U.S. patent application number 12/230659 was filed with the patent office on 2009-03-12 for flat heat transfer tube.
This patent application is currently assigned to SHOWA DENKO K.K.. Invention is credited to Daisuke Uneno.
Application Number | 20090065183 12/230659 |
Document ID | / |
Family ID | 40340294 |
Filed Date | 2009-03-12 |
United States Patent
Application |
20090065183 |
Kind Code |
A1 |
Uneno; Daisuke |
March 12, 2009 |
Flat heat transfer tube
Abstract
A flat heat transfer tube has upper and lower walls and fluid
channels. Two to five inner fins are formed on each of two surfaces
of the flat walls facing each fluid channel. The tube height is 1.8
mm or less; the tube width is 20 mm or less; the fluid channel
height is 1.0 mm or less; the fluid channel width w1 is 2.0 mm or
less; the fluid diameter is 0.3 to 1.2 mm; and the thickness t of
each wall is 0.4 mm or less. The ratio h2/t of the fin height h2 to
the wall thickness t satisfies the relation
0.5.ltoreq.h2/t.ltoreq.2.0. The ratio p1/w1 of the fin pitch p1 to
the fluid channel width w1 satisfies the relation
0.15.ltoreq.p1/w1.ltoreq.1/n (where n is the number of the inner
fins formed on one of the two surfaces).
Inventors: |
Uneno; Daisuke; (Oyama-shi,
JP) |
Correspondence
Address: |
EDWARDS ANGELL PALMER & DODGE LLP
P.O. BOX 55874
BOSTON
MA
02205
US
|
Assignee: |
SHOWA DENKO K.K.
Tokyo
JP
|
Family ID: |
40340294 |
Appl. No.: |
12/230659 |
Filed: |
September 3, 2008 |
Current U.S.
Class: |
165/152 ;
165/173 |
Current CPC
Class: |
F28F 3/048 20130101;
F28F 1/40 20130101; F28F 1/022 20130101; F28F 1/04 20130101 |
Class at
Publication: |
165/152 ;
165/173 |
International
Class: |
F28D 1/02 20060101
F28D001/02; F28F 9/02 20060101 F28F009/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 6, 2007 |
JP |
2007-231185 |
Claims
1: A flat heat transfer tube which assumes a flat form having a
pair of flat walls facing each other and has a plurality of fluid
channels arranged along the width of the flat heat transfer tube;
in which an inner fin in the form of an elongated projection
extending along the length of the flat heat transfer tube is formed
on each of two surfaces of the respective flat walls, the two
surfaces facing each of the fluid channels; and which has a tube
height H of 1.8 mm or less, a tube width W of 20 mm or less, a
height h1 of the fluid channel of 1.0 mm or less, a width w1 of the
fluid channel of 2.0 mm or less, and a fluid diameter Dh of 0.3 mm
to 1.2 mm; wherein a thickness t of each of the flat walls is 0.4
mm or less; two to five inner fins are formed on at least one of
the two surfaces of the respective flat walls, the two surfaces
facing at least one fluid channel; a ratio h2/t or h2a/t, which is
the ratio of a height h2 or h2a of the inner fin to the thickness t
of the flat wall, satisfies a relation 0.5.ltoreq.h2/t.ltoreq.2.0
or 0.5.ltoreq.h2a/t.ltoreq.2.0, respectively; and a ratio p1/w1,
p2/w1, or p3/w1, which is the ratio of a fin pitch p1, p2, or p3 of
the plurality of inner fins to the width w1 of the fluid channel,
satisfies a relation 0.15.ltoreq.p1/w1.ltoreq.1/n,
0.15.ltoreq.p2/w1.ltoreq.1/n, or 0.15.ltoreq.p3/w1.ltoreq.1/n,
respectively (where n is the number of the inner fins formed on at
least one of the two surfaces of the respective flat walls).
2: A flat heat transfer tube according to claim 1, wherein a
plurality of the inner fins are formed on each of the two surfaces
of the respective flat walls, the two surfaces facing each of the
fluid channels, and the number of the inner fins is the same
between the two surfaces.
3: A flat heat transfer tube according to claim 2, wherein the
ratio of the height h2 or h2a of the inner fin to the height h1 of
the fluid channel satisfies a relation h2/h1<0.5 or
h2a/h1<0.5, respectively, and the positions of the inner fins
along the width of each of the fluid channels are the same between
the two surfaces of the respective flat walls.
4: A flat heat transfer tube according to claim 2, wherein the
ratio of the height h2 or h2a of the inner fin to the height h1 of
the fluid channel satisfies a relation h2/h1.gtoreq.0.5 or
h2a/h1.gtoreq.0.5, respectively, and the positions of the inner
fins along the width of each of the fluid channels differ between
the two surfaces of the respective flat walls.
5: A flat heat transfer tube according to claim 1, wherein a
plurality of the inner fins are formed on each of the two surfaces
of the respective flat walls, the two surfaces facing each of the
fluid channels, and the number of the inner fins differs between
the two surfaces.
6: A flat heat transfer tube according to claim 5, wherein the
positions of the inner fins along the width of each of the fluid
channels differ between the two surfaces of the respective flat
walls.
7: A flat heat transfer tube according to claim 2, wherein the
height h2a of at least one of the inner fins formed on at least one
of the two surfaces of the respective flat walls, the two surfaces
facing each of the fluid channels, differs from the height h2 of
the remaining inner fins.
8: A flat heat transfer tube which assumes a flat form having a
pair of flat walls facing each other and has a plurality of fluid
channels arranged along the width of the flat heat transfer tube;
in which an inner fin in the form of an elongated projection
extending along the length of the flat heat transfer tube is formed
on each of two surfaces of the respective flat walls, the two
surfaces facing each of the fluid channels; and which has a tube
height H of 1.8 mm or less, a tube width W of 20 mm or less, a
height h1 of the fluid channel of 1.0 mm or less, a width w1 of the
fluid channel of 2.0 mm or less, and a fluid diameter Dh of 0.3 mm
to 1.2 mm; wherein a thickness t of each of the flat walls is 0.4
mm or less; a single inner fin is formed on at least one of the two
surfaces of the respective flat walls, the two surfaces facing at
least one fluid channel; a ratio h2/t, which is the ratio of a
height h2 of the inner fin to the thickness t of the flat wall,
satisfies a relation 0.5.ltoreq.h2/t.ltoreq.2.0; and a ratio
w2c/w1, which is the ratio of a distance w2c between the single
inner fin and a side surface of the fluid channel to the width w1
of the fluid channel, satisfies a relation
1/4.ltoreq.w2c/w1.ltoreq.1/2.
9: A flat heat transfer tube according to claim 8, wherein a single
inner fin is formed on each of the two surfaces of the respective
flat walls, the two surfaces facing each of the fluid channels; the
ratio of the height h2 of the inner fin to the height h1 of the
fluid channel satisfies a relation h2/h1<0.5; and the position
of the inner fin along the width of each of the fluid channels is
the same between the two surfaces of the respective flat walls.
10: A flat heat transfer tube according to claim 8, wherein a
single inner fin is formed on each of the two surfaces of the
respective flat walls, the two surfaces facing each of the fluid
channels; the ratio of the height h2 of the inner fin to the height
h1 of the fluid channel satisfies a relation h2/h1.gtoreq.0.5; and
the position of the inner fin along the width of each of the fluid
channels differs between the two surfaces of the respective flat
walls.
11: A heat exchanger including a pair of header tanks arranged
apart from each other; a plurality of flat heat exchange tubes
extending between the two header tanks, arranged at predetermined
intervals along the length of the header tanks, and having opposite
end portions brazed to the header tanks after being inserted into
respective tube insertion holes formed in the header tanks; and
corrugate fins each disposed between and brazed to the adjacent
heat exchange tubes; wherein each of the heat exchange tubes is the
flat heat transfer tube according to claim 1.
12: A heat exchanger including a pair of header tanks arranged
apart from each other; a plurality of flat heat exchange tubes
extending between the two header tanks, arranged at predetermined
intervals along the length of the header tanks, and having opposite
end portions brazed to the header tanks after being inserted into
respective tube insertion holes formed in the header tanks; and
corrugate fins each disposed between and brazed to the adjacent
heat exchange tubes; wherein each of the heat exchange tubes is the
flat heat transfer tube according to claim 2.
13: A heat exchanger including a pair of header tanks arranged
apart from each other; a plurality of flat heat exchange tubes
extending between the two header tanks, arranged at predetermined
intervals along the length of the header tanks, and having opposite
end portions brazed to the header tanks after being inserted into
respective tube insertion holes formed in the header tanks; and
corrugate fins each disposed between and brazed to the adjacent
heat exchange tubes; wherein each of the heat exchange tubes is the
flat heat transfer tube according to claim 3.
14: A heat exchanger including a pair of header tanks arranged
apart from each other; a plurality of flat heat exchange tubes
extending between the two header tanks, arranged at predetermined
intervals along the length of the header tanks, and having opposite
end portions brazed to the header tanks after being inserted into
respective tube insertion holes formed in the header tanks; and
corrugate fins each disposed between and brazed to the adjacent
heat exchange tubes; wherein each of the heat exchange tubes is the
flat heat transfer tube according to claim 4.
15: A heat exchanger including a pair of header tanks arranged
apart from each other; a plurality of flat heat exchange tubes
extending between the two header tanks, arranged at predetermined
intervals along the length of the header tanks, and having opposite
end portions brazed to the header tanks after being inserted into
respective tube insertion holes formed in the header tanks; and
corrugate fins each disposed between and brazed to the adjacent
heat exchange tubes; wherein each of the heat exchange tubes is the
flat heat transfer tube according to claim 5.
