U.S. patent application number 13/575727 was filed with the patent office on 2013-02-07 for heat exchanger.
This patent application is currently assigned to THE UNIVERSITY OF TOKYO. The applicant listed for this patent is Shiro Ikuta, Kazuaki Iwamoto, Isamu Kandori, Naoki Shikazono, Tsunehito Wake. Invention is credited to Shiro Ikuta, Kazuaki Iwamoto, Isamu Kandori, Naoki Shikazono, Tsunehito Wake.
Application Number | 20130032320 13/575727 |
Document ID | / |
Family ID | 44355324 |
Filed Date | 2013-02-07 |
United States Patent
Application |
20130032320 |
Kind Code |
A1 |
Shikazono; Naoki ; et
al. |
February 7, 2013 |
HEAT EXCHANGER
Abstract
A plurality of heat-exchange tubes 30 each including a flat pipe
including a groove 36 and wavelike depression-and-projection
portions 33, 34 are arranged in parallel in such a manner that each
of respective longitudinal directions thereof is a vertical
direction, and a heat exchange medium is made to flow from an inlet
31 at each lower portion to an outlet 32 at each upper portion.
Guide walls 43, 44 are provided in a shell 40, and exhaust gas is
made to flow an inlet 41 at an upper portion to an outlet 42 at a
lower portion, thereby making the exhaust gas meander in flow paths
46a to 46d and a space between the plurality of heat-exchange tubes
30. The exhaust gas and the heat exchange medium have flows opposed
to each other as a whole, and a secondary flow of the exhaust gas
is made to occur by the wavelike depression-and-projection portions
33, 34, thereby enhancing the heat exchange efficiency, and the
arrangement in such a manner that each of the longitudinal
directions is the vertical direction and the formation of a groove
36 and the wavelike depression-and-projection portions 33, 34
enable acceleration of downward discharge of condensed water.
Inventors: |
Shikazono; Naoki; (Tokyo,
JP) ; Wake; Tsunehito; (Tokyo, JP) ; Ikuta;
Shiro; (Tokyo, JP) ; Kandori; Isamu;
(Nukata-gun, JP) ; Iwamoto; Kazuaki; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shikazono; Naoki
Wake; Tsunehito
Ikuta; Shiro
Kandori; Isamu
Iwamoto; Kazuaki |
Tokyo
Tokyo
Tokyo
Nukata-gun
Tokyo |
|
JP
JP
JP
JP
JP |
|
|
Assignee: |
THE UNIVERSITY OF TOKYO
Tokyo
JP
M K SALE CO., LTD.
Tokyo
JP
KANDORI INDUSTRY LTD.
Nukata-gun, Aichi
JP
WAKI FACTORY INC.
Tokyo
JP
|
Family ID: |
44355324 |
Appl. No.: |
13/575727 |
Filed: |
January 27, 2011 |
PCT Filed: |
January 27, 2011 |
PCT NO: |
PCT/JP2011/051617 |
371 Date: |
October 22, 2012 |
Current U.S.
Class: |
165/175 ;
165/177 |
Current CPC
Class: |
F28F 3/046 20130101;
F28D 7/1692 20130101; F28D 21/0003 20130101; F28D 9/0043 20130101;
F28F 17/005 20130101; F28F 9/22 20130101 |
Class at
Publication: |
165/175 ;
165/177 |
International
Class: |
F28D 1/053 20060101
F28D001/053; F28F 13/06 20060101 F28F013/06; F28F 9/02 20060101
F28F009/02; F28F 1/04 20060101 F28F001/04; F28F 1/06 20060101
F28F001/06 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 2, 2010 |
JP |
2010-021027 |
Claims
1. A finless heat exchanger for recovering heat of exhaust gas
resulting from combustion via heat exchange between said exhaust
gas and a heat exchange medium, the heat exchanger comprising: a
plurality of heat-exchange tubes each formed as a flat pipe using a
metal plate material having an excellent acid corrosion resistance,
said plurality of heat-exchange tubes being arranged in parallel in
such a manner that each of respective longitudinal directions
thereof is mainly a vertical direction; and a shell that houses
said plurality of heat-exchange tubes and forms a flow path for
said exhaust gas to pass therethrough between said plurality of
heat-exchange tubes and said shell, wherein said plurality of
heat-exchange tubes each include an inlet for said heat exchange
medium at a vertically lower portion thereof and an outlet for said
heat exchange medium at a vertically upper portion thereof; wherein
said shell includes an inlet for said exhaust gas at a vertically
upper portion thereof and an outlet for said exhaust gas at a
vertically lower portion thereof, and wherein said plurality of
heat-exchange tubes and/or said shell include a meandering guiding
section formed so that said exhaust gas flows in a space between
the plurality of heat-exchange tubes while meandering downward from
the vertically upper portion.
