BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a heat exchanger that is formed by a plurality of
plate-shaped fins and a plurality of flat pipes each having a plurality of coolant
flow channels, and exchanges heat between air flowing between the plurality of fins
and a coolant flowing in the coolant flow channels of the plurality of flat pipes.
Description of the Related Art
[0002] Conventional heat exchangers are known which are formed by a plurality of plate-shaped
fins that are arranged at predetermined intervals and a plurality of flat pipes having
a plurality of coolant flow channels that are perpendicularly inserted into the fins.
[0003] As the heat exchanger of this type, a heat exchanger that has a plurality of cut-and-raised
parts on each fin is disclosed (see Patent Literature 1, for example).
[0004] FIG. 24 is a plan view of fins of the conventional heat exchanger described in Patent
Literature 1 in the x-y plane, in which the x direction is the direction of air flow,
and the y direction is the direction of arrangement of flat pipes.
[0005] As shown in FIG 24, a heat exchanger 1 is formed by plate-shaped fins 2 and a plurality
of flat pipes 4 having a plurality of coolant flow channels 3 that are perpendicularly
inserted into the fins 2, and the rear edge part of a cut-and-raised part of a plurality
of cut-and-raised parts 5 provided on the fins 2 that is located on the downstream
side of the air flow (in the +x direction) is located downstream from the rear edge
part of the flat pipe 4 in the direction of the air flow (in the +x direction).
[0006] As a result, the dead water region of the flat pipe on the downstream side of the
air flow (in the +x direction) is reduced, and the ventilation resistance can be reduced.
[0007] Patent literature 1: Japanese Patent Laid-Open No.
2010-54060
SUMMARY OF THE INVENTION
[0008] However, the conventional configuration has a problem that the boundary layer formed
from the front rear edge of the flat pipe increases in thickness as air flows to the
downstream side (in the +x direction), and heat transfer on other side surfaces of
the flat pipe than the front edge part is suppressed, so that of the plurality of
coolant flow channels formed in the flat pipe, the amount of heat exchanged with the
coolant flowing in coolant flow channels in other parts than the front edge part decreases,
and the heat exchange capability decreases.
[0009] The present invention has been devised to solve the problem of the prior art described
above, and an object of the present invention is to provide a heat exchanger using
a flat pipe, in which heat transfer on other side surfaces of the flat pipe than a
front edge part of the flat pipe is promoted to increase the amount of heat exchanged
with a coolant flowing in coolant flow channels in other parts than the front edge
part of a plurality of coolant flow channels formed in the flat pipe and improve a
heat exchange capability.
[0010] To solve the problem of the prior art described above, a heat exchanger according
to the present invention includes: a plurality of plate-shaped fins arranged at predetermined
intervals; and a plurality of flat pipes that are arranged in parallel with each other,
that are perpendicularly inserted into the fins and that have a plurality of coolant
flow channels, the fin includes a flat part and a heat transfer promoting part raised
from the flat part, the heat transfer promoting part is formed between adjacent flat
pipes and between a front edge part of the flat pipe and a rear edge part of the flat
pipe, and of boundary lines formed by the heat transfer promoting part and the flat
part, a boundary line located on an upstream side of air flow extends from the upstream
side to a downstream side of the air flow and is inclined to come closer to the flat
pipe.
[0011] With such a configuration, the air passing through the gaps between the plurality
of adjacent flat pipes collides with a surface of the heat transfer promoting part
raised from the boundary line to form a flow toward a side surface of the flat pipe,
so that the boundary layer on the side surface of the flat pipe is reduced in thickness.
[0012] The heat exchanger according to the present invention can promote heat transfer on
the other side surfaces of the flat pipe than the front edge part, so that the amount
of heat exchanged with the coolant flowing in coolant flow channels in the other parts
than the front edge parts of the plurality of coolant flow channels formed in the
flat pipes increases, and the heat exchange capability can be improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013]
FIG. 1 is a perspective view of a heat exchanger according to a first embodiment of
the present invention.
FIG. 2 is a plan view of fins of the heat exchanger according to the first embodiment
of the present invention in an x-y plane.
FIG. 3 is a side view of fins of the heat exchanger according to the first embodiment
of the present invention in a z-y plane viewed in the x direction.
