratio ) of the tensile strength between before and after welding calculated by dividing a tensile strength after welding by a tensile strength before welding, and the elongation rate (a), a length (L) in a direction in which the curvature varies during bending of a length in a long diameter direction and a length in a short diameter direction of the cross section, and a radius of curvature (r) of a portion that is curved with the largest curvature during bending have a relationship of the following equation:

Assignees

• Hokazono Keisuke
• Mitsubishi Electric Corp

Inventors

• Hokazono Keisuke

Classifications

• F28F1/32 Primary

  the means having portions engaging further tubular elements · CPC title

• B23P15/26

  heat exchangers {or the like (making heat exchangers by methods covered by other subclasses B21D53/02)} · CPC title

• Y10T29/4935

  Heat exchanger or boiler making · CPC title

• F28F1/022

  with multiple channels · CPC title

• F28F1/10 Primary

  Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses (crimped or corrugated elements F28F1/06, F28F1/08) · CPC title