16: A heat exchanger including a pair of header tanks arranged
apart from each other; a plurality of flat heat exchange tubes
extending between the two header tanks, arranged at predetermined
intervals along the length of the header tanks, and having opposite
end portions brazed to the header tanks after being inserted into
respective tube insertion holes formed in the header tanks; and
corrugate fins each disposed between and brazed to the adjacent
heat exchange tubes; wherein each of the heat exchange tubes is the
flat heat transfer tube according to claim 6.
17: A heat exchanger including a pair of header tanks arranged
apart from each other; a plurality of flat heat exchange tubes
extending between the two header tanks, arranged at predetermined
intervals along the length of the header tanks, and having opposite
end portions brazed to the header tanks after being inserted into
respective tube insertion holes formed in the header tanks; and
corrugate fins each disposed between and brazed to the adjacent
heat exchange tubes; wherein each of the heat exchange tubes is the
flat heat transfer tube according to claim 7.
18: A heat exchanger including a pair of header tanks arranged
apart from each other; a plurality of flat heat exchange tubes
extending between the two header tanks, arranged at predetermined
intervals along the length of the header tanks, and having opposite
end portions brazed to the header tanks after being inserted into
respective tube insertion holes formed in the header tanks; and
corrugate fins each disposed between and brazed to the adjacent
heat exchange tubes; wherein each of the heat exchange tubes is the
flat heat transfer tube according to claim 8.
19: A heat exchanger including a pair of header tanks arranged
apart from each other; a plurality of flat heat exchange tubes
extending between the two header tanks, arranged at predetermined
intervals along the length of the header tanks, and having opposite
end portions brazed to the header tanks after being inserted into
respective tube insertion holes formed in the header tanks; and
corrugate fins each disposed between and brazed to the adjacent
heat exchange tubes; wherein each of the heat exchange tubes is the
flat heat transfer tube according to claim 9.
20: A heat exchanger including a pair of header tanks arranged
apart from each other; a plurality of flat heat exchange tubes
extending between the two header tanks, arranged at predetermined
intervals along the length of the header tanks, and having opposite
end portions brazed to the header tanks after being inserted into
respective tube insertion holes formed in the header tanks; and
corrugate fins each disposed between and brazed to the adjacent
heat exchange tubes; wherein each of the heat exchange tubes is the
flat heat transfer tube according to claim 10.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a flat heat transfer tube,
and more particularly to a flat heat transfer tube for use as a
heat exchange tube of a heat exchanger, such as a condenser or an
evaporator of a car air conditioner, an automotive radiator, or an
automotive oil cooler.
[0002] Herein, the term "aluminum" encompasses aluminum alloys in
addition to pure aluminum.
[0003] In recent years, a so-called multiflow condenser has been
widely used as, for example, a condenser for use in a car air
conditioner using a chlorofluorocarbon-based refrigerant, since the
multiflow condenser can implement high performance, low pressure
loss, and ultracompactness. As shown in FIG. 14, the multiflow
condenser includes a first header 60 and a second header 61
arranged in parallel with and apart from each other; a plurality of
flat heat exchange tubes 62 of aluminum arranged in parallel and
having opposite ends connected to the respective first and second
headers 60 and 61; corrugate fins 63 of aluminum, each being
arranged in an air-passing clearance between adjacent heat exchange
tubes 62 and brazed to the two heat exchange tubes 62; an inlet
member 64 connected to an upper end portion of a circumferential
wall of the first header 60; an outlet member 65 connected to a
lower end portion of a circumferential wall of the second header
61; a first partition plate 66 provided in the interior of the
first header 60 above a vertically intermediate position; and a
second partition plate 67 provided in the interior of the second
header 61 below a vertically intermediate position. The heat
exchange tubes 62 arranged above the first partition plate 66, the
heat exchange tubes 62 arranged between the first partition plate
66 and the second partition plate 67, and the heat exchange tubes
62 arranged below the second partition plate 67 sequentially reduce
in number and constitute respective passes. In the condenser, a
gas-phase refrigerant having flowed into the condenser through the
inlet member 64 flows through the passes in a serpentine fashion
until the refrigerant flows out of the outlet member 65 in a liquid
phase.
[0004] The heat exchange tube 62 of the above-mentioned condenser
is required to have not only an excellent heat exchange efficiency
but also a resistance to pressure, since a high-pressure gas
refrigerant is introduced thereinto.
[0005] A flat heat transfer tube for use as the heat exchange tube
62 of the above-mentioned condenser is disclosed in, for example,
Japanese Patent Application Laid-Open (kokai) No. 6-185885. The
flat heat transfer tube described in the publication is an aluminum
extrudate; assumes a flat form having a pair of flat walls facing
each other; and has a plurality of fluid channels arranged along
the width of the flat heat transfer tube. A plurality of inner
fins, each assuming the form of an elongated projection extending
along the length of the flat heat transfer tube, are formed on each
of two surfaces of the respective flat walls, the two surfaces
facing each of the fluid channels. The height of the flat heat
transfer tube is 2.0 mm or less; the height of the fluid channel is
1.2 mm or less; the ratio of the width of the fluid channel to the
height of the fluid channel is to 6.0; the ratio of the height of
the inner fin to the height of the fluid channel is 0.055 to 0.25;
and the inner-fin pitch is 0.25 mm to 0.6 mm.
[0006] Table 1 shows the flat heat transfer tubes described as
examples in the above-mentioned publication.
TABLE-US-00001 TABLE 1 RATIO RATIO OF THE OF THE INNER HEIGHT FIN
WIDTH OF OF THE PITCH THE FLUID FLUID INNER TO THE CHANNEL HEIGHT
HEIGHT DIAMETER FIN WIDTH OPPO- OF THE OF THE INNER OPPO- TO THE OF
THE TUBE TUBE THICK- SITE FLUID INNER FIN SITE THICK- FLUID WIDTH
HEIGHT NESS CENTER ENDS CHANNEL FIN PITCH CENTER ENDS NESS CHANNEL
1 17 mm 1.8 mm 0.45 mm 3.87 mm 3.755 mm 0.9 mm 0.15 mm 0.48 mm 1.06
mm 1.14 mm 0.33 0.12 2 '' '' '' '' '' '' '' 1.03 mm 1.21 mm 1.21 mm
'' 0.27 3 '' '' '' '' '' '' '' 1.24 mm 1.24 mm '' '' 4 '' '' '' ''
'' '' '' '' 1.28 mm 1.28 mm '' '' 5 '' '' '' '' '' '' '' '' 1.33 mm
1.33 mm '' '' 6 '' '' '' 1.81 mm 1.81 mm '' '' -- 1.07 mm 1.07 mm
'' --
[0007] In the flat heat transfer tube No. 6 in Table 1, a single
inner fin in the form of an elongated projection extending along
the length of the flat heat transfer tube is formed on each of two
surfaces of the respective flat walls, the two surfaces facing each
of the fluid channels.
[0008] Recently, further improvement of heat exchange performance
is required of the above-mentioned condenser. However, referring to
Table 1 showing the flat heat transfer tubes described in the
above-mentioned publication, there exists no flat heat transfer
tube in which all of the tube width, the tube height, the thickness
of the flat wall, the width of the fluid channel, the height of the
fluid channel, the height of the inner fin, the inner-fin pitch,
the fluid diameter, the ratio of the height of the inner fin to the
thickness of the flat wall, and the ratio of the inner-fin pitch to
the width of the fluid channel fall within respective optimum
ranges. Particularly, since the thickness of the flat wall is
large, and the ratio of the height of the inner fin to the
thickness of the flat wall is low, heat transfer performance is
insufficient. Therefore, the required further improvement of heat
exchange performance of the condenser cannot be implemented.
SUMMARY OF THE INVENTION
[0009] An object of the present invention is to solve the
above-mentioned problem and to provide a flat heat transfer tube
capable of improving heat exchange performance of a heat
exchanger.
[0010] To fulfill the above object, the present invention comprises
the following modes.
[0011] 1) A flat heat transfer tube which assumes a flat form
having a pair of flat walls facing each other and has a plurality
of fluid channels arranged along the width of the flat heat
transfer tube; in which an inner fin in the form of an elongated
projection extending along the length of the flat heat transfer
tube is formed on each of two surfaces of the respective flat
walls, the two surfaces facing each of the fluid channels; and
which has a tube height H of 1.8 mm or less, a tube width W of 20
mm or less, a height h1 of the fluid channel of 1.0 mm or less, a
width w1 of the fluid channel of 2.0 mm or less, and a fluid
diameter Dh of 0.3 mm to 1.2 mm;
[0012] wherein a thickness t of each of the flat walls is 0.4 mm or
less; two to five inner fins are formed on at least one of the two
surfaces of the respective flat walls, the two surfaces facing at
least one fluid channel; a ratio h2/t or h2a/t, which is the ratio
of a height h2 or h2a of the inner fin to the thickness t of the
flat wall, satisfies a relation 0.5.ltoreq.h2/t.ltoreq.2.0 or
0.5.ltoreq.h2a/t.ltoreq.2.0, respectively; and a ratio p1/w1,
p2/w1, or p3/w1, which is the ratio of a fin pitch p1, p2, or p3 of
the plurality of inner fins to the width w1 of the fluid channel,
satisfies a relation 0.15.ltoreq.p1/w1.ltoreq.1/n,
0.15.ltoreq.p2/w1.ltoreq.1/n, or 0.15.ltoreq.p3/w1.ltoreq.1/n,
respectively (where n is the number of the inner fins formed on at
least one of the two surfaces of the respective flat walls).
[0013] 2) A flat heat transfer tube according to par. 1), wherein a
plurality of the inner fins are formed on each of the two surfaces
of the respective flat walls, the two surfaces facing each of the
fluid channels, and the number of the inner fins is the same
between the two surfaces.
[0014] 3) A flat heat transfer tube according to par. 2), wherein
the ratio of the height h2 or h2a of the inner fin to the height h1
of the fluid channel satisfies a relation h2/h1<0.5 or
h2a/h1<0.5, respectively, and the positions of the inner fins
along the width of each of the fluid channels are the same between
the two surfaces of the respective flat walls.
