U.S. patent application number 11/732097 was filed with the patent office on 2007-10-04 for heat exchanger.
This patent application is currently assigned to DENSO Corporation. Invention is credited to Akira Itoh, Masahiro Shimoya.
Application Number | 20070227715 11/732097 |
Document ID | / |
Family ID | 38513656 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070227715 |
Kind Code |
A1 |
Shimoya; Masahiro ; et
al. |
October 4, 2007 |
Heat exchanger
Abstract
A heat exchanger has tubes defining refrigerant passages therein
and fins disposed between the tubes. The tubes have tube main walls
opposed to each other. The fins are joined to the tube main walls.
The tube main walls have projections that project inside of the
tubes and define recesses on outer sides of the tubes. Each of the
tubes has an outer dimension, in a direction perpendicular to the
tube main walls, in a range between equal to or greater than 0.8 mm
and equal to or less than 1.9 mm.
Inventors: |
Shimoya; Masahiro;
(Kariya-city, JP) ; Itoh; Akira; (Kariya-city,
JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
DENSO Corporation
Kariya-city
JP
|
Family ID: |
38513656 |
Appl. No.: |
11/732097 |
Filed: |
April 2, 2007 |
Current U.S.
Class: |
165/152 ;
165/177 |
Current CPC
Class: |
F28F 3/042 20130101;
F28F 1/426 20130101; F28F 1/42 20130101; F28D 1/05366 20130101 |
Class at
Publication: |
165/152 ;
165/177 |
International
Class: |
F28D 1/02 20060101
F28D001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 4, 2006 |
JP |
2006-103093 |
Claims
1. A heat exchanger for performing heat exchange between a
refrigerant and an external fluid, comprising: tubes defining
passages therein for allowing the refrigerant to flow, the tubes
having tube main walls opposed to each other; and fins disposed
between the tubes and joined with the tube main walls, wherein the
tube main walls have projections that project inside of the tubes
and define recesses outside of the tubes for allowing the external
fluid to flow, and each of the tubes has a tube outer dimension in
a range between at least 0.8 mm and at most 1.9 mm, in a direction
perpendicular to the tube main walls.
2. The heat exchanger according to claim 1, wherein the tube outer
dimension is in a range between at least 1.0 mm and at most 1.6
mm.
3. The heat exchanger according to claim 2, wherein the tube outer
dimension is in a range between at least 1.2 mm and at most 1.4
mm.
4. The heat exchanger according to claim 1, wherein the projections
are arranged at a predetermined pitch with respect to a
longitudinal direction of the tube, and the predetermined pitch is
in a range between at least 1.0 mm and at most 6.5 mm.
5. The heat exchanger according to claim 4, wherein the
predetermined pitch is in a range between at least 1.6 mm and at
most 5.7 mm.
6. The heat exchanger according to claim 5, wherein the
predetermined pitch is in a range between at least 2.3 mm and at
most 5.0 mm.
7. The heat exchanger according to claim 1, wherein each of the
fins has a fin outer dimension in a range between at least 2.0 mm
and at most 9.0 mm, in the direction perpendicular to the tube main
walls.
8. The heat exchanger according to claim 7, wherein the fin outer
dimension is in a range between at least 3.0 mm and at most 7.3
mm.
9. The heat exchanger according to claim 8, wherein the fin outer
dimension is in a range between at least 4.0 mm and at most 6.0
mm.
10. The heat exchanger according to claim 1, wherein the
projections extend continuously from upstream ends to downstream
ends of the tubes with respect to a flow direction of the external
fluid flowing outside of the tubes.
11. The heat exchanger according to claim 1, wherein each of the
tubes has a first tube member and a second tube member joined with
the first tube member, and the tube main walls of each tube are
included in the first and second tube members.
12. The heat exchanger according to claim 11, wherein the first
tube member and the second tube member have an identical shape.
13. The heat exchanger according to claim 1 wherein each of the
tubes has a separation wall for separating an inner space of the
tube into a plurality of spaces in a direction perpendicular to a
longitudinal direction of the tube, and the separation wall is
integrated with the tube main walls.
14. The heat exchanger according to claim 1, wherein the
projections have curved shapes extending along the tube main walls
in a meandering manner in a direction perpendicular to a
longitudinal direction of the tubes.
15. The heat exchanger according to claim 1, wherein the
projections have straight shapes extending along the tube main
walls and obliquely with respect to a longitudinal direction of the
tubes.
16. The heat exchanger according to claim 1, wherein the
projections have V-shapes that extend along the tube main walls and
diverging in a longitudinal direction of the tubes.
17. The heat exchanger according to claim 1, wherein the
projections are meshed along the tube main walls.
18. The heat exchanger according to claim 1, wherein the
projections have side walls extending perpendicular to outer
surfaces of the tube main walls, and the side walls define edged
corners with the outer surfaces of the tube main walls.
19. The heat exchanger according to claim 1, wherein the
projections have side walls extending perpendicular to outer
surfaces of the tube main walls, and the side walls define curved
corners with the outer surfaces of the tube main walls.
20. The heat exchanger according to claim 1, wherein the fins are
corrugated fins including first fin walls and second fin walls
connecting the first fin walls, and the first fin walls are flat
and joined with outer surfaces of the tube main walls.
21. The heat exchanger according to claim 20, wherein the second
fin walls have louvers that are angled with respect to a flow
direction of the external fluid flowing through the fins.
