U.S. patent application number 11/730249 was filed with the patent office on 2007-10-25 for method for manufacturing a heat exchanger.
This patent application is currently assigned to Xenesys Inc.. Invention is credited to Toyoaki Matsuzaki, Taro Watanabe.
Application Number | 20070245560 11/730249 |
Document ID | / |
Family ID | 38255314 |
Filed Date | 2007-10-25 |
United States Patent
Application |
20070245560 |
Kind Code |
A1 |
Matsuzaki; Toyoaki ; et
al. |
October 25, 2007 |
Method for manufacturing a heat exchanger
Abstract
Heat exchange plates are stacked, with a pressing force applied
to the plates so as to maintain parallelism of them and prevent
deformation of them during a diffusion bonding process. The
stacking condition is maintained and adjacent plates come into
contact with each other at projections and peripheral edges. Space
surrounding the contact portions of the plates is put in a vacuum
or low pressure state in which only an inner gas atmosphere exists.
The plates are kept at a temperature at which the diffusion bonding
occurs by a predetermined period of time to diffusion-bond portions
of the plates, which are only brought into contact with each other
and have not been bonded together.
Inventors: |
Matsuzaki; Toyoaki;
(Izunokuni-shi, JP) ; Watanabe; Taro; (Tokyo,
JP) |
Correspondence
Address: |
RADER FISHMAN & GRAUER PLLC
LION BUILDING
1233 20TH STREET N.W., SUITE 501
WASHINGTON
DC
20036
US
|
Assignee: |
Xenesys Inc.
Hyogo-Ken
JP
|
Family ID: |
38255314 |
Appl. No.: |
11/730249 |
Filed: |
March 30, 2007 |
Current U.S.
Class: |
29/890.039 |
Current CPC
Class: |
F28D 9/0037 20130101;
B23K 20/023 20130101; Y10T 29/49366 20150115; F28F 2235/00
20130101; B23K 2101/14 20180801; F28F 2275/061 20130101; F28F
2240/00 20130101 |
Class at
Publication: |
029/890.039 |
International
Class: |
B21D 53/04 20060101
B21D053/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2006 |
JP |
P2006-95838 |
Claims
1. A method for manufacturing a heat exchanger comprising the steps
of: placing a plurality of heat exchange plates one upon another,
each of which is formed of a metallic plate member having a
predetermined pattern of irregularity and combining the plates into
a heat exchanger, in which each of the heat exchange plates is
formed into a predetermined shape by a press-forming process so
that each of the heat exchange plates includes on at least part
thereof a heat transfer section having the pattern of irregularity
and first and second opposite surfaces with which first and second
heat exchange fluids come into contact, respectively, the heat
exchange plates as combined come into contact with each other on at
least one part of peripheries thereof, and first gap portions
through which the first heat exchange fluid is to pass and second
gap portions through which the second heat exchange fluid is to
pass are provided alternately between the heat exchange plates,
wherein, the method further comprising the steps of: placing a
predetermined number of the heat exchange plates one upon another
to apply a pressing force to the heat exchange plates in a stacking
direction thereof to an extent that at least parallelism of the
heat exchange plates as placed is maintained and the heat exchange
plates are not plastically deformed even when a temperature thereof
increases to a predetermined temperature at which a diffusion
bonding associated with material of the heat exchange plates
occurs, maintaining such a stacking condition and bringing adjacent
plates at projections and peripheral edges that protrude from the
heat exchange plates into contact with each other; and putting
space surrounding at least contact portions of the plates in a
vacuum state or a low pressure state in which only an inner gas
atmosphere exists, keeping the plates at a predetermined
temperature at which the diffusion bonding occurs by a
predetermined period of time and diffusion-bonding portions of the
plates, which are only brought into contact with each other and
have not been bonded together.
2. The method as claimed in claim 1, further comprising the steps
of: welding, at a stage of the step of placing the heat exchange
plates one upon another, the adjacent plates at the peripheral
edges thereof to form a welded assembly in which no variation in a
positional relationship between the plates occurs; and placing the
welded assembly in a vacuum state or a low pressure state in which
only an inner gas atmosphere exists, keeping the plates at a
predetermined temperature at which the diffusion bonding occurs by
a predetermined period of time and diffusion bonding portions of
the plates, which are only brought into contact with each other and
have not been bonded together.
3. The method as claimed in claim 2, wherein: the step of welding
the heat exchange plates is carried out to combine the plates into
the welded assembly so that each of the first and second gap
portions is isolated from outside, excluding first fluid inlet and
outlet portions communicating with the first gap portion and second
fluid inlet and outlet portions communicating with the second gap
portion, and the method further comprising the steps of: connecting
first supply/discharge conduits, which permit supply of a fluid
into the first gap portion and/or discharge of the fluid therefrom,
to the first inlet and out let portions, and connecting second
supply/discharge conduits, which permit supply of a fluid into the
second gap portion and/or discharge of the fluid therefrom;
removing a gas from the first gap portion through the first
supply/discharge conduits to provide the vacuum state therein or
supplying an inert gas into the first gap portion while removing a
gas therein, through the first supply/discharge conduits, to
provide the low pressure state, and supplying an inert gas having a
predetermined high temperature and a predetermined pressure into
the second gap portion while removing a gas therein, through the
second supply/discharge conduits, to provide a higher pressure
state than the first gap portion, and then keeping the contact
portions of the projections, which are placed in the heat transfer
section of each of the plates and exist in the first gap portion,
at the predetermined temperature at which the diffusion bonding
occurs by the predetermined period of time and diffusion-bonding
the contact portions of the plates; and then, removing a gas from
the second gap portion through the second supply/discharge conduits
to provide the vacuum state therein or supplying an inert gas into
the second gap portion while removing a gas therein, through the
second supply/discharge conduits, to provide the low pressure
state, and supplying an inert gas having a predetermined high
temperature and a predetermined pressure into the first gap portion
while removing a gas therein, through the first supply/discharge
conduits, to provide a higher pressure state than the second gap
portion, and then keeping the contact portions of the projections,
which are placed in the heat transfer section of each of the plates
and exist in the second gap portion, at the predetermined
temperature at which the diffusion bonding occurs by the
predetermined period of time and diffusion-bonding the contact
portions of the plates.
