Heat exchange – Tubular structure
Reexamination Certificate
1999-10-18
2001-09-18
Flanigan, Allen (Department: 3743)
Heat exchange
Tubular structure
C165S110000
Reexamination Certificate
active
06289981
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-bored flat tube for use in a heat-exchanger and, more particularly, to a multi-bored flat tube made of a metal such as an aluminum for use in a condenser for an air conditioner. The present invention further relates to a heat exchanger including the multi-bored flat tubes.
2. Description of the Related Art
FIGS.
14
(A)-(C) show cross-sectional views of a conventional multi-bored flat tube of this kind. The multi-bored flat tube
51
is made by extruding an aluminum. The tube
51
has a peripheral wall
52
having an elongated circular cross-sectional shape and a plurality of divisional wall
53
,
53
a
connecting flat wall portions
52
a
,
52
a
of the peripheral wall
52
. The divisional walls
53
divide an inside space of the tube
51
to form a plurality of unit passages
54
,
55
arranged in a lateral direction of the tube
51
. Each divisional wall
53
,
53
a
has a constant thickness along the height thereof so that a contact area with the heat exchanging medium can be enlarged, thereby enhancing the heat exchanging performance of the tube
51
. The tube
51
includes outermost unit passages
54
,
54
and intermediate unit passages
55
located between the outermost unit passages
54
,
54
. Each intermediate passage
55
has a rectangular cross-sectional shape, and each outermost unit passage
54
has a semi-circular cross-sectional shape at a lateral outside portion and a rectangular cross-sectional shape at lateral inside portion. Further, each portion of the tube
51
, i.e., the peripheral wall
52
and the divisional walls
53
,
53
a
, are formed to be as thin as possible for the purpose of lightening the weight of the tube
51
.
Japanese unexamined Utility Model Publication No. S60-196181 and Japanese examined Utility Model Publication No. H3-45034 disclose a tube having unit passages with inner fins formed on an inner surface of each unit passage to enlarge a contact area with the heat exchanging medium for the purpose of enhancing the heat exchanging performance. For example, as shown in
FIGS. 15A and 15B
, a tube
52
has a plurality of inner fins
62
formed on the inner surface of the unit passages
54
,
55
surrounded by the peripheral wall
52
and the divisional walls
53
,
53
a
. Each fin
62
has a triangular cross-sectional shape and extends in the longitudinal direction of the tube
61
.
Japanese unexamined Patent Publication No. H5-215482 discloses another type of heat exchanging multi-bored flat tube. The tube has a plurality of unit passages each having a round cross-sectional shape for the purpose of equalizing the flow speed of the heat exchanging medium and lowering the flow resistance of the heat exchanging medium in each unit passage. In
FIGS. 14 and 15
, the reference numeral
57
denotes a corrugate fin interposed between the adjacent tubes
61
.
In a heat exchanger including the above-mentioned flat tubes
51
,
61
, a stress caused by an inner pressure of the heat exchanging medium passing through the tube is concentrated on connecting portions between the divisional wall
53
,
53
a
and the peripheral wall
52
. The lateral middle portion of the tube
51
,
61
can withstand such a stress because the flat wall portions
52
a
of the peripheral wall
52
are supported and reinforced by the corrugate fins
57
,
57
. However, the lateral end portions of the tube
51
,
61
are not strong enough to withstand such a stress because reinforcing effects obtained by the corrugate fins
57
,
57
are not enough. Therefore, such a stress tends to be concentrated on the connecting portions between the outermost dividing wall
53
a
and the peripheral wall
52
to cause a breakage.
Further, as shown in
FIGS. 14B and 14C
, the above-mentioned tubes used in a condenser mounted in an automobile may sometimes be damaged and cause leakage of the heat exchanging medium when a stone, or the like, hits the tube while the automobile is moving.
The above-mentioned problems may be solved by thickening the dividing wall portion
53
,
53
a
and the peripheral wall
52
. However, this causes an increase in the tube weight, resulting in an increase in the heat exchanger weight.
In a tube having a plurality of unit passages each having a perfect circular cross-sectional shape, a flow resistance of heat exchanging medium passing through the unit passage can be decreased and the pressure resistance can be improved. However, upper and lower portions of each dividing wall are thicker than the middle portion thereof, which requires larger amount of material for forming the tube, thereby increasing the manufacturing costs. Further, within a limited tube thickness, a heat transferring area of the circular cross-sectional unit passage is smaller than that of the rectangular cross-sectional unit passage, resulting in a lower heat exchanging efficiency.
SUMMARY OF THE INVENTION
The present invention has been made to overcome the disadvantages in the conventional multi-bored flat tube for use in a heat exchanger as described above.
An object of the present invention is to provide a multi-bored flat tube having an improved strength against a stone or the like which hits the tube, and an excellent heat exchanging performance by keeping a large contact area with a heat exchanging medium.
Another object of the present invention is to provide a heat exchanger including the above-mentioned flat tubes.
According to the one aspect of the present invention, the above-referenced objects can be achieved by a multi-bored flat tube for use in a heat exchanger, comprising:
a peripheral wall including flat wall portions facing each other at a certain distance and sidewall portions connecting lateral ends of the flat wall portions; and
dividing walls connecting the flat wall portions and dividing an inner space defined by the peripheral wall into a plurality of unit passages arranged in a lateral direction of the tube.
The plurality of unit passages include outermost unit passages located at both lateral ends of the tube and intermediate unit passages located between the outermost unit passages.
Each of the outermost unit passages has a circular-based inner surface in cross-section, and each of the intermediate unit passages has a non-circular inner surface in cross-section.
In the tube according to the present invention, since the outermost unit passages have a circular-based inner surface in cross-section, a stress concentration on connecting portions between the outermost dividing wall and the peripheral wall can be decreased. Accordingly, a high pressure resistance can be obtained throughout the tube. In a heat exchanger including the multi-bored flat tube, a high pressure resistance can be obtained by the structure even at both lateral ends of the tube where reinforcing effect by the outer fins is not enough.
In particular, when the outermost unit passage is designed to have a circular cross-sectional shape, an inner pressure of the heat exchanging medium passing through the passage acts on the inner surface of the passages equally in the circumferential direction thereof. Therefore, a higher pressure resistance can be obtained. This effect is remarkable when the outermost unit passage is designed to have a perfect circular shape.
Furthermore, since the outermost unit passage is designed to have circular-based inner surface in cross-section, a stress concentration on connecting portions between the outermost dividing wall and the peripheral wall can be reduced even when a small article such as a stone hits the tube. Consequently, the peripheral wall at the connecting portions can be prevented from being damaged, resulting in superior breaking strength against an outside stress caused when small article such as a stone hits the tube.
The outermost unit passage may have a circumferentially smooth curved shape in cross-section. This circumferentially smooth curved shape in cross-section includes various kinds of circular shapes such as a perfect circular shape, an elliptical shape, a
Go Nobuaki
Higo Yutaka
Ichiyanagi Shigeharu
Tokizaki Kazumi
Flanigan Allen
Showa Denko K.K.
LandOfFree
Multi-bored flat tube for use in a heat exchanger and heat... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multi-bored flat tube for use in a heat exchanger and heat..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-bored flat tube for use in a heat exchanger and heat... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2518904