2. A heat exchanger according to claim 1, wherein said plurality of
heat-exchange tubes each include a vertical groove at a substantial
center of a flat surface thereof.
3. A heat exchanger according to claim 2, wherein said groove in
each of said plurality of heat-exchange tubes is fixed by bonding
inside the heat-exchange tube.
4. A heat exchanger according to claim 1, wherein said meandering
guiding section includes a guide wall formed inside said shell so
that said exhaust gas flows in a substantially horizontal direction
orthogonal to said plurality of heat-exchange tubes.
5. A heat exchanger according to claim 4, wherein said meandering
guiding section includes a rib formed toward said guide wall at a
flat surface of each of said plurality of heat-exchange tubes at a
position aligned with said guide wall of said shell, in addition to
said guide wall.
6. A heat exchanger according to claim 1, wherein said meandering
guiding section includes a plurality of ribs formed at a plurality
of positions in a substantially horizontal direction on a flat
surface of each of said plurality of heat-exchange tubes; and
wherein an inner side of an outer wall of said shell is in contact
with one side surface and another side surface alternately from an
uppermost position to a lower position from among opposite side
surfaces of said plurality of heat-exchange tubes at positions
where said plurality of ribs are formed and is not in contact with
a side surface opposite to said side surface that is in contact
with the inner side from among opposite side surfaces at a same
position.
7. A heat exchanger according to claim 1, wherein said plurality of
heat-exchange tubes each include a plurality of wavelike
depression-and-projection portions formed over a substantial
entirety of a flat surface thereof, each of said plurality of
wavelike depression-and-projection portions including a depression
portion and a projection portion flexed at an angle ranging from 10
to 80 degrees relative to a main flow direction of said exhaust gas
to be continuous with each other.
8. A heat exchanger according to claim 7, wherein said plurality of
heat-exchange tubes are each formed so that an angle of said
wavelike depression-and-projection portions in a region positioned
in a vertically upper portion of the flat surface relative to the
main flow direction of said exhaust gas is smaller than an angle of
said wavelike depression-and-projection portions in a region
positioned in a vertically lower portion of the flat surface
relative to the main flow direction of said exhaust gas.
9. A heat exchanger according to claim 8, wherein said plurality of
heat-exchange tubes are each formed so that the angle of said
wavelike depression-and-projection portions in the region
positioned in the vertically upper portion of the flat surface
relative to the main flow direction of said exhaust gas falls
within a range of 10 to 45 degrees and the angle of said wavelike
depression-and-projection portions in the region positioned in the
vertically lower portion of the flat surface relative to the main
flow direction of said exhaust gas falls within a range of 45 to 80
degrees.
Description
TECHNICAL FIELD
[0001] The present invention relates to a heat exchanger and
specifically relates to a finless heat exchanger that recovers heat
of exhaust gas, which results from combustion, via heat exchange
with a heat exchange medium.
BACKGROUND ART
[0002] Conventionally, for this type of heat exchanger, one in
which cooling water is made to flow in a plurality of tubes each
formed into a U-shape and exhaust gas is made to flow substantially
perpendicular to the cooling water in the plurality of tubes from
the side of the plurality of tubes close to outlets for the cooling
water, thereby recovering heat of the exhaust gas (see, for
example, non-patent literature 1). In this heat exchanger, i.e.,
the plurality of tubes are formed using stainless steel to prevent
corrosion caused by exhaust gas, and corrugated fins are inserted
between the plurality of tubes to enhance the heat exchange
efficiency.
CITATION LIST
Non Patent Literature
[0003] Non Patent Literature 1: Transactions of the Japan Society
of Mechanical Engineers, Series B, Vol. 72, No 713, pp. 96-103,
2006
DISCLOSURE OF THE INVENTION
[0004] Where a heat exchanger for latent heat recovery, which
recovers heat of exhaust gas, is downsized, the heat exchange
efficiency may be lowered by condensed water resulting from heat
exchange with the exhaust gas.
[0005] Although a heat exchanger is downsized by flattening the
tubes and reducing the spaces between the tubes to enhance the
efficiency of heat exchange with exhaust gas, if the spaces between
the tubes are reduced, the condensed water remains between the
tubes, hindering the flow of the exhaust gas, which results in a
decrease in heat exchange efficiency. In particular, in a heat
exchanger with fins attached between the tubes, the fins hinder
discharge of condensed water, resulting in a significant decrease
in heat exchange efficiency in addition to a decrease in fin
efficiency.
[0006] A main object of a heat exchanger according to the present
invention is to achieve downsizing and enhancement of heat exchange
efficiency of a heat exchanger for a heat exchanger for latent heat
recovery, which recovers heat of exhaust gas.
[0007] The present invention accomplishes at least part of the
demands mentioned above and the other relevant demands by the
following configurations applied to the heat exchanger.