[0015] 4) A flat heat transfer tube according to par. 2), wherein
the ratio of the height h2 or h2a of the inner fin to the height h1
of the fluid channel satisfies a relation h2/h1.gtoreq.0.5 or
h2a/h1 0.5, respectively, and the positions of the inner fins along
the width of each of the fluid channels differ between the two
surfaces of the respective flat walls.
[0016] 5) A flat heat transfer tube according to par. 1), wherein a
plurality of the inner fins are formed on each of the two surfaces
of the respective flat walls, the two surfaces facing each of the
fluid channels, and the number of the inner fins differs between
the two surfaces.
[0017] 6) A flat heat transfer tube according to par. 5), wherein
the positions of the inner fins along the width of each of the
fluid channels differ between the two surfaces of the respective
flat walls.
[0018] 7) A flat heat transfer tube according to par. 2), wherein
the height h2a of at least one of the inner fins formed on at least
one of the two surfaces of the respective flat walls, the two
surfaces facing each of the fluid channels, differs from the height
h2 of the remaining inner fins.
[0019] 8) A flat heat transfer tube which assumes a flat form
having a pair of flat walls facing each other and has a plurality
of fluid channels arranged along the width of the flat heat
transfer tube; in which an inner fin in the form of an elongated
projection extending along the length of the flat heat transfer
tube is formed on each of two surfaces of the respective flat
walls, the two surfaces facing each of the fluid channels; and
which has a tube height H of 1.8 mm or less, a tube width W of 20
mm or less, a height h1 of the fluid channel of 1.0 mm or less, a
width w1 of the fluid channel of 2.0 mm or less, and a fluid
diameter Dh of 0.3 mm to 1.2 mm;
[0020] wherein a thickness t of each of the flat walls is 0.4 mm or
less; a single inner fin is formed on at least one of the two
surfaces of the respective flat walls, the two surfaces facing at
least one fluid channel; a ratio h2/t, which is the ratio of a
height h2 of the inner fin to the thickness t of the flat wall,
satisfies a relation 0.5.ltoreq.h2/t.ltoreq.2.0; and a ratio
w2c/w1, which is the ratio of a distance w2c between the single
inner fin and a side surface of the fluid channel to the width w1
of the fluid channel, satisfies a relation
1/4.ltoreq.w2c/w1.ltoreq.1/2.
[0021] 9) A flat heat transfer tube according to par. 8), wherein a
single inner fin is formed on each of the two surfaces of the
respective flat walls, the two surfaces facing each of the fluid
channels; the ratio of the height h2 of the inner fin to the height
h1 of the fluid channel satisfies a relation h2/h1<0.5; and the
position of the inner fin along the width of each of the fluid
channels is the same between the two surfaces of the respective
flat walls.
[0022] 10) A flat heat transfer tube according to par. 8), wherein
a single inner fin is formed on each of the two surfaces of the
respective flat walls, the two surfaces facing each of the fluid
channels; the ratio of the height h2 of the inner fin to the height
h1 of the fluid channel satisfies a relation h2/h1.gtoreq.0.5; and
the position of the inner fin along the width of each of the fluid
channels differs between the two surfaces of the respective flat
walls.
[0023] 11) A heat exchanger including a pair of header tanks
arranged apart from each other; a plurality of flat heat exchange
tubes extending between the two header tanks, arranged at
predetermined intervals along the length of the header tanks, and
having opposite end portions brazed to the header tanks after being
inserted into respective tube insertion holes formed in the header
tanks; and corrugate fins each disposed between and brazed to the
adjacent heat exchange tubes;
[0024] wherein each of the heat exchange tubes is the flat heat
transfer tube according to any one of pars. 1) to 10).
[0025] In the flat heat transfer tube of par. 1) or 8), the term
"fluid diameter" means an equivalent diameter of a circular tube on
the assumption that the heat transfer tube having a plurality of
fluid channels each having a noncircular cross section is the
circular tube having a single passage, and is defined by the
following expression.
[0026] Dh=4Ac/L, where Ac is the total cross-sectional area of
fluid channels, and L is the total wetted perimeter (total wetted
side length) of fluid channels.
[0027] According to the flat heat transfer tube of any one of pars.
1) to 10), the tube width, the tube height, the thickness of the
flat wall, the width of the fluid channel, the height of the fluid
channel, the height of the inner fin, the fin pitch of the inner
fins, the fluid diameter, the ratio of the height of the inner fin
to the thickness of the flat wall, and the ratio of the fin pitch
to the width of the fluid channel fall within respective optimum
ranges. Therefore, the flat heat transfer tube exhibits excellent
heat transfer performance. Accordingly, through use of the flat
heat transfer tubes, a heat exchanger can further improve heat
exchange performance.
[0028] According to the flat heat transfer tube of any one of pars.
5) to 10), an increase in pressure drop can be restrained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a cross-sectional view showing a flat heat
transfer tube according to Embodiment 1 of the present
invention;
[0030] FIG. 2 is a fragmentary enlarged view showing a single fluid
channel of the flat heat transfer tube of FIG. 1;
[0031] FIG. 3 is a front view showing a sheet-like member from
which the flat heat transfer tube of FIG. 1 is manufactured;
[0032] FIG. 4 is a front view showing a step in the course of
manufacture of the flat heat transfer tube of FIG. 1 from the
sheet-like member of FIG. 3;
[0033] FIG. 5 is a cross-sectional view showing a flat heat
transfer tube according to Embodiment 2 of the present
invention;
[0034] FIG. 6 is a fragmentary enlarged view showing a single fluid
channel of the flat heat transfer tube of FIG. 5;
[0035] FIG. 7 is a fragmentary enlarged view showing a single fluid
channel of a flat heat transfer tube according to Embodiment 3 of
the present invention;
[0036] FIG. 8 is a fragmentary enlarged view showing a single fluid
channel of a flat heat transfer tube according to Embodiment 4 of
the present invention;
[0037] FIG. 9 is a fragmentary enlarged view showing a single fluid
channel of a flat heat transfer tube according to Embodiment 5 of
the present invention;
[0038] FIG. 10 is a fragmentary enlarged view showing a single
fluid channel of a flat heat transfer tube according to Embodiment
6 of the present invention;
[0039] FIG. 11 is a fragmentary enlarged view showing a single
fluid channel of a flat heat transfer tube according to Embodiment
7 of the present invention;
[0040] FIG. 12 is a graph showing the results of Evaluation Test 1
for Examples 1 to 3 and Comparative Examples 1 and 2;
[0041] FIG. 13 is a graph showing the results of Evaluation Test 1
for Examples 4 to 10 and Comparative Example 3; and
[0042] FIG. 14 is a perspective view showing a condenser for use in
a car air conditioner.
BEST MODE FOR CARRYING OUT THE INVENTION
[0043] Embodiments of the present invention will next be described
with reference to the drawings. In the following description, the
upper, lower, left-hand, and right-hand sides of FIGS. 1 to 11 will
be referred to as "upper," "lower," "left," and "right,"
respectively.
[0044] In the drawings, like sections or components throughout the
several views are denoted by like reference numerals, and repeated
description thereof is omitted.
EMBODIMENT 1
[0045] The present embodiment is shown in FIGS. 1 to 4.
[0046] FIG. 1 shows the overall configuration of a flat heat
transfer tube according to Embodiment 1 of the present invention.
FIG. 2 shows, on an enlarged scale, a single fluid channel of the
flat heat transfer tube according to Embodiment 1 of the present
invention. FIG. 3 shows a sheet-like member from which the flat
heat transfer tube is manufactured. FIG. 4 shows a step in the
course of manufacture of the flat heat transfer tube from the
sheet-like member.
[0047] In FIGS. 1 and 2, a flat heat transfer tube 1 is made of
aluminum and includes flat upper and lower walls 2 and 3 (a pair of
flat walls) facing each other; left and right side walls 4 and 5
extending between the left ends of the upper and lower walls 2 and
3 and between the right ends of the upper and lower walls 2 and 3,
respectively; and a plurality of reinforcement walls 6 arranged at
predetermined intervals between the left and right side walls 4 and
5 and extending between the upper and lower walls 2 and 3 and along
the length of the flat heat transfer tube 1. Accordingly, the flat
heat transfer tube 1 has a plurality of fluid channels 7 arranged
therein along its width. Although unillustrated, a plurality of
communication holes for establishing communication between the
adjacent fluid channels 7 are formed in all of the reinforcement
walls 6 in a staggered arrangement as viewed in plane.
[0048] Two to five; herein, three, inner fins 8, each assuming an
elongated projection extending along the length of the flat heat
transfer tube 1, are formed on surfaces 2a and 3a of the upper and
lower walls 2 and 3, the surfaces 2a and 3a facing each of the
fluid channels 7; i.e., are disposed on the upper and lower
surfaces of each of the fluid channels 7. The number of the inner
fins 8 is the same between the two surfaces 2a and 3a. All of the
inner fins 8 have the same height. Further, the inner fins 8 formed
on the surface 2a of the upper wall 2 and the inner fins 8 formed
on the surface 3a of the lower wall 3 are located at the same
positions along the width of the flat heat transfer tube 1.
[0049] The left side wall 4 is formed such that a side-wall-forming
elongated projection 9 and a side-wall-forming elongated projection
11 are butt-brazed together. The side-wall-forming elongated
projection 9 is formed integrally with a left end of the upper wall
2 in a downwardly projecting condition. The side-wall-forming
elongated projection 11 is formed integrally with a left end of the
lower wall 3 in an upwardly projecting condition. The right side
wall 5 is formed integrally with the upper and lower walls 2 and
3.