22. The heat exchanger according to claim 1, wherein the external
fluid is air for cooling the refrigerant.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on Japanese Patent Application No.
2006-103093 filed on Apr. 4, 2006, the disclosure of which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a heat exchanger, which is
for example used as a refrigerant radiator for cooling a
refrigerant flowing in tubes.
BACKGROUND OF THE INVENTION
[0003] U.S. Pat. No. 6,595,273 B2 (JP-A-2004-3787) discloses a heat
exchanger having flat tubes, as a refrigerant radiator. The flat
tubes have recesses on flat walls (tube main walls) thereof for
allowing air to flow, thereby to improve the efficiency of heat
exchange. The recesses are defined by projections formed on the
tube main walls.
[0004] The projections have serpentine side walls such that air
flows in the recesses in a serpentine or meandering manner. Because
the flow of air adjacent to outer surfaces of the tube main walls
is disturbed, development of a temperature boundary layer adjacent
to the outer surfaces of the tube main walls is reduced. Thus, a
coefficient of heat transfer of the air improves.
[0005] The recesses are formed by pressing the outer surfaces of
the tube main walls in an inward direction of the tubes. Therefore,
inside of the flat tubes, the refrigerant flows over the inward
projections in a serpentine manner, and hence the flow of
refrigerant is disturbed. Because development of a temperature
boundary layer adjacent to inner surfaces of the tube main walls is
reduced, a coefficient of heat transfer of the refrigerant
improves. Accordingly, in this heat exchanger, the coefficient of
heat transfer of both of the air and the refrigerant is improved by
disturbing the flows of air and refrigerant, thereby improving the
efficiency of heat exchange.
[0006] However, since the refrigerant flows in the serpentine
manner, resistance to flow of the refrigerant increases, resulting
in pressure loss of the refrigerant. If the temperature of the
refrigerant reduces due to the pressure loss of the refrigerant,
the temperature difference between the refrigerant and the air
reduces. Further, this will affect the efficiency of heat
exchange.
SUMMARY OF THE INVENTION
[0007] The present invention is made in view of the foregoing
matter, and it is an object of the present invention to provide a
heat exchanger having tubes with projections for disturbing flows
of an internal fluid and an external fluid, which is capable of
sufficiently maintaining or improving efficiency of heat
exchange.
[0008] According to an aspect of the present invention, a heat
exchanger has tubes and fins. The tubes define passages therein
through which a refrigerant as an internal fluid flows. The tubes
have tube main walls opposed to each other. The fins are disposed
between the tubes and joined to the tube main walls. The tube main
walls have projections projecting inside of the tubes and defining
recesses outside of the tubes for allowing an external fluid to
flow. Each of the tubes has a tube outer dimension (tube height),
in a direction perpendicular to the tube main walls, in a range
between equal to or greater than 0.8 mm and equal to or less than
1.9 mm.
[0009] As the tube outer dimension increases, a passage area of a
refrigerant passage increases and resistance to flow of the
refrigerant reduces. Therefore, pressure loss of the refrigerant is
reduced and hence the decrease of efficiency of heat exchange may
be suppressed. However, if the tube outer dimension is increased
more than necessarily, the resistance to flow of the refrigerant is
reduced excessively. In this case, although the refrigerant flows
smoothly, disturbing effect of the refrigerant is reduced.
[0010] Accordingly, the tube outer dimension is set in a range
between equal to or greater than 0.8 mm and equal to or less than
1.9 mm. When the tube outer dimension is in this range, the
pressure loss of the refrigerant is reduced while the disturbing
effect of the refrigerant is maintained. Therefore, the efficiency
of heat exchange is sufficiently provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Other objects, features and advantages of the present
invention will become more apparent from the following detailed
description made with reference to the accompanying drawings, in
which like parts are designated by like reference numbers and in
which:
[0012] FIG. 1 is a perspective view of a heat exchanger according
to a first embodiment of the present invention;
[0013] FIG. 2 is a schematic perspective view of a part of the heat
exchanger according to the first embodiment;
[0014] FIG. 3A is a perspective view for showing a step of forming
projections and recesses on a plate member for the heat exchanger
according to the first embodiment;
[0015] FIG. 3B is a perspective view for showing a step of folding
the plate member according to the first embodiment;
[0016] FIG. 4 is a perspective view for showing a step of joining
formed tube members as another example of forming a tube for the
heat exchanger according to the first embodiment;
[0017] FIG. 5 is a graph showing a relationship between the height
of the tube and efficiency of heat transfer of air according to the
first embodiment;
[0018] FIG. 6 is a graph showing a relationship between pitch of
projections of the tubes and efficiency of heat transfer of air
according to the first embodiment;
[0019] FIG. 7 is a graph showing a relationship between the height
of fins of the heat exchanger and efficiency of heat transfer of
air according to the first embodiment;
[0020] FIG. 8 is a schematic perspective view of a part of a heat
exchanger according to a second embodiment of the present
invention;
[0021] FIG. 9 is a schematic perspective view of a part of a heat
exchanger according to a third embodiment of the present
invention;
[0022] FIG. 10 is a schematic perspective view of a part of a heat
exchanger according to a fourth embodiment of the present
invention;
[0023] FIG. 11 is a schematic perspective view of a part of a heat
exchanger according to a fifth embodiment of the present
invention;
[0024] FIG. 12 is a schematic perspective view of a part of a heat
exchanger according to a sixth embodiment of the present
invention;
[0025] FIG. 13 is a schematic perspective view of a part of a heat
exchanger according to a seventh embodiment of the present
invention;
[0026] FIG. 14 is a schematic perspective view of a part of a heat
exchanger according to an eighth embodiment of the present
invention;
[0027] FIG. 15 is a perspective view for showing a step of forming
a tube of the heat exchanger according to the eighth embodiment;
and
[0028] FIG. 16 is a schematic perspective view of a part of a heat
exchanger according to a ninth embodiment of the present
invention.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT
First Embodiment
[0029] A first embodiment will be described with reference to FIGS.
