Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a heat exchanger.
Ire present invention will ox illustrated by way
of the accompanying drawings, in which:
Figs i and i to Figs I and I show a
heat exchanger having conventional needle fins, Fig. l (a)
is a front elevation Al view, Fig. i is a cross-sectional
view, Fig. 2 is a partial perspective view, Fig. I is a
lo partial cross-sectional view, and Fig. 3 (b) is a partial
cross-sectional view of the needle fins;
Figs I, (b) and (c) and Fig. 5 show a first
embodinlent of the heat exchanger according to the present
invention, Fig. I is a partial cross-sectional view, Fig.
I is a partial cross-sectional view of the needle fins,
Fig. I is a partial front elevation Al view, and Fig. 5 is
an enlarged perspective view of the needle fins;
Fig. I and (b) and Fig. 7 show a second embody-
mint of the heat exchanger according to the present invent
lion, Fig. I and (b) are partial cross-sectional views,
respectively, Fig. 7 is an enlarged perspective view of the
fin portions;
Fig. I and (b) and Fig. 9 show a fourth embody-
merit of the heat exchanger according to the present invent
lion, Fig. I is a partial cross-sectional view of the
needle fins, Fig. I is an enlarged perspective view of
the needle fins, Fig. 9 is a diagram showing an air-side
heat transfer rate according to the heat exchanger thus-
treated in Fig. 8 for comparison with that of the previous
heat exchanger.
The heat exchanger is a device for transnlitting
heat energy from a high-temperature fluid to a low-tempera-
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lure fluid through a partition wall in order to accomplish heat-
in or cooling. If the heat exchangers are classified struck
rurally, there will be found a pipe type heat exchanger having
fins. When a gas is caused to flow outside a heat transfer pipe,
a heat transfer rate between the heat transfer pipe and the gas
is small, therefore the pipe type heat exchanger having fins is
employed in which the fins are fixed on the surfaces of the heat
transfer pipe to increase heat fluxes.
lo As be definite from the foregoing, fitting a variety of
fins on the heat transfer pipe is commonly carried out with the
intention of improving the heat transfer performance of the heat
exchanger, and various configurations of the fins have been sup-
gusted. The inventors of the present invention have also pro-
15 posed, in place of conventional corrugate fins, a high-perfor-
mange heat exchanger having needle fins ~srltish Patents Nos.
15,689/l909 and 1,204,675).
This suggested heat exchanger equipped with the needle
fins is excellent as a condenser in an elf conditioner for a car
and a house, an evaporator or the like, and its structure is, for
example, as shown in Figs l to 3.
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attached hereto. That is to say, as a heat transfer pipe,
there is used an extruded flat pipe 1 having chambers
therein defined by a plurality of partition walls lay flat
surfaces lb of the flat pipe 1 are confronted with each
other at an interval and disposed in parallel; and a
needle fin group 2, which is formed by corrugating a strip
metal plate, is disposed between the confronted flat
surfaces lb of the flat pipe 1 in a manner normal to the
lengthwise direction of the flat pipe 1. In operation,
a heat exchange medium is fed into the flat pipe 1 through
union joints 3 at opposite ends thereof, and a fluid such
as air is caused to flow whereinto from outside in a
direction normal to the lengthwise direction of the flat
pipe 1 it in a direction along straight portions of
lo the corrugate needle fins 2) in order to carry out heat
exchange.
The needle fin group 2 can be prepared by forming
numerous rectangular punched portions 2b in the strip
metal plate (plate width h), slightly leaving opposite
width direction end portions pa thereof, so that the plate
is shaped into a ladder-like form. The thus formed needle
fin group 2 is corrugated by causing it to meander along
the lengthwise direction of the flat pipe at a meander
width w, and the opposite width direction end portions
of the needle fin group are brazed or caused to adhere to
I
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the confronted flat surfaces lb of the flat pipe 1 by use
of a brazing material or an adhesive previously applied
on the flat surfaces lb. In this case, the needle fin
group 2 having numerous needle fins 2c is arranged so that
each fin pitch parallel to the flow direction of sir 4
may be PLY and each fin pitch normal to the flow direction
of the air 4 may be PT.