FIG. 4 is a characteristic diagram showing a relationship between an air-side heat
transfer rate k and w1/w according to the first embodiment of the present invention.
FIG. 5 is a characteristic diagram showing a relationship between the air-side heat
transfer rate k and a ventilation resistance ΔP and h1/h according to the first embodiment
of the present invention.
FIG. 6 is a characteristic diagram showing a relationship between the air-side heat
transfer rate k and the ventilation resistance ΔP and θ according to the first embodiment
of the present invention.
FIG. 7 is a plan view of fins of a heat exchanger according to a first modification
of the first embodiment of the present invention in the x-y plane.
FIG. 8 is a plan view of fins of a heat exchanger according to a second modification
of the first embodiment of the present invention in the x-y plane.
FIG. 9 is a side view of fins of the heat exchanger according to the second modification
of the first embodiment of the present invention in the z-y plane viewed in the x
direction.
FIG. 10 is a plan view of fins of a heat exchanger according to a third modification
of the first embodiment of the present invention in the x-y plane.
FIG. 11 is a plan view of fins of a heat exchanger according to a fourth modification
of the first embodiment of the present invention in the x-y plane.
FIG. 12 is a side view of fins of the heat exchanger according to the fourth modification
of the first embodiment of the present invention in the z-y plane viewed in the x
direction.
FIG. 13 is a side view of fins of a heat exchanger according to a fifth modification
of the first embodiment of the present invention in the z-y plane viewed in the x
direction.
FIG. 14 is a plan view of fins of a heat exchanger according to a second embodiment
of the present invention in the x-y plane.
FIG. 15 is a side view of fins of the heat exchanger according to the second embodiment
of the present invention in the z-y plane viewed in the x direction.
FIG. 16 is a cross-sectional view of the heat exchanger according to the second embodiment
of the present invention taken along the line indicated by the arrows A.
FIG. 17 is a characteristic diagram showing a relationship between the air-side heat
transfer rate k and the ventilation resistance ΔP and α according to the second embodiment
of the present invention.
FIG. 18 is a plan view of fins of a heat exchanger according to a first modification
of the second embodiment of the present invention in the x-y plane.
FIG. 19 is a side view of fins of the heat exchanger according to the first modification
of the second embodiment in the z-y plane viewed in the x direction.
FIG. 20 is a plan view of fins of a heat exchanger according to a second modification
of the second embodiment of the present invention in the x-y plane.
FIG. 21 is a side view of fins of the heat exchanger according to the second modification
of the second embodiment of the present invention in the z-y plane viewed in the x
direction.
FIG. 22 is a characteristic diagram showing a relationship between the air-side heat
transfer rate k and the ventilation resistance ΔP and I1/I according to the second
modification of the second embodiment of the present invention.
FIG. 23 is a side view of fins of a heat exchanger according to a third modification
of the second embodiment of the present invention in the z-y plane viewed in the x
direction.
FIG. 24 is a plan view of fins of a conventional heat exchanger in an x-y plane.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] A first invention is a heat exchanger, comprising: a plurality of plate-shaped fins
arranged at predetermined intervals; and a plurality of flat pipes that are arranged
in parallel with each other, that are perpendicularly inserted into the fins and that
have a plurality of coolant flow channels, wherein the fin includes a flat part and
a heat transfer promoting part raised from the flat part, the heat transfer promoting
part is formed between adjacent flat pipes and between a front edge part of the flat
pipe and a rear edge part of the flat pipe, and of boundary lines formed by the heat
transfer promoting part and the flat part, a boundary line located on an upstream
side of air flow extends from the upstream side to a downstream side of the air flow
and is inclined to come closer to the flat pipe.
[0015] With such a configuration, the air passing through the gaps between the plurality
of adjacent flat pipes collides with a surface of the heat transfer promoting part
raised from the boundary line to form a flow toward a side surface of the flat pipe,
so that the boundary layer on the side surface of the flat pipe is reduced in thickness.
[0016] Therefore, heat transfer on the other side surfaces of the flat pipe than the front
edge part can be promoted, so that the amount of heat exchanged with the coolant flowing
in coolant flow channels in the other parts than the front edge parts of the plurality
of coolant flow channels formed in the flat pipe increases, and the heat exchange
capability can be improved.