[0050] The reinforcement walls 6 are formed such that
reinforcement-wall-forming elongated projections 12 and 13 are
butt-brazed to reinforcement-wall-forming elongated projections 15
and 14, respectively. The reinforcement-wall-forming elongated
projections 12 and 13 are formed integrally with the upper wall 2
in a downwardly projecting condition. The
reinforcement-wall-forming elongated projections 14 and 15 are
formed integrally with the lower wall 3 in an upwardly projecting
condition. Two kinds of the reinforcement-wall-forming elongated
projections 12 and 13 having different thicknesses are formed on
the upper wall 2 in such a manner as to alternate with each other
along the left-right direction. Two kinds of the
reinforcement-wall-forming elongated projections 14 and 15 having
different thicknesses are formed on the lower wall 3 in such a
manner as to alternate with each other along the left-right
direction. The thick reinforcement-wall-forming elongated
projections 12 integral with the upper wall 2 are brazed to the
respective thin reinforcement-wall-forming elongated projections 15
integral with the lower wall 3. The thin reinforcement-wall-forming
elongated projections 13 integral with the upper wall 2 are brazed
to the respective thick reinforcement-wall-forming elongated
projections 14 integral with the lower wall 3. Hereinafter, the
thick reinforcement-wall-forming elongated projections 12 and 14 of
the upper and lower walls 2 and 3, respectively, are referred to as
the first reinforcement-wall-forming elongated projections.
Similarly, the thin reinforcement-wall-forming elongated
projections 13 and 15 of the upper and lower walls 2 and 3,
respectively, are referred to as the second
reinforcement-wall-forming elongated projections. The first
reinforcement-wall-forming elongated projections 12 and 14 of the
upper and lower walls 2 and 3 have grooves 16 and 17, respectively,
formed on their distal end faces along their entire lengths. Distal
end portions of the second reinforcement-wall-forming elongated
projections 15 and 13 of the lower and upper walls 3 and 2 are
fitted into the grooves 16 and 17 of the respective first
reinforcement-wall-forming elongated projections 12 and 14 of the
upper and lower walls 2 and 3, respectively. While distal end
portions of the second reinforcement-wall-forming elongated
projections 15 of the lower wall 3 are press-fitted into the
grooves 16 of the respective first reinforcement-wall-forming
elongated projections 12 of the upper wall 2, and distal end
portions of the second reinforcement-wall-forming elongated
projections 13 of the upper wall 2 are press-fitted into the
grooves 17 of the respective first reinforcement-wall-forming
elongated projections 14 of the lower wall 3, the
reinforcement-wall-forming elongated projections 12 and 15 are
brazed together, and the reinforcement-wall-forming elongated
projections 13 and 14 are brazed together.
[0051] The tube height H of the heat transfer tube 1 is 1.8 mm or
less; the tube width W of the heat transfer tube 1 is 20 mm or
less; the height h1 of the fluid channel 7 is 1.0 mm or less; the
width w1 of the fluid channel 7 (the distance between the opposite
side surfaces of a single fluid channel 7; i.e., the distance
between the surfaces of the second reinforcement-wall-forming
elongated projections 13 and 15 of the two reinforcement walls 6
located on the opposite sides of the fluid channel 7, the surfaces
facing the fluid channel 7) is 2.0 mm or less; the fluid diameter
Dh is 0.3 mm to 1.2 mm; and the thickness t of each of the upper
and lower walls 2 and 3 is 0.4 mm or less. The ratio of the height
h2 of the inner fin 8 to the thickness t of each of the upper and
lower walls 2 and 3; i.e., the ratio h2/t, satisfies the relation
0.5.ltoreq.h2/t.ltoreq.2.0. The ratio of the fin pitch (the
distance between the thicknesswise centers of the inner fins 8) p1
of a plurality of the inner fins 8 to the width w1 of the fluid
channel 7; i.e., the ratio p1/w1, satisfies the relation
0.15.ltoreq.p1/w1.ltoreq.1/n (n is the number of the inner fins 8
formed on each of the two surfaces 2a and 3a of the upper and lower
walls 2 and 3). When the tube height H, the tube width W, the
height h1 of the fluid channel 7, the width w1 of the fluid channel
7, the fluid diameter Dh, the thickness t of each of the upper and
lower walls 2 and 3, the ratio of the height h2 of the inner fin 8
to the thickness t of each of the upper and lower walls 2 and 3;
i.e., the ratio h2/t, and the ratio of the fin pitch p1 of the
plurality of the inner fins 8 to the width w1 of the fluid channel
7; i.e., the ratio p1/w1, satisfy the above-mentioned respective
requirements, the heat transfer performance of the flat heat
transfer tube 1 is improved while an increase in pressure loss is
restrained. Particularly, when the number of the inner fins 8
exceeds five or when the ratio of the height h2 of the inner fin 8
to the width t of each of the upper and lower walls 2 and 3; i.e.,
the ratio h2/t, exceeds 2.0, pressure loss increases greatly.
[0052] The inner fins 8 formed on the surface 2a of the upper wall
2, the surface 2a facing each of the fluid channels 7, and the
inner fins 8 formed on the surface 3a of the lower wall 3, the
surface 3a facing each of the fluid channels 7, are located at the
same positions along the width of the flat heat transfer tube 1.
Thus, in order to prevent the distal ends of the upper and lower
inner fins 8 from butting against each other, the ratio of the
height h2 of the inner fin 8 to the height h1 of the fluid channel
7; i.e., the ratio h2/h1, satisfies the relation h2/h1<0.5.
[0053] As shown in FIGS. 1 and 2, when the number of the inner fins
8 formed on each of the surfaces 2a and 3a of the upper and lower
walls 2 and 3, the surfaces 2a and 3a facing each of the fluid
channels 7, is three, preferably, the ratio w2/w1 is 1/12 to 7/20
inclusive, where w1 is the width of the fluid channel 7, and w2 is
the distance between the thickness wise center of the left- or
right-end inner fin 8 and the surface of the second
reinforcement-wall-forming elongated projection 15 or 13 of the
left- or right-hand reinforcement wall 6, the surface facing the
fluid channel 7. In the case where four inner fins 8 are formed on
each of the surfaces 2a and 3a of the upper and lower walls 2 and
3, the surfaces 2a and 3a facing each of the fluid channels 7, the
ratio w2/w1 is preferably 1/16 to 11/40 inclusive. In the case
where five inner fins 8 are formed, the ratio w2/w1 is preferably
1/20 to 1/5 inclusive.
[0054] The flat heat transfer tube 1 is manufactured from a
heat-transfer-tube-forming sheet-like member 20 shown in FIG.
3.
[0055] In FIG. 3, the heat-transfer-tube-forming sheet-like member
20 is formed, by rolling, from a blank aluminum brazing sheet
having a brazing material layer on each of opposite sides thereof.
The heat-transfer-tube-forming sheet-like member 20 includes a flat
upper-wall-forming portion 21 and a flat lower-wall-forming portion
22 having the same width and the same thickness and adapted to form
the upper and lower walls 2 and 3, respectively; a connection
portion 23 being slightly thicker than the upper- and
lower-wall-forming portions 21 and 22, integrally connecting the
upper- and lower-wall-forming portions 21 and 22, and adapted to
form the right side wall 5; the side-wall-forming elongated
projections 9 and 11, which are formed integrally with the side
ends of the upper- and lower-wall-forming portions 21 and 22
opposite the connection portion 23, in an upwardly projecting
condition and which are adapted to form the left side wall 4; a
plurality of first and second reinforcement-wall-forming elongated
projections 12, 13, 14, and 15, which are formed integrally with
the upper- and lower-wall-forming portions 21 and 22 in an upwardly
projecting condition and which are arranged at predetermined
intervals in the left-right direction; and the inner fins 8, which
are formed integrally with the upper- and lower-wall-forming
portions 21 and 22 in an upwardly projecting condition in regions
between the adjacent reinforcement-wall-forming elongated
projections 12, 13, 14, and 15. The side-wall-forming elongated
projections 9 and 11 are located symmetrically with respect to the
centerline of the left-right direction of the connection portion
23; the first reinforcement-wall-forming elongated projections 12
of the upper-wall-forming portion 21 and the second
reinforcement-wall-forming elongated projections 15 of the
lower-wall-forming portion 22 are located symmetrically with
respect to the centerline; the first reinforcement-wall-forming
elongated projections 14 of the lower-wall-forming portion 22 and
the second reinforcement-wall-forming elongated projections 13 of
the upper-wall-forming portion 21 are located symmetrically with
respect to the centerline; and the inner fins 8 of the
upper-wall-forming portion 21 and the inner fins 8 of the
lower-wall-forming portion 22 are located symmetrically with
respect to the centerline.
[0056] The groove 16 is formed on the distal end face of each of
the first reinforcement-wall-forming elongated projections 12 of
the upper-wall-forming portion 21. The second
reinforcement-wall-forming elongated projections 15 of the
lower-wall-forming portion 22 are press-fitted into the respective
grooves 16. The groove 17 is formed on the distal end face of each
of the first reinforcement-wall-forming elongated projections 14 of
the lower-wall-forming portion 22. The second
reinforcement-wall-forming elongated projections 13 of the
upper-wall-forming portion 21 are press-fitted into the respective
grooves 17. The side-wall-forming elongated projections 9 and 11 of
the upper- and lower-wall-forming portions 21 and 22 have the same
dimensions; specifically, the same height and the same thickness.
The first reinforcement-wall-forming elongated projections 12 of
the upper-wall-forming portion 21 and the first
reinforcement-wall-forming elongated projections 14 of the
lower-wall-forming portion 22 have the same dimensions;
specifically, the same height, the same thickness, the same width
of the grooves 16 and 17, and the same depth of the grooves 16 and
17. Further, the second reinforcement-wall-forming elongated
projections 13 of the upper-wall-forming portion 21 and the second
reinforcement-wall-forming elongated projections 15 of the
lower-wall-forming portion 22 have the same dimensions;
specifically, the same height and the same thickness.
[0057] Next, the method of manufacturing the flat heat transfer
tube 1 from the heat-transfer-tube-forming sheet-like member 20
will be described with reference to FIG. 4.
