Technical Field
[0001] The present invention relates to a parallel-flow-type heat exchanger.
Background Art
[0002] A parallel-flow-type heat exchanger having a plurality of flat tubes arranged between
a plurality of header pipes, with refrigerant passages inside the flat tubes communicating
with the insides of the header pipes, and with corrugated fins arranged between the
flat tubes, is widely used in car air conditioners and the like. Examples are seen
in Patent Documents 1 and 2.
[0003] The heat exchanger described in Patent Document 1 has a plurality of header pipes
arranged horizontally, and has a plurality of flat tubes arranged vertically, and
corrugated fins between the flat tubes are shaped like valleys with their bottom at
a central part of the heat exchanger in the depth direction. At the valley-bottom
part of the corrugated fins, where they join the flat tubes, through holes are formed;
when defrosting operation is performed to melt frost sticking to the heat exchanger,
the water resulting from the frost melting is drained through the through holes.
[0004] Patent Document 2 describes a heat exchanger in which a plurality of tongue-like
pieces are cut to raise from one and the opposite faces of the flat-plate part of
corrugated fins, with a view to increasing heat exchange efficiency at the corrugated
fins.
[Patent Document 1]
JP-A-2005-24187
[Patent Document 2]
JP-A-2001-66083
Disclosure of the Invention
Problems to be Solved by the Invention
[0005] An object of the present invention is to improve the shape of corrugated fins to
achieve improved heat efficiency performance in a parallel-flow-type heat exchanger.
Another object is to achieve smooth drainage of defrost water and condensed water.
Means for Solving the Problem
[0006] To achieve the above objects, according to the present invention, a heat exchanger
comprises: a plurality of horizontal header pipes arranged parallel at an interval
from one another; a plurality of vertical flat tubes arranged with a predetermined
pitch between the plurality of header pipes, with vertical refrigerant passages provided
inside the flat tubes communicating with the insides of the header pipes; and corrugated
fins arranged between the flat tubes. Here, the corrugated fins comprise upwind-side
corrugated fins whose fin surface has a downward slope toward the downwind side and
downwind-side corrugated fins whose fin surface has an upward slope toward the downwind
side. Moreover, the downwind-side ends of the upwind-side corrugated fins and the
upwind-side ends of the downwind-side corrugated fins are kept in contact with ribs
formed on the side faces of the flat tubes.
[0007] With this structure, owing to the fact that the upwind-side corrugated fins have
a downward slope and the downwind-side corrugated fins have an upward slope, the length
over which the upwind-side corrugated fins and the downwind-side corrugated fins make
contact with air can be made large compared with the depth of the flat tubes, resulting
in improved heat exchange performance. Moreover, as a result of the downwind-side
ends of the upwind-side corrugated fins and the upwind-side ends of the downwind-side
corrugated fins being kept in contact with ribs formed on the side faces of the flat
tubes, it is possible to accurately position the flat tubes, the upwind-side corrugated
fins, and the downwind-side corrugated fins, and thereby to reduce assembly errors.
[0008] In the heat exchanger structured as described above, it is preferable that the ribs
be continuous in the vertical direction.
[0009] With this structure, it is possible to form the ribs and the flat tubes simultaneously
by extrusion.
[0010] In the heat exchanger structured as described above, it is preferable that, as a
result of the upwind-side corrugated fins and the downwind-side corrugated fins being
kept in contact with the ribs, a predetermined gap be formed between the upwind-side
corrugated fins and the downwind-side corrugated fins.
[0011] With this structure, it is possible to efficiently drain defrost water and condensed
water through the gap across which the upwind-side corrugated fins and the downwind-side
corrugated fins are put together.
Advantages of the Invention
[0012] According to the present invention, it is possible to increase the length over which
the corrugated fins make contact with air and thereby to achieve satisfactory heat
exchange, and it is possible to accurately position and assemble the flat tubes and
the corrugated fins. It is also possible to achieve quick drainage of defrost water
and condensed water.