[0008] The present invention is directed to a finless heat
exchanger for recovering heat of exhaust gas resulting from
combustion via heat exchange between the exhaust gas and a heat
exchange medium. The heat exchanger includes a plurality of
heat-exchange tubes each formed as a flat pipe using a metal plate
material having an excellent acid corrosion resistance. The
plurality of heat-exchange tubes is arranged in parallel in such a
manner that each of respective longitudinal directions thereof is
mainly a vertical direction. The finless heat exchanger further
includes a shell that houses the plurality of heat-exchange tubes
and forms a flow path for the exhaust gas to pass therethrough
between the plurality of heat-exchange tubes and the shell. The
plurality of heat-exchange tubes each include an inlet for the heat
exchange medium at a vertically lower portion thereof and an outlet
for the heat exchange medium at a vertically upper portion thereof.
The shell includes an inlet for the exhaust gas at a vertically
upper portion thereof and an outlet for the exhaust gas at a
vertically lower portion thereof. The plurality of heat-exchange
tubes and/or the shell include a meandering guiding section formed
so that the exhaust gas flows in a space between the plurality of
heat-exchange tubes while meandering downward from the vertically
upper portion.
[0009] In the heat exchanger according to the present invention, a
plurality of heat-exchange tubes each formed as a flat pipe using a
metal plate material having an excellent acid corrosion resistance
are arranged in parallel in such a manner that each of respective
longitudinal directions thereof is mainly a vertical direction, and
the plurality of heat-exchange tubes arranged are housed in a
shell. Consequently, a flow path for exhaust gas to pass through is
formed between the shell and the plurality of heat-exchange tubes.
The plurality of heat-exchange tubes each include an inlet for a
heat exchange medium at a vertically lower portion thereof and an
outlet for the heat exchange medium at a vertically upper portion
thereof, and the shell includes an inlet for the exhaust gas at a
vertically upper portion thereof and an outlet for the exhaust gas
in a vertically lower portion thereof. Then, a meandering guiding
section is formed in either or both of the plurality of
heat-exchange tubes and the shell so that the exhaust gas flows in
spaces between the plurality of heat-exchange tubes while
meandering downward from the vertically upper portion. As described
above, a plurality of heat-exchange tubes formed as flat pipes are
arranged in parallel and housed in a shell, enabling provision of a
small-size heat exchanger.
[0010] In the heat exchanger according to the present invention
configured as described above, a heat exchange medium flows in from
the inlets formed at the vertically lower portions of the plurality
of heat-exchange tubes and flow in the plurality of heat-exchange
tubes arranged in parallel from the vertically lower portions to
the vertically upper portions, and flows out from the outlets
formed at the vertically upper portions of the plurality of
heat-exchange tubes. Meanwhile, exhaust gas flows in from the inlet
formed at the vertically upper portion of the shell, flows in the
flow path formed between the shell and the plurality of
heat-exchange tubes, and flows out from the outlet formed at the
vertically lower portion of the shell. In the flow path formed
between the shell and the plurality of heat-exchange tubes, the
exhaust gas flows in the spaces between the plurality of
heat-exchange tubes while meandering downward from the vertically
upper portion via the meandering guiding section formed in either
or both of the plurality of heat-exchange tubes and the shell.
Accordingly, the heat exchange medium flows from the vertically
lower portions to the vertically upper portions, while the exhaust
gas flows from the vertically upper portion to the vertically lower
portion as a whole although the exhaust gas is made to meander by
the meandering guiding section, and thus, the heat exchange medium
and the exhaust gas have flows opposed to each other, enhancing the
heat exchange efficiency. As a result of heat exchange with the
exhaust gas, condensed water is generated on flat surfaces of the
plurality of heat-exchange tubes, however, the plurality of
heat-exchange tubes are arranged in parallel in such a manner that
each of the respective longitudinal directions thereof is mainly
the vertical direction, and thus, the condensed water is collected
toward the vertically lower portions and discharged. Consequently,
the generated condensed water can be prevented from remaining and
hindering the flow of the exhaust gas, and thus, the pressure loss
of the exhaust gas can be reduced. Furthermore, since the heat
exchanger according to the present invention is configured as a
finless heat exchanger, the discharge of condensed water can be
accelerated compared to those with fins attached between the
plurality of heat-exchange tubes. Consequently, a heat exchanger
having a small size and good heat exchange efficiency can be
provided.
[0011] In the heat exchanger according to the present invention,
the plurality of heat-exchange tubes can each include a vertical
groove at a substantial center of a flat surface thereof.
Consequently, condensed water generated on the flat surfaces of the
plurality of heat-exchange tubes flows along the grooves to the
vertically lower portions, enabling enhancement of the condensed
water discharge performance, and thus, a heat exchanger having a
small size and good heat exchange efficiency can be provided.