However, it has been found that the heat exchanger
equipped with such needle fins has the following faults:
(1) Since the punched portions 2b are provided in
the strip metal plate in order to leave the needle fins
2c, an amount of the plate material corresponding to the
punched portions is wasteful, which is undesirable from
the viewpoints of resources saving and material cost, and
particularly when aluminum is employed as the strip metal
plate source, its wastage is serious.
(2) The needle fin group 2 is structurally weak in
stiffness in the direction of a plate width (height) h.
Therefore, when the application of pressure is carried out
to secure the needle fin group on the flat surfaces lb,
the needle fins 2c are prone to curve, so that the fin
pitches PLY PUT would be uninformed and many reject
articles would be manufactured.
(3) Further, with regard to heat transfer performance,
since the needle fins 2c are arranged in a straight line
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along the direction of the air flow 4, the downstream
needle fins 2c get into a boundary layer flow formed by
the upstream needle fins 2c. This leads to deterioration
in efficiency of the fins.
(4) Furthermore, in the case of the heat exchanger
equipped with such fins 2c as mentioned above, the entrance
of the air flow 4 into the needle fin group 2 is accom-
polished through the curved portions of the corrugated
plate, i.e. top and bottom portions of the group, and
the discharge of the air flow is also done through the same
curved portions. Therefore, inflow and outflow of the
air 4 are greatly obstructed by the needle phony. As a
result, a flow velocity vector pa of the air 4 at the
curved portions of the corrugated plate is small and a
flow velocity vector 4b at the straight portions of the
corrugated plate is large. Finally, pressure loss at
the inlet and outlet sides of the heat exchanger is great,
and heat transfer rate is lowered due to the uninformed
flow velocity, which facts lead to the deterioration in
heat transfer performance.
(5) Still further, since a sectional shape of the
needle fins is rectangular and their edge portions are
sharp, a gas which is streaming near the edge portions
brings about turbulence. In consequence, pressure loss
is large and noise occurs, and additionally the flow
I I
velocity of the gas is reduced due to the pressure loss and heat
transfer rate is thus deteriorated. Moreover, since the needle
portions 2c are arranged in a straight line along the direction
of the air flow 4, contact of the downstream needle portions 2c
with the air flow 4 is obstructed by the upstream needle portions
2c. As a result, the air-side heat transfer rate at the down-
stream needle portions 2c is poor, and it is accordingly impost-
isle to improve the heat transfer rate to an enough extent.
lo The present invention provides a heat exchanger which
can eliminate conventional drawbacks described above, and
improves yield of a fin material, rigidity of fin and performance
of heat transfer and is hard to become a reject article.
According to the present invention there is provided a
heat exchanger comprising an elongated flat plate adapted to pass
a heat exchange medium there through, said flat plate having a
pelf of oppositely disposed flat surfaces, said flat plate being
bent along the elongated direction thereof in a meandering lash-
ion into a plurality of generally rectilinear sections lntercon-
netted by curved sections with the flat surfaces of adjacent fee-
tllinear sections disposed in spaced facing generally parallel
relation, fins extending between said facing flat surfaces of
adjacent said rectilinear sections, said fins comprising an eon-
grated sheet material plate corrugated to form alternating curved sections and straight sections, said plate having a pair of fat-
orally spaced elongated edges with each said edge connected to a
different one of said facing flat surfaces, said plate being slit
in the direction between the elongated edges between locations
adjacent to and spaced inwardly from said elongated edges, said
plates being slit so that no portion of said plate is punched out
and removed, said slitted plate forming adjacent fins extending
for the
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length of the slits in said plate, and said curved sections
of said plate being punched out between locations adjacent
said elongated edges whereby said fins extend along said
straight section of said plate with said curved sections
being free of said fins and being open.