4. The method as claimed in claim 1, further comprising the steps
of: placing the heat exchange plates as combined, in a vessel that
is flexibly deformable at least in the stacking direction of the
plates and has air inlet and outlet portions, the vessel providing
an air-tight property, excluding the air inlet and outlet portions;
applying the pressing force to the plates in the stacking direction
thereof and discharging a gas in the vessel through the air inlet
and outlet portions; and then closing the air inlet and outlet
portions to keep an inside of the vessel, which includes the space
surrounding the contact portions of the plates, in the vacuum state
or the low pressure state. portions of the plates.
5. The method as claimed in claim 2, further comprising the steps
of: placing the heat exchange plates as combined, in a vessel that
is flexibly deformable at least in the stacking direction of the
plates and has air inlet and outlet portions, the vessel providing
an air-tight property, excluding the air inlet and outlet portions;
applying the pressing force to the plates in the stacking direction
thereof and discharging a gas in the vessel through the air inlet
and outlet portions; and then closing the air inlet and outlet
portions to keep an inside of the vessel, which includes the space
surrounding the contact portions of the plates, in the vacuum state
or the low pressure state.
6. The method as claimed in claim 1, comprising the steps of:
causing the heat exchange plate placed on one end side in the
stacking direction of the heat exchange plates as combined to be
electrically connectable to one electrode of an electric power
supply for heating through current application, and causing the
heat exchange plate placed on another end side in the stacking
direction thereof to be electrically connectable to another
electrode of the electric power supply; and applying electric
current to the plates placed on the opposite end sides in the
stacking direction of the plates to pass a current through all the
heat exchange plates, while keeping the space surrounding at least
the contact portions of the plates in the vacuum state or the low
pressure state, keeping the plates at a predetermined temperature
at which the diffusion bonding occurs through heating through
current application by a predetermined period of time and
diffusion-bonding the portions of the plates, which are only
brought into contact with each other and have not been bonded
together.
7. The method as claimed in claim 2, comprising the steps of:
causing the heat exchange plate placed on one end side in the
stacking direction of the heat exchange plates as combined to be
electrically connectable to one electrode of an electric power
supply for heating through current application, and causing the
heat exchange plate placed on another end side in the stacking
direction thereof to be electrically connectable to another
electrode of the electric power supply; and applying electric
current to the plates placed on the opposite end sides in the
stacking direction of the plates to pass a current through all the
heat exchange plates, while keeping the space surrounding at least
the contact portions of the plates in the vacuum state or the low
pressure state, keeping the plates at a predetermined temperature
at which the diffusion bonding occurs through heating through
current application by a predetermined period of time and
diffusion-bonding the portions of the plates, which are only
brought into contact with each other and have not been bonded
together.
8. The method as claimed in claim 4, comprising the steps of:
causing the heat exchange plate placed on one end side in the
stacking direction of the heat exchange plates as combined to be
electrically connectable to one electrode of an electric power
supply for heating through current application, and causing the
heat exchange plate placed on another end side in the stacking
direction thereof to be electrically connectable to another
electrode of the electric power supply; and applying electric
current to the plates placed on the opposite end sides in the
stacking direction of the plates to pass a current through all the
heat exchange plates, while keeping the space surrounding at least
the contact portions of the plates in the vacuum state or the low
pressure state, keeping the plates at a predetermined temperature
at which the diffusion bonding occurs through heating through
current application by a predetermined period of time and
diffusion-bonding the portions of the plates, which are only
brought into contact with each other and have not been bonded
together. the plates, in the vacuum state or the low pressure
state.
9. The method as claimed in claim 5, comprising the steps of:
causing the heat exchange plate placed on one end side in the
stacking direction of the heat exchange plates as combined to be
electrically connectable to one electrode of an electric power
supply for heating through current application, and causing the
heat exchange plate placed on another end side in the stacking
direction thereof to be electrically connectable to another
electrode of the electric power supply; and applying electric
current to the plates placed on the opposite end sides in the
stacking direction of the plates to pass a current through all the
heat exchange plates, while keeping the space surrounding at least
the contact portions of the plates in the vacuum state or the low
pressure state, keeping the plates at a predetermined temperature
at which the diffusion bonding occurs through heating through
current application by a predetermined period of time and
diffusion-bonding the portions of the plates, which are only
brought into contact with each other and have not been bonded
together.