Furthermore, as a result of formation of the grooves, the strength
of the plurality of heat-exchanges can be enhanced. Consequently,
the plurality of heat-exchange tubes can be formed using a thinner
metal plate material. In such case, the groove in each of the
plurality of heat-exchange tubes can be fixed by bonding inside the
heat-exchange tube. Consequently, the strength of the plurality of
heat-exchange tubes can further be enhanced.
[0012] In the heat exchanger according to the present invention,
the meandering guiding section can include a guide wall formed
inside the shell so that the exhaust gas flows in a substantially
horizontal direction orthogonal to the plurality of heat-exchange
tubes. In this case, the meandering guiding section can further
include a rib formed toward the guide wall at a flat surface of
each of the plurality of heat-exchange tubes at a position aligned
with the guide wall of the shell, in addition to the guide wall.
Consequently, the exhaust gas can be made to more reliably flow in
the spaces between the plurality of heat-exchange tubes while
meandering, enabling enhancement in heat exchange efficiency.
[0013] Further, in the heat exchanger according to the present
invention, the meandering guiding section can include a plurality
of ribs formed at a plurality of positions in a substantially
horizontal direction on a flat surface of each of the plurality of
heat-exchange tubes, and an inner side of an outer wall of the
shell can be in contact with one side surface and another side
surface alternately from an uppermost position to a lower position
from among opposite side surfaces of the plurality of heat-exchange
tubes at positions where the plurality of ribs are formed and is
not in contact with a side surface opposite to the side surface
that is in contact with the inner side from among opposite side
surfaces at a same position. Consequently, the plurality of ribs
formed on the flat surfaces of the heat-exchange tubes and the
shell can make the exhaust gas flow in the spaces between the
plurality of heat-exchange tubes while meandering without forming
guide walls inside the shell, enabling enhancement of the heat
exchange efficiency.
[0014] Alternatively, in the heat exchanger according to the
present invention, the plurality of heat-exchange tubes can each
include a plurality of wavelike depression-and-projection portions
formed over a substantial entirety of a flat surface thereof, each
of the plurality of wavelike depression-and-projection portions
including a depression portion and a projection portion flexed at
an angle ranging from 10 to 80 degrees relative to a main flow
direction of the exhaust gas to be continuous with each other. When
the exhaust gas flows in the spaces between the plurality of
heat-exchange tubes, the exhaust gas flows accompanied by a
secondary flow caused by the plurality of wavelike
depression-and-projection portions formed on the flat surfaces of
the plurality of heat-exchange tubes. Consequently, the heat
exchange efficiency is enhanced. Furthermore, the condensed water
is guided to the depression portions of the wavelike
depression-and-projection portions by means of the flow of the
exhaust gas and the effect of the surface tension, and thus, the
depression portions of the wavelike depression-and-projection
portions have the role of a discharge flow path for the condensed
water. In other words, formation of the wavelike
depression-and-projection portions at the flat surfaces of the
plurality of heat-exchange tubes enables enhancement of the
condensed water discharge performance.
[0015] In the heat exchanger that includes a plurality of wavelike
depression-and-projection portions formed over a flat surface of
plurality of heat-exchange tubes according to the present
invention, the plurality of heat-exchange tubes can be each formed
so that an angle of the wavelike depression-and-projection portions
in a region positioned in a vertically upper portion of the flat
surface relative to the main flow direction of the exhaust gas is
smaller than an angle of the wavelike depression-and-projection
portions in a region positioned in a vertically lower portion of
the flat surface relative to the main flow direction of the exhaust
gas. As a result of making the angle of the wavelike
depression-and-projection portion in the region positioned in each
of the vertically upper portions of the flat surfaces of the
plurality of heat-exchange tubes relative to the direction of the
main flow of the exhaust gas be small, the secondary flow of the
exhaust gas can be accelerated, enabling enhancement of the
efficiency of heat exchange between the exhaust gas and the heat
exchange medium, and as a result of making the angle of the
wavelike depression-and-projection portion in the region positioned
in each of the vertically lower portions of the flat surfaces of
the plurality of heat-exchange tubes relative to the direction of
the main flow of the exhaust gas be large, an angle of the
depression portions of the wavelike depression-and-projection
portions relative to the vertical direction can be made to be
small, enabling condensed water to easily flow to the vertically
lower portions. In this case, the plurality of heat-exchange tubes
can be each formed so that the angle of the wavelike
depression-and-projection portions in the region positioned in the
vertically upper portion of the flat surface relative to the main
flow direction of the exhaust gas falls within a range of 10 to 45
degrees and the angle of the wavelike depression-and-projection
portions in the region positioned in the vertically lower portion
of the flat surface relative to the main flow direction of the
exhaust gas falls within a range of 45 to 80 degrees.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a configuration diagram illustrating a schematic
configuration of a heat exchanger 20 in one embodiment of the
invention;
[0017] FIG. 2 is a side view of an outer appearance of a plurality
of heat-exchange tubes 30 used in the heat exchanger 20;
[0018] FIG. 3 is an enlarged diagram illustrating a heat-exchange
tube 30 with a part thereof enlarged;
[0019] FIG. 4 is a pattern diagram illustrating a flow of an
exhaust gas in the heat exchanger 20 of the invention;
[0020] FIG. 5 schematically illustrates the configuration of
another heat exchanger 20B in one modified example;
[0021] FIG. 6 schematically illustrates the configuration of
another heat exchanger 20C in another modified example;
[0022] FIG. 7 schematically illustrates the configuration of
another heat exchanger 20D in another modified example;
[0023] FIG. 8 schematically illustrates the configuration of
another heat exchanger 20E in another modified example;
[0024] FIG. 9 schematically illustrates the configuration of
another heat-exchange tube 30F in one modified example;
[0025] FIG. 10 schematically illustrates the configuration of
another heat exchanger 20G in one modified example.
