U.S. patent application number 14/344364 was filed with the patent office on 2014-11-20 for plate fin-tube heat exchanger and refrigeration-and-air-conditioning system including the same.
This patent application is currently assigned to MITSUBISHI ELECTRIC CORPORATION. The applicant listed for this patent is Keisuke Hokazono. Invention is credited to Keisuke Hokazono.
Application Number | 20140338876 14/344364 |
Document ID | / |
Family ID | 48781116 |
Filed Date | 2014-11-20 |
United States Patent
Application |
20140338876 |
Kind Code |
A1 |
Hokazono; Keisuke |
November 20, 2014 |
PLATE FIN-TUBE HEAT EXCHANGER AND
REFRIGERATION-AND-AIR-CONDITIONING SYSTEM INCLUDING THE SAME
Abstract
A plate fin-tube heat exchanger is provided in which surfaces of
flat tubes and fins each have concavities and convexities in which
a length between one of peak portions that has the smallest height
and one of trough portions that has the smallest depth is 10 .mu.m
or larger.
Inventors: |
Hokazono; Keisuke; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hokazono; Keisuke |
Tokyo |
|
JP |
|
|
Assignee: |
MITSUBISHI ELECTRIC
CORPORATION
Tokyo
JP
|
Family ID: |
48781116 |
Appl. No.: |
14/344364 |
Filed: |
January 11, 2012 |
PCT Filed: |
January 11, 2012 |
PCT NO: |
PCT/JP2012/000130 |
371 Date: |
March 12, 2014 |
Current U.S.
Class: |
165/181 |
Current CPC
Class: |
F28F 1/126 20130101;
F25B 39/022 20130101; F28F 2215/10 20130101; F28F 1/12 20130101;
F28F 17/005 20130101; F25B 2500/01 20130101; F28F 2215/12 20130101;
F28D 2021/007 20130101; F28F 1/32 20130101; F28F 2275/06
20130101 |
Class at
Publication: |
165/181 |
International
Class: |
F28F 1/12 20060101
F28F001/12; F25B 39/02 20060101 F25B039/02 |
Claims
1. A plate fin-tube heat exchanger in which flat tubes each having
a flat cross-sectional shape whose long sides are linear and whose
short sides are curved in a semicircular manner are fitted in
notches provided in fins, wherein a surface of at least either one
of each of the flat tubes and each of the fins has a plurality of
concavities and convexities in which a difference in height between
one of peak portions that has a smallest height and one of trough
portions that has a smallest depth is 10 .mu.m or larger, and a
foreign substance having a higher melting point than a weld
material used for welding the flat tubes and the fins is added to
the weld material in advance.
2. The plate fin-tube heat exchanger of claim 1, wherein the
concavities and convexities are formed such that an angle formed
between the surface of at least either one of each of the flat
tubes and each of the fins and a line is 60 degrees or smaller, the
line being tangent to an end of a portion of a dewdrop being
present in contact with the surface of at least either one of each
of the flat tubes and each of the fins.
3. The plate fin-tube heat exchanger of claim 1, wherein the
concavities and convexities are provided in an oxide film that is
formed by heat generated when the flat tubes and the fins are
welded to each other.
4. (canceled)
5. (canceled)
6. A refrigeration-and-air-conditioning system, wherein the plate
fin-tube heat exchanger of claim 1 is used as an evaporator.
7. A plate fin-tube heat exchanger in which flat tubes each having
a flat cross-sectional shape whose long sides are linear and whose
short sides are curved in a semicircular manner are fitted in
notches provided in fins, wherein a surface of at least either one
of each of the flat tubes and each of the fins has a plurality of
concavities and convexities in which a difference in height between
one of peak portions that has a smallest height and one of trough
portions that has a smallest depth is 10 .mu.m or larger, and a
foreign substance having a higher melting point than a flux used
for surfaces of the flat tubes and the fins is added to the flux in
advance.
8. The plate fin-tube heat exchanger of claim 7, wherein the
concavities and convexities are formed such that an angle formed
between the surface of at least either one of each of the flat
tubes and each of the fins and a line is 60 degrees or smaller, the
line being tangent to an end of a portion of a dewdrop being
present in contact with the surface of at least either one of each
of the flat tubes and each of the fins.
9. The plate fin-tube heat exchanger of claim 7, wherein the
concavities and convexities are provided in an oxide film that is
formed by heat generated when the flat tubes and the fins are
welded to each other.
10. A refrigeration-and-air-conditioning system, wherein the plate
fin-tube heat exchanger of claim 7 is used as an evaporator.
Description
TECHNICAL FIELD
[0001] The present invention relates to a plate fin-tube heat
exchanger in which heat transfer tubes are fitted in a plurality of
plate-like fins arranged at predetermined intervals, and a
refrigeration-and-air-conditioning system including the same.
BACKGROUND ART
[0002] A hitherto known plate fin-tube heat exchanger includes, for
example, heat transfer tubes each having a flat cross-sectional
shape (hereinafter referred to as flat tubes) and being fitted in
plate-like fins that are arranged at predetermined intervals. The
plate-like fins each have notches that are provided in the same
number and at the same intervals as the flat tubes in a
plate-long-axis direction. Meanwhile, a corrugated fin-tube heat
exchanger that includes plate-like fins each having a wavy shape
and flat tubes being in contact with the fins at peaks and troughs
of the wavy shape of the fins is in general used in, for example,
an automobile and so forth (see Patent Literature 1, for
example).