10. The method as claimed in claim 1, further comprising the steps
of: holding the heat exchange plates as stacked, between cooling
plates in the stacking direction of the heat exchange plates, each
of the cooling plates being made of material, which does not
diffusion-bond to the heat exchange plates under diffusion bonding
conditions of the heat exchange plates, and having a hollow
structure, ensuring a state in which heat transfer occurs between
the cooling plates and the heat exchange plates, and connecting
cooling conduits to the cooling plates so as to enable cooling
fluid to be supplied into the cooling plates and discharged
therefrom; and supplying, after completion of diffusion bonding
between the heat exchange plates, the cooling fluid into the
cooling plates to decrease temperature of the heat exchange plates,
while keeping the vacuum state or the low pressure state in which
only the inner gas atmosphere exists.
11. The method as claimed in claim 2, further comprising the steps
of: holding the heat exchange plates as stacked, between cooling
plates in the stacking direction of the heat exchange plates, each
of the cooling plates being made of material, which does not
diffusion-bond to the heat exchange plates under diffusion bonding
conditions of the heat exchange plates, and having a hollow
structure, ensuring a state in which heat transfer occurs between
the cooling plates and the heat exchange plates, and connecting
cooling conduits to the cooling plates so as to enable cooling
fluid to be supplied into the cooling plates and discharged
therefrom; and supplying, after completion of diffusion bonding
between the heat exchange plates, the cooling fluid into the
cooling plates to decrease temperature of the heat exchange plates,
while keeping the vacuum state or the low pressure state in which
only the inner gas atmosphere exists.
12. The method as claimed in claim 3, further comprising the steps
of: holding the heat exchange plates as stacked, between cooling
plates in the stacking direction of the heat exchange plates, each
of the cooling plates being made of material, which does not
diffusion-bond to the heat exchange plates under diffusion bonding
conditions of the heat exchange plates, and having a hollow
structure, ensuring a state in which heat transfer occurs between
the cooling plates and the heat exchange plates, and connecting
cooling conduits to the cooling plates so as to enable cooling
fluid to be supplied into the cooling plates and discharged
therefrom; and supplying, after completion of diffusion bonding
between the heat exchange plates, the cooling fluid into the
cooling plates to decrease temperature of the heat exchange plates,
while keeping the vacuum state or the low pressure state in which
only the inner gas atmosphere exists.
13. The method as claimed in claim 4, further comprising the steps
of: holding the heat exchange plates as stacked, between cooling
plates in the stacking direction of the heat exchange plates, each
of the cooling plates being made of material, which does not
diffusion-bond to the heat exchange plates under diffusion bonding
conditions of the heat exchange plates, and having a hollow
structure, ensuring a state in which heat transfer occurs between
the cooling plates and the heat exchange plates, and connecting
cooling conduits to the cooling plates so as to enable cooling
fluid to be supplied into the cooling plates and discharged
therefrom; and supplying, after completion of diffusion bonding
between the heat exchange plates, the cooling fluid into the
cooling plates to decrease temperature of the heat exchange plates,
while keeping the vacuum state or the low pressure state in which
only the inner gas atmosphere exists.
14. The method as claimed in claim 5, further comprising the steps
of: holding the heat exchange plates as stacked, between cooling
plates in the stacking direction of the heat exchange plates, each
of the cooling plates being made of material, which does not
diffusion-bond to the heat exchange plates under diffusion bonding
conditions of the heat exchange plates, and having a hollow
structure, ensuring a state in which heat transfer occurs between
the cooling plates and the heat exchange plates, and connecting
cooling conduits to the cooling plates so as to enable cooling
fluid to be supplied into the cooling plates and discharged
therefrom; and supplying, after completion of diffusion bonding
between the heat exchange plates, the cooling fluid into the
cooling plates to decrease temperature of the heat exchange plates,
while keeping the vacuum state or the low pressure state in which
only the inner gas atmosphere exists.
15. The method as claimed in claim 6, further comprising the steps
of: holding the heat exchange plates as stacked, between cooling
plates in the stacking direction of the heat exchange plates, each
of the cooling plates being made of material, which does not
diffusion-bond to the heat exchange plates under diffusion bonding
conditions of the heat exchange plates, and having a hollow
structure, ensuring a state in which heat transfer occurs between
the cooling plates and the heat exchange plates, and connecting
cooling conduits to the cooling plates so as to enable cooling
fluid to be supplied into the cooling plates and discharged
therefrom; and supplying, after completion of diffusion bonding
between the heat exchange plates, the cooling fluid into the
cooling plates to decrease temperature of the heat exchange plates,
while keeping the vacuum state or the low pressure state in which
only the inner gas atmosphere exists.
16. The method as claimed in claim 7, further comprising the steps
of: holding the heat exchange plates as stacked, between cooling
plates in the stacking direction of the heat exchange plates, each
of the cooling plates being made of material, which does not
diffusion-bond to the heat exchange plates under diffusion bonding
conditions of the heat exchange plates, and having a hollow
structure, ensuring a state in which heat transfer occurs between
the cooling plates and the heat exchange plates, and connecting
cooling conduits to the cooling plates so as to enable cooling
fluid to be supplied into the cooling plates and discharged
therefrom; and supplying, after completion of diffusion bonding
between the heat exchange plates, the cooling fluid into the
cooling plates to decrease temperature of the heat exchange plates,
while keeping the vacuum state or the low pressure state in which
only the inner gas atmosphere exists.