[0058] The heat-transfer-tube-forming sheet-like member 20 is
gradually folded at the left and right sides of the connection
portion 23 by a roll forming process (see FIG. 4(a)) until a
hairpin shape is formed in the following conditions. The distal end
faces of the two side-wall-forming elongated projections 9 and 11
butt against each other. The distal end portions of the second
reinforcement-wall-forming elongated projections 13 and 15 are
press-fitted into the grooves 17 and 16 of the first
reinforcement-wall-forming elongated projections 14 and 12,
respectively. A folded member 20A (see FIG. 4(b)) thus is
yielded.
[0059] Subsequently, the folded member 20A is heated at a
predetermined temperature for carrying out the following brazing
through utilization of the above-mentioned brazing material layers:
brazing together distal end portions of the two side-wall-forming
elongated projections 9 and 11 so as to form the left side wall 4,
brazing together distal end portions of the first and second
reinforcement-wall-forming elongated projections 12 and 15 so as to
form the reinforcement walls 6, and brazing together distal end
portions of the first and second reinforcement-wall-forming
elongated projections 14 and 13 so as to form the reinforcement
walls 6. The connection portion 23 forms as the right side wall 5;
the upper-wall-forming portion 21 forms the upper wall 2; and the
lower-wall-forming portion 22 forms the lower wall 3. The flat heat
transfer tube 1 thus is manufactured.
[0060] In the case where the flat heat transfer tubes 1 are used
as, for example, heat exchange tubes 62 of a condenser shown in
FIG. 14, the manufacture of the flat heat transfer tubes 1 may
proceed simultaneously with the manufacture of the condenser.
Specifically, the condenser is manufactured as follows. First, a
plurality of the folded members 20A are prepared. Also are prepared
a pair of aluminum headers 60 and 61 each having a plurality of
folded-member insertion holes, and a plurality of aluminum
corrugate fins 63. Then, the paired headers 60 and 61 are arranged
apart from each other. The fins 63 and the same number of the
folded members 20A as the number of the folded-member insertion
holes are arranged in alternating layers such that opposite end
portions of the folded members 20A are inserted into the respective
folded-member insertion holes of the headers 60 and 61.
Subsequently, the resultant assembly is heated at a predetermined
temperature, whereby the flat heat transfer tubes 1 are
manufactured as mentioned above, and, at the same time, the
following brazing is simultaneously carried out through utilization
of the brazing material layers of the heat-transfer-tube-forming
sheet-like members 20: brazing together the flat heat transfer
tubes 1 and the headers 60 and 61, and brazing together the flat
heat transfer tubes 1 and the corrugate fins 63. The condenser thus
is manufactured.
[0061] In the case where a refrigeration cycle using a
chlorofluorocarbon-based refrigerant and having a compressor, a
condenser, and an evaporator is used as a car air conditioner
mounted on a vehicle; for example, an automobile, the heat
exchanger provided with the above-mentioned flat heat transfer
tubes 1 is used as the condenser of the refrigeration cycle. Also,
the heat exchanger is used as the evaporator of the refrigeration
cycle. Further, the heat exchanger may be mounted on an automobile
as an oil cooler or a radiator provided with the above-mentioned
flat heat transfer tubes 1.
[0062] In the case where a supercritical refrigeration cycle using
a supercritical refrigerant, such as a CO.sub.2 refrigerant, and
having a compressor, a gas cooler, an evaporator, a
pressure-reducing device, and an intermediate heat exchanger for
performing heat exchange between the refrigerant flowing out from
the gas cooler and the refrigerant flowing out from the evaporator
is used as a car air conditioner mounted on a vehicle; for example,
an automobile, the above-mentioned flat heat transfer tubes 1 may
be used in the gas cooler or the evaporator.
[0063] In the above-described Embodiment 1, the inner fins 8 formed
on a surface of the upper wall 2, the surface facing each of the
fluid channels 7, and the inner fins 8 formed on a surface of the
lower wall 3, the surface facing each of the fluid channels 7, are
located at the same positions along the width of the flat heat
transfer tube 1. However, the present invention is not limited
thereto. The positions along the width of the flat heat transfer
tube 1 may differ between the upper and lower walls 2 and 3. In
this case, the ratio of the height h2 of the inner fin 8 to the
height h1 of the fluid channel 7 may be higher than 0.5; i.e.,
h2/h1>0.5.
EMBODIMENT 2
[0064] The present embodiment is shown in FIGS. 5 and 6.
[0065] FIG. 5 shows the overall configuration of a flat heat
transfer tube according to Embodiment 2 of the present invention.
FIG. 6 shows, on an enlarged scale, a single fluid channel of the
flat heat transfer tube according to Embodiment 2 of the present
invention.
[0066] As shown in FIG. 5, two to five inner fins 8 and 26, each
assuming an elongated projection extending along the length of a
flat heat transfer tube 25, are formed on surfaces 2a and 3a of the
upper and lower walls 2 and 3, the surfaces 2a and 3a facing each
of the fluid channels 7; i.e., are disposed on the upper and lower
surfaces of each of the fluid channels 7. The number of the inner
fins 8 formed on one surface 2a differs from the number of the
inner fins 26 formed on the other surface 3a. In FIG. 6, two inner
fins 8 are formed on the surface 2a of the upper wall 2, whereas
three inner fins 26 are formed on the surface 3a of the lower wall
3. The fluid channel 7 in which two inner fins 8 are formed on the
surface 2a of the upper wall 2 and the fluid channel 7 in which
three inner fins 26 are formed on the surface 2a of the upper wall
2 alternate along the width of the flat heat transfer tube 1. In
the fluid channels 7, the height h2a of each of the three inner
fins 26 formed on one surface 2a or 3a is lower than the height h2
of the two inner fins 8 formed on the other surface 3a or 2a. Other
configurational features of the flat heat transfer tube 25 is the
same as those of the flat heat transfer tube 1 of Embodiment 1. The
flat heat transfer tube 25 is manufactured in a manner similar to
that of Embodiment 1. Also, in Embodiment 2, the tube height H of
the heat transfer tube 25 is 1.8 mm or less; the tube width W of
the heat transfer tube 25 is 20 mm or less; the height h1 of the
fluid channel 7 is 1.0 mm or less; the width w1 of the fluid
channel 7 is 2.0 mm or less; the fluid diameter Dh is 0.3 mm to 1.2
mm; and the thickness t of each of the upper and lower walls 2 and
3 is 0.4 mm or less. The ratio of the height h2a of the inner fin
26 to the thickness t; i.e., the ratio h2a/t satisfies the relation
0.5.ltoreq.h2a/t.ltoreq.2.0, and the ratio of the height h2 of the
inner fin 8 to the thickness t; i.e., the ratio h2/t, satisfies the
relation 0.5.ltoreq.h2/t.ltoreq.2.0. Further, the ratio of the fin
pitch p1 of the inner fins 26 to the width w1 of the fluid channel
7; i.e., the ratio p1/w1, satisfies the relation
0.15.ltoreq.p1/w1.ltoreq.1/n, and the ratio of the fin pitch p2 of
the inner fins 8 to the width w1 of the fluid channel 7; i.e., the
ratio p2/w1, satisfies the relation 0.15.ltoreq.p2/w1.ltoreq.1/n (n
is the number of the inner fins 26 or 8 formed on each of the two
surfaces 2a and 3a of the upper and lower walls 2 and 3). When the
tube height H, the tube width W, the height h1 of the fluid channel
7, the width w1 of the fluid channel 7, the fluid diameter Dh, the
thickness t of each of the upper and lower walls 2 and 3, the ratio
of the height h2a of the inner fin 26 to the thickness t; i.e., the
ratio h2a/t, the ratio of the height h2 of the inner fin 8 to the
thickness t; i.e., the ratio h2/t, the ratio of the fin pitch p1 of
the inner fins 26 to the width w1 of the fluid channel 7; i.e., the
ratio p1/w1, and the ratio of the fin pitch p2 of the inner fins 8
to the width w1 of the fluid channel 7; i.e., the ratio p2/w1,
satisfy the above-mentioned respective requirements, the heat
transfer performance of the flat heat transfer tube 25 is improved
while an increase in pressure loss is restrained.
[0067] Notably, the ratio of the height h2 or h2a of the inner fin
8 or 26 to the height h1 of the fluid channel 7 may be less than
0.5 or greater than 0.5; i.e., (h2/h1 or h2a/h1)<0.5 or (h2/h1
or h2a/h1)>0.5.
[0068] When the number of the inner fins 8 formed on the surface 2a
of the upper wall 2 or on the surface 3a of the lower wall 3, the
surfaces 2a and 3a facing each of the fluid channels 7, is two,
preferably, the ratio w2a/w1 is 1/8 to 17/40 inclusive, where w1 is
the width of the fluid channel 7, and w2a is the distance between
the thicknesswise center of the left- or right-hand inner fin 8 and
the surface of the second reinforcement-wall-forming elongated
projection 15 or 13 of the left- or right-hand reinforcement wall
6, the surface facing the fluid channel 7.
EMBODIMENT 3
[0069] The present embodiment is shown in FIG. 7.
[0070] FIG. 7 shows, on an enlarged scale, a single fluid channel
of a flat heat transfer tube according to Embodiment 3 of the
present invention.
[0071] As shown in FIG. 7, in each of the fluid channels 7 of the
flat heat transfer tube 30, the height h2 of the three inner fins 8
formed on one surface 2a or 3a is equal to the height h2 of the two
inner fins 8 formed on the other surface 3a or 2a.