Thus, the heat exchanger comprises a flat pipe for
allowing a heat exchange medium to pass there through, flat
surfaces of the flat pipe being confronted with each other
at an interval and being disposed in parallel, and fins
formed by corrugating a strip material plate, the fins being
arranged between the confronted flat surfaces above and
along their lengthwise direction, in which the fins take the
configuration of a needle fin group which is prepared by
lo punching out the strip metal plate in the portions
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corresponding to curved portions of the corrugated plate, leaving
its opposite width direction end portions; forming numerous width
direction notches in portions corresponding to straight portions
of the corrugated plate in order to provide fins there between;
and causing the respective adjacent fins to alternately oppo-
Seattle project.
The present invention again provides a heat exchanger
which can overcome the aforementioned conventional drawbacks and
has less pressure loss and high heat transfer performance. In
accordance with the present invention the heat exchanger come
proses a flat pipe for allowing a heat exchange medium to pass
there through, flat surface of the flat pipe being confronted with
each other at an interval and being disposed in parallel, and
fins formed by corrugating a strip material plate, the fins being
arranged between the confronted flat surfaces above and along
their lengthwise direction, in which the fins take the configure-
lion of a ladder-like fin group which is formed by punching out
the strip metal plate in the portions corresponding to curved
portions of the corrugated plate, leaving its opposite width
direction end portions; and punching out the strip metal plate in
the portions corresponding to straight portions of the corrugated
plate in order to form numerous slits therein.
The present invention again provides a heat exchanger
adapted to have great heat transfer rate and to generate less
noise. Thus, the invention provides a heat exchanger comprising
a flat pipe for allowing a heat exchanger medium to pass
there through, flat surfaces of the flat pipe being confronted
with each other at an interval and being disposed in parallel,
and fins formed by corrugating a strip material plate, the fins
being arranged between the confronted flat surfaces above and
along their lengthwise direction, in which the fins are removed
partially to form portions for allowing a fluid to pass
there through, and outer peripheral surfaces of the fins are made
in the state of a smooth curvy surface.
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Jo The present invention further provides a heat exchanger
which can further improve an air-side heat transfer rate.
According to the present invention the heat exchanger comprises a
flat pipe, in cross-section, meanderlngly arranged so that its
flat surfaces may be parallel to each other at a predetermined
interval, and a ladder-like needle corrugate fin meanderingly
arranged in a space defined by the flat surfaces above so as to
be parallel to each other in the width direction of the flat
pipe, in which the needle portions of the corrugate fin are
shaped into a circular form in
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I
cross section, and the respective adjacent needle portions
are caused to alternately oppositely project from a standard
plane.
Now, the present invention will be described with
regard to its first embodiment on the basis of Figs 4 to 5:
A heat exchanger of the present invention makes
use of an extruded flat pipe 1, by way of a heat transfer
pipe, in which partition walls lo are installed therein in
its lengthwise direction, as in a conventional one. The one
extruded flat pipe 1 may be caused to meander so that its
flat surfaces lb may be confronted with each other at an
interval and disposed in parallel, alternatively many
extruded flat pipes lay be connected to each other with
the interposition of headers. In the spaces defined by the
flat surfaces lb, there is secured a needle fin group 20 in
a manner normal to the lengthwise direction of the flat
plate I by use of a brazing material or adhesive, the needle
fin group 20 being formed by corrugating a strip metal
plate.
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The needle fin group 20 can be formed from the
strip metal plate as follows: The strip metal plate having
a wall thickness of T and a width of h is employed; the
strip metal plate is punched out in the portions correspond-
in to curved portions R of the corrugated plate, slightly
leaving opposite width direction end portions
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aye thereof, in order to form punched portions 20b; the
strip metal plate is formed with width direction notches
in the portions corresponding to straight portions L of
the corrugated plate at an interval substantially equal to
the wall thickness T in order to form needle fins 20c
between the respective notches; and the adjacent needle
fins 20c are caused to alternately project in order to
obtain a needle fin group 20 as shown enlargedly in FIG. 5.