1 to 7. As shown in FIG. 1, a heat exchanger 10 is for example used
as a refrigerant condenser of a refrigerating cycle for a vehicle
air conditioner, and is mounted in an engine compartment of a
vehicle at a position where outside air is sufficiently supplied
when the vehicle is running.
[0030] The heat exchanger 10 has a generally rectangular outline
and includes a heat exchanging part 13 and tanks 14, 15. The heat
exchanging part 13 includes flat tubes and fins 12. The flat tubes
11 define refrigerant passages therein through which a refrigerant
flows. The fins 12 are for example corrugated fins. The heat
exchanging part 13 performs heat exchange between the refrigerant
and air flowing outside of the flat tubes 11.
[0031] The tanks 14, 15 are coupled to opposite longitudinal ends
of the tubes 11. The refrigerant is distributed into the flat tubes
11 from one of the tanks 14, 15 (e.g., a left tank in FIG. 1) and
is collected in the other one of the tanks 14, 15 (e.g., a right
tank in FIG. 1). At the ends of the heat exchanging part 13, i.e.,
at longitudinal ends of the tanks 14, 15, side plates 16, 17 are
provided as members for maintaining the outline of the heat
exchanger 10. The side plates 16, 17 are arranged parallel to the
tubes 11 and ends of the side plates 16, 17 are connected to the
tanks 14, 15. The tubes 11, the fins 12, and the tanks 14, 15 are
integrally joined by brazing, for example.
[0032] The tanks 14, 15 are made of metal such as aluminum alloy,
and in the form of cylindrical container. The tanks 14, 15 are
formed with slits (not shown), and the slits are arranged at
predetermined intervals in a longitudinal direction of the tanks
14, 15. The longitudinal ends of the tubes 11 are inserted in the
slits to make communication with the tanks 14, 15.
[0033] The tanks 14, 15 are provided with connecting blocks 14a,
15a. For example, a first connecting block 14a is brazed to the
left tank 14 at a position adjacent to one end (e.g., lower end in
FIG. 1). An inlet pipe (not shown) is coupled to the connecting
block 14a for introducing a high temperature, high pressure
refrigerant, which has been discharged from a compressor (not
shown) of the refrigerating cycle, into the left tank 14.
[0034] Also, a second connecting block 15a is brazed with the right
tank 15 at a position adjacent to an opposite end (e.g., upper end
in FIG. 1). An outlet pipe (not shown) is coupled to the connecting
block 15a for discharging a liquid-phase refrigerant, which has
passed through the heat exchanger 10, toward an expansion valve
(not shown) of the refrigerating cycle.
[0035] Further, the tanks 14, 15 are provided with engaging
projections 14b, 15b at ends thereof (lower ends in FIG. 1) for
fixing the heat exchanger 10 to a body of the vehicle.
[0036] Next, a structure of the heat exchanging part 13 will be
described with reference to FIG. 2.
[0037] Each of the tubes 11 has generally flat walls 20, 21
(hereafter, referred to as tube main walls) opposed to each other.
The tube main walls 20, 21 extend substantially parallel to a
general flow direction Ar1 of the air. The tubes 11 and the fins 12
are stacked in a direction perpendicular to the tube main walls 20,
21, thereby to construct the heat exchanging part 13. The tubes 11
are joined to the fins 12 through the tube main walls 20, 21.
[0038] Here, each tube 11 has an outer dimension (hereafter,
referred to as a tube height) H in a direction perpendicular to the
tube main walls 20, 21. The tube height H is in a range between
equal to or greater than 0.8 mm and equal to or less than 1.9 mm.
Also, each fin 12 has a height (hereafter, referred to as a fin
height) F in the direction perpendicular to the tube main walls 20,
21. The fin height F is in a range between equal to or greater than
2.0 mm and equal to or less than 9.0 mm.
[0039] Each of the tube main walls 20 has projections 22 projecting
inside of the tube 11. For example, the projections 22 are formed
by pressing or embossing corresponding portions of the tube main
wall 20 from the outer side to the inner side. Thus, the
projections 22 define recesses 20a on a tube outer side for
allowing air to pass through as shown by an arrow Ar2. Similarly,
the tube main walls 21 have projections 23 that define recesses 21
a on the tube outer side.
[0040] Specifically, each of the projections 22, 23 (recesses 20a,
21a) extends in a serpentine or meandering manner with a constant
width along the tube main wall 20, 21. Also, the projection 22, 23
extends entirely from an air upstream end to an air downstream end
of the tube 11 with respect to the air general flow direction Ar1.
In this embodiment, the projections 22 of the tube main wall 20 and
the projections 23 of the tube main wall have the same shape.