CITATION LIST
Patent Literature
[0003] Patent Literature 1: Japanese Unexamined Patent Application
Publication No. 2001-296088 (FIGS. 1 and 2 and others)
SUMMARY OF INVENTION
Technical Problem
[0004] The corrugated fin-tube heat exchanger is suitable for use
as a condenser included in a refrigeration cycle, but is not
suitable for use as an evaporator. Specifically, in a case where
the corrugated fin-tube heat exchanger is used as an evaporator, if
the temperature of a refrigerant flowing in the flat tubes drops
below the dew point of air with which the refrigerant exchanges
heat, moisture in the air forms dew on surfaces of the heat
exchanger and condenses into dew water (drain water). The dew water
generated on the surfaces of the heat exchanger does not cause any
problems if it is quickly drained from end facets of the fins and
surfaces of the flat tubes.
[0005] The corrugated fin-tube heat exchanger, however, has two
factors that deteriorate the drainability: (1) dew water tends to
accumulate in trough portions of the wavy-shaped fins, and (2) dew
water tends to accumulate on upper surfaces of the flat tubes
(surfaces extending in the long-side direction of the flat tubes).
If the drainability is poor and dew water accumulates, the stack
loss on the surfaces of the heat exchanger increases, whereby the
volume of airflow passing through the heat exchanger is reduced
significantly. Accordingly, the ability as a heat exchanger is
reduced significantly. Consequently, a vicious cycle occurs in
which the evaporating temperature is further lowered, the dew water
is transformed and grows into frost, the stack loss further
increases, the volume of airflow is reduced, and the ability is
lowered.
[0006] The present invention is to solve the above problems and to
provide a plate fin-tube heat exchanger including fins and flat
tubes having improved drainability, and a
refrigeration-and-air-conditioning system including the same.
Solution to Problem
[0007] In a plate fin-tube heat exchanger according to the present
invention, flat tubes each having a flat cross-sectional shape
whose long sides are linear and whose short sides are curved in a
semicircular manner are fitted in notches provided in fins. A
surface of at least one of each of the flat tubes and each of the
fins has a plurality of concavities and convexities in which a
length between one of peak portions that has the smallest height
and one of trough portions that has the smallest depth is 10 .mu.m
or larger.
[0008] In a refrigeration-and-air-conditioning system according to
the present invention, the above plate fin-tube heat exchanger is
used as an evaporator.
Advantageous Effects of Invention
[0009] In the plate fin-tube heat exchanger according to the
present invention, since the surface of at least one of each of the
fins and each of the flat tubes has the plurality of concavities
and convexities, an effect of hydrophilicity is produced on the
surface of the fin or the flat tube, whereby the drainability is
improved significantly.
[0010] The refrigeration-and-air-conditioning system according to
the present invention includes the above plate fin-tube heat
exchanger. Therefore, even if the plate fin-tube heat exchanger is
used as an evaporator, the increase in stack loss due to dew water
is reduced significantly, and the heat exchangeability is
maintained.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is a diagram schematically illustrating welding steps
employed for a heat exchanger according to Embodiment 1 of the
present invention.
[0012] FIG. 2 is a diagram illustrating a weld material used for
welding flat tubes and fins included in the heat exchanger
according to Embodiment 1 of the present invention.
[0013] FIG. 3 is an enlarged schematic perspective view
illustrating a part of an existing corrugated fin-tube heat
exchanger.
[0014] FIG. 4 is a graph illustrating the relationship between the
water contact angle on and the hydrophilicity of a surface of each
flat tube or each fin included in the heat exchanger according to
Embodiment 1 of the present invention before and after the
welding.
[0015] FIG. 5 includes schematic diagrams illustrating the
relationship between the water contact angle and the
hydrophilicity.
[0016] FIG. 6 includes observation diagrams schematically
illustrating the surface of the flat tube or the fin included in
the heat exchanger according to Embodiment 1 of the present
invention before and after the welding.
[0017] FIG. 7 is a schematic cross-sectional view illustrating the
cross-sectional shape of a part of the fin or the flat tube
included in the heat exchanger according to Embodiment 1 of the
present invention and having concavities and convexities.
[0018] FIG. 8 includes diagrams illustrating an effect produced in
the heat exchanger according to Embodiment 1 of the present
invention.
[0019] FIG. 9 is a diagram illustrating a weld material used for
welding fiat tubes and fins included in a heat exchanger according
to Embodiment 2 of the present invention.
[0020] FIG. 10 includes diagrams illustrating a heat exchanger
according to Embodiment 3 of the present invention.
[0021] FIG. 11 is a graph illustrating the thickness of each of
fins and flat tubes included in the heat exchanger according to
Embodiment 3 of the present invention.
[0022] FIG. 12 is a circuit diagram schematically illustrating a
basic configuration of a refrigeration-and-air-conditioning system
according to Embodiment 4 of the present invention.
DESCRIPTION OF EMBODIMENTS
[0023] Embodiments of the present invention will now be described
with reference to the drawings.