BEST MODES OF CARRYING OUT THE INVENTION
[0026] One mode of carrying out the invention is discussed below as
a preferred embodiment.
[0027] FIG. 1 is a configuration diagram illustrating a schematic
configuration of a heat exchanger 20, which is an embodiment of the
present invention; FIG. 2 is a side view of an outer appearance of
a plurality of heat-exchange tubes 30 used in the heat exchanger 20
according to the embodiment; FIG. 3 is an enlarged diagram
illustrating a heat-exchange tube 30 with a part thereof enlarged.
The heat exchanger 20 according to the embodiment is configured as
a finless heat exchanger that recovers heat of exhaust gas
resulting from combustion via heat exchange between the exhaust gas
and a heat exchange medium such as cooling water, and as
illustrated, includes a plurality of (for example, 22)
heat-exchange tubes 30 arranged in parallel in such a manner that
each of respective longitudinal directions thereof is a vertical
direction, and a shell 40 that houses the plurality of
heat-exchange tubes 30.
[0028] Each heat-exchange tube 30 is formed as a flat pipe using a
plate material having a thickness of 0.3 mm and including a metal
material having an excellent acid corrosion resistance (for
example, stainless steel), the flat pipe having a substantially
rectangular shape in its entirety, which has a height (length) of
150 mm, a width of 30 mm and an inner heat exchange medium flow
path thickness of 2.4 mm (an entire thickness of 3.0 mm including
the thickness of the plate), and is arranged in parallel with an
adjacent heat-exchange tube 30 so as to provide a space of 1.6 mm
therebetween in such a manner that the longitudinal direction
thereof is the vertical direction. An inlet 31 for a heat exchange
medium is formed in the vicinity of a lower end of a vertically
lower portion of each heat-exchange tube 30, and the respective
inlets 31 of the respective heat-exchange tubes 30 communicate with
one another via a connecting pipe 31a. Also, an outlet 32 for the
heat exchange medium is formed in the vicinity of an upper end of a
vertically upper portion of each heat-exchange tube 30, and the
respective outlets 32 of the respective heat-exchange tubes 30 via
a connecting pipe 32a. Accordingly, a heat exchange medium flows in
from the respective inlets 31 positioned in the vertically lower
portions of the respective heat-exchange tubes 30, flows in the
respective heat-exchange tubes 30 toward the vertically upper
portions, and flows out from the respective outlets 32 positioned
in the vertically upper portions of the respective heat-exchange
tubes 30.
[0029] At a center of each flat surface of each heat-exchange tube
30, as illustrated in FIGS. 1 and 3, a vertical groove 36
projecting inward, the groove 36 having a depth of 1.2 mm and a
width of 1.6 mm is formed. Since the groove 36 is formed in each of
the opposite flat surfaces of the heat-exchange tube 30, the
grooves 36 at the opposite flat surfaces are in contact with each
other. In the embodiment, the grooves 36 at the opposite flat
surfaces, the grooves 36 being in contact with each other inside
the tube, are fixed by bonding using, e.g., brazing. Consequently,
the strength of the heat-exchange tubes 30 can be enhanced.
Furthermore, the grooves 36 each collect condensed water generated
on the surfaces of the respective heat-exchange tube 30 as a result
of heat exchange with exhaust gas and guide the condensed water to
the respective vertically lower portion, enabling enhancement of
the condensed water discharge performance.
[0030] Furthermore, wavelike depression-and-projection portions 33,
34 each including depression portions 33 and projection portions 34
having a shape formed by making "V" or "W"-shapes be continuous
with one another by rotating the "V" or "W"-shapes by 90 degrees,
the "V" or "W"-shapes being flexed at a predetermined angle .alpha.
relative to a horizontal direction are formed over an entirety of
each flat surface of each heat-exchange tube 30. The angle .alpha.
of the wavelike depression-and-projection portions 33, 34 relative
to the horizontal direction falls within a range of 10 to 80
degrees, preferably a range of 30 to 60 degrees, more preferably a
range of 30 to 45 degrees, and is 30 degrees in the embodiment. The
wavelike depression-and-projection portions 33, 34 formed at each
flat surface of each heat-exchange tube 30, upon exhaust gas
flowing substantially horizontally, makes a secondary flow of the
exhaust gas occur in addition to a main flow of the exhaust gas.