The thus formed needle fin group 20 is corrugated so that
a corrugation width and a fin pitch of the straight
portions L may be w and PUT, respectively and the eon-
rugated needle fin group 20 is inserted between the flat
surfaces lb of the flat pipe 1. Then, the fin group is
secured on the flat surfaces lb by the aid of the brazing
material or adhesive which is previously affixed on the
flat surfaces lb. In the case of the thus secured needle
fin group 20, a fin pitch parallel to the flow direction
of air 4 is PLY a fin pitch, normal to the flow direction
of the air 4, of the straight portions L of the corrugated
plate is PUT, a fin pitch between the needle fins 20c on
the straight line L is Pi, a height of the fins (plate
width) is h, and a wave height of the fins (meander width)
lo W.
With regard to the heat exchanger including the thus
formed needle fin group 20, the portions 20b corresponding
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to the curved portions after completion of corrugation are
only punched out in forming the needle fin group 20,
therefore the yield of the used material can be improved
to a great degree. Further, in the needle fin group 20,
the notches are provided and the respective adjacent needle
fins 20c are caused to alternately project, therefore the
fin rigidity can be improved noticeably. As a result,
even if a pressure is applied at the time of securing the
needle fin group on the flat surfaces lb, it will not be
deformed. This makes it possible to obtain a stable heat
exchanger without any deformation. Furthermore, since
being different from the conventional constitution that the
punched portions are alternately provided to form the
ladder-like structure, the needle fin group of the present
invention can increase the fins by the number correspond-
in to the punched portions. In consequence, a heat
transfer area can be enlarged and a heat transfer per-
pheromones can thus be enhanced. Additionally, when it is
attempted to obtain the same performance as in the con-
ventional one, the heat exchanger according to the present
invention can be miniaturized. Moreover, since the needle
fins are arranged so as to project alternately oppositely,
the development of boundary layers can be restrained and
the heat transfer performance can thus be improved.
FIGS. 6 and 7 attached hereto show a second embodiment
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of the present invention.
In this embodiment, as a heat transfer, there is used
an extruded flat pipe l in which partition walls lo (which
may be disposed along a longer axis, in cross section,
of the pipe, though FIG. 1 (b) shows its arrangement along
a shorter axis) are installed therein in its lengthwise
direction as in the case of the conventional one. The one
flat pipe l may be caused to meander so that its flat
surfaces lb may be confronted with each other at an inter-
vet and disposed in parallel, as shown in FIG. 1, alterna-
lively many flat pipes 1 may be connected to each other
with the interposition of headers. In the space defined
by the flat surfaces lb, there is arranged a needle fin
group 30 in a securing manner by use of the brazing
material or adhesive, the needle fin group 30 being formed
by corrugating a strip metal plate and being disposed
there in a style normal to the lengthwise direction of
the flat pipe 1 or in an inclined style.
When the conventional needle fin group (see FIGS. 3
(a) and 3 by was reviewed in detail, it has been found
that the increase in pressure loss and the decrease in heat
transfer rate are attributed to the fact the inflow and
outflow of the air 4 are obstructed by the needle fins 2c
at the curved portions of the corrugated plate, i.e. at
the tops and bottoms of the meander. Therefore, the needle
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fin group 30 of this embodiment is formed as follows:
The strip metal thin plate which is a fin material is
extensively punched out in the portions corresponding to
the curved portions R of the corrugated plate, slightly
leaving opposite width direction end portions aye thereof,
in order to form punched portions 30b; and the portions,
of the strip metal plate, corresponding to the straight
portions L of the corrugated plate are formed with numerous
rectangular slits 30c, slightly leaving the opposite width
direction end portions aye thereof, in order to leave
ladder-like needle fins 30d which constitute the needle
fin group 30. The thus formed group 30 is corrugated by
meandering it along the lengthwise direction of the flat
surfaces lb of the flat pipe 1. And, securing the needle
fin group 30 on the flat surfaces lb of the flat pipe 1
as a heat transfer pipe can be carried out by brazing or
bonding the opposite width direction end portions of the
corrugated needle fin group 30 to the flat surfaces lb with
the aid of the brazing material or adhesive which is
previously applied on the flat surfaces, but at this
securing operation, the straight portions L of the eon=
rugated plate may be arranged so as to be parallel to the
width direction of the flat pipe 1 or to be inclined as
much as an angle I.