Embodiment 1
[0024] FIG. 1 is a diagram schematically illustrating welding steps
employed for a heat exchanger 50 according to Embodiment 1 of the
present invention. Referring to FIG. 1, the heat exchanger 50
according to Embodiment 1 of the present invention will be
described. In the drawings including FIG. 1 to be referred to
below, individual elements are not necessarily scaled in accordance
with their actual sizes.
[0025] As illustrated in FIG. 1, the heat exchanger 50 includes a
plurality of flat tubes 51 made of aluminum or the like and each
having a flat cross-sectional shape whose long sides are linear and
whose short sides are curved in, for example, a semicircular manner
or the like. The plurality of flat tubes 51 are arranged parallel
to one another at arbitrary intervals in a direction orthogonal to
a direction of a passage of a refrigerant that is made to flow in
the tubes. The heat exchanger 50 further includes a plurality of
flat-plate-like (rectangular) fins 52 made of aluminum or the like.
The fins 52 are arranged parallel to one another at predetermined
arbitrary intervals in the direction of the passage of the
refrigerant (a direction orthogonal to the direction in which the
flat tubes 51 are arranged side by side). The fins 52 each have a
rectangular shape with a larger length in the direction in which
the flat tubes 51 are arranged side by side than in the width
direction of the flat tubes 51 (the horizontal direction in FIG.
1). Therefore, in the following description, the width direction of
the flat tubes 51 is referred to as short-side direction, and the
direction in which the flat tubes 51 are arranged side by side is
referred to as long-side direction.
[0026] The flat tubes 51 each have thereinside a plurality of holes
53 arranged side by side in the width direction. A refrigerant, for
example, is made to flow in the holes 53. The refrigerant exchanges
heat with air flowing through the heat exchanger 50. The fins 52
each have a plurality of U-shaped notches 54 in the long-side
direction. The notches 54 are provided in correspondence with the
flat tubes 51. That is, for example, the notches 54 are provided in
the same number and at the same arbitrary intervals (excluding the
ones at both ends) as the flat tubes 51. Furthermore, the notches
54 each have substantially the same length as a corresponding one
of the flat tubes 51 in the long-side direction of the fin 52. The
notches 54 are provided such that one end of the fin 52 is open.
That is, the notches 54 are arranged side by side in a comb-like
pattern in the long-side direction of the fin 52.
[0027] Steps of manufacturing the heat exchanger 50 will now be
described.
[0028] First, the flat tubes 51 are each fitted into a
corresponding one of the notches 54 of each of the fins 52 from a
secondary side of the airflow (the right side in FIG. 1) and with a
predetermined clearance 52A interposed between an end facet of the
fin 52 that is on a primary side of the airflow (the left side in
FIG. 1) and an end of the flat tube 51 (the end on the left side in
FIG. 1). Subsequently, the fin 52 and the flat tube 51 are welded
to each other with a weld material such as a solder material. In
this manner, a core portion (main portion) of the heat exchanger 50
is manufactured. In addition, although not illustrated in FIG. 1
the fin 52 may have gate-type (bridge-type) cut-raised portions
formed by cutting and raising portions of the fin 52 between the
notches 54. In such a case, the cut-raised portions promote the
heat exchange between the air and the refrigerant.
[0029] FIG. 2 is a diagram illustrating the weld material used for
welding the flat tube 51 and the fin 52. Referring to FIG. 2, the
welding of the fin 52 and the flat tube 51 will be described
briefly. The fin 52 and the flat tube 51 are welded to each other
with a weld material such as a solder material. When performing the
welding, another material prepared separately from a base material
55 may be used as the weld material. Alternatively, as illustrated
in FIG. 2, a surface of the base material 55 that is to form the
fin 52 and the flat tube 51 may be covered (cladded) with the weld
material as a cladding layer 56 in advance. The base material 55 is
a material for the flat tube 51 and the fin 52.
[0030] FIG. 3 is an enlarged schematic perspective view
illustrating a part of an existing corrugated fin-tube heat
exchanger (hereinafter denoted as heat exchanger 50'). Referring to
FIG. 3, the heat exchanger 50' will be described briefly. FIG. 3
also illustrates dew water 59.
[0031] As illustrated in FIG. 3, the heat exchanger 50 includes
flat tubes (hereinafter denoted as flat tubes 51'), as with the
heat exchanger 50. As with the flat tube 51, the flat tubes 51' are
heat transfer tubes each having several holes, specifically, a
plurality of holes 53' each having a flat contour. The heat
exchanger 50' further includes wavy-shaped fins (hereinafter
denoted as fins 52'). In the heat exchanger 50', the fins 52' are
in contact with the flat tubes 51' at peaks and troughs thereof.
The heat exchanger 50 is in general used in an automobile and so
forth.
[0032] As described above, however, the heat exchanger 50 has two
factors that deteriorate the drainability: a fact that dew water
tends to accumulate in trough portions of the fins 52', and a fact
that dew water tends to accumulate on upper surfaces of the flat
tubes 51' (surfaces extending in the long-side direction of the
flat tubes 51').