Thus, the efficiency of heat exchange between the exhaust gas and
the heat exchange medium can be enhanced. Furthermore, the wavelike
depression-and-projection portions 33, 34 make the condensed water
adhered thereto by the flow of the exhaust gas and the effect of
the surface tension be collected in the depression portions 33, and
further guided to the respective vertically lower portions,
enabling the condensed water discharge performance.
[0031] The shell 40 is formed as a case having a substantial
rectangular parallelepiped shape that houses the plurality of
heat-exchange tubes 30 connected via the connecting pipes 31a, 32a,
using a plate material having a thickness of 0.3 mm and including a
metal material having an excellent acid corrosion resistance (for
example, stainless steel) as with the respective heat-exchange
tubes 30, and forms flow paths 46a, 46b, 46c, 46d for exhaust gas
jointly with the plurality of heat-exchange tubes 30. On the left
side in FIG. 1 of a vertically upper portion of the shell 40, an
inlet 41 for exhaust gas is formed, and on the right side in FIG. 1
of a vertically lower portion of the shell 40, an outlet for the
exhaust gas is formed. Furthermore, inside the shell 40, guide
walls 43, 44 that separate the flow paths 46a, 46b, 46c, 46d for
exhaust gas, which are formed jointly with the plurality of
heat-exchange tubes and guide the flow of exhaust gas are attached.
Accordingly, as indicated by the white arrows in FIG. 4, exhaust
gas flows in from the inlet 41 formed at the vertically upper
portion of the shell 40, passes through the spaces between the
plurality of heat-exchange tubes 30 and the flow paths 46a, 46b,
46c, 46d while meandering, and flows out from the outlet 42 formed
at the vertically lower portion of the shell 40. Accordingly, the
exhaust gas and the heat exchange medium flowing in the plurality
of heat-exchange tubes 30 have flows opposed to each other as a
whole, enabling enhancement of the heat exchange efficiency.
[0032] In the heat exchanger 20 according to the above-described
embodiment, a plurality of heat-exchange tubes 30, each having a
substantially rectangular shape and formed as a flat pipe, are
arranged in parallel at an interval of 1.6 mm in such a manner that
each of the respective longitudinal directions thereof is a
vertical direction, the heat exchange medium is made to flow in
from the respective inlets 31 positioned at the vertically lower
portions, flow in the respective heat-exchange tubes 30 toward the
vertically upper portions, and flow out from the respective outlets
32 positioned at the vertically upper portions of the respective
heat-exchange tubes 30. Meanwhile, the exhaust gas is made to flow
in from the inlet 41 formed at the vertically upper portion of the
shell 40, flow in the flow paths 46a, 46b, 46c, 46d formed by the
shell 40, the plurality of heat-exchange tubes 30 and the guide
walls 43, 44 and the spaces between the plurality of heat-exchange
tubes 30 while meandering, and flow out from the outlet 42 formed
at the vertically lower portion of the shell 40, whereby the
exhaust gas and the heat-exchange medium flowing in the plurality
of heat-exchange tubes 30 have flows opposed to each other as a
whole, enabling enhancement of the heat exchange efficiency. As a
result of arranging the plurality of heat-exchange tubes 30 in
parallel in such a manner that each of the longitudinal directions
thereof is the vertical direction, condensed water generated on the
flat surfaces of the plurality of heat-exchange tubes 30 as a
result of heat exchange with the exhaust gas is collected toward
the vertically lower portions and discharged. Consequently, the
generated condensed water can be prevented from remaining and
hindering the flow of the exhaust gas, enabling reduction of the
pressure loss of the exhaust gas. In addition, since the heat
exchanger 20 according to embodiment is configured as a finless
heat exchanger, discharge of condensed water can be accelerated
compared to those with fins attached between a plurality of
heat-exchange tubes 30. Consequently, a heat exchanger having a
small size and good heat exchange efficiency can be provided.
[0033] Furthermore, in the heat exchanger 20 according to the
embodiment, as a result of forming the vertical groove 36 at a
center of each of the flat surfaces of the heat-exchange tubes 30,
condensed water generated on the flat surfaces of the heat-exchange
tubes 30 as a result of heat exchange with the exhaust gas can be
collected and guided to the vertically lower portions, enabling
enhancement of the condensed water discharge performance, and the
strength of the plurality of heat-exchange tubes 30 can be
enhanced, and the plurality of heat-exchange tubes 30 can be formed
using a metal material having a small thickness, whereby a heat
exchanger having a smaller size can be provided. In addition, the
grooves are fixed by bonding inside the respective tubes, enabling
enhancement of the strength of the heat-exchange tubes 30.