17. The method as claimed in claim 8, further comprising the steps
of: holding the heat exchange plates as stacked, between cooling
plates in the stacking direction of the heat exchange plates, each
of the cooling plates being made of material, which does not
diffusion-bond to the heat exchange plates under diffusion bonding
conditions of the heat exchange plates, and having a hollow
structure, ensuring a state in which heat transfer occurs between
the cooling plates and the heat exchange plates, and connecting
cooling conduits to the cooling plates so as to enable cooling
fluid to be supplied into the cooling plates and discharged
therefrom; and supplying, after completion of diffusion bonding
between the heat exchange plates, the cooling fluid into the
cooling plates to decrease temperature of the heat exchange plates,
while keeping the vacuum state or the low pressure state in which
only the inner gas atmosphere exists.
18. The method as claimed in claim 9, further comprising the steps
of: holding the heat exchange plates as stacked, between cooling
plates in the stacking direction of the heat exchange plates, each
of the cooling plates being made of material, which does not
diffusion-bond to the heat exchange plates under diffusion bonding
conditions of the heat exchange plates, and having a hollow
structure, ensuring a state in which heat transfer occurs between
the cooling plates and the heat exchange plates, and connecting
cooling conduits to the cooling plates so as to enable cooling
fluid to be supplied into the cooling plates and discharged
therefrom; and supplying, after completion of diffusion bonding
between the heat exchange plates, the cooling fluid into the
cooling plates to decrease temperature of the heat exchange plates,
while keeping the vacuum state or the low pressure state in which
only the inner gas atmosphere exists.
19. The method as claimed in any one of claims 1 to 18, further
comprising the steps of: placing, during combining the heat
exchange plates together or in a combined state thereof, a spacer
between a pair of contact edges of the heat exchange plates and
another adjacent pair of contact edges thereof on opposite sides of
the combined heat exchange plates, to apply a uniform pressure to
the pairs of contact edges of the heat exchange plates, said spacer
being made of material, which does not diffusion-bond to the heat
exchange plates under diffusion bonding conditions of the heat
exchange plates.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates a method for manufacturing a
heat exchanger in which a plurality of heat exchange plates each
made of a thin metallic plate are combined in parallel and
integrally with each other, and especially to a method for
manufacturing such a heat exchanger in which the press-formed heat
exchange plates are placed one upon another and firmly combined
integrally with each other at contact portions thereof to provide
strength bearing a high pressure for the heat exchanger.
[0003] 2. Description of the Related Art
[0004] If there is a demand that heat transfer coefficient is
increased to enhance heat exchange efficiency, utilizing a heat
exchanger by which transfer of heat (i.e., heat exchange) is made
between a high temperature fluid and a low temperature fluid, a
plate-type heat exchanger has conventionally been used widely. The
plate-type heat exchanger has a structure in which a plurality of
heat transfer plates are placed parallelly one upon another at
prescribed intervals so as to form passages, which are separated by
means of the respective heat transfer plates. A high temperature
fluid and a low temperature fluid flow alternately in the
above-mentioned passages to make heat exchange through the
respective heat transfer plates.
[0005] In the conventional plate-type heat exchanger, gasket
members formed of elastic material are placed between the adjacent
two plates to make the distance between them constant and define
passages for fluid. However, a high pressure of the heat exchange
fluid flowing between the plates may cause deformation of the
gasket member, thus disabling an appropriate separation of the
fluids from being ensured or leading to an unfavorable variation in
distance between the plates. In such a case, an effective heat
exchange may not be carried out, thus causing a problem. In view of
these facts, the conventional heat exchanger involves a problem
that the heat exchange fluids can be utilized only in a pressure
range in which the gasket member withstands.
[0006] There has recently been proposed a heat exchanger having a
structure in which metallic thin plates, which are placed at
predetermined intervals, are joined together, without using any
gasket members, at their ends by welding to assemble the plates
into a single unit so as to form passages for heat exchange fluids,
on the opposite sides of the respective plates. Japanese Patent
Provisional Publication No. 2003-194490 describes such a kind of a
heat exchanger, as an example of an invention made by the present
inventor.
[0007] In most cases of the conventional heat exchangers utilizing
a bonding process such as a welding, the plates that are placed one
upon another are combined through a welding applied only to a
periphery of the plate, due to restriction of an operation such as
welding. As a result, difference in pressure between heat exchange
fluids flowing along the respective opposite surfaces of the plates
becomes larger, the distance between the adjacent plates at a
non-bonded portion such as a central portion may vary, not only
deteriorating heat exchange performance, but also leading to damage
of the heat exchanger. Therefore, such a heat exchanger may not be
used under a relatively high pressure condition.
[0008] There have been proposed other types of heat exchangers
utilizing diffusion bonding applied to all the contact portions of
the assembled plates. Japanese Patent Publication No. S54-18232 and
Japanese Patent Provisional Publication No. 2003-262489 disclose
such heat exchangers.
[0009] The conventional heat exchangers have structures as
described in the above-mentioned prior art documents. In the heat
exchangers as described in Japanese Patent Publication No.
S54-18232 and Japanese Patent Provisional Publication No.