[0017] According to a second invention, the heat transfer promoting part has a shape such
that the flat part is cut, and a cut part of the flat part is raised along the boundary
line.
[0018] By providing the cut-and-raised part as described above, the rise angle of the heat
transfer promoting part from the flat part can be increased.
[0019] The air colliding with the surface of the heat transfer promoting part raised from
the boundary line is prevented from getting over the heat transfer promoting part,
and an air flow toward the side surface of the flat pipe is formed with reliability,
so that the boundary layer at the side surface of the flat pipe is further reduced
in thickness.
[0020] Therefore, even in a high capacity operation in which the speed of the airflow is
higher, heat transfer on the other side surfaces of the flat pipe than the front edge
part can be promoted, so that the amount of heat exchanged with the coolant flowing
in coolant flow channels in other parts than the front edge parts of the plurality
of coolant flow channels formed in the flat pipe increases, and the heat exchange
capability can be improved.
[0021] In the following, embodiments of the present invention will be described with reference
to the drawings. Note that the present invention is not limited to these embodiments.
(First Embodiment)
[0022] FIG. 1 is a perspective view of a heat exchanger according to a first embodiment
of the present invention. An x direction is an air flow direction, a y direction is
a direction of arrangement of flat pipes, and a z direction is a direction of arrangement
of fins.
[0023] In FIG. 1, a heat exchanger 10 includes a plurality of plate-shaped fins 11 arranged
at predetermined intervals and a plurality of flat pipes 12 arranged in parallel with
each other and perpendicularly inserted into the plurality of fins 11, and exchanges
heat between air flowing between the plurality of fins 11 and a coolant flowing in
a plurality of coolant flow channels 13 formed in the plurality of flat pipes 12.
[0024] As the coolant, R410A, R32 or a mixture coolant containing R32 is used, for example.
The flat pipes 12 may be connected to form a single pipe or may be separate pipes.
Each of the flat pipes 12 may have a plurality of inlet ports or outlet ports.
[0025] FIG. 2 is a plan view of fins of the heat exchanger according to the first embodiment
of the present invention in an x-y plane, and FIG. 3 is a side view of fins of the
heat exchanger according to the first embodiment of the present invention in a z-y
plane viewed in the x direction.
[0026] A y-direction side surface of the flat pipe 12 located on an upstream side of the
air flow (in the -x direction) forms a front edge part 12a, and a y-direction side
surface of the flat pipe 12 located on a downstream side of the air flow (in the +x
direction) forms a rear edge part 12b.
[0027] The fin 11 is formed by a flat part 14 and a heat transfer promoting part 15 that
rises from the flat part 14 to the side of a passage of the air flow (in the +z direction).
[0028] The heat transfer promoting part 15 has a V-shape and extends obliquely with respect
to the air flow direction (x direction). A part of the heat transfer promoting part
15 is provided between adjacent flat pipes 12 and between the front edge part 12a
and the rear edge part 12b of each flat pipe 12.
[0029] Of boundary lines formed by the heat transfer promoting part 15 and the flat part
14, a boundary line 16 that is substantially in parallel with a ridge of the heat
transfer promoting part 15 and located on the upstream side of the air flow and has
a greater dimension extends from the upstream side to the downstream side of the air
flow and is inclined to come closer to the flat pipe 12.
[0030] The heat transfer promoting part 15 further has a heat transfer promoting surface
17 that rises from the boundary line 16 with which the air collides.
[0031] An end part of the boundary line 16 on the downstream side of the air flow (in the
+x direction) is located upstream from the rear edge part 12b of the flat pipe 12
in the direction of the air flow (in the -x direction). A line L1, which is an extension
of the ridge of the heat transfer promoting part 15 on the downstream side of the
air flow (in the +x direction), is inclined θ° with respect to the direction of the
air flow (the +x direction) and intersects with the flat pipe 12 at a point upstream
from the rear edge part 12b of the flat pipe 12 in the direction of the air flow (in
the -x direction).
[0032] Next, the air flow will be described.
[0033] A part of the air flowing into gaps between the fins 11 collides with the front edge
parts 12a of the flat pipes 12, and another part of the air does not collide with
the flat pipes 12 but passes through the plurality of adjacent flat pipes 12.