[0033] In contrast, unlike that the heat exchanger 50, the heat
exchanger 50 including the fins 52 each having a flat-plate-like
shape does not have the factor of dew water tending to accumulate
in trough portions of the fins 52'. Moreover, in the heat exchanger
50, since a predetermined clearance (the clearance 52A illustrated
in FIG. 1) is interposed between the end facet of each fin 52 that
is on the primary side of the airflow and each flat tube 51, dew
water is quickly drained along the end facet of the fin 52. That
is, since the end facet of the fin 52 that is on the primary side
of the airflow is not sectioned by the notches 54, nothing prevents
dew water from flowing. Accordingly, smooth drainage is realized.
This solves the first one of the factors that deteriorate the
drainability.
[0034] Now, a mechanism of improving the hydrophilicity of the
surfaces of the heat exchanger 50 will be described.
[0035] FIG. 4 is a graph illustrating the relationship between the
water contact angle on and the hydrophilicity of the surface of the
flat tube 51 or the fin 52 before and after the welding. FIG. 4
illustrates the hydrophilicity of the surface of the flat tube 51
or the fin 52 for different water contact angles (degrees) obtained
before the welding, after the welding, and after a reliability test
conducted after the welding.
[0036] The water contact angle is an index indicating the
"wettability" of the surface of the flat tube 51 or the fin 52.
Herein, the water contact angle is defined as an angle .theta.
formed between the surface of the flat tube 51 or the fin 52 and a
line tangent to a dewdrop produced by dropping water onto the
surface of the flat tube 51 or the fin 52, the line being tangent
to an end of a portion of the dewdrop that is in contact with the
surface of the flat tube 51 or the fin 52. The water contact angle
is determined by the relationship of interfacial energy acting
among the gas, the liquid, and the solid. In general, the smaller
the water contact angle, the higher the hydrophilicity; the larger
the water contact angle, the lower the hydrophilicity.
[0037] As illustrated in FIG. 4, the water contact angle before the
welding of the flat tube 51 and the fin 52 is about 90 degrees,
whereas the water contact angle after the welding is reduced to 40
degrees to 50 degrees. This shows that the hydrophilicity is
improved after the welding. This is because the surfaces of the fin
52 and the flat tube 51 are oxidized by heat generated in the
welding, and the resulting oxide forms microscopic concavities and
convexities in the surfaces. With the microscopic concavities and
convexities formed in the surfaces of the fin 52 and the flat tube
51, the water contact angle on each of the surfaces is reduced,
improving the flowability and the drainability of the water (dew
water or drain water, for example) on the surfaces. This solves the
second one of the factors that deteriorate the drainability. Note
that, if the water contact angle is 60 degrees or smaller, the
flowability of water on the surfaces of the fin 52 and the flat
tube 51 is improved.
[0038] FIG. 5 includes schematic diagrams illustrating the
relationship between the water contact angle and the
hydrophilicity. FIG. 5(a) illustrates a case where dewdrops each
have a shape forming a large water contact angle. FIG. 5(b)
illustrates a case where dewdrops each have a shape forming a small
water contact angle.
[0039] As illustrated in FIG. 5(a), if the water contact angle is
large, the dewdrops each have a nearly spherical shape in side
view. Hence, the surface tension of the dewdrops is high. That is,
the larger the water contact angle, the lower the hydrophilicity.
In contrast, as illustrated in FIG. 5(b), if the water contact
angle is small, the dewdrops each have a nearly flat shape in side
view. Hence, the surface tension of the dewdrops is low. Low
hydrophilicity means poor drainability. That is, if the water
contact angle is large, dewdrops tend to remain on the fins as
illustrated in FIG. 5(a); if the water contact angle is small,
dewdrops do not tend to remain on the fins as illustrated in FIG.
5(b).
[0040] If any coating material such as a post-coat is applied so as
to provide hydrophilicity, the coating material is deteriorated
with age and accordingly the effect of its hydrophilicity is
eventually reduced. Specifically, since the aluminum base having
low hydrophilicity is exposed with the deterioration of the
post-coating, the hydrophilicity is deteriorated. In contrast, in
the heat exchanger 50 according to Embodiment 1, the contact angle
tends to be reduced even after an accelerated test (after the
reliability test in FIG. 4) conducted for checking the aging
deterioration of the heat exchanger 50, whereby the effect of
hydrophilicity is maintained or further improved. This is because
oxidation gradually progresses after the accelerated test, and more
concavities and convexities are formed in the surfaces with finer
sizes and at a higher density. Such a fact shows the superiority in
terms of maintenance of hydrophilicity.
[0041] FIG. 6 includes observation diagrams schematically
illustrating the surface of the flat tube 51 or the fin 52 before
and after the welding. FIG. 6(a) illustrates the surface of the
flat tube 51 or the fin 52 before the welding. FIG. 6(b)
illustrates the surface of the flat tube 51 or the fin 52 after the
welding. FIG. 6(c) illustrates the surface of the flat tube 51 or
the fin 52 after the reliability test conducted after the
welding.
[0042] As can be seen from FIG. 6, there are differences in surface
roughness between the states observed before the welding, after the
welding, and after the accelerated test. That is, FIG. 6 shows that
the surface roughness before the welding is low, the surface
roughness after the welding is high, and the surface roughness
after the accelerated test is much higher. This means that the
concavities and convexities are formed with finer sizes and at a
higher density in order of that before the welding, that after the
welding, and that after the accelerated test. Furthermore, as
described above, if the surface of the base material is covered
(cladded) with a weld material in advance, concavities and
convexities tend to be formed uniformly in the surfaces of the fin
52 and the flat tube 51. Accordingly, the uniformity in the effect
of hydrophilicity is further promoted.