Brief Description of Drawings
[0013]
[Fig. 1] A schematic vertical sectional view showing an outline of the structure of
a heat exchanger
[Fig. 2] A sectional view cut along line A-A in Fig. 1
[Fig. 3] An enlarged partial horizontal sectional view of the heat exchanger [Fig.
4] A front view of the part shown in Fig. 3 as viewed along line B-B
[Fig. 5] An enlarged partial horizontal sectional view similar to Fig. 3 but showing
a second embodiment
List of Reference Symbols
[0014]
- 1
- heat exchanger
- 2, 3
- header pipe
- 4
- flat tube
- 5
- refrigerant passage
- 6
- corrugated fin
- 6U
- upwind-side corrugated fin
- 6D
- downwind-side corrugated fin
- 9
- gap
- 12
- rib
Best Mode for Carrying Out the Invention
[0015] Hereinafter, embodiments of the present invention will be described with reference
to the accompanying drawings. A heat exchanger 1 has two horizontal header pipes 2
and 3 arranged parallel at an interval from one another in the up/down direction,
and has a plurality of vertical flat tubes 4 arranged with a predetermined pitch between
the header pipes 2 and 3. The flat tubes 4 are elongate members formed by extrusion
of a metal with high thermal conductivity, such as aluminum, and has, formed inside
them, refrigerant passages for circulation of refrigerant. As shown in Fig. 3, inside
the flat tubes 4 are arranged a plurality of refrigerant passages 5 with an identical
cross-sectional shape and an identical cross-sectional area; thus the flat tubes 4
appear to have a cross section like a harmonica. Incidentally, the refrigerant passages
5 need not have a uniform cross-sectional shape and a uniform cross-sectional area,
but may have different cross-sectional shapes and different cross-sectional areas.
[0016] The flat tubes 4 are arranged with their extrusion direction vertical, and accordingly
the direction of the circulation of refrigerant through the refrigerant passages 5
is vertical. The individual refrigerant passages 5 communicate with the insides of
the header pipes 2 and 3. Incidentally, in Fig. 1, the top side of the page is the
top side in the vertical direction, and the bottom side of the page is the bottom
side in the vertical direction. Between the top-side header pipe 2 and the bottom-side
header pipe 3, a plurality of flat tubes 4 are arranged with a predetermined pitch
with their length direction vertical.
[0017] The header pipes 2 and 3 and the flat tubes 4 are fixed by welding. Between the flat
tubes 4, corrugated fins 6 are arranged, and the flat tubes 4 and the corrugated fins
6 are also fixed by welding. Like the flat tubes 4, the header pipes 2 and 3 and the
corrugated fins 6 are formed of a metal with high thermal conductivity (for example,
aluminum).
[0018] At one end of the bottom-side header pipes 3, a refrigerant inflow port 7 is provided,
and at one end of the top-side header pipes 2, a refrigerant outflow port 8 is provided
at a position diagonal to the refrigerant inflow port 7.
[0019] Owing to the structure in which a large number of flat tubes 4 are provided between
the header pipes 2 and 3 and corrugated fins 6 are provided between the flat tubes
4, the heat-dissipation (heat-absorption) area of the heat exchanger 1 is large, allowing
efficient heat exchange.
[0020] Next, the structure of the corrugated fins 6 will be described with reference to
Figs. 2, 3, and 4. In Figs. 2 and 3, the left side of the page is the upwind side,
and the right side of the page is the downwind side.
[0021] As shown in Figs. 2 and 3, the corrugated fins 6 divide into upwind-side corrugated
fins 6U and downwind-side corrugated fins 6D. The upwind-side corrugated fins 6U have
a fin surface with a downward slope toward the downwind side; the downwind-side corrugated
fins 6D have a fin surface with an upward slope toward the downwind side. The downward
slope of the upwind-side corrugated fins 6U and the upward slope of the downwind-side
corrugated fins has the same angle. In the air flow direction, the horizontal direction
length of the upwind-side corrugated fins 6U and the horizontal direction length of
the downwind-side corrugated fins 6D are equal.