[0034] Furthermore, in the heat exchanger 20 according to the
embodiment, as a result of forming the wavelike
depression-and-projection portions 33, 34 over an entirety of each
of the flat surfaces of the plurality of heat-exchange tubes 30,
the wavelike depression-and-projection portions 33, 34 including
the depression portions 33 and the projection portions 34 flexed at
the predetermined angle .alpha. relative to a horizontal direction
in which the exhaust gas mainly flow to be continuous with one
another, a secondary flow of the exhaust gas can be made to occur
in addition to the main flow thereof, and consequently, the
efficiency of heat exchange between the exhaust gas and the heat
exchange medium can be enhanced. Furthermore, the wavelike
depression-and-projection portions 33, 34 collect condensed water
adhered thereto by the flow of the exhaust gas into the depression
portions 33 and guide the condensed water to the vertically lower
portions, enabling further enhancement of the condensed water
discharge performance.
[0035] Although the heat exchanger 20 according to the embodiment
includes the groove 36 formed at the center of each of the flat
surfaces of the plurality of heat-exchange tubes 30 and the
wavelike depression-and-projection portions 33, 34 formed over the
substantial entirety of the flat surface, as in a heat exchanger
20B according to an alteration in FIG. 5, it is possible that a
groove 36 is formed at a center of each of flat surfaces of a
plurality of heat-exchange tubes 30B but no wavelike
depression-and-projection portions 33, 34 are formed at the flat
surface, and conversely, as in a heat exchanger 20C according to an
alteration in FIG. 6, it is possible that no groove 36 is formed at
a center of each of flat surfaces of heat-exchange tubes 30C but
wavelike depression-and-projection portions 33C, 34C are formed at
the flat surface. In this case, the wavelike
depression-and-projection portions 33C, 34C may be formed also at
the center of each of the flat surfaces of the plurality of
heat-exchange tubes 30C. Alternatively, it is possible that neither
groove 36 nor wavelike depression-and-projection portions 33, 34
are formed at each of the flat surfaces of the plurality of
heat-exchange tubes.
[0036] Although the heat exchanger 20 according to the embodiment
includes the groove 36 formed at the center of each of the flat
surfaces of the plurality of heat-exchange tubes 30 and the
wavelike depression-and-projection portions 33, 34 formed over the
substantial entirety of the flat surface, as in a heat exchanger
20D according to an alteration in FIG. 7, ribs 37a to 37d, which
project outward, may be formed at positions in each of flat
surfaces of a plurality of heat-exchange tubes 30D, the positions
being aligned with guide walls 43, 44. Consequently, meandering of
exhaust gas can be guided more reliably. In this case, the adjacent
ribs 37a and rib 37b, and the adjacent ribs 37c and rib 37d are
preferably separated, respectively, by a groove 36. Thus, where
ribs are formed at positions at the flat surface of the plurality
of heat-exchange tubes 30D, the positions being aligned with the
guide walls 43, 44, as in a heat exchanger 20E according to an
alteration in FIG. 8, only ribs 37a, 37d extending from respective
parts of each of the flat surfaces of the plurality of
heat-exchange tubes 30E, the parts being adjacent to the guide
walls 43, 44, to the groove 36 may be formed.
[0037] Although in the plurality of heat-exchange tubes 30 in the
heat exchanger 20 according to the embodiment, the angle .alpha. of
the wavelike depression-and-projection portions 33, 34 formed at
the flat surfaces relative to the horizontal direction is 30
degrees, the angle .alpha. only needs to fall within a range of 10
to 80 degrees, preferably a range of 30 to 60 degrees. Also, as in
a heat-exchange tube 30F according to an alteration in FIG. 9, it
is possible that an angle .alpha. of wavelike
depression-and-projection portions 33Fa, 34Fa positioned on the
exhaust gas inflow side relative to the horizontal direction is
small, and an angle .beta. of wavelike depression-and-projection
portions 33Fb, 34Fb positioned in the exhaust gas outflow side
relative to the horizontal direction is larger than the angle
.alpha.. For example, the angle .alpha. is preferably 10 to 45
degrees and the angle .beta. is preferably 45 to 80 degrees. The
heat-exchange tube 30F according to the alteration, an angle of 30
degrees is employed for the angle .alpha. and an angle of 60
degrees is employed for the angle .beta.. This is based on setting
of the angle .alpha. so as to accelerate a secondary flow of
exhaust gas to enhance the heat exchange efficiency for the
wavelike depression-and-projection portions 33Fa, 34Fa positioned
on the exhaust gas inflow side and setting of the angle .beta. so
as to accelerate downward discharge of condensed water for the
wavelike depression-and-projection portions 33Fb, 34Fb positioned
on the exhaust gas outflow side. Accordingly, wavelike
depression-and-projection portions 33, 34 may be formed in such a
manner that the angles of the wavelike depression-and-projection
portions 33, 34 relative to the horizontal direction are larger
from the exhaust gas inflow side toward the exhaust gas outflow
side successively or stepwise.