In the heat exchanger equipped with such a needle fin
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group 30, the curved portions R of the corrugated plate
have no needle fins dry therefore the inflow and outflow
of the air 4 can smoothly and uniformly carried out
without any obstruction. As a result, the flow velocity
vector pa of the air 4 at the curved portions R is equal
to the flow velocity vector 4b of the air 4 at the straight
portions L, and thus the pressure loss of the air is
reduced and the heat transfer rate is improved. Therefore,
when it is contemplated to obtain the same performance as
in the conventional one, the heat exchanger according to
the present invention can be miniaturized.
FIG. 8 shows a third embodiment of the present invent
lion, and it is directed to an improved heat exchanger of
the second embodiment illustrated.
This heat exchanger, as shown in FIG. 8 (a), comprises
a flat pipe in cross section and a corrugate fin 50 meander-
tingly arranged in a space defined by the flat surfaces lb
of the flat pipe 1. As shown in FIG. 8 (b), in the case of
this corrugate fin 50, needle portions 50b are formed in
a ladder-like form between opposite end portions aye, aye,
and the respective needle portions 50b are shaped into a
substantially circular form in cross section. Further,
between the respective needle portions 50b, there are
formed openings 50c, and at the curved portions aye' of the
end portions aye, there are formed fin-free portions 50d
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in order to facilitate the inflow and outflow of the air
flow 4. Furthermore, bending portions eye are formed
between the needle portions 50b and the opposite end
portions aye, aye so that the respective adjacent needle
portions 50b, 50b may be caused to alternately oppositely
project by a predetermined distance from a plane comprising
the opposite end portions aye, aye.
The thus prepared corrugate fins 50 are arranged so
that they may be in parallel with each other in the width
lo direction of the flat surfaces lb of the flat pipe 1, and
the fin pitch of the needle portions 50b is Puts.
According to the heat exchanger above, the needle port
lions 50b are caused to alternately project from the plane
of the opposite end portions aye, therefore the downstream
needle portions 50b can efficiently be heat exchanged with
the air flow 4, which improves the air-side heat transfer
rate. In the case of PUTS = TAO tin the case that the
needle portions of the previous heat exchanger are caused
to project without any processing), an effect on the
improvement in a kcal/m.C.hr aroused heat transfer
rate) has been investigated, and obtained results are set
forth in FIG. 9. In this drawing, an abscissa axis repro-
sets an air flow velocity (TV < m/sec) and an ordinate
axis represents an improvement ratio of the air-side heat
transfer rate of the heat exchanger regarding this
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1 ~3087;~
embodiment with respect to that of the previous heat
exchanger.
According to the results in FIG. 9, it is definite that
the heat exchanger of this embodiment is better in the pa
than the previous one. Further, the improvement ratio of
the pa tends to decrease with the increase in the air flow
velocity, but within the range usually employed (TV < 3
m/sec), it improves as much as 35% or more.
Since improving in the air-side heat transfer rate,
the aforesaid heat exchanger can be miniaturized and
lightened, if it is attempted to have the same performance
as in the conventional one. Therefore, when this heat
exchanger is applied as an air conditioner for a car,
effects such as saving of a car fuel and expansion of
a car space can be obtained.
In addition, the ladder-like needle corrugate fin 50
can be formed by in-line punching and circularization in
cross section, and its punching pitch is a fin pitch for
permitting acquisition of a maximum air-side heat transfer
rate aye. In the case of the corrugate fin of this embody-
mint, the maximum value of the air-side heat transfer
rate aye can be obtained at a position where the fin pitch
PUTS is narrower than TAO. For this reason, the fin pitch
PUTS is to be narrowed, which serves to improve the yield
of a used material.
i2~0872
Since the needle portions are circularized in cross
section and are caused to project alternately normal to
the direction of the air flow as described above, the heat
exchanger having such needle portions can obtain noticeable
effects of improvement in the air-side heat transfer rate,
miniaturization and lightening of the heat exchanger body,
betterment in the yield of the material, and the like.
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