[0041] Each projection 22, 23 has an end wall, which corresponds to
a bottom of each recess 20a, 21a, and side walls. The end wall
defines a substantially flat wall. The side walls connect to the
outer surfaces of the tube main wall, but form rounded corners with
the outer surface of the tube main wall. Namely, corners 22a, 23a
between the side walls of the projection 22, 23 and the outer
surfaces of the tube main wall are chamfered in an arc shape.
[0042] The projections 22, 23 are arranged at predetermined
intervals (pitch) P with respect to a general flow direction Rf1 of
the refrigerant, i.e., a longitudinal direction of the tube 11.
Here, the pitch P is within a range between equal to or greater
than 1.0 mm and equal to or less than 6.5 mm.
[0043] The end walls of the projections 22, 23 have first depressed
portions 22b, 23b at positions corresponding to apexes or most
curved portions of the meandering recesses 20a, 21a. The first
depressed portions 22b, 23b are further recessed inside of the tube
11 from the end walls of the projections 22, 23 in stepwise.
[0044] The projections 22 of the tube main wall 20 and the
projections 23 of the tube main wall 21 are staggered with respect
to the refrigerant general flow direction Rf1. Further, the
projection 22 of the tube main wall 20 and the projection 23 of the
tube main wall 21 overlap with each other at the first depressed
portions 22b, 23b. Also, the tube main walls 20, 21 are in contact
with and joined to each other at the first depressed portions 22b,
23b.
[0045] Also, the end wall of the projections 22, 23 have second
depressed portions 22c, 23c at positions corresponding to upstream
and downstream ends of the projections 22, 23 with respect to the
air general flow direction Ar1. The second depressed portions 22c,
23c are further recessed from the end walls of the projections 22,
23 inside of the tube 11, similar to the first depressed portions
22b, 23b. Thus, the second depressed portions 22c, 23c are in
contact with and joined to each other. In this embodiment, the
dimension of the first and second depressed portions 22b, 23b, 22c,
23c from the outer surfaces of the tube main walls 20, 21 in the
direction perpendicular to the tube main walls 20, 21 is 0.65 mm,
for example.
[0046] FIGS. 3A, 3B show an example of a method of forming the tube
11. As shown in FIG. 3A, first, the projections and recesses as
described above are formed on a metal plate, which is for example
made of aluminum alloy, by roll forming using rollers 24, 25. Then,
the formed metal plate is folded relative to its centerline, as
shown by an arrow B in FIG. 3B, and joined. In this case,
therefore, the tube main walls 20, 21 of the tube 11 are formed
from a single metal plate member. Instead of the roll forming shown
in FIG. 3A, the metal plate can be shaped by pressing.
[0047] FIG. 4 shows an another example of the method of forming the
tube 11. The tube 11 can be formed by joining two metal plates.
Specifically, the projections and recesses are formed on a first
tube member 11a and a second tube member 11b, separately.
Thereafter, the first member 11a and the second member 11b are
arranged opposite to each other and joined to each other. Thus, the
tube main walls 20, 21 are provided by the first and second tube
members 11a, 11b.
[0048] In this embodiment, the projections 22, 23 of the tube main
walls 20, 21 have the same shape. Thus, the first tube member 11a
and the second tube member 11b are shaped into the same shape. That
is, the first tube member and the second tube member 11a, 11b are
provided by the same members. Therefore, productivity of the tubes
11 improves, and hence manufacturing costs of the tubes 11
reduces.
[0049] As shown in FIG. 2, complex refrigerant passages are
provided inside of each tube 11. Since the meandering projections
22, 23 are formed on the tube main walls to project inside of the
tube 11, refrigerant passages are formed in a serpentine or
meandering manner with respect to the direction perpendicular to
the tube main walls 20, 21, as shown by arrows Rf2.
[0050] Specifically, since inner surfaces of the first depressed
portions 22b, 23b of the projections 22, 23 are in contact with
each other, the refrigerant passages are divided over the first
depressed portions 22b, 23b and then merged together. The flows of
the refrigerant repeat the divergence and mergence while flowing
along the tube main walls 20, 21 in the meandering manner.
[0051] The fins 12 are for example corrugated fins. Each of the
fins 12 is formed by bending a thin plate member, which is for
example made of aluminum alloy, into a corrugated shape. The fin 12
has joining walls (first walls) 12a, 12b to be joined to the outer
surfaces of the tube main walls 20, 21.
[0052] Also, the fin 12 has connecting walls (second walls) 12c,
12d extending perpendicular to the joining walls 12a, 12b. The
connecting walls 12c, 12d are formed with louvers 12e, 12f. The
louvers 12e, 12f are formed by cutting out from the flat walls 12c,
12d and bending relative to the connecting walls 12c, 12d so as to
oppose a flow of air passing through the connecting walls 12c, 12d
(arrow Ar3).
[0053] Next, an operation of the heat exchanger 10 will be briefly
described. The high temperature, high pressure refrigerant, which
has been discharged from the compressor (not shown), flows into the
left tank 14 of heat exchanger 10 through the first connector block
14a. The refrigerant is distributed into the tubes 11 from the left
tank 14.
[0054] While the refrigerant flowing in the tubes 11, heat of the
refrigerant is transferred to the air flowing outside of the tubes
11 through entire surfaces of the tubes 11 and the fins 12. Thus,
the refrigerant is condensed into the liquid-phase. The
liquid-phase refrigerant is collected in the right tank 15 and
discharged from the heat exchanger 10 through the second connecting
block 15a. Then, the refrigerant is introduced into the expansion
valve (not shown), for example.