[0034] At the front edge part 12a of the flat pipe 12 with which the air collides, a boundary
layer is reduced in thickness, so that the heat transfer rate is highest in the flat
pipe 12. The boundary layer around the flat pipe 12 increases in thickness and the
heat transfer rate of the flat pipe 12 decreases as it goes toward the downstream
side of the air flow (in the +x direction)
[0035] The air having collided with the front edge part 12a of each flat pipe 12 exchanges
heat with the coolant flowing in a coolant flow channel 13 on the side of the front
edge part 12a of the flat pipe 12 and then passes through the gaps between the adjacent
flat pipes 12.
[0036] The air passing through the gaps between the adjacent flat pipes 12 collides with
the heat transfer promoting surfaces 17 of the heat transfer promoting parts 15 provided
on the fins 11, which promotes the heat transfer with the fins 11.
[0037] As the air experiences heat exchange on the upstream side of the air flow, the temperature
of the air comes closer to the temperature of the coolant flowing in each coolant
flow channel 13 of the flat pipe 12. Thus, the difference in temperature between the
air and the coolant decreases as the air flows to the downstream side of the air flow.
[0038] With the heat exchanger configured as described above, the air flowing between the
plurality of adjacent flat pipes 12 collides with the heat transfer promoting surface
17 of each heat transfer promoting part 15 and then is guided along the heat transfer
promoting surface 17 toward a side surface of the flat pipe 12, so that the boundary
layer at the side surface of the flat pipe 12 is reduced in thickness.
[0039] As a result, heat transfer on other side surfaces of each flat pipe 12 than the front
edge part 12a can be promoted, and therefore, the amount of heat exchanged with the
coolant flowing in coolant flow channels 13 formed in other parts of each flat pipe
12 than the front edge part 12a can be increased, and the heat exchange capability
can be improved.
[0040] A length of the flat pipe 12 in a longer-side direction (the x direction) is denoted
by w, a distance from an intersection A between the line L1 and a line that extends
in the direction of the air flow (the x direction) and passes through a center of
the flat pipe 12 in a shorter-side direction (the y direction) to the rear edge part
12b of the flat pipe 12 is denoted by W1, a distance between adjacent fins 11 is denoted
by h, and a height of the heat transfer promoting part 15 in the +z direction is denoted
by h1. FIG. 4 is a characteristic diagram showing a relationship between an air-side
heat transfer rate k and w1/w, FIG. 5 is a characteristic diagram showing a relationship
between the air-side heat transfer rate k and a ventilation resistance ΔP and h1/h,
and FIG. 6 is a characteristic diagram showing a relationship between the air-side
heat transfer rate k and the ventilation resistance ΔP and the angle θ. In the first
embodiment, the length w in the longer-side direction (the x direction) of the flat
pipe 12 is 16 mm (w = 16 mm), and the distance h between adjacent fins 11 is 1.3 mm
(h = 1.3 mm).
[0041] As shown in FIG. 4, as w1 decreases, k increases, and the heat exchange capability
improves. If the heat transfer promoting part 15 is arranged so that w1 ≤ 0.45w, the
heat exchanger can have a high heat transfer capability. Therefore, the heat transfer
promoting part 15 is desirably arranged so that w1 ≤ 7.2 mm, since w = 16 mm. By setting
w1 ≤ 7.2 mm, the boundary layer around the flat pipe 12, which increases in thickness
as it goes to the downstream side of the air flow (in the +x direction), can be reduced
in thickness, so that heat transfer can be promoted on the other side surfaces than
the front edge part 12a of the flat pipe 12, and the heat exchange capability can
be improved.
[0042] In particular, if w1 = 0 mm, the line L1 intersects with the rear edge part 12b of
the flat pipe 12, so that the air flow is more likely to be guided to the side surfaces
of the flat pipe 12 closer to the rear edge part 12b, at which the difference in temperature
between the air and the coolant is small and heat exchange is less likely to occur,
and the heat transfer on the side surfaces of the flat pipe 12 closer to the rear
edge part 12b can be promoted. As a result, sufficient heat exchange occurs on the
entire flat pipe 12, and the heat exchange capability can be improved even in a high
capacity operation in which the total coolant circulation amount is high.