[0038] While in the heat exchanger 20 according to the embodiment,
the plurality of heat-exchange tubes 30 are formed so as to be a
flat pipe, using a plate material having a thickness of 0.3 mm and
including stainless steel, the flat pipe having a substantially
rectangular shape in its entirety, which has a height (length) of
150 mm, a width of 30 mm and an inner heat exchange medium flow
path thickness of 2.4 mm (an entire thickness of 3.0 mm including
the thickness of the plate), and are arranged in parallel so as to
provide a space of 1.6 mm between respective adjacent heat-exchange
tubes 30 in such a manner that each of the longitudinal directions
thereof is the vertical direction, any plate material may be
employed as long as such plate material is one including a metal
material having an excellent acid corrosion resistance other than
stainless steel, and the thickness of the plate material may be
smaller or larger than 0.3 mm if the strength can be maintained.
Also, the height, the width and the inner heat exchange medium flow
path thickness are not limited to 150 mm, 30 mm and 2.4 mm,
respectively, and any height, any width and any inner heat exchange
medium flow path thickness may be employed as long as the inner
heat exchange medium flow path thickness is no more than 3 mm.
Furthermore, it is not essential that each of the plurality of
heat-exchange tubes 30 have a shape of a substantially-rectangular
flat hollow pipe, and the shape may be, for example, an oval flat
hollow pipe. In addition, the interval of adjacent heat-exchange
tubes 30 is not limited to 1.6 mm, and an interval with any size
may be employed as long as such interval is no more than 3 mm.
Furthermore, it is not essential that the plurality of
heat-exchange tubes 30 be arranged in parallel in such a manner
that each of the respective longitudinal directions thereof is
exactly the vertical direction, and the plurality of heat-exchange
tubes 30 may be arranged in parallel in such a manner that each of
the respective longitudinal directions thereof is the vertical
direction when a certain degree is added thereto.
[0039] Although in the heat exchanger 20 according to the
embodiment, the shell 40 is formed as a case having a
substantially-rectangular parallelepiped shape that houses the
plurality of heat-exchange tubes 30 using a plate material having a
thickness of 0.3 mm and including stainless steel, any plate
material having an excellent acid corrosion resistance other than
stainless steel may be employed, and the thickness of the plate
material may be smaller or larger than 0.3 mm if the strength can
be maintained.
[0040] Although in the heat exchanger 20 according to the
embodiment, the shell 40 is formed as a case having a
substantially-rectangular parallelepiped shape that houses the
plurality of heat-exchange tubes 30, and the guide walls 43, 44 are
provided inside the shell 40 so that exhaust gas flows in the
spaces between the plurality of heat-exchange tubes 30 and the flow
paths 46a, 46b, 46c, 46d while meandering, as in a heat exchanger
20G according to an alteration in FIG. 10, using a plurality of
heat-exchange tubes 30D each including ribs 37a to 37d formed
thereon, it is possible that the inner side of an outer wall of a
shell 40G is in contact with side surfaces of the plurality of
heat-exchange tubes 30D where the respective ribs 37a are formed
and side surface of the plurality of heat-exchange tubes 30D where
the respective ribs 37d are formed, that is, the inner side of the
outer wall is in contact with one side surface (side surface at a
position where the rib 37a is formed) and another side surface
(side surface at a position where the rib 37d is formed)
alternately from an uppermost position to lower positions from
among opposite side surfaces of the plurality of heat-exchange
tubes 30D at positions where the plurality of rib 37a to 37d are
formed and is not in contact with side surfaces (side surface at
positions where the ribs 37b, 37c are formed) opposite to the side
surfaces that are in contact with the inner side of the outer wall
(side surfaces at the positions where the ribs 37a, 37d are formed)
from among the opposite side surfaces at same positions.
Consequently, the plurality of ribs 37a to 37d formed on the flat
surfaces of the plurality of heat-exchange tubes 30D and the shell
40G can make exhaust gas flow in spaces between the plurality of
heat-exchange tubes 30D while meandering without forming guide
walls inside the shell 40G, enabling enhancement of the heat
exchange efficiency.
[0041] The embodiment and its applications discussed above are to
be considered in all aspects as illustrative and not restrictive.
There may be many modifications, changes, and alterations without
departing from the scope or spirit of the main characteristics of
the present invention.
INDUSTRIAL APPLICABILITY
[0042] The present invention is preferably applied to the
manufacturing industries of heat exchangers.
* * * * *