[0055] Next, an effect of heat exchange between the refrigerant and
the air in the heat exchanging part 13 will be described. As shown
by the arrows Rf2 in FIG. 2, since the refrigerant flows in the
tubes 11 while meandering complexly, the flow of the refrigerant is
disturbed. As such, the coefficient of heat transfer from the
refrigerant improves. Accordingly, efficiency of heat transfer
improves.
[0056] On the other hand, the air that flows at positions separated
from the tube main walls 20, 21 flows along the fins 12, as shown
by the arrow Ar3 in FIG. 2. This air receives heat from the fin 12
and then flows out of the fins 12. Thus, the fins 12 are cooled by
the air passing through the fins 12.
[0057] Also, the air flowing adjacent to the tube main walls
receives heat from the tubes 11 and is discharged from the heat
exchanging part 13 after cooling the tube 11. In this case, as the
air flows through the recesses 20a, 21a in the meandering manner,
as shown by the arrows Ar2, the flow of this air is disturbed. As
such, the coefficient of heat transfer of the air improves.
[0058] In addition, as the air is contracted when flowing into the
recesses 20a, 21a, the coefficient of heat transfer of the air
improves. Further, because the surface of heat transfer is
increased by the recesses 20a, 21a, the amount of heat radiation
from the tube 11 to the air is increased.
[0059] FIG. 5 shows a graph showing a relationship between the tube
height H and efficiency Q of heat transfer. The efficiency Q is
represented by the following equation (1):
Q=.phi.Cp.rho.Wa(Tr-Ta) (1)
[0060] Here, .phi. represents temperature efficiency of the heat
exchanger 10; Cp represents specific heat of air; .rho. represents
density of air; Wa represents the volume of air; Tr represents
temperature of refrigerant; and Ta represents inlet temperature of
air.
[0061] In FIG. 5, a solid line L1 shows a measured result of the
heat exchanger 10 of this embodiment in which the projection pitch
P is 3.6 mm and the fin height F is 5.0 mm. In FIG. 5, a vertical
axis represents the efficiency Q. When the tube height H is 0.8 mm
and 1.9 mm, the efficiency Q is set to 100%.
[0062] As shown by the solid line L1 in FIG. 5, when the tube
height H is 1.3 mm, the efficiency Q is at the maximum level.
Namely, as the tube height H reduces smaller than 1.3 mm, a passage
area inside of the tube 11 reduces. Thus, the flow speed of the
refrigerant increases. Because pressure loss of the refrigerant
increases, the pressure of the refrigerant reduces. As a result,
the refrigerant temperature Tr reduces, and hence the difference
between the refrigerant temperature Tr and the air inlet
temperature Ta reduces. Accordingly, the efficiency Q expressed by
the equation (1) reduces.
[0063] On the other hand, as the tube height H increases larger
than 1.3 mm, the passage area inside of the tube 11 increases.
Although the refrigerant flows smoothly, the disturbing effect of
the refrigerant reduces. Thus, the coefficient of heat transfer of
the refrigerant reduces. With the decrease of the coefficient of
heat transfer of the refrigerant, the temperature efficiency .phi.
of the heat exchanger 10 reduces. Accordingly, the efficiency Q
reduces.
[0064] In the case that the tube height H is in a range between
equal to or greater than 0.8 mm and equal to or less than 1.9 mm,
the pressure loss of the refrigerant is reduced while maintaining
the disturbing effect of the refrigerant. As such, the decrease of
the efficiency Q due to the pressure loss of the refrigerant is
suppressed. That is, when the tube height H is in the above range,
the efficiency Q is provided sufficiently.
[0065] Also, in the case that the tube height H is in a range
between equal to or greater than 1.0 mm and equal to or less than
1.6 mm, the decrease of the efficiency Q due to the pressure loss
of the refrigerant is further suppressed.
[0066] Further, in the case that the tube height H is in a range
between equal to or greater than 1.2 mm and equal to or less than
1.4 mm, the decrease of the efficiency Q due to the pressure loss
of the refrigerant is further effectively suppressed.
[0067] In FIG. 5, a dashed line L2 shows a measured result of the
heat exchanger 10 without having the projections 22, 23, as a
comparative example. In the comparative example without having the
projections 22, 23, the efficiency Q is at the maximum level when
the tube height H is 1.0 mm. With the decrease or increase of the
tube height H relative to 1.0 mm, the efficiency Q reduces by the
same reason described in the above.
[0068] Accordingly, the efficiency Q of this embodiment having the
projections 22, 23 improves, as compared with the comparative
example without having the projections 22, 23. Also, in this
embodiment, the tube height H where the efficiency Q is at the
maximum level is greater than that of the comparative example.
Namely, in the comparative example, the efficiency Q is at the
maximum level when the tube height H is 1.0 mm. On the other hand,
in this embodiment, the efficiency Q is at the maximum level when
the tube height H is 1.3 mm.
[0069] In this embodiment, the flow of the refrigerant is disturbed
by the projections 22, 23. Therefore, the pressure loss of the
refrigerant of this embodiment is larger than the pressure loss of
the refrigerant of the comparative example even when the tube
height H is the same between this embodiment and the comparative
example.