[0022] The downward slope of the upwind-side corrugated fins 6U and the upward slope of
the downwind-side corrugated fins 6D do not necessarily have to have the same angle,
but may have different angles. The length of the upwind-side corrugated fins 6U and
the length of the downwind-side corrugated fins 6D in the air flow direction do not
necessarily have to be equal, but may be different.
[0023] Seen from the direction perpendicular to the flow of air, the upwind-side corrugated
fins 6U and the downwind-side corrugated fins 6D appear to be a large number of V
shapes arranged in the up/down direction. The V shapes here, however, are not closed
but open at their bottom part. Specifically, the upwind-side corrugated fins 6U and
the downwind-side corrugated fins 6D are not in close contact with each other, but
are arranged with a gap 9 secured between them. The gap 9 is so sized as to enable
water droplets sticking to the downwind-side ends of the upwind-side corrugated fins
6U and water droplets sticking to the upwind-side ends downwind-side corrugated fins
6D to coalesce.
[0024] On upwind-side ends of the flat tubes 4, ridge-shaped ribs 10U are provided that
protrude parallel to the air circulation direction (in other words, toward the upwind
side); on downwind-side ends of he flat tubes 4, ridge-shaped ribs 10D are provided
that protrude parallel to the air circulation direction (in other words, toward the
downwind side). Incidentally, in this embodiment, the ribs 10U and 10D are formed
integrally with the flat tubes 4 by extrusion, and extend continuously in the length
direction of the vertically arranged flat tubes, from a position slightly lower than
the top end of the flat tubes to a position slightly higher than the bottom end of
the flat tubes.
[0025] Owing to the fact that, as described above, instead of the ribs 10U and 10D being
given the same length as the flat tubes 4, small distances are secured between the
top and bottom ends of the flat tubes 4 and the top and bottom ends of the ribs I0U
and 10D respectively, the header pipes 2 and 3 only need to have a diameter large
enough to receive the body parts of the flat tubes 4, and this helps reduce the diameter
of the header pipes 2 and 3 compared with in a case where they need to receive the
ribs 10U and 10D as well.
[0026] Incidentally, the upwind-side ends of the upwind-side corrugated fins 6U extend to
close to a position flush with the tip ends of the ribs 10U provided on the upwind-side
ends of the flat tubes 4 (in this embodiment, the upwind-side ends of the upwind-side
corrugated fins 6U are approximately flush with tip ends of the ribs 10U), and the
downwind-side ends of the downwind-side corrugated fins 6D extend to close to a position
flush with the tip ends of the ribs 10D provided on the downwind-side ends of the
flat tubes 4 (in this embodiment, the downwind-side ends of the downwind-side corrugated
fins 6D are approximately flush with the tip ends of the ribs 10D).
[0027] Instead of the structure described above in which the upwind-side ends of the upwind-side
corrugated fins 6U are flush with the tip ends of the ribs 10U and the downwind-side
ends of the downwind-side corrugated fins 6D are flush with (level with) the tip ends
of the ribs 10D, it is also possible to adopt a structure in which the upwind-side
ends of the upwind-side corrugated fins 6U do not reach a position flush with the
tip ends of the ribs 10U and the downwind-side ends of the downwind-side corrugated
fins 6D do not reach a position flush with the tip ends of the ribs 10D, or a structure
in which the upwind-side ends of the upwind-side corrugated fins 6U extend beyond
a position flush with the tip ends of the ribs 10U and the downwind-side ends of the
downwind-side corrugated fins 6D extend beyond a position flush with the tip ends
of the ribs 10D. These structures may be combined together in any way.
[0028] As seen from the front, the width of the ribs 10U and 10D is smaller than the width
of the flat tubes 4. Thus, between the ribs 10U and the upwind-side corrugated fins
6U, gaps are left, and these gaps form vertical drain grooves 11U. Likewise, between
the ribs 10D and the downwind-side corrugated fins, gaps are left, and these gaps
form vertical drain grooves 11D.