2003-262489, the stacked plates are bonded at all the contact
portions, thus providing a high strength by which deformation of
the heat exchanger may not occur. However, in general, not only
heat, but also a high pressing force is applied to the stacked
plates in a vacuum vessel during the diffusion bonding.
Accordingly, Japanese Patent Publication No. S54-18232 uses a
combination of flat plates and corrugated plates having an
optimized shape preventing deformation even when a pressure is
applied. Japanese Patent Provisional Publication No. 2003-262489
uses plates having specific configurations, which are provided with
partition wall sections and flow control sections that are obtained
by subjecting the surface of the plate, serving as a heat transfer
section, to an etching or a machining process, or fixing partition
wall sections and flow control sections previously formed in
separate parts on a flat plate.
[0010] Therefore, it is difficult to apply the technique of the
heat exchanger described in Japanese Patent Publication No.
S54-18232 and Japanese Patent Provisional Publication No.
2003-262489 in which shapes of the plates serving as a primary part
of the heat exchanger is restricted, to the other type of heat
exchanger. This technique cannot be applied, without modification,
to bonding of the plates for the plate-type heat exchanger in which
all the press-formed plates are placed one upon another so that
projections of the adjacent plates come into contact with each
other, in the same manner as the heat exchanger described in
Japanese Patent Provisional Publication No. 2003-194490, due to
problems of deformation.
SUMMARY OF THE INVENTION
[0011] An object of the present invention, which was made to solve
the above-mentioned problems, is therefore to provide a method for
manufacturing a heat exchanger, in which heat exchange plates are
combined together by diffusion-bonding contact portions of heat
exchange plates that are caused by placing the plates one upon
another, to remarkably increase integrally bonded areas of the
adjacent plates, to substantially enhance a pressure proof strength
of the heat exchanger composed of the heat exchange plates, thus
permitting application to various types of heat exchange.
[0012] In order to attain the aforementioned object, a method of
the first aspect of the present invention for manufacturing a heat
exchanger, comprises the steps of: placing a plurality of heat
exchange plates one upon another, each of which is formed of a
metallic plate member having a predetermined pattern of
irregularity and combining the plates into a heat exchanger, in
which each of the heat exchange plates is formed into a
predetermined shape by a press-forming process so that each of the
heat exchange plates includes on at least part thereof a heat
transfer section having the pattern of irregularity and first and
second opposite surfaces with which first and second heat exchange
fluids come into contact, respectively, the heat exchange plates as
combined come into contact with each other on at least one part of
peripheries thereof, and first gap portions through which the first
heat exchange fluid is to pass and second gap portions through
which the second heat exchange fluid is to pass are provided
alternately between the heat exchange plates, wherein, the method
further comprises the steps of: placing a predetermined number of
the heat exchange plates one upon another to apply a pressing force
to the heat exchange plates in a stacking direction thereof to an
extent that at least parallelism of the heat exchange plates as
placed is maintained and the heat exchange plates are not
plastically deformed even when a temperature thereof increases to a
predetermined temperature at which a diffusion bonding associated
with material of the heat exchange plates occurs, maintaining such
a stacking condition and bringing adjacent plates at projections
and peripheral edges that protrude from the heat exchange plates
into contact with each other; and putting space surrounding at
least contact portions of the plates in a vacuum state or a low
pressure state in which only an inner gas atmosphere exists,
keeping the plates at a predetermined temperature at which the
diffusion bonding occurs by a predetermined period of time and
diffusion-bonding portions of the plates, which are only brought
into contact with each other and have not been bonded together.
[0013] According to the first aspect of the present invention, the
heat exchange plates are placed one upon another and a minimum
pressure is applied to the stacked plates only in the stacking
direction, to ensure a contact state at positions where the
adjacent plates should come into contact with each other, and the
stacked plates are put in a temperature condition and an
atmospheric condition under which diffusion bonding of metal of
which the plates are made, appropriately progresses, to bond the
adjacent plates together at a plurality of contact portions thereof
by diffusion bonding. It is therefore possible to manufacture the
heat exchanger in which the stacked plates are combined firmly
together not only at the peripheral edges of the plates, but also
at a large number of contact portions thereof, by using normal heat
exchange plates obtained by a press-forming process, without
impairment of the press-formed shapes of the plates. Accordingly, a
pressure proof strength for each part of the heat exchanger can be
substantially enhanced to permit increase in pressure of a heat
exchange fluid as introduced or increase in difference in pressure
between the heat exchange fluids, thus making it possible to set
appropriate conditions under which an effective heat exchange is
made. A high performance heat exchanger can therefore be
provided.
[0014] In the second aspect of the method of the present invention
for manufacturing the heat exchanger, the method may further
comprise the steps of: welding, at a stage of the step of placing
the heat exchange plates one upon another, the adjacent plates at
the peripheral edges thereof to form a welded assembly in which no
variation in a positional relationship between the plates occurs;
and placing the welded assembly in a vacuum state or a low pressure
state in which only an inner gas atmosphere exists, keeping the
plates at a predetermined temperature at which the diffusion
bonding occurs by a predetermined period of time and diffusion
bonding portions of the plates, which are only brought into contact
with each other and have not been bonded together.