[0070] In FIG. 5, the projection pitch P is 3.6 mm and the fin
height F is 5.0 mm, for example. When the projection pitch P and
the fin height F are varied from these values, the relationship
between the tube height H and the efficiency Q have the similar
trend as FIG. 5, though the efficiency Q entirely, slightly
reduces. That is, even when the projection pitch P and the fin
height F are varied, the efficiency Q is at the maximum level when
the tube height H is approximately 1.3 mm. Also, the efficiency Q
reduces when the tube height H is reduced or increased relative to
approximately 1.3 mm.
[0071] A graph of FIG. 6 shows a relationship between the
projection pitch P and the efficiency Q of this embodiment in which
the tube height H is 1.3 mm and the fin height F is 5.0 mm. In FIG.
6, a vertical axis represents the efficiency Q. When the projection
pitch P is 1.0 mm and 6.5 mm, the efficiency Q is set to 100%.
[0072] As shown in FIG. 6, when the projection pitch P is 3.6 mm,
the efficiency Q of the heat exchanger 10 is at the maximum level.
As the projection pitch P reduces from 3.6 mm, the number of the
projections 22, 23 of the tube 11 increases. Therefore, the
disturbing effect of the flow of the refrigerant increases, and
hence the pressure loss of the refrigerant increases. As a result,
the pressure of the refrigerant reduces, and the temperature
difference between the refrigerant temperature Tr and the air inlet
temperature Ta reduces. Accordingly, the efficiency Q reduces.
[0073] On the other hand, as the projection pitch P increases from
3.6 mm, the number of the projections 22, 23 of the tubes 10
reduces. Therefore, the disturbing effect of the flow of the
refrigerant reduces, and hence the flow of the refrigerant becomes
close to a natural convection current. As a result, the coefficient
of heat transfer of the refrigerant reduces. Thus, the temperature
efficiency .phi. reduces, and hence the efficiency Q reduces.
[0074] Accordingly, when the projection pitch P is in a range
between equal to or greater than 1.0 mm and equal to or less than
6.5 mm, the efficiency Q is improved by effectively providing the
disturbing effect of the refrigerant.
[0075] Also, when the projection pitch P is in a range between
equal to or greater than 1.6 mm and equal to or less than 5.7 mm,
the efficiency Q is improved by providing the disturbing effect of
the refrigerant further effectively.
[0076] Further, when the projection pitch P is in a range between
equal to or greater than 2.3 mm and equal to or less than 5.0 mm,
the disturbing effect of the refrigerant is further effectively
improved. Thus, the efficiency Q is improved.
[0077] In FIG. 6, the tube height H is 1.3 mm and the fin height F
is 5.0 mm, for example. When the tube height H and the fin height F
are varied relative to these values, the relationship between the
tube height H and the efficiency Q has the similar trend as FIG. 6,
though the efficiency Q entirely, slightly reduces. That is, even
when the tube height H and the fin height F are varied, the
efficiency Q is at the maximum level when the projection pitch P is
approximately 3.6 mm. Also, as the projection pitch P is reduced or
increased from approximately 3.6 mm, the efficiency Q reduces.
[0078] In this embodiment, the end walls of the projections 22, 23
have the first and second depressed portions 22b, 23b, 22c, 23c
that are further projected inside of the tube 11 in a stepwise
manner. Therefore, the flows of air in the recesses 20a, 21a are
further disturbed. As such, the coefficient of heat transfer of the
air is further improved.
[0079] A graph of FIG. 7 shows a relationship between the fin
height F and the efficiency Q of the heat exchanger 10 of this
embodiment. Here, the tube height H and the projection pitch P are
set to optimum values. Specifically, the tube height H is 1.3 mm
and the projection pitch P is 3.6 mm. In FIG. 7, a vertical axis
represents the efficiency Q. When the fin height F is 2 mm and 9
mm, the efficiency Q is set to 100%.
[0080] As shown in FIG. 7, in this embodiment, the efficiency Q is
at the maximum level when the fin height F is 5.0 mm. As the fin
height F reduces smaller than 5.0 mm, the heat transfer area
reduces. As a result, the temperature efficiency .phi. reduces.
Therefore, the efficiency Q reduces.
[0081] On the other hand, as the fin height F increases greater
than 5.0 mm, the heat transfer area excessively increases. As a
result, because the fin efficiency reduces, the temperature
efficiency .phi. reduces. Therefore, the efficiency Q reduces.
[0082] Accordingly, when the fin height F is in a range between
equal to or greater than 2.0 mm and equal to or less than 9.0 mm,
heat radiation is effectively performed by the fin 12. As such, the
efficiency Q improves.
[0083] Also, when the fin height F is in a range between equal to
or greater than 3.0 mm and equal to or less than 7.3 mm, the heat
radiation is further effectively performed by the fin 12. As such,
the efficiency Q improves.
[0084] Further, when the fin height F is in a range between equal
to or greater than 4.0 mm and equal to or less than 6.0 mm, the
heat radiation is much further effectively performed by the fin 12.
As such, the efficiency Q further improves.
[0085] In FIG. 7, the tube height is 1.3 mm and the projection
pitch P is 3.6 mm. Even when the tube height H and the projection
pitch P are varied from these values, the relationship between the
tube height H and the efficiency Q have the similar trend as FIG.
7, though the efficiency Q entirely, slightly reduces. That is,
even when the tube height H and the projection pitch P are varied,
the efficiency Q is at the maximum level when the fin height F is
approximately 5.0 mm. Also, as the fin height F is reduced or
increased relative to approximately 5.0 mm, the efficiency Q
reduces.