[0043] FIG. 7 is a schematic cross-sectional view illustrating the
cross-sectional shape of a part of the fin 52 or the flat tube 51
having concavities and convexities. To obtain the above effect of
hydrophilicity, in the concavities and convexities formed in the
fin 52 and the flat tube 51, the length between one of peak
portions that has the smallest height and one of trough portions
that has the smallest depth may be 10 .mu.m or larger. If this
value is taken as the minimum value for forming concavities and
convexities, a small water contact angle and high hydrophilicity
are obtained. The concavities and convexities are desirably to be
formed uniformly but are not necessarily uniform, as long as the
length between the peak portion having the smallest height and the
trough portion having the smallest depth is 10 .mu.m or larger.
[0044] FIG. 8 includes diagrams illustrating an effect produced in
the heat exchanger 50. FIG. 8(a) is a perspective view of the heat
exchanger 50. FIG. 8(b) is a side view of the heat exchanger 50
seen from a side from which the flat tubes 51 are fitted into the
fins 52. White arrows illustrated in FIG. 8 represent the flow of
air. In FIG. 8, the flows of dewdrops are represented by arrow (1)
and arrow (2). In each of FIGS. 8(a) and 8(b), the flat tubes 51
are illustrated in cross-sectional view.
[0045] As described above, the fins 52 of the heat exchanger 50
each have a flat-plate-like shape. Therefore, unlike the heat
exchanger 50', the heat exchanger 50 does not have the factor of
dew water tending to accumulate in trough portions of the fins 52'.
Moreover, in the heat exchanger 50, since a predetermined clearance
(the clearance 52A illustrated in FIG. 1) is interposed between the
end facet of each fin 52 that is on the primary side of the airflow
and each flat tube 51, dew water is quickly drained along the end
facet of the fin 52 (arrow (1)). This solves the first one of the
factors that deteriorate the drainability.
[0046] Furthermore, in the heat exchanger 50, the surfaces of the
fin 52 and the flat tube 51 are oxidized by heat generated when the
flat tube 51 and the fin 52 are welded to each other, and the
resulting oxide forms microscopic concavities and convexities in
the surfaces. With the concavities and convexities, the
hydrophilicity of the surfaces of the fin 52 and the fiat tube 51
is improved, the flowability of water (dew water or drain water,
for example) on the surfaces is improved, and the drainability is
improved (arrow (2)). This solves the second one of the factors
that deteriorate the drainability.
[0047] To summarize, in the heat exchanger 50, since the surface
roughness of the fin 52 and the flat tube 51 is increased and an
effect of hydrophilicity is produced, the drainability is improved.
Furthermore, in the heat exchanger 50, since the hydrophilicity of
the surfaces of the fin 52 and the fiat tube 51 is provided only by
performing welding, no hydrophilic treatment with a post-coat or
the like is necessary. This is also expected to contribute to the
ease of production and the cost reduction. Furthermore, since no
hydrophilic treatment with a post-coat or the like is necessary,
the heat exchanger 50 does not have problems such as aging
deterioration of a coating material such as a post-coat. Hence, the
hydrophilicity of the surfaces of the fin 52 and the flat tube 51
is maintained at a highly reliable level.
Embodiment 2
[0048] FIG. 9 is a diagram illustrating a weld material used for
welding flat tubes and fins included in a heat exchanger according
to Embodiment 2 of the present invention. Referring to FIG. 9, the
weld material used for welding the flat tubes and the fins included
in the heat exchanger according to Embodiment 2 of the present
invention will now be described. Description of Embodiment 2
focuses on differences from Embodiment 1. Elements that are the
same as those of Embodiment 1 are denoted by corresponding
reference numerals, and description thereof is thus omitted.
[0049] In Embodiment 1, the surface roughness is changed by
utilizing an oxide formed on the surfaces of the fins 52 and the
flat tubes 51 with heat generated in the welding, whereby an effect
of hydrophilicity is produced. On the other hand, in Embodiment 2,
a foreign substance is added to the weld material in advance, and
the surface roughness of the fins and the flat tubes is increased
by utilizing the weld material. Consequently, an effect of
hydrophilicity is produced while the oxidation of the fins and the
flat tubes themselves is suppressed.
[0050] In Embodiment 2 also, as described in Embodiment 1 referring
to FIG. 2, the fins and the flat tubes are welded to each other
with a weld material such as a solder material. In Embodiment 2
also, as in Embodiment 1, the welding may be performed by using a
weld material prepared separately from the base material 55 or by
using a weld material that has been added to the surface of the
base material 55. Note that, as illustrated in FIG. 9, Embodiment 2
concerns a case where the fins and the flat tubes that have been
covered (cladded) with a weld material to which a foreign substance
57 has been added in advance are welded to each other.