[0072] Other configurational features of the flat heat transfer
tube 30 is the same as those of the flat heat transfer tube of
Embodiment 2. The flat heat transfer tube 30 is manufactured in a
manner similar to that of Embodiment 2. Also, in Embodiment 3, the
tube height H of the heat transfer tube 30 is 1.8 mm or less; the
tube width W of the heat transfer tube 30 is 20 mm or less; the
height h1 of the fluid channel 7 is 1.0 mm or less; the width w1 of
the fluid channel 7 is 2.0 mm or less; the fluid diameter Dh is 0.3
mm to 1.2 mm; and the thickness t of each of the upper and lower
walls 2 and 3 is 0.4 mm or less. The ratio of the height h2 of the
inner fin 8 to the thickness t; i.e., the ratio h2/t, satisfies the
relation 0.5.ltoreq.h2/t.ltoreq.2.0. Further, the ratio of the fin
pitch p1 of the inner fins 8 to the width w1 of the fluid channel
7; i.e., the ratio p1/w1, satisfies the relation
0.15.ltoreq.p1/w1.ltoreq.1/n, and the ratio of the fin pitch p2 of
the inner fins 8 to the width w1 of the fluid channel 7; i.e., the
ratio p2/w1, satisfies the relation 0.15.ltoreq.p2/w1.ltoreq.1/n (n
is the number of the inner fins 8 formed on each of the two
surfaces 2a and 3a of the upper and lower walls 2 and 3). When the
tube height H, the tube width W, the height h1 of the fluid channel
7, the width w1 of the fluid channel 7, the fluid diameter Dh, the
thickness t of each of the upper and lower walls 2 and 3, the ratio
of the height h2 of the inner fin 8 to the thickness t; i.e., the
ratio h2/t, the ratio of the fin pitch p1 of the inner fins 8 to
the width w1 of the fluid channel 7; i.e., the ratio p1/w1, and the
ratio of the fin pitch p2 of the inner fins 8 to the width w1 of
the fluid channel 7; i.e., the ratio p2/w1, satisfy the
above-mentioned respective requirements, the heat transfer
performance of the flat heat transfer tube 30 is improved while an
increase in pressure loss is restrained.
[0073] Notably, the ratio of the height h2 of the inner fin 8 to
the height h1 of the fluid channel 7 may be less than 0.5 or
greater than 0.5; i.e., h2/h1.ltoreq.0.5 or h2/h1>0.5.
EMBODIMENT 4
[0074] The present embodiment is shown in FIG. 8.
[0075] FIG. 8 shows, on an enlarged scale, a single fluid channel
of a flat heat transfer tube according to Embodiment 4 of the
present invention.
[0076] As shown in FIG. 8, in each of the fluid channels 7 of a
flat heat transfer tube 35, the height of at least one of the three
inner fins 8 and 26 formed on one surface 2a or 3a; herein, the
height h2a of the center inner fin 26, is lower than the height h2
of the remaining two inner fins 8. Also, the height h2 of the two
inner fins 8 formed on the other surface 3a or 2a is equal to the
height h2 of the opposite-side inner fins 8 of the three inner fins
8 and 26 formed on the one surface 2a or 3a.
[0077] Other configurational features of the flat heat transfer
tube 35 is the same as those of the flat heat transfer tube of
Embodiment 3. The flat heat transfer tube 35 is manufactured in a
manner similar to that of Embodiment 3. Also, in Embodiment 4, the
tube height H of the heat transfer tube 35 is 1.8 mm or less; the
tube width W of the heat transfer tube 35 is 20 mm or less; the
height h1 of the fluid channel 7 is 1.0 mm or less; the width w1 of
the fluid channel 7 is 2.0 mm or less; the fluid diameter Dh is 0.3
mm to 1.2 mm; and the thickness t of each of the upper and lower
walls 2 and 3 is 0.4 mm or less. The ratio of the height h2 of the
inner fin 8 to the thickness t; i.e., the ratio h2/t, satisfies the
relation 0.5.ltoreq.h2/t.ltoreq.2.0, and the ratio of the height
h2a of the inner fin 26 to the thickness t; i.e., the ratio h2a/t
satisfies the relation 0.5.ltoreq.h2a/t.ltoreq.2.0. Further, the
ratio of the fin pitch p1 of the inner fins 8 and 26 to the width
w1 of the fluid channel 7; i.e., the ratio p1/w1, satisfies the
relation 0.15.ltoreq.p1/w1.ltoreq.1/n, and the ratio of the fin
pitch p2 of the inner fins 8 to the width w1 of the fluid channel
7; i.e., the ratio p2/w1, satisfies the relation
0.15.ltoreq.p2/w1.ltoreq.1/n (n is the number of the inner fins 26
or 8 formed on each of the two surfaces 2a and 3a of the upper and
lower walls 2 and 3). When the tube height H, the tube width W, the
height h1 of the fluid channel 7, the width w1 of the fluid channel
7, the fluid diameter Dh, the thickness t of each of the upper and
lower walls 2 and 3, the ratio of the height h2 of the inner fin 8
to the thickness t; i.e., the ratio h2/t, the ratio of the height
h2a of the inner fin 26 to the thickness t; i.e., the ratio h2a/t,
the ratio of the fin pitch p1 of the inner fins 8 and 26 to the
width w1 of the fluid channel 7; i.e., the ratio p1/w1, and the
ratio of the fin pitch p2 of the inner fins 8 to the width w1 of
the fluid channel 7; i.e., the ratio p2/w1, satisfy the
above-mentioned respective requirements, the heat transfer
performance of the flat heat transfer tube 35 is improved while an
increase in pressure loss is restrained.
[0078] Notably, the ratio of the height h2 or h2a of the inner fin
8 or 26 to the height h1 of the fluid channel 7 may be less than
0.5 or greater than 0.5; i.e., (h2/h1 or h2a/h1)<0.5 or (h2/h1
or h2a/h1)>0.5.
EMBODIMENT 5
[0079] The present embodiment is shown in FIG. 9.
[0080] FIG. 9 shows, on an enlarged scale, a single fluid channel
of a flat heat transfer tube according to Embodiment 5 of the
present invention.
[0081] As shown in FIG. 9, in each of the fluid channels 7 of a
flat heat transfer tube 40, the height h2a of the opposite-side
inner fins 26 of the three inner fins 8 and 26 formed on one
surface 2a or 3a is lower than the height h2 of the center inner
fin 8. Also, the height h2 of the two inner fins 8 formed on the
other surface 3a or 2a is equal to the height h2 of the center
inner fin 8 of the three inner fins 8 and 26 formed on the one
surface 2a or 3a.
[0082] Other configurational features of the flat heat transfer
tube 40 is the same as those of the flat heat transfer tube of
Embodiment 3. The flat heat transfer tube 40 is manufactured in a
manner similar to that of Embodiment 3. Also, in Embodiment 5, the
tube height H of the heat transfer tube 40 is 1.8 mm or less; the
tube width W of the heat transfer tube 40 is 20 mm or less; the
height h1 of the fluid channel 7 is 1.0 mm or less; the width w1 of
the fluid channel 7 is 2.0 mm or less; the fluid diameter Dh is 0.3
mm to 1.2 mm; and the thickness t of each of the upper and lower
walls 2 and 3 is 0.4 mm or less. The ratio of the height h2 of the
inner fin 8 to the thickness t; i.e., the ratio h2/t, satisfies the
relation 0.5.ltoreq.h2/t.ltoreq.2.0, and the ratio of the height
h2a of the inner fin 26 to the thickness t; i.e., the ratio h2a/t
satisfies the relation 0.5.ltoreq.h2a/t.ltoreq.2.0. Further, the
ratio of the fin pitch p1 of the inner fins 8 and 26 to the width
w1 of the fluid channel 7; i.e., the ratio p1/w1, satisfies the
relation 0.15.ltoreq.p1/w1.ltoreq.1/n, and the ratio of the fin
pitch p2 of the inner fins 8 to the width w1 of the fluid channel
7; i.e., the ratio p2/w1, satisfies the relation
0.15.ltoreq.p2/w1.ltoreq.1/n (n is the number of the inner fins 26
or 8 formed on each of the two surfaces 2a and 3a of the upper and
lower walls 2 and 3). When the tube height H, the tube width W, the
height h1 of the fluid channel 7, the width w1 of the fluid channel
7, the fluid diameter Dh, the thickness t of each of the upper and
lower walls 2 and 3, the ratio of the height h2 of the inner fin 8
to the thickness t; i.e., the ratio h2/t, the ratio of the height
h2a of the inner fin 26 to the thickness t; i.e., the ratio h2a/t,
the ratio of the fin pitch p1 of the inner fins 8 and 26 to the
width w1 of the fluid channel 7; i.e., the ratio p1/w1, and the
ratio of the fin pitch p2 of the inner fins 8 to the width w1 of
the fluid channel 7; i.e., the ratio p2/w1, satisfy the
above-mentioned respective requirements, the heat transfer
performance of the flat heat transfer tube 40 is improved while an
increase in pressure loss is restrained.
[0083] Notably, the ratio of the height h2 or h2a of the inner fin
8 or 26 to the height h1 of the fluid channel 7 may be less than
0.5 or greater than 0.5; i.e., (h2/h1 or h2a/h1)<0.5 or (h2/h1
or h2a/h1)>0.5.
[0084] According to the heat transfer tubes of Embodiments 2 to 5
described above, the fluid channel 7 in which three inner fins 8
are formed on the surface 2a of the upper wall 2 and the fluid
channel 7 in which two inner fins 8 are formed on the surface 2a of
the upper wall 2 alternate along the width of the flat heat
transfer tube 1, 25, 30, 35, or 40. Alternatively, all of the fluid
channels 7 may be the same in the number of the inner fins 8 (e.g.,
three) formed on the surface 2a of the upper wall 2 and the same in
the number of the inner fins 8 and 26 (e.g., two) formed on the
surface 3a of the lower wall 3.
EMBODIMENT 6
[0085] The present embodiment is shown in FIG. 10.
[0086] FIG. 10 shows, on an enlarged scale, a single fluid channel
of a flat heat transfer tube according to Embodiment 6 of the
present invention.