[0086] Since the projections 20, 21 extend continuously from the
air upstream end to the air downstream end of the tube 11, the flow
of air is introduced by the projections 20, 21 (recesses 20a, 21a).
Thus, the disturbing effect of the air improves, and the efficiency
of heat transfer improves. Further, the projections 20, 21 extend
in the serpentine or curved manner, the disturbing effect of the
air improves.
Second Embodiment
[0087] A second embodiment will be described with reference to FIG.
8. As shown in FIG. 8, the fins 12 do not have the louvers 12e, 12f
on the flat walls 12c, 12d. Structures of the heat exchanger 10
other than the louvers 12e, 12f are similar to those of the heat
exchanger 10 of the first embodiment.
[0088] In the heat exchanger 10 of the second embodiment, because
the efficiency of heat radiation of the fins 12 slightly reduces
due to elimination of the louvers 12e, 12f, the efficiency Q
slightly reduces as compared with the efficiency Q of the first
embodiment. However, the tubes. 11 have the similar structure as
the first embodiment. Therefore, effects substantially similar to
the effects of the first embodiment are provided in the second
embodiment.
[0089] Accordingly, the relationships between the efficiency Q and
the tube height H, projection pitch P and fin height F have the
similar trends as those of the first embodiment, though the
efficiency Q is slightly reduced in this embodiment.
Third Embodiment
[0090] A third embodiment will be described with reference to FIG.
9. In the third embodiment, the heat exchanger 10 has the similar
structure as that of the second embodiment other than corners 22a,
23a of the projections 22, 23.
[0091] In the second embodiment, the corners 22a, 23a are chamfered
into the arc shape. In the third embodiment, on the other hand, the
corners 22a, 23a are not chamfered. Instead, the side walls of the
projections 22, 23 and the outer surfaces of the tube main walls
20, 21 form edged corners, as shown in FIG. 9.
[0092] Also in this case, the effects similar to the second
embodiment are provided. Therefore, the relationships between the
efficiency Q and the tube height H, projection pitch P and fin
height F have the similar trends as those of the second
embodiment.
Fourth Embodiment
[0093] A fourth embodiment will be described with reference to FIG.
10. In the third embodiment, the projections 22, 23 have the
serpentine shape for allowing the air to flow in the serpentine
manner. On the other hand, in the fourth embodiment, the
projections 22, 23 have straight shape.
[0094] As shown in FIG. 10, the projections 22, 23 extend straight
in a direction oblique to the general air flow direction along the
tube main walls 20, 21 with a constant width. Also in this
embodiment, the projections 22 of the tube main wall 20 and the
projections 23 of the tube main wall 21 have the same shape.
However, the projections 22, 23 are not parallel to each other. The
projections 22, 23 are arranged to intersect with each other at a
predetermined angle. With this arrangement, the refrigerant
passages are formed inside of the tubes 11 in complexly serpentine
manner.
[0095] On the other hand, the air flowing adjacent to the tubes 11
are biased and disturbed by the recesses 20a, 21a. Therefore, the
coefficient of heat transfer of the air improves.
[0096] Accordingly, even when the projections 22, 23 are formed to
extend straight in the oblique direction relative to the general
air flow direction Ar1, the effects similar to the third embodiment
are provided. Therefore, the relationships between the efficiency Q
and the tube height H, projection pitch P and fin height F have the
similar trends as those of the third embodiment.
Fifth Embodiment
[0097] A fifth embodiment will be described with reference to FIG.
11. In the fifth embodiment, the projections 22, 23 are formed into
V-shape that extend in the refrigerant general flow direction Rf1
along the tube main walls 20, 21 with a constant width, as shown in
FIG. 11.
[0098] Also in this case, the projections 22 of the tube main wall
20 and the projections 23 of the tube main wall 21 have the same
V-shape, but are arranged in opposite directions with respect to
the refrigerant general flow direction Rf1. The diverged ends of
the V-shaped projection 22 are opposed to the diverged ends of the
V-shaped projection 23. Therefore, the projections 22, 23 intersect
with each other at the predetermined angle. Accordingly, the
refrigerant passages are formed inside of the tubes 11 in complexly
serpentine manner.
[0099] On the other hand, the air flowing adjacent to the tube main
walls 20, 21 are biased and disturbed by the recesses 20a, 21a.
Therefore, the coefficient of heat transfer of the air
improves.
[0100] Accordingly, even when the projections 22, 23 are formed in
the V-shape diverging in the refrigerant general flow direction
Rf1, the effects similar to the third embodiment will be provided.
Further, the relationships between the efficiency Q and the tube
height H, projection pitch P and fin height F have the similar
trends as those of the third embodiment.
Sixth Embodiment
[0101] A sixth embodiment will be described with reference to FIG.
12. In the third embodiment, the projections 22, 23 entirely extend
from the upstream end to the downstream end of the tube 11 with
respect to the air general flow direction Ar1. In the sixth
embodiment, on the other hand, the projections 22, 23 are ended
between the upstream end and the downstream end of the tube 11 with
respect to the air general flow direction Ar1.