[0051] As illustrated in FIG. 9, a cladding layer 56A as a weld
material is provided in advance on a surface of the base material
55. The cladding layer 56A contains particles of the foreign
substance 57 whose melting point is higher than that of the weld
material forming the cladding layer 56A. The foreign substance 57
may be selected from any materials having higher melting points
than the weld material forming the cladding layer 56A: for example,
alumina and so forth. Furthermore, the foreign substance 57 may be
selected from any materials having such particle sizes as to form
concavities and convexities in the surfaces of the fins and the
flat tubes after the welding. Furthermore, the foreign substance 57
may be selected from any materials having intentionally lower
potentials than the materials forming the fins and the flat tubes.
In such a case, if any moisture is added to the heat exchanger with
age, the surfaces of the fins and the flat tubes are
electrolytically oxidized and corroded. Hence, the formation of
concavities and convexities in the surfaces of the fins and the
flat tubes is further promoted.
[0052] To summarize, in the heat exchanger according to Embodiment
2, the surface roughness of the fins and the flat tubes is
increased while the oxidation of the fins and the flat tubes
themselves is suppressed, whereby an effect of hydrophilicity is
produced. Hence, in the heat exchanger according to Embodiment 2,
the fins and the flat tubes themselves can be made thinner
correspondingly, and a cost reduction is thus realized. Moreover,
if the foreign substance 57 having a lower potential than the
material of the fins and the flat tubes is added, hydrophilicity as
a countermeasure for aging deterioration is maintained at a highly
reliable level.
[0053] Furthermore, in the heat exchanger according to Embodiment
2, since an oxide layer is made of a weld material, which is
originally necessary, no hydrophilic treatment with a post-coat or
the like is necessary. This is also expected to contribute to the
ease of production and the cost reduction. Furthermore, since no
hydrophilic treatment with a post-coat or the like is necessary,
the heat exchanger according to Embodiment 2 does not have problems
such as aging deterioration of a coating material such as a
post-coat. Hence, the hydrophilicity of the surfaces of the fins
and the flat tubes is maintained at a highly reliable level.
Embodiment 3
[0054] FIG. 10 includes diagrams illustrating a heat exchanger 50B
according to Embodiment 3 of the present invention. Referring to
FIG. 10, the heat exchanger 50B according to Embodiment 3 of the
present invention will now be described.
[0055] FIG. 10(a) is a side view of the heat exchanger 50B seen
from a side from which flat tubes 51 are fitted into fins 52. FIG.
10(b) is a top view of the heat exchanger 50B. Description of
Embodiment 3 focuses on differences from Embodiment 1 and
Embodiment 2. Elements that are the same as those of Embodiment 1
and Embodiment 2 are denoted by corresponding reference numerals,
and description thereof is thus omitted. In FIG. 10(a), the flat
tubes 51 are illustrated in cross-sectional view.
[0056] In Embodiment 2, the foreign substance 57 is added to the
weld material forming the cladding layer 56A, and the surface
roughness of the fins and the flat tubes is increased while the
oxidation of the fins and the flat tubes themselves is suppressed.
On the other hand, in Embodiment 3, the foreign substance 57 is
added to a flux 58 provided on the surface of the base material 55,
and the surface roughness of the fins 52 and the flat tubes 51 is
increased while the oxidation of the fins 52 and the flat tubes 51
themselves is suppressed. The flux 58 protects the surface of the
base material 55. The foreign substance 57 is the same as that
described in Embodiment 2.
[0057] If the flux 58 containing the foreign substance 57 is
provided on the surface of the base material 55 that is to form the
fins 52, the flux 58 is diffused over the entirety of the surface
of each of the fins 52 as illustrated in FIG. 10(a) (as represented
by arrows in FIG. 10(a)). If the flux 58 containing the foreign
substance 57 is provided on the surface of the base material 55
that is to form the flat tubes 51, the flux 58 is diffused over the
entirety of the surface of each of the flat tubes 51 as illustrated
in FIG. 10(b) (as represented by arrows in FIG. 10(b)).
[0058] FIG. 11 is a graph illustrating the thickness of each fin 52
or each flat tube 51. Referring to FIG. 11, the thickness of the
fin 52 or the flat tube 51 will now be described. In FIG. 11, the
horizontal axis represents the thickness of the base material 55
that is to form the fin 52 or the flat tube 51, and the vertical
axis represents the residual thickness of the base material 55 that
is to form the fin 52 or the flat tube 51 excluding the oxide
layer.
[0059] The base material 55 that is to form the fin 52 or the flat
tube 51 needs to have at least a minimum thickness with which heat
transferability and compressive strength are assuredly provided,
with an oxide layer having concavities and convexities that are
required for providing hydrophilicity. Accordingly, as illustrated
in FIG. 11, the minimum thickness of the base material 55 may be
determined within a thickness range in which the welding
temperature, time, and the oxygen concentration are controllable.
This also applies to Embodiments 1 and 2. Note that the graph in
FIG. 11 varies with the characteristics of the base material, the
characteristics of the weld material, the characteristics of the
flux, and the characteristics of the foreign substance, and
therefore values of the welding temperature, time, and the oxygen
concentration do not necessarily fall within predetermined
ranges.
[0060] To summarize, in Embodiment 3, manufacturing the heat
exchanger increases the surface roughness of the fins and the flat
tubes while suppressing the oxidation of the fins and the flat
tubes themselves, whereby an effect of hydrophilicity is produced.