[0087] As shown in FIG. 10, two inner fins 8, each assuming an
elongated projection extending along the length of a flat heat
transfer tube 45, are formed on the surfaces 2a and 3a of the upper
and lower walls 2 and 3; i.e., are disposed on the upper and lower
surfaces of each of the fluid channels 7. All of the inner fins 8
have the same height. The inner fins 8 formed on the surface 2a of
the upper wall 2 differ in position along the width of the flat
heat transfer tube 45 from the inner fins 8 formed on the surface
3a of the lower wall 3.
[0088] In FIG. 10, the distance between the right-hand inner fin 8
of the two inner fins 8 formed on the surface 2a of the upper wall
2, and the surface of the second reinforcement-wall-forming
elongated projection 13 of the right-hand reinforcement wall 6, the
surface facing the fluid channel 7, is shorter than the distance
between the left-hand inner fin 8 and the surface of the second
reinforcement-wall-forming elongated projection 15 of the left-hand
reinforcement wall 6, the surface facing the fluid channel 7. The
distance between the left-hand inner fin 8 of the two inner fins 8
formed on the surface 3a of the lower wall 3, and the surface of
the second reinforcement-wall-forming elongated projection 15 of
the left-hand reinforcement wall 6, the surface facing the fluid
channel 7, is shorter than the distance between the right-hand
inner fin 8 and the surface of the second
reinforcement-wall-forming elongated projection 13 of the
right-hand reinforcement wall 6, the surface facing the fluid
channel 7. In this case, preferably, the ratio w2b/w1 is 1/8 to
17/40 inclusive, where w1 is the width of the fluid channel 7, and
w2b is the distance between the thicknesswise center of one of the
two inner fins 8, whichever closer to the second
reinforcement-wall-forming elongated projection 13 or 15 of the
reinforcement wall 6, formed on the upper or lower wall 2 or 3, and
the surface of the second reinforcement-wall-forming elongated
projection 13 or 15 of the reinforcement wall 6, the surface facing
the closer inner fin 8 and the fluid channel 7.
[0089] Other configurational features of the flat heat transfer
tube 25 is the same as those of the flat heat transfer tube 1 of
Embodiment 1. The flat heat transfer tube 45 is manufactured in a
manner similar to that of Embodiment 1. Also, in Embodiment 6, the
tube height H of the heat transfer tube 45 is 1.8 mm or less; the
tube width W of the heat transfer tube 45 is 20 mm or less; the
height h1 of the fluid channel 7 is 1.0 mm or less; the width w1 of
the fluid channel 7 is 2.0 mm or less; the fluid diameter Dh is 0.3
mm to 1.2 mm; and the thickness t of each of the upper and lower
walls 2 and 3 is 0.4 mm or less. The ratio of the height h2 of the
inner fin 8 to the thickness t of each of the upper and lower walls
2 and 3; i.e., the ratio h2/t, satisfies the relation
0.5.ltoreq.h2/t.ltoreq.2.0. Further, the ratio of the fin pitch p3
of the inner fins 8 to the width w1 of the fluid channel 7; i.e.,
the ratio p3/w1, satisfies the relation
0.15.ltoreq.p3/w1.ltoreq.1/2. When the tube height H, the tube
width W, the height h1 of the fluid channel 7, the width w1 of the
fluid channel 7, the fluid diameter Dh, the thickness t of each of
the upper and lower walls 2 and 3, the ratio of the height h2 of
the inner fin 8 to the thickness t of each of the upper and lower
walls 2 and 3; i.e., the ratio h2/t, and the ratio of the fin pitch
p3 of the inner fins 8 to the width w1 of the fluid channel 7;
i.e., the ratio p3/w1, satisfy the above-mentioned respective
requirements, the heat transfer performance of the flat heat
transfer tube 45 is improved while an increase in pressure loss is
restrained.
[0090] Notably, the ratio of the height h2 of the inner fin 8 to
the height h1 of the fluid channel 7 may be less than 0.5 or
greater than 0.5; i.e., h2/h1<0.5 or h2/h1>0.5.
[0091] In the flat heat transfer tube 45 of Embodiment 6 described
above, the two inner fins 8 of the upper wall 2 and the two inner
fins 8 of the lower wall 3 may be formed at the same positions
along the width of the fluid channel 7. In this case, the ratio of
the height h2 of the inner fin 8 to the height h1 of the fluid
channel 7 is less than 0.5; i.e., h2/h1<0.5.
EMBODIMENT 7
[0092] The present embodiment is shown in FIG. 11.
[0093] As shown in FIG. 11, a single inner fin 8 assuming an
elongated projection extending along the length of a flat heat
transfer tube 50 is formed on surfaces 2a and 3a of the upper and
lower walls 2 and 3, the surfaces 2a and 3a facing each of the
fluid channels 7; i.e., is disposed on the upper and lower surfaces
of each of the fluid channels 7. The inner fin 8 formed on the
surface 2a of the upper wall 2 differs in position along the width
of the flat heat transfer tube 1 from the inner fin 8 formed on the
surface 3a of the lower wall 3.
[0094] In FIG. 11, the inner fin 8 formed on the surface 2a of the
upper wall 2 is offset rightward from the widthwise center of the
fluid channel 7. In this case, the ratio of the distance w2c
between the thicknesswise center of the inner fin 8 and the surface
of the second reinforcement-wall-forming elongated projection 13,
which is formed on the upper wall 2, of the right-hand
reinforcement wall 6, the surface facing the fluid channel 7, to
the width w1 of the fluid channel 7; i.e., the ratio w2c/w1,
satisfies the relation 1/4.ltoreq.w2c/w1.ltoreq.1/2. Also, the
inner fin 8 formed on the surface 3a of the lower wall 3 is offset
leftward from the widthwise center of the fluid channel 7. In this
case, the ratio of the distance w2c between the thicknesswise
center of the inner fin 8 and the surface of the second
reinforcement-wall-forming elongated projection 15, which is formed
on the lower wall 3, of the left-hand reinforcement wall 6, the
surface facing the fluid channel 7, to the width w1 of the fluid
channel 7; i.e., the ratio w2c/w1, satisfies the relation
1/4.ltoreq.w2c/w1.ltoreq.1/2.
[0095] Other configurational features of the flat heat transfer
tube 50 is the same as those of the flat heat transfer tube 1 of
Embodiment 1. The flat heat transfer tube 50 is manufactured in a
manner similar to that of Embodiment 1. Also, in Embodiment 7, the
tube height H of the heat transfer tube 50 is 1.8 mm or less; the
tube width W of the heat transfer tube 50 is 20 mm or less; the
height h1 of the fluid channel 7 is 1.0 mm or less; the width w1 of
the fluid channel 7 is 2.0 mm or less; the fluid diameter Dh is 0.3
mm to 1.2 mm; and the thickness t of each of the upper and lower
walls 2 and 3 is 0.4 mm or less. The ratio of the height h2 of the
inner fin 8 to the thickness t of each of the upper and lower walls
2 and 3; i.e., the ratio h2/t, satisfies the relation
0.5.ltoreq.h2/t.ltoreq.2.0. When the tube height H, the tube width
W, the height h1 of the fluid channel 7, the width w1 of the fluid
channel 7, the fluid diameter Dh, the thickness t of each of the
upper and lower walls 2 and 3, the ratio of the height h2 of the
inner fin 8 to the thickness t of each of the upper and lower walls
2 and 3; i.e., the ratio h2/t, the ratio of the distance w2c
between the thicknesswise center of the inner fin 8 of the upper
wall 2 and the surface of the second reinforcement-wall-forming
elongated projection 13, which is formed on the upper wall 2, of
the right-hand reinforcement wall 6, the surface facing the fluid
channel 7, to the width w1 of the fluid channel 7; i.e., the ratio
w2c/w1, and the ratio of the distance w2c between the thicknesswise
center of the inner fin 8 of the lower wall 3 and the surface of
the second reinforcement-wall-forming elongated projection 15,
which is formed on the lower wall 3, of the left-hand reinforcement
wall 6, the surface facing the fluid channel 7, to the width w1 of
the fluid channel 7; i.e., the ratio w2c/w1, satisfy the
above-mentioned respective requirements, the heat transfer
performance of the flat heat transfer tube 50 is improved while an
increase in pressure loss is restrained.
[0096] Notably, the ratio of the height h2 of the inner fin 8 to
the height h1 of the fluid channel 7 may be less than 0.5 or
greater than 0.5; i.e., h2/h1<0.5 or h2/h1>0.5.
[0097] In the flat heat transfer tube 50 of Embodiment 7 described
above, the inner fin 8 of the upper wall 2 and the inner fin 8 of
the lower wall 3 may be formed at the same position along the width
of the fluid channel 7. In this case, in order for the
above-mentioned ratio w2c/w1 to satisfy the relation
1/4.ltoreq.w2c/w1.ltoreq.1/2, both of the inner fins 8 are formed
at the widthwise center of the fluid channel 7. The ratio of the
height h2 of the inner fin 8 to the height h1 of the fluid channel
7 is less than 0.5; i.e., h2/h1<0.5.
[0098] According to the flat heat transfer tubes 25, 30, 35, 40,
45, and 50 of Embodiments 2 to 7 described above, in each of the
fluid channel 7, the distance between the distal end of one of a
plurality of the inner fins 8 or 26 formed on one surface 2a or 3a
and the distal end of an inner fin adjacent to the said inner fin
and formed on the other surface 3a or 2a is greater than that in
the flat heat transfer tube of Embodiment 1. Thus, an increase in
pressure loss can be restrained.
[0099] The flat heat transfer tubes of Embodiments 1 to 7 described
above are formed by subjecting the respective sheet-like members to
folding and brazing. However, the flat heat transfer tube according
to the present invention can also be applied to extrudates.
[0100] Next, specific examples of the flat heat transfer tube of
the present invention will be described together with Comparative
Examples.