[0043] As shown in FIG. 5, as h1 increases, k increases, and the heat exchange capability
improves. In addition, ΔP increases, and an input to an air blower increases. In particular,
if the heat transfer promoting part 15 is arranged so that h1 ≤ 0.60h, the heat exchanger
can have a high heat exchange capability. Therefore, the heat transfer promoting part
15 is desirably arranged so that h1 ≤ 7.8 mm, since h = 1.3 mm.
[0044] With such a configuration, the air flow is more likely to be guided to the side surfaces
of the flat pipe 12 closer to the rear edge part 12b, and the heat transfer on the
side surfaces of the flat pipe 12 closer to the rear edge part 12b can be promoted,
while reducing an increase of the ventilation resistance ΔP, which is due to inhibition
of the air flow (in the +x direction) so that the ventilation resistance ΔP is equal
to or less than an allowable value, so that the heat exchange capability can be improved.
[0045] As shown in FIG. 6, as θ increases, k increases, and the heat exchange capability
improves. In addition, ΔP increases, and the input to the air blower increases. In
particular, the heat transfer promoting part 15 is desirably arranged so that θ ≤
60°.
[0046] With such a configuration, the air flow is more likely to be guided to the side surfaces
of the flat pipe 12 closer to the rear edge part 12b, and the heat transfer on the
side surfaces of the flat pipe 12 closer to the rear edge part 12b can be promoted,
while reducing an increase of the ventilation resistance ΔP, which is due to contraction
of the air flow that occurs when the air passes through the heat transfer promoting
part 15 so that the ventilation resistance ΔP is equal to or less than an allowable
value, so that the heat exchange capability can be improved.
[0047] In this example, two heat transfer promoting parts 15 are arranged symmetrically
with respect to a center line between the adjacent flat pipes 12. However, the heat
transfer promoting parts 15 may not be arranged symmetrically with respect to the
center line, or the number of heat transfer promoting parts may be one, three or more.
Furthermore, although the boundary line 16 is showed as a straight line, of course,
the same effects can be achieved if the boundary line is curved in a parabola and
extends from the upstream side to downstream side of the air flow to come closer to
the flat pipe 12.
[0048] FIG. 7 is a plan view of fins of a heat exchanger according to a first modification
of the first embodiment of the present invention in the x-y plane.
[0049] As shown in FIG. 7, at least one heat transfer promoting part 15 is arranged downstream,
in the direction of the airflow (in the +x direction), from a central part in the
width direction of the flat pipe 12 in the longer-side direction (the x direction).
[0050] With such a configuration, the air passing through the gaps between the adjacent
flat pipes 12 collides with the heat transfer promoting surface 17 of the heat transfer
promoting part 15 raised from the boundary line 16 at a point downstream in the direction
of the air flow (in the +x direction) from the central part in the width direction
of the flat pipe 12 in the longer-side direction (the x direction). Therefore, on
the downstream side of the air flow (in the +x direction), at which the difference
in temperature between the air and the coolant is small and heat exchange is less
likely to occur, the heat transfer promoting surface 17 of the heat transfer promoting
part 15 disturbs the airflow to promote heat transfer between the air and the fin
11, so that the heat exchange capability can be improved even in a low capacity operation
in which the speed of the air flow is low.
[0051] FIG. 8 is a plan view of fins of a heat exchanger according to a second modification
of the first embodiment of the present invention in the x-y plane, FIG. 9 is a side
view of fins of the heat exchanger according to the second modification of the first
embodiment of the present invention in the z-y plane viewed in the x direction, and
FIG. 10 is a plan view of fins of a heat exchanger according to a third modification
of the first embodiment of the present invention in the x-y plane.
[0052] As shown in FIGS. 8 and 9, the heat transfer promoting part 15 has the shape of a
triangular pyramid, and the heat transfer promoting part 15 and the flat part 14 form
two boundary lines 16 on the upstream side of the air flow. Thus, a single heat transfer
promoting part 15 has two heat transfer promoting surfaces 17.
[0053] The two boundary lines 16 extend from the upstream side to the downstream side of
the air flow in such a manner that the boundary lines 16 are inclined toward the respective
closer flat pipes 12. The heat transfer promoting surfaces 17 raised from the respective
boundary lines 16 with which the air collides are arranged in the x-y plane in such
a manner that lines L2 and L3 do not intersect with each other, provided that the
line L2 is a straight line that connects an apex of the heat transfer promoting part
15 in the height direction (the +z direction) and the rear edge part 12b of the flat
pipe 12 to each other and the line L3 is an extension of the boundary line 16 toward
the flat pipe from the upstream side to the downstream side of the airflow.