[0102] In the example of FIG. 12, the projections 22, 23 are ended
at positions upstream of the downstream end of the tube 11 with
respect to the air general flow direction Ar1. That is, the
projections 22, 23 do not extend to the downstream end of the tube
11. Alternatively, the projections 22, 23 can be ended adjacent to
the upstream end of the tube 11 or at middle positions of the tube
11 with respect to the air general flow direction Ar1. Also, it is
not always necessary that all of the projections 22, 23 are ended
at the same position with respect to the air general flow direction
Ar1. The projections 22, 23 may be ended at different positions
with respect to the air general flow direction Ar1,
appropriately.
[0103] Also in this embodiment, the projections 22, 23 provide the
disturbing effect of the flows of the refrigerant and air, similar
to the third embodiment. Accordingly, the similar effects as the
third embodiment are provided. Also, the relationships between the
efficiency Q and the tube height H, projection pitch P and fin
height F have the similar trends as those of the third
embodiment.
Seventh Embodiment
[0104] A seventh embodiment will be described with reference to
FIG. 13. In the seventh embodiment, the projections 22, 23 are
formed as mesh, as shown in FIG. 13.
[0105] Also in this embodiment, the refrigerant passages are formed
inside of the tube 11 in the complexly serpentine manner. On the
outside of the tube 11, the recesses 20a, 21a are formed as mesh.
Thus, the air flows in the recesses 20a, 21a while diverging and
merging repetitively, and is disturbed sufficiently. Therefore, the
coefficient of heat transfer of the air improves.
[0106] Accordingly, even when the projections 22, 23 have the
meshed shape, the similar effects as the third embodiment are
provided. Also, the relationships between the tube height H,
projection pitch P and fin height F and the efficiency Q have the
similar trends as those of the third embodiment.
Eighth Embodiment
[0107] An eighth embodiment will be described with reference to
FIGS. 14 and 15. In the above embodiments, the tube 11 is formed by
folding the single plate member into two or joining two plate
members after the projections and recessed are formed. In the
eighth embodiment, on the other hand, the tube 11 is integrally
formed without folding or joining.
[0108] As shown in FIG. 14, the tube 11 has separation walls 13
therein for separating the inner space of the tube 11 into plural
spaces with respect to the air general flow direction Ar1. The
separation walls 13 extend between inner surfaces of the tube main
walls. Also, the separation walls 13 for example have flat plate
shape and extend in the refrigerant general flow direction Rf1
(i.e., in the longitudinal direction of the tube 11). Thus, the
refrigerant passages are aligned in the air general flow direction
Ar1 inside of the tube 11.
[0109] In this embodiment, the projections 22, 23 have the
serpentine shape, similar to the projections 22, 23 of the third
embodiment. However, the end walls of the projections 22, 23 do not
have the first and second depressed portions 22b, 23b, 22c,
23c.
[0110] FIG. 15 shows an example of a method of forming the tube 11
of this embodiment. First, a flat multi-passage tube 30 having the
separation walls 31 therein is formed by extrusion using an
extrusion die (not shown) that includes a female die and a male
die. Then, the projections and recesses having the predetermined
shape are formed on the flat multi-passage tube 30 by roll forming
using a pair of rollers 32, 33. The separation walls 31 are
maintained even after the projections and recesses are formed.
Therefore, the inner space of the tube 11 is separated into the
plural spaces with respect to the air general flow direction Ar1 by
the separation wall 31. Here, the projections and recesses can be
formed by pressing, instead of the roll forming.
[0111] In the tube 11 formed in the above-described manner, the
effects similar to the third embodiment will be provided.
Therefore, the relationships between the tube height H, projection
pitch P and fin height F and the efficiency Q have the similar
trends as those of the third embodiments. Also, since the
separation walls 31 are integrally formed into the tube 11,
strength of the tube 11 against pressure improves.
Ninth Embodiment
[0112] A ninth embodiment will be described with reference to FIG.
16. In the ninth embodiment, the tube 11 is integrally formed,
similar to the eighth embodiment. However, the projections 22, 23
have the straight shape, similar to the fourth embodiment, as shown
in FIG. 16.
[0113] Also in this case, the similar effects as the eighth
embodiment will be provided. Thus, the relationships between the
tube height H, projection pitch P and fin height F and the
efficiency Q have the similar trends as those of the eighth
embodiments.
[0114] Further, since the tube 11 has the separation walls 31
therein, the strength of the tube 11 against pressure improves,
similar to the eighth embodiment. The shape of the projections 22,
23 can be changed into any other shapes as the above first to
seventh embodiments.
Other Embodiments
[0115] In the above embodiments, the projections 22, 23 have the
constant width. However, it is not always necessary that the
projections 22, 23 have the constant width. The width of the
projections 22, 23 can be changed or varied appropriately.
[0116] In the third to ninth embodiments, the fins 12 do not have
the louvers 12e, 12f. However, the fins 12 may have the louvers
12e, 12f in the third to ninth embodiments. Also, the heat
exchanger 10 may be implemented by any combinations of the above
first to ninth embodiments.
[0117] In the above embodiments, the heat exchanger 10 is exemplary
employed as the refrigerant condenser. However, the heat exchanger
10 can be employed as a refrigerant radiator of a supercritical
refrigerating cycle in which the pressure of a refrigerant exceeds
a critical pressure at a high pressure side. Further, use of the
heat exchanger 10 may not be limited to the above.
[0118] The example embodiments of the present invention are
described above. However, the present invention is not limited to
the above example embodiment, but may be implemented in other ways
without departing from the spirit of the invention.
* * * * *