EXAMPLES 1 TO 3
[0101] The flat heat transfer tubes of Examples 1 to 3 use the
configuration of Embodiment 1 described above. Prepared were the
flat heat transfer tubes each having a tube length of 100 mm, a
tube height H of 1.20 mm, a tube width W of 16 mm, a thickness t of
each of the upper and lower walls of 0.25 mm, a height h1 of the
fluid channel of 0.7 mm, a width w1 of the fluid channel of 1.33
mm, a number n of the inner fins formed on a surface of each of the
upper and lower walls, the surface facing each of the fluid
channels, of 3, a fin pitch p1 of the inner fins of 0.25 mm, a
fluid diameter Dh of 0.45 mm, and a height h2 of the inner fin of
0.2 mm (Example 1), 0.25 mm (Example 2), and 0.3 mm (Example 3).
The ratio of the height h2 of the inner fin to the thickness t of
each of the upper and lower walls; i.e., the ratio h2/t, is 0.8 for
the flat heat transfer tube of Example 1, 1.0 for the flat heat
transfer tube of Example 2, or 1.2 for the flat heat transfer tube
of Example 3.
COMPARATIVE EXAMPLES 1 AND 2
[0102] The flat heat transfer tube of Comparative Example 1 was
prepared under the same conditions as for Examples 1 to 3 except
that the inner fins are not formed. The flat heat transfer tube of
Comparative Example 2 was prepared under the same conditions as for
Examples 1 to 3 except that the height h2 of the inner fin was 0.1
mm. The ratio of the height h2 of the inner fin to the thickness t
of each of the upper and lower walls; i.e., the ratio h2/t, is 0
for the flat heat transfer tube of Comparative Example 1 and 0.4
for the flat heat transfer tube of Comparative Example 2.
EXAMPLES 4 TO 10
[0103] The flat heat transfer tubes of Examples 4 to 10 use the
configuration of Embodiment 1 described above. Prepared were the
flat heat transfer tubes each having a tube length of 100 mm, a
tube height H of 1.20 mm, a tube width W of 16 mm, a thickness t of
each of the upper and lower walls of 0.25 mm, a height h1 of the
fluid channel of 0.7 mm, a width w1 of the fluid channel of 1.33
mm, a number n of the inner fins formed on a surface of each of the
upper and lower walls, the surface facing each of the fluid
channels, of 3, a height h2 of the inner fin of 0.25 mm, a fluid
diameter Dh of 0.45 mm, and a fin pitch p1 of the inner fins of
0.20 mm (Example 4), 0.25 mm (Example 5), 0.30 mm (Example 6), 0.35
mm (Example 7), 0.40 mm (Example 8), 0.45 mm (Example 9), and 0.50
mm (Example 10). The ratio of the fin pitch p1 of a plurality of
the inner fins to the width w1 of the fluid channel; i.e., the
ratio p1/w1, is 0.1504 for the flat heat transfer tube of Example
4, 0.1880 for the flat heat transfer tube of Example 5, 0.2256 for
the flat heat transfer tube of Example 6, 0.2632 for the flat heat
transfer tube of Example 7, 0.300 for the flat heat transfer tube
of Example 8, 0.3383 for the flat heat transfer tube of Example 9,
and 0.3759 for the flat heat transfer tube of Example 10.
COMPARATIVE EXAMPLE 3
[0104] The flat heat transfer tube of Comparative Example 3 was
prepared under the same conditions as for Examples 4 to 10 except
that the fin pitch p1 of the inner fins was 0.16 mm. The ratio of
the fin pitch p1 of a plurality of the inner fins to the width w1
of the fluid channel; i.e., the ratio p1/w1, is 0.12 for the flat
heat transfer tube of Comparative Example 3.
Evaluation Test 1:
[0105] A refrigerant vapor (R134a) having a temperature of
60.degree. C. was passed through the flat heat transfer tubes of
Examples 1 to 10 and Comparative Examples 1 to 3; the temperature
of an atmosphere around the flat heat transfer tubes was set to
27.degree. C.; and while the refrigerant vapor and the atmosphere
were maintained at the above-mentioned respective temperatures, the
average overall heat transfer coefficient was measured. With the
average overall heat transfer coefficient of the flat heat transfer
tube of Comparative Example 1 taken as 1.00, an
average-overall-heat-transfer-coefficient ratio was obtained for
the remaining flat heat transfer tubes. FIG. 12 shows the test
results of Examples 1 to 3 and Comparative Examples 1 and 2. FIG.
13 shows the test results of Examples 4 to 10 and Comparative
Example 3.
[0106] As is apparent from FIG. 12, when the ratio of the height h2
of the inner fin to the thickness t of each of the upper and lower
walls; i.e., the ratio h2/t, is 0.5 or higher, the average overall
heat transfer coefficient markedly increases. As is apparent from
FIG. 13, when the ratio of the fin pitch p1 of a plurality of the
inner fins to the width w1 of the fluid channel; i.e., the ratio
p1/w1, is 0.15 or higher, the average overall heat transfer
coefficient markedly increases.
EXAMPLE 11
[0107] The flat heat transfer tube of Example 11 uses the
configuration of Embodiment 3 described above. Prepared was the
flat heat transfer tube having a tube length of 100 mm, a tube
height H of 1.0 mm, a tube width W of 16 mm, a thickness t of each
of the upper and lower walls of 0.2 mm, a height h1 of the fluid
channel of 0.6 mm, a width w1 of the fluid channel of 1.33 mm, a
number n of the inner fins formed on one of two surfaces of the
upper and lower walls, the two surfaces facing each of the fluid
channels, of 3, a number n of the inner fins formed on the other
surface of the two surfaces of 2, a fin pitch p1 of the three inner
fins formed on the one of the two surfaces of the upper and lower
walls of 0.3 mm, a fin pitch p2 of the two inner fins formed on the
other surface of the two surfaces of 0.35 mm, a distance w2 between
the opposite-side inner fins of the three inner fins formed on the
one of the two surfaces of the upper and lower walls, the two
surfaces facing each of the fluid channels, and the second
reinforcement-wall-forming elongated projections of the respective
opposite-side reinforcement walls of 0.33 mm, a distance w2a
between the two inner fins formed on the other surface of the two
surfaces of the upper and lower walls, the two surfaces facing each
of the fluid channels, and the second reinforcement-wall-forming
elongated projections of the respective opposite-side reinforcement
walls of 0.49 mm, a fluid diameter Dh of 0.546 mm, and a height h2
of the inner fin of 0.25 mm. The ratio of the height h2 of the
inner fin to the thickness t of each of the upper and lower walls;
i.e., the ratio h2/t, is 1.25. The ratio of the fin pitch p1 of the
three inner fins formed on the one surface of the two surfaces to
the width w1 of the fluid channel; i.e., the ratio p1/w1, is 0.23.
The ratio of the fin pitch p2 of the two inner fins formed on the
other surface of the two surfaces to the width w1 of the fluid
channel; i.e., the ratio p2/w1, is 0.26.
EXAMPLE 12
[0108] The flat heat transfer tube of Example 12 uses the
configuration of Embodiment 4 described above. The flat heat
transfer tube of Example 12 was prepared under the same conditions
as for Example 11 except for the following: the fluid diameter Dh
was 0.560 mm, and the height h2a of the center inner fin of the
three inner fins formed on one of two surfaces of the upper and
lower walls, the two surfaces facing each of the fluid channels,
was 0.2 mm. In the case of the inner fin having a height h2 of 0.25
mm, the ratio of the height h2 of the inner fin to the thickness t
of each of the upper and lower walls; i.e., the ratio h2/t, is
1.25. In the case of the inner fin having a height h2a of 0.2 mm,
the ratio of the height h2a of the inner fin to the thickness t of
each of the upper and lower walls; i.e., the ratio h2a/t, is 1.
EXAMPLE 13
[0109] The flat heat transfer tube of Example 13 uses the
configuration of Embodiment 5 described above. The flat heat
transfer tube of Example 13 was prepared under the same conditions
as for Example 11 except for the following: the fluid diameter Dh
was 0.576 mm, and the height h2a of the opposite-side inner fins of
the three inner fins formed on one of two surfaces of the upper and
lower walls, the two surfaces facing each of the fluid channels,
was 0.2 mm. In the case of the inner fin having a height h2 of 0.25
mm, the ratio of the height h2 of the inner fin to the thickness t
of each of the upper and lower walls; i.e., the ratio h2/t, is
1.25. In the case of the inner fin having a height h2a of 0.2 mm,
the ratio of the height h2a of the inner fin to the thickness t of
each of the upper and lower walls; i.e., the ratio h2a/t, is 1.
Evaluation Test 2:
[0110] By use of the flat heat transfer tubes of Examples 11 to 13,
the average overall heat transfer coefficient was measured in a
manner similar to that of Evaluation Test 1 described above. When
the average overall heat transfer coefficient was measured, the
differential pressure between the inlet and the outlet of each of
the flat heat transfer tubes was also measured by use of a
differential pressure gauge so as to determine a pressure loss for
the flat heat transfer tubes.
[0111] Table 2 shows the average-overall-heat-transfer-coefficient
ratios of the flat heat transfer tubes of Examples 11 to 13 which
were obtained with the average overall heat transfer coefficient of
the flat heat transfer tube of Comparative Example 1 taken as 1.00,
and the pressure-loss ratios of Examples 12 and 13 which were
obtained with the pressure loss of Example 11 taken as 1.00.
TABLE-US-00002 TABLE 2 AVERAGE OVERALL PRESSURE LOSS HEAT TRANSFER
RATIO COEFFICIENT RATIO EXAMPLES 11 1.00 2.30 12 0.95 2.21 13 0.90
2.11
[0112] As is apparent from Table 2, the average overall heat
transfer coefficients of the flat heat transfer tubes of Examples
11 to 13 are markedly increased as compared with the flat heat
transfer tube in which no inner fins are formed. Also, as the
distance between the distal ends of the laterally adjacent inner
fins formed on the upper and lower walls, respectively, increases,
the pressure loss lowers.
* * * * *