[0054] With the heat exchanger configured as described above, a plurality of heat transfer
promoting parts 15 are not provided for each fin, and the air flow can be guided to
the side surfaces of the plurality of adjacent flat pipes 12 by a reduced number of
heat transfer promoting parts 15. Therefore, the possibility of a break or creasing
of the fins can be prevented from increasing due to providing a plurality of heat
transfer promoting parts 15 for each fin.
[0055] If the heat transfer promoting part 15 is arranged so that the lines L2 and L3 are
in parallel with each other, the air flow is more likely to be guided to the side
surfaces of the flat pipe 12 closer to the rear edge part 12b, at which the difference
in temperature between the air and the coolant is smallest and heat exchange is less
likely to occur, and the heat transfer on the side surfaces of the flat pipe 12 closer
to the rear edge part 12b can be promoted. As a result, sufficient heat exchange occurs
on the entire flat pipe 12, and the heat exchange capability can be improved even
in a high capacity operation in which the total coolant circulation amount is high.
[0056] Although the heat transfer promoting part 15 has the shape of a triangular pyramid
in this example, of course, the same effects can be achieved even if the heat transfer
promoting part 15 has a quadrangular pyramid as shown in FIG. 10.
[0057] FIG. 11 is a plan view of fins of a heat exchanger according to a fourth modification
of the first embodiment of the present invention in the x-y plane, FIG. 12 is a side
view of fins of the heat exchanger according to the fourth modification of the first
embodiment of the present invention in the z-y plane viewed in the x direction, and
FIG. 13 is a plan view of fins of a heat exchanger according to a fifth modification
of the first embodiment of the present invention in the x-y plane.
[0058] As shown in FIGS. 11 and 12, a plurality of heat transfer promoting parts 15a, 15b
and 15c are provided on each fin 11. The heat transfer promoting parts 15a and 15b
have a V-shape and extend obliquely with respect to the airflow direction (the x direction).
The heat transfer promoting part 15c has the shape of a triangular pyramid and is
arranged downstream in the direction of the airflow (the +x direction) from the heat
transfer promoting parts 15a and 15b.
[0059] With such a configuration, the air passing through the gaps between the heat transfer
promoting parts 15a and 15b is likely to be guided to the side surfaces of the flat
pipes 12 by the heat transfer promoting part 15c arranged on the downstream side of
the air flow (in the +x direction), and the heat transfer can be promoted on the entire
side surfaces of the flat pipes 12, so that the heat exchange capability can be improved.
[0060] Although the plurality of heat transfer promoting parts 15a, 15b and 15c are shown
as being raised to the same height in the +z direction, of course, the same effects
can be achieved even if the plurality of heat transfer promoting parts 15a, 15b and
15c are raised to different heights in the +z direction.
[0061] Although the plurality of heat transfer promoting parts 15a, 15b and 15c are raised
into the air flow passage on the same side (in the +z direction) in this example,
of course, the same effects can be achieved even if the plurality of heat transfer
promoting parts are raised into the air flow passages on the different sides, for
example, the heat transfer promoting parts 15a and 15b are raised in the +z direction
and the heat transfer promoting part 15c is raised in the -z direction, as shown in
FIG. 13.
[0062] Furthermore, although the heat transfer promoting parts 15a and 15b are shown as
having a V-shape, and the heat transfer promoting part 15c is shown as having the
shape of a triangular pyramid, of course, the same effects can be achieved even if
different combinations of the shapes of the heat transfer promoting parts are adopted,
for example, the heat transfer promoting parts 15a and 15b have a V-shape, and the
heat transfer promoting part 15c has the shape of a quadrangular pyramid, or even
if combinations of three or more shapes are adopted, for example, the heat transfer
promoting part 15a has a V-shape, the heat transfer promoting part 15b has the shape
of a triangular pyramid, and the heat transfer promoting part 15c has the shape of
a quadrangular pyramid.
(Second Embodiment)
[0063] FIG. 14 is a plan view of fins of a heat exchanger according to a second embodiment
of the present invention in the x-y plane, FIG. 15 is a side view of fins of the heat
exchanger according to the second embodiment of the present invention in the z-y plane
viewed in the x direction, and FIG. 16 is a cross-sectional view taken along the line
indicated by the arrows A.