[0015] According to the second aspect of the present invention, the
stacked heat exchange plates are previously welded at the
peripheral edges of the plates to prepare a welded assembly and
then the welded assembly are bonded together by diffusion bonding
at portions thereof, which are brought into contact with each other
and have not been bonded together. The plates can therefore be
previously combined into the welded assembly, prior to the
diffusion bonding, to ensure an appropriate stacking state of the
plates so that the welded assembly can be easily handled. This step
may be applied as a subsequent step in the conventional method of
manufacturing a heat exchanger in which only peripheral edges of
plates are welded together, thus enabling the plates as combined in
accordance with the conventional method of a heat exchanger to be
more firmly combined together. Therefore, a pressure proof strength
can be substantially enhanced to permit to introduce a high
pressure heat exchange fluid into a gap between the adjacent
plates. As a result, a heat exchange efficiency can be improved in
accordance with various types of heat exchange conditions.
[0016] In the third aspect of the method of the present invention
for manufacturing the heat exchanger, the step of welding the heat
exchange plates may be carried out to combine the plates into the
welded assembly so that each of the first and second gap portions
is isolated from outside, excluding first fluid inlet and outlet
portions communicating with the first gap portion and second fluid
inlet and outlet portions communicating with the second gap
portion, and the method may further comprises the steps of:
connecting first supply/discharge conduits, which permit supply of
a fluid into the first gap portion and/or discharge of the fluid
therefrom, to the first inlet and out let portions, and connecting
second supply/discharge conduits, which permit supply of a fluid
into the second gap portion and/or discharge of the fluid
therefrom; removing a gas from the first gap portion through the
first supply/discharge conduits to provide the vacuum state therein
or supplying an inert gas into the first gap portion while removing
a gas therein, through the first supply/discharge conduits, to
provide the low pressure state, and supplying an inert gas having a
predetermined high temperature and a predetermined pressure into
the second gap portion while removing a gas therein, through the
second supply/discharge conduits, to provide a higher pressure
state than the first gap portion, and then keeping the contact
portions of the projections, which are placed in the heat transfer
section of each of the plates and exist in the first gap portion,
at the predetermined temperature at which the diffusion bonding
occurs by the predetermined period of time and diffusion-bonding
the contact portions of the plates; and then, removing a gas from
the second gap portion through the second supply/discharge conduits
to provide the vacuum state therein or supplying an inert gas into
the second gap portion while removing a gas therein, through the
second supply/discharge conduits, to provide the low pressure
state, and supplying an inert gas having a predetermined high
temperature and a predetermined pressure into the first gap portion
while removing a gas therein, through the first supply/discharge
conduits, to provide a higher pressure state than the second gap
portion, and then keeping the contact portions of the projections,
which are placed in the heat transfer section of each of the plates
and exist in the second gap portion, at the predetermined
temperature at which the diffusion bonding occurs by the
predetermined period of time and diffusion-bonding the contact
portions of the plates.
[0017] According to the third aspect of the present invention, the
gap portion including portions of the plates to be diffusion-bonded
is put in the vacuum state or the low pressure state in which only
the inner gas atmosphere exists, and the inert gas having a high
temperature is introduced into the adjacent gap portion, which is
placed on the opposite side to the above-mentioned gap portion
relative to the portions of the plates to be diffusion-bonded, to
provide a state in which diffusion bonding easily occurs at the
contact portions of the plates. After completion of the diffusion
bonding of the contact portions, the same process environment
conditions are applied to the other gap portion and the contact
portions of the plates are diffusion-bonded together in the other
gap portion, with the result that substantially the equal pressing
force is applied to the contact portions of the plates due to
difference in pressure between the adjacent gap portions, thus
complementing the contact pressure applied to the contact portions
of the plates. Appropriate contact areas of the plates can
therefore be ensured, irrespective of a pattern of irregularity of
the plates to permit to carry out effectively the diffusion
bonding. Putting only one of the adjacent gap portions in the
vacuum or low pressure state suffices, when carrying out the
diffusion bonding, with the result that a space to be subjected to
a degassing process to provide the vacuum state may be reduced to
reduce a pump load, thus controlling energy consumption required to
carry out the diffusion bonding and reducing manufacturing costs of
the heat exchanger.
[0018] In the fourth aspect of the method of the present invention
for manufacturing the heat exchanger, the method may further
comprise the steps of: placing the heat exchange plates as
combined, in a vessel that is flexibly deformable at least in the
stacking direction of the plates and has air inlet and outlet
portions, the vessel providing an air-tight property, excluding the
air inlet and outlet portions; applying the pressing force to the
plates in the stacking direction thereof and discharging a gas in
the vessel through the air inlet and outlet portions; and then
closing the air inlet and outlet portions to keep an inside of the
vessel, which includes the space surrounding the contact portions
of the plates, in the vacuum state or the low pressure state.
[0019] According to the fourth aspect of the present invention, the
stacked heat exchange plates are received in the flexibly
deformable vessel so that an internal space of the vessel is put
into the vacuum or low pressure state by removing a gas from the
vessel. The vessel is flexibly deformed and puts the space
surrounding the contact portions of the plates in the vacuum or low
pressure state, thus enhancing reliability of the diffusion bonding
and providing an improved contact of the plates.