[0029] On the side faces of the flat tubes 4, at their center, ribs 12 are formed that are
continuous in the length direction of the flat tubes 4 (in this embodiment, the vertical
direction). The downwind-side ends of the upwind-side corrugated fins 6U and the upwind-side
ends of the downwind-side corrugated fins 6D are kept in contact with these ribs 12.
Thus a gap 9 is formed that has a width equal to the thickness of the ribs 12. The
ribs 12 also are formed integrally with the flat tubes 4 by extrusion, and are continuous,
in the length direction of the vertically arranged flat tubes, from a position slightly
lower than the flat tube top ends to a position slightly higher than the flat tube
bottom ends. This eliminates the need to form, in the header pipes 2 and 3, openings
in which to insert the ribs 12, and makes simple the process of forming, in the header
pipes 2 and 3, openings in which to insert the flat tubes 4.
[0030] The position of the ribs 12 does not necessarily have to be coincident with the position
of the center of the side faces of the flat tubes 4, but may be displaced from it.
In this case, if the upwind-side corrugated fins 6U and the downwind-side corrugated
fins 6D need be located within the width of the flat tubes 4 in the air flow direction,
their respective lengths in the air flow direction are adjusted. If they may extend
out of the width of the flat tubes 4 in the air flow direction, their respective lengths
in the air flow direction may be equal to or different from each other.
[0031] Although in this embodiment the ribs 12 are formed continuous in the vertical direction,
they may instead be each formed of discrete parts, or may be provided only at several
places (for example, at a total of three places corresponding to a top, a middle,
and a bottom part of the corrugated fins, or at a total of two places corresponding
to a top and a bottom part of the corrugated fins). Possible ways of forming such
discontinuous ribs 12 include: fitting ribs 12 as separate parts to the body of the
flat tubes by welding; machine-removing desired parts of continuous ribs 12 formed
integrally with the flat tubes 4; and machine-cutting part of the flat tubes 4 into
ribs.
[0032] When refrigerant is passed through the heat exchanger 1 while air is circulated with
an unillustrated fan, in an operation mode in which the heat exchanger 1 is used as
an evaporator (for example, when heating operation is performed by use of the heat
exchanger 1 in the outdoor unit of a separate-type air conditioner comprising an indoor
unit and an outdoor unit, the heat exchanger 1 acts as an evaporator), the heat exchanger
1 absorbs heat from the air, and in return releases cold into the air. Since the upwind-side
corrugated fins 6U and the downwind-side corrugated fins 6D each have a sloped fin
surface, compared with in a case where corrugated fins have no slope and are arranged
horizontally, the corrugated fins 6 as a whole extend longer in the air flow direction,
achieving high heat exchange performance.
[0033] As operation that absorbs heat from the air continues, on the surface of the upwind-side
corrugated fins 6U, on the surface of the downwind-side corrugated fins 6D, and also
on the surface of the flat tubes 4, moisture in the air condenses. Initially fine
water droplets combine into larger water droplets, which are then drained through
the upwind-side drain grooves 11U and the downwind-side drain grooves 11D of the flat
tubes 4. At these places, a flow of air prompts the breaking of the surface tension
of water; thus the so-called bridging phenomenon in which water forms a film by its
surface tension is unlikely to occur, and water can be made to flow out quickly.
[0034] Part of the water droplets flow down along the slanted surfaces of the upwind-side
corrugated fins 6U or the downwind-side corrugated fins 6D, and meet at the gap 9.
The gap 9 is so sized as to enable water droplet sticking to the downwind-side ends
of the upwind-side corrugated fins 6U and water droplets sticking to the upwind-side
ends of the downwind-side corrugated fins 6D to coalesce; thus, when water droplets
on the upwind-side corrugated fins 6U and water droplets on the downwind-side corrugated
fins 6D meet at the gap 9, they break each other's surface tension and coalesce, and
flow out quickly through the gap 9 without causing the bridging phenomenon.