[0064] As shown in FIGS. 14, 15 and 16, the heat transfer promoting part 15 has a shape
such that the flat part 14 is cut, and a cut part of the flat part 14 is raised along
the boundary line 14 in the +z direction.
[0065] Thus, the heat transfer promoting surface 17 of the heat transfer promoting part
15 is formed by cutting and raising, so that the rise angle α from the flat part 14
can be increased.
[0066] The heat transfer promoting part 15 is arranged so that a line L4, which is an extension
of the upper side in the +z direction of the heat transfer promoting surface 17 to
the downstream side of the air flow (in the +x direction), intersects with the flat
pipe 12 at a point upstream from the rear edge part 12b of the flat pipe 12 in the
direction of the air flow (in the -x direction).
[0067] As a result, the air colliding with the heat transfer promoting surface 17 of the
heat transfer promoting part 15 raised from the boundary line 16 is prevented from
flowing in the +z direction to get over the heat transfer promoting surface 17, and
the air flow toward the side surface of the flat pipe 12 is formed with reliability,
so that the boundary layer at the side surface of the flat pipe 12 is further reduced
in thickness.
[0068] Therefore, even in a high capacity operation in which the speed of the airflow is
high, heat transfer on other side surfaces of each flat pipe 12 than the front edge
part 12a can be promoted, and therefore, the amount of heat exchanged with the coolant
flowing in the coolant flow channels 13 formed in other parts of each flat pipe 12
than the front edge part 12a can be increased, and the heat exchange capability can
be improved.
[0069] If the heat transfer promoting part 15 is arranged so that the line L4 intersects
with the rear edge part 12b of the flat pipe 12, the air flow is more likely to be
guided to the side surfaces of the flat pipe 12 closer to the rear edge part 12b,
at which the difference in temperature between the air and the coolant is smallest
and heat exchange is less likely to occur, and the heat transfer on the side surfaces
of the flat pipe 12 closer to the rear edge part 12b can be promoted. As a result,
sufficient heat exchange occurs on the entire flat pipe 12, and the heat exchange
capability can be improved even in a high capacity operation in which the total coolant
circulation amount is high.
[0070] FIG. 17 is a characteristic diagram showing a relationship between the air-side heat
transfer rate k and the ventilation resistance ΔP and the rise angle α. As α increases,
k increases, and the heat exchange capability improves. In addition, ΔP increases,
and the input to the air blower increases. In particular, the heat transfer promoting
part 15 is desirably arranged so that 60° ≤ α ≤ 90°.
[0071] With such a configuration, an effect of disturbing the air flow to promote the heat
transfer between the air and the fins 11 due to the air having passed through the
gaps between the adjacent flat pipes 12 colliding with the heat transfer promoting
surface 17 of the heat transfer promoting part 15 raised from the boundary line 16
and an effect of forming the air flow toward the side surfaces of the flat pipes 12
to reduce the thickness of the boundary layers at the side surfaces of the flat pipes
12, thereby promoting the heat transfer between the air and the flat pipes 12 can
be achieved, while reducing an increase of the ventilation resistance ΔP so that the
ventilation resistance ΔP is equal to or less than an allowable value.
[0072] Furthermore, even if the speed of the air flow is high, the air flow is prevented
from flowing in the +z direction to get over the heat transfer promoting surface 17,
and the air flow is guided to the side surfaces of the flat pipes 12 with reliability.
Therefore, even in a maximum capacity operation in which the speed of the airflow
is still higher, the heat exchange capability can be improved.
[0073] FIG. 18 is a plan view of fins of a heat exchanger according to a first modification
of the second embodiment of the present invention in the x-y plane, and FIG. 19 is
a side view of fins of the heat exchanger according to the first modification of the
second embodiment in the z-y plane viewed in the x direction.
[0074] Of course, the same effects can be achieved even if a single heat transfer promoting
part 15 is formed by a plurality of cut-and-raised parts as shown in FIGS. 18 and
19.