[0020] In the fifth aspect of the method of the present invention
for manufacturing the heat exchanger, the method may comprise the
steps of: causing the heat exchange plate placed on one end side in
the stacking direction of the heat exchange plates as combined to
be electrically connectable to one electrode of an electric power
supply for heating through current application, and causing the
heat exchange plate placed on another end side in the stacking
direction thereof to be electrically connectable to another
electrode of the electric power supply; and applying electric
current to the plates placed on the opposite end sides in the
stacking direction of the plates to pass a current through all the
heat exchange plates, while keeping the space surrounding at least
the contact portions of the plates in the vacuum state or the low
pressure state, keeping the plates at a predetermined temperature
at which the diffusion bonding occurs through heating through
current application by a predetermined period of time and
diffusion-bonding the portions of the plates, which are only
brought into contact with each other and have not been bonded
together.
[0021] According to the fifth aspect of the present invention, the
electric current is applied to the stacked heat exchange plates to
directly increase a temperature of the plates by Joule heat to
provide an appropriate temperature at which the diffusion bonding
properly occurs. There is no need to increase the temperature of
the entire space in which the diffusion bonding occurs, so as to
heat the plates. Energy consumption required to carry out the
diffusion bonding is controlled and manufacturing costs of the heat
exchanger is reduced.
[0022] In the sixth aspect of the method of the present invention
for manufacturing the heat exchanger, the method may comprise the
steps of: holding the heat exchange plates as combined, between
cooling plates in the stacking direction of the heat exchange
plates, each of the cooling plates being made of material, which
does not diffusion-bond to the heat exchange plates under diffusion
bonding conditions of the heat exchange plates, and having a hollow
structure, ensuring a state in which heat transfer occurs between
the cooling plates and the heat exchange plates, and connecting
cooling conduits to the cooling plates so as to enable cooling
fluid to be supplied into the cooling plates and discharged
therefrom; and supplying, after completion of diffusion bonding
between the heat exchange plates, the cooling fluid into the
cooling plates to decrease temperature of the heat exchange plates,
while keeping the vacuum state or the low pressure state in which
only the inner gas atmosphere exists.
[0023] According to the sixth aspect of the present invention, the
heat exchange plates as stacked are held between the cooling plates
in the stacking direction of the heat exchange plates, and the
cooling fluid is supplied, after completion of the diffusion
bonding, into the cooling plates to cool the cooling plates so that
the combined heat exchange plates can rapidly be cooled. It is
therefore possible to shorten a period of time, as small as
possible, when the plates as combined are kept, after completion of
the diffusion bonding, in a high temperature state which may change
characteristic properties of the plate material. Therefore, the
temperature of the plates can be reduced to a room temperature
without causing unnecessary change in characteristic properties of
the plates, thus permitting to manufacture the heat exchanger
having no defects and stable performance at a short period of
time.
[0024] In the seventh aspect of the method of the present invention
for manufacturing the heat exchanger, the method may comprise the
steps of: placing, during combining the heat exchange plates
together or in a combined state thereof, a spacer between a pair of
contact edges of the heat exchange plates and another adjacent pair
of contact edges thereof on opposite sides of the combined heat
exchange plates, to apply a uniform pressure to the pairs of
contact edges of the heat exchange plates.
[0025] According to the seventh aspect of the present invention,
the spacer is placed between the pair of contact edges of the heat
exchange plates and the other adjacent pair of contact edges
thereof on the opposite sides of the combined heat exchange plates,
to apply a uniform pressure to the pairs of contact edges of the
heat exchange plates, so that the pairs of contact edges of the
plates are restricted by means of the spacers. The spacer as placed
in this manner provide the adjacent pairs of contact edges of the
plates with no space where the contact edges may be deformed, thus
preventing the contact edges from being inappropriately deformed,
even when increase in a temperature of the plates during the
diffusion bonding puts parts of the plates in an annealing
condition, thus causing unfavorable deformation of the edges of the
plates. Therefore, an appropriate contact state of the adjacent
plates can be ensured to cause the diffusion bonding to
appropriately progress.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a schematic structural view of a plate assembly
manufacture in accordance with a heat exchanger manufacturing
method according to the first embodiment of the present
invention;
[0027] FIGS. 2(A) and 2(B) are descriptive views illustrating a
stacking state of heat exchange plates in the heat exchanger
manufacturing method according to the first embodiment of the
present invention;
[0028] FIG. 3 is a descriptive view illustrating a placing state of
cover plates in the heat exchanger manufacturing method according
to the first embodiment of the present invention;
[0029] FIG. 4 is a descriptive view illustrating a placing state of
cooling plates in the heat exchanger manufacturing method according
to the first embodiment of the present invention;
[0030] FIG. 5 is a descriptive view illustrating a state in which
the cooling plates and the heat exchange plates are combined
together, in the heat exchanger manufacturing method according to
the first embodiment of the present invention;
[0031] FIG. 6 is a descriptive view illustrating a state in which
the heat exchange plates are received in a vessel for bonding the
plates, in the heat exchanger manufacturing method according to the
first embodiment of the present invention;
[0032] FIG. 7 is a descriptive view illustrating an inside of the
vessel for bonding the plates during a diffusion bonding process,
in the heat exchanger manufacturing method according to the first
embodiment of the present invention;
[0033] FIGS. 8(A) and 8(B) are descriptive views illustrating a