Hence, in the heat exchanger according to Embodiment 3, the fins
and the flat tubes themselves can be made thinner correspondingly,
and a cost reduction is thus realized. Moreover, if the foreign
substance 57 having a lower potential than the material of the fins
and the flat tubes is added, hydrophilicity as a countermeasure for
aging deterioration is maintained at a highly reliable level.
[0061] Furthermore, in the heat exchanger according to Embodiment
3, since an oxide layer is made of a flux, which is originally
necessary, no hydrophilic treatment with a post-coat or the like is
necessary. This is also expected to contribute to the ease of
production and the cost reduction. Furthermore, since no
hydrophilic treatment with a post-coat or the like is necessary,
the heat exchanger according to Embodiment 3 does not have problems
such as aging deterioration of a coating material such as a
post-coat. Hence, the hydrophilicity of the surfaces of the fins
and the flat tubes is maintained at a highly reliable level.
[0062] While the present invention has been described above in
three Embodiments, this does not deny any combinations of features
described in different Embodiments. Moreover, while each of
Embodiments concerns a case where the surfaces of both the fins 52
and the flat tubes 51 have concavities and convexities, the above
effect is also produced by forming concavities and convexities in
the surfaces of one of the fins 52 and the flat tubes 51, needless
to say.
Embodiment 4
[0063] FIG. 12 is a circuit diagram schematically illustrating a
basic configuration of a refrigeration-and-air-conditioning system
100 according to Embodiment 4 of the present invention. Referring
to FIG. 12, the configuration and operations of the
refrigeration-and-air-conditioning system 100 will now be
described. The refrigeration-and-air-conditioning system 100
performs a cooling operation or a heating operation by causing a
refrigerant to circulate through devices that form a refrigeration
cycle. The refrigeration-and-air-conditioning system 100 according
to Embodiment 4 includes any of the heat exchangers according to
Embodiments 1 to 3. In FIG. 12, solid lines represent the flow of
the refrigerant when cooling is performed, and dotted lines
represent the flow of the refrigerant when heating is
performed.
[0064] As described above, corrugated fin-tube heat exchangers are
suitable for use as condensers but are not suitable for use as
evaporators. In contrast, the heat exchangers according to
Embodiments 1 to 3 are much superior in drainability. Therefore,
the increase in stack loss due to dew water is reduced
significantly, and heat exchangeability is maintained. Hence, the
heat exchangers according to Embodiments 1 to 3 are also suitable
for use as evaporators. Therefore, the
refrigeration-and-air-conditioning system 100 employs any of the
heat exchangers according to Embodiments 1 to 3 as a
heat-source-side heat exchanger and load-side heat exchangers that
are each required to function as both a condenser and an
evaporator.
[0065] The refrigeration-and-air-conditioning system 100 includes
the following devices: a compressor 1, a heat-source-side heat
exchanger 3, expansion devices 102, and load-side heat exchangers
101 that are connected to one another by pipes. Among the foregoing
devices, the compressor 1 and the heat-source-side heat exchanger 3
are included in an outdoor unit, while the expansion devices 102
and the load-side heat exchangers 101 are included in indoor units.
The expansion devices 102 may be included in the outdoor unit 101,
not in the indoor units. Furthermore, a four-way valve 2 configured
to switch the flow of the refrigerant in accordance with the
operation requested is provided on a discharge side of the
compressor 1.
[0066] The compressor 1 sucks the refrigerant and compresses the
refrigerant, whereby the refrigerant has a high temperature and a
high pressure. The compressor 1 is, for example, an inverter
compressor or the like whose capacity is controllable. The
heat-source-side heat exchanger 3 allows the refrigerant and air
that is forcibly supplied thereto from a non-illustrated fan to
exchange heat therebetween. Any of the heat exchangers according to
Embodiments 1 to 3 is employed as the heat-source-side heat
exchanger 3. The expansion devices 102 each expand the refrigerant
by reducing the pressure of the refrigerant and each include, for
example, an electronic expansion valve or the like whose opening
degree is variably controllable. The load-side heat exchangers 101
each allow the refrigerant and air that is forcibly supplied
thereto from a non-illustrated air-sending device such as a fan to
exchange heat therebetween. Any of the heat exchangers according to
Embodiments 1 to 3 is employed as each of the load-side heat
exchangers 101.
[0067] The cooling operation and the heating operation performed by
the refrigeration-and-air-conditioning system 100 will now be
described briefly.
[Cooling Operation]
[0068] When the compressor 1 is driven, the compressor 1 raises the
pressure of the refrigerant, whereby the refrigerant has a high
temperature and a high pressure and is discharged. The resulting
high-temperature, high-pressure gas refrigerant discharged from the
compressor 1 flows into the heat-source-side heat exchanger 3 via
the four-way valve 2 and is cooled while exchanging heat with air,
whereby the refrigerant falls into a low-temperature, high-pressure
liquid state and is discharged from the heat-source-side heat
exchanger 3. The liquid refrigerant then undergoes pressure
reduction by being expanded by the expansion devices 102, and turns
into a low-temperature, low-pressure two-phase refrigerant. The
two-phase refrigerant flows into the load-side heat exchangers 101
and evaporates while exchanging heat with air, thereby turning into
a low-temperature, low-pressure gas refrigerant. In this step,
cooling air is provided from the indoor units, whereby
air-conditioned spaces are cooled. The low-pressure gas refrigerant
discharged from the load-side heat exchangers 101 flows into the
compressor 1 again.