[0075] FIG. 20 is a plan view of fins of a heat exchanger according to a second modification
of the second embodiment of the present invention in the x-y plane, FIG. 21 is a side
view of fins of the heat exchanger according to the second modification of the second
embodiment of the present invention in the z-y plane viewed in the x direction, and
FIG. 23 is a side view of fins of a heat exchanger according to a third modification
of the second embodiment of the present invention in the z-y plane viewed in the x
direction.
[0076] As shown in FIGS. 20 and 21, a plurality of heat transfer promoting parts 15a, 15b
and 15c are provided for each fin 11, the heat transfer promoting parts 15a and 15b
are formed by cutting and raising, and the heat transfer promoting part 15c has the
shape of a triangular pyramid and is arranged downstream from the heat transfer promoting
parts 15a and 15b in the direction of the air flow (in the +x direction).
[0077] With such a configuration, the air passing through the gaps between the heat transfer
promoting parts 15a and 15b is likely to be guided to the side surfaces of the flat
pipes 12 by the heat transfer promoting part 15c arranged on the downstream side of
the air flow (in the +x direction), and the heat transfer can be promoted on the entire
flat pipes 12, so that the heat exchange capability can be improved.
[0078] Although the plurality of heat transfer promoting parts 15a, 15b and 15c are shown
as being raised to the same height in the +z direction, of course, the same effects
can be achieved even if the plurality of heat transfer promoting parts 15a, 15b and
15c are raised to different heights in the +z direction.
[0079] Provided that the distance between the plurality of adjacent flat pipes 12 is denoted
by I, and the length in the y direction of the heat transfer promoting surfaces 17a,
17b and 17c of the heat transfer promoting parts 15a, 15b and 15c projected onto the
downstream side of the air flow (in the +x direction) is denoted by I1, FIG. 22 is
a characteristic diagram showing a relationship between the air-side heat transfer
rate k and the ventilation resistance ΔP and I1/I. In the second embodiment, the distance
I between the plurality of adjacent flat pipes 12 is 8.4 mm (I = 8.4 mm).
[0080] As shown in FIG. 22, as I1 increases, k increases, and the heat exchange capability
improves. In addition, ΔP increases, and the input to the air blower increases. In
particular, if the heat transfer promoting part 15 is arranged so that I1 ≤ 0.65I,
the heat exchanger can have a high heat exchange capability. Therefore, the heat transfer
promoting part 15 is desirably arranged so that I1 ≤ 5.4 mm, since I = 8.4 mm.
[0081] With such a configuration, the air flow is more likely to be guided to the side surfaces
of the flat pipe 12 closer to the rear edge part 12b, and the heat transfer on the
side surfaces of the flat pipe 12 closer to the rear edge part 12b can be promoted,
while reducing an increase of the ventilation resistance ΔP so that the ventilation
resistance ΔP is equal to or less than an allowable value, so that the heat exchange
capability can be improved.
[0082] Although the plurality of heat transfer promoting parts 15a, 15b and 15c are raised
into the air flow passage on the same side (in the +z direction) in this example,
of course, the same effects can be achieved even if the plurality of heat transfer
promoting parts are raised into the airflow passages on the different sides, for example,
the heat transfer promoting parts 15a and 15b are raised in the +z direction and the
heat transfer promoting part 15c is raised in the -z direction, as shown in FIG. 23.
[0083] Furthermore, although the heat transfer promoting parts 15a and 15b are shown as
having the cut-and-raised shape, and the heat transfer promoting part 15c is shown
as having the shape of a triangular pyramid, of course, the same effects can be achieved
even if different combinations of the shapes of the heat transfer promoting parts
are adopted, for example, the heat transfer promoting parts 15a and 15b have the cut-and-raised
shape, and the heat transfer promoting part 15c has shape of a quadrangular pyramid.
Industrial Applicability
[0084] The present invention is a heat exchanger using a flat pipe that is improved in heat
exchange capability by promoting heat transfer on the flat pipe on the downstream
side of air flow and can be used in applications, such as a freezer, an air conditioner
or an air conditioning and hot water supply complex system.
Reference Signs List
[0085]
1 heat exchanger
2 fin
3 coolant flow channel
4 flat pipe
5 cut-and-raised part
10 heat exchanger
11 fin
12 flat pipe
12a front edge part
12b rear edge part
13 coolant flow channel
14 flat part
15, 15a, 15b, 15c heat transfer promoting part
16 boundary line
17, 17a, 17b, 17c heat transfer promoting surface