[0035] In an operation mode in which the heat exchanger 1 is used as an evaporator (an operation
mode in which the heat exchanger 1 absorbs heat from the outdoor air), depending on
the ambient air temperature condition and the operation condition, moisture in the
air may, in the form of frost, stick to the surface of the flat tubes 4 and the corrugated
fins 6. As time passes, frost gets thicker and lowers heat exchange performance; thus
it is necessary to perform, from time to time, defrosting operation, in which the
heat exchanger 1 is turned to a condenser, to melt frost. Like condensed water, defrost
water resulting from frost melting also is drained smoothly through the drain grooves11U
and 11D and the gap 9. Thus, on return from defrosting operation to normal operation,
it will not occur that water droplets that have remained without being drained freeze
and impair heat exchange performance. In this way, it is also possible to achieve
an object of smoothly draining defrost water and condensed water.
[0036] When the upwind-side corrugated fins 6U and the downwind-side corrugated fins 6D
are welded to the flat tubes 4, by keeping the downwind-side ends of the upwind-side
corrugated fins 6U and the upwind-side ends of the downwind-side corrugated fins 6D
in contact with the ribs 12 on the side faces of the flat tubes 4, it is possible
to accurately position the flat tubes 4, the upwind-side corrugated fins 6U, and the
downwind-side corrugated fins 6D, and to reduce assembly errors. Production efficiency
is also improved.
[0037] The downward slope of the upwind-side corrugated fins 6U and the upward slope of
the downwind-side corrugated fins 6D can be selected within the range of 5° to 40°.
The sharper the slope, the larger the heat exchange area and thus the easier it is
to drain, but the higher the resistance to the circulation of air. It is therefore
advisable to set the angle at an appropriate value through experiments. Other relevant
dimensions are as follows: the interval between the flat tubes 4 is 5.5 mm; the thickness
of the flat tubes 4 is 1.3 mm; in the air flow direction, the horizontal direction
length of both the upwind-side corrugated fins 6U and the downwind-side corrugated
fins 6D is 18 mm; the ridge-valley pitch of both the upwind-side corrugated fins 6U
and the downwind-side corrugated fins 6D is 2 mm to 3 mm; the size of the gap 9 is
0.5 mm at the maximum. Needless to say, these values are merely examples, and are
not meant to limit the contents of the invention. For example, since the gap 9 has
simply to be so sized as to enable water droplets sticking to the downwind-side ends
of the upwind-side corrugated fins 6U and water droplets sticking to the upwind-side
ends of the downwind-side corrugated fins 6D to coalesce, its size can be set within
the range up to 4 mm at the maximum.
[0038] A second embodiment of the present invention is shown in Fig. 5. In the first embodiment,
since the thickness of the ribs 12 is just as large as the width of the gap 9, to
give the gap 9 a size of 0.5 mm at the maximum, the ribs 12 need to be given a thickness
of 0.5 mm or less. In the second embodiment, in downwind-side corners of the upwind-side
corrugated fins 6U and in upwind-side corners of the downwind-side corrugated fins
6D, cuts 13 are formed that receive the ribs 12. This makes it possible to give the
gap 9 a width smaller than the thickness of the ribs 12. Thus, even when, for reasons
associated with mold production, the ribs 12 have a large thickness, it is possible
to give the gap 9 such a size as to enable water droplets sticking to the downwind-side
ends of the upwind-side corrugated fins 6U and water droplets sticking to the upwind-side
ends of the downwind-side corrugated fins 6D to coalesce.
[0039] Incidentally, the ribs 12 are easier to form by extrusion when they have a thickness
that is large to a certain degree (for example, 2 mm). In a case where the gap 9 can
be made large (for example, 2 mm), the thickness of the ribs 12 can itself be made
use of, and thus there is no need to form cuts 13.
[0040] The embodiments by way of which the present invention has been described above are
not meant to limit the scope of the present invention; the present invention may be
implemented with many modifications and variations made within the spirit of the invention.
Industrial Applicability
[0041] The present invention finds wide application in parallel-flow-type heat exchangers.