[0069] In each of the load-side heat exchangers 101, if the
temperature of the refrigerant flowing in the flat tubes (flat
tubes 51) drops below the dew point of the air, the moisture
contained in the air forms dew on the surfaces of the heat
exchanger, whereby dew water (drain water) is generated. There is
no problem if the dew water generated on the surfaces of the heat
exchanger is quickly drained from the end facets of the fins or the
surfaces of the flat tubes. However, dew water may form bridges
between the fins or accumulate on the upper surfaces of the flat
tubes because of surface tension. If dew water accumulates, the
stack loss on the surfaces of the heat exchanger increases, whereby
the volume of airflow passing through the heat exchanger is reduced
significantly. Accordingly, the ability as a heat exchanger is
reduced significantly. Consequently, a vicious cycle may occur in
which the evaporating temperature is further lowered, the dew water
is transformed and grows into frost, the stack loss further
increases, the volume of airflow is reduced, and the ability is
lowered.
[0070] To address such a problem, the
refrigeration-and-air-conditioning system 100 employs any of the
heat exchangers according to Embodiments 1 to 3 as each of the
load-side heat exchangers 101. Therefore, even if moisture forms
dew on the surfaces of the heat exchanger, good drainability
efficiently suppresses the accumulation of dew water. Hence, the
refrigeration-and-air-conditioning system 100 does not have
problems of the increase in the stack loss on the surfaces of each
of the heat exchangers and the reduction in the volume of airflow
passing through the heat exchanger that may occur with the
accumulation of dew water. Thus, the reduction in the ability as a
heat exchanger is suppressed.
[Heating Operation]
[0071] When the compressor 1 is driven, the compressor 1 raises the
pressure of the refrigerant, whereby the refrigerant has a high
temperature and a high pressure and is discharged. The resulting
high-temperature, high-pressure gas refrigerant discharged from the
compressor 1 flows into the load-side heat exchangers 101 via the
four-way valve 2 and is cooled while exchanging heat with air,
whereby the refrigerant falls into a low-temperature, high-pressure
liquid state and is discharged from the load-side heat exchangers
101. In this step, heating air is provided from the indoor units,
whereby the air-conditioned spaces are heated. The liquid
refrigerant then undergoes pressure reduction by being expanded by
the expansion devices 102, and turns into a low-temperature,
low-pressure two-phase refrigerant. The two-phase refrigerant flows
into the heat-source-side heat exchanger 3 and evaporates while
exchanging heat with air, thereby turning into a low-temperature,
low-pressure gas refrigerant. The low-pressure gas refrigerant
discharged from the heat-source-side heat exchanger 3 flows into
the compressor 1 again.
[0072] In the heat-source-side heat exchanger 3, if the temperature
of the refrigerant flowing in the flat tubes (flat tubes 51) drops
below the dew point of the air, the moisture contained in the air,
forms dew on the surfaces of the heat exchanger, whereby dew water
(drain water) is generated. There is no problem if the dew water
generated on the surfaces of the heat exchanger is quickly drained
from the end facets of the fins or the surfaces of the flat tubes.
However, dew water may form bridges between the fins or accumulate
on the upper surfaces of the flat tubes because of surface tension.
If dew water accumulates, the stack loss on the surfaces of the
heat exchanger increases, whereby the volume of airflow passing
through the heat exchanger is reduced significantly. Accordingly,
the ability as a heat exchanger is reduced significantly.
Consequently, a vicious cycle may occur in which the evaporating
temperature is further lowered, the dew water is transformed and
grows into frost, the stack loss further increases, the volume of
airflow is reduced, and the ability is lowered.
[0073] To address such a problem, the
refrigeration-and-air-conditioning system 100 employs any of the
heat exchangers according to Embodiments 1 to 3 as the
heat-source-side heat exchanger 3. Therefore, even if moisture
forms dew on the surfaces of the heat exchanger, good drainability
efficiently suppresses the accumulation of dew water. Hence, the
refrigeration-and-air-conditioning system 100 does not have
problems of the increase in the stack loss on the surfaces of the
heat exchanger and the reduction in the volume of airflow passing
through the heat exchanger that may occur with the accumulation of
dew water. Thus, the reduction in the ability as a heat exchanger
is suppressed.
[0074] To summarize, since the refrigeration-and-air-conditioning
system 100 includes any of the heat exchangers according to
Embodiments 1 to 3, the increase in the stack loss due to dew water
is reduced significantly even if the heat exchangers are used as
evaporators. Thus, the refrigeration-and-air-conditioning system
100 maintains its heat exchangeability.
Reference Signs List
[0075] 1 compressor 2 four-way valve 3 heat-source-side heat
exchanger 50 heat exchanger 50' heat exchanger 50B heat exchanger
51 flat tube 51' flat tube 52 fin 52A clearance between fin and
flat tube 52' fin 53 hole 53' hole 54 notch 55
[0076] base material 56 cladding layer 56A cladding layer 57
[0077] foreign substance 58 flux 59 dew water 100
refrigeration-and-air-conditioning system 101 load-side heat
exchanger 102 expansion device
* * * * *