diffusion bonding state of the plates, in the heat exchanger
manufacturing method according to the first embodiment of the
present invention;
[0034] FIGS. 9(A), 9(B) and 9(C) are descriptive views illustrating
a stacking state of the heat exchange plates in the heat exchanger
manufacturing method according to the second embodiment of the
present invention;
[0035] FIG. 10 is a descriptive view illustrating the inside of the
vessel for bonding the plates during the diffusion bonding process,
in the heat exchanger manufacturing method according to the second
embodiment of the present invention;
[0036] FIGS. 11(A), 11(B) and 11(C) are descriptive views
illustrating the diffusion bonding state of the plates, in the heat
exchanger manufacturing method according to the second embodiment
of the present invention; and
[0037] FIG. 12 is a descriptive view illustrating a state in which
the heat exchange plates manufactured by the method according to
the other embodiment of the present invention are received in a
vessel.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment of the Present Invention
[0038] Now, the first embodiment of the present invention will be
described in detail below with reference to FIGS. 1 to 8. FIG. 1 is
a schematic structural view of a plate assembly manufacture in
accordance with a heat exchanger manufacturing method according to
the first embodiment of the present invention; FIGS. 2(A) and 2(B)
are descriptive views illustrating a stacking state of heat
exchange plates in the heat exchanger manufacturing method
according to the first embodiment of the present invention; FIG. 3
is a descriptive view illustrating a placing state of cover plates
in the heat exchanger manufacturing method according to the first
embodiment of the present invention; FIG. 4 is a descriptive view
illustrating a placing state of cooling plates in the heat
exchanger manufacturing method according to the first embodiment of
the present invention; FIG. 5 is a descriptive view illustrating a
state in which the cooling plates and the heat exchange plates are
combined together, in the heat exchanger manufacturing method
according to the first embodiment of the present invention; FIG. 6
is a descriptive view illustrating a state in which the heat
exchange plates are received in a vessel for bonding the plates, in
the heat exchanger manufacturing method according to the first
embodiment of the present invention; FIG. 7 is a descriptive view
illustrating an inside of the vessel for bonding the plates during
a diffusion bonding process, in the heat exchanger manufacturing
method according to the first embodiment of the present invention;
and FIGS. 8(A) and 8(B) are descriptive views illustrating a
diffusion bonding state of the plates, in the heat exchanger
manufacturing method according to the first embodiment of the
present invention.
[0039] As shown in the above-mentioned figures, the method
according to the first embodiment of the present invention for
manufacturing a heat exchanger comprises placing a plurality of
heat exchange plates 10, which are formed of a metallic plate
member having a rectangular shape, one upon another to prepare a
set of stacked plates 10, disposing a cover plate 18 and a cooling
plate 19 on the opposite outermost plates 10, respectively, putting
the stacked plates 10 and the cover plate 18 and the cooling plate
19 in such a stacked state, into a bonding vessel 60 that provides
a bonding space, increasing a temperature of each of the plates to
a diffusion temperature to diffusion-bond the plates at the entire
contacting areas, thus manufacturing a united body 17 in which the
plates are firmly bonded together at many contacting areas.
[0040] The heat exchange plate 10 has a structure in which a heat
transfer section 11 having a pattern of irregularity is formed on
the central portion of a rectangular metallic thin sheet and
flanges 12 are formed in the periphery of the plate so as to
surround the heat transfer section 11, utilizing a prescribed
press-forming device (not shown).
[0041] The heat transfer section 11 is a region, which has the
optimized pattern of irregularities, so that a high temperature
heat exchange fluid (i.e., the first heat exchange fluid) is to
come into contact with one surface of the heat transfer section 11
and a low temperature heat exchange fluid (i.e., the second heat
exchange fluid) is to come into contact with the other surface
thereof, in order to make heat exchange, and more specifically has
a plurality of projections 13 that are placed in a predetermined
arrangement on a surface of the metallic plate and a plurality of
recesses 14 each of which is placed between the projections 13 on
the surface of the metallic plate so as to dent in an opposite
direction to a protruding direction of the projections 13.
[0042] The pattern of irregularity of the heat transfer section 11
is symmetric in a positional relationship between the projections
and the recesses with respect to the center of the vertical
direction (i.e., the longitudinal direction) of the plate. When the
heat exchange plate 10 is placed on the other heat exchange plate
having the same configuration so that the inner surfaces of them
face each other and the latter is positioned upside down, the
projections and recesses of the former coincide with those of the
latter, respectively, and the projections of the central pattern
portion and the projections of the boundary pattern portion of the
one heat transfer member come into close contact with those of the
other heat transfer member, respectively. The pattern of
irregularities has a known wave-shaped cross section, which
provides an excellent heat transfer property and groove portions
through which condensed water can be discharged rapidly. The
above-mentioned wave-shaped cross section and the groove portions
are known and description of them will be omitted.
[0043] The projections 13 and recesses 14, which formed on the
upper surface of the heat transfer section 11, form recess-portions
and projection-portions on the lower surface of the heat transfer
section 11, respectively. The upper surface configuration of the
heat transfer section 11 including the recesses 14 and the lower
surface configuration thereof including the recess-portions
corresponding to the projections 13 may be symmetric so as to
provide the same configuration each other, and the upper surface
configuration of the heat transfer section 11 including the
projections 13 and the lower surface configuration thereof
including the projection-portions corresponding to the recesses 14
may be symmetric so as to provide the same configuration. To the
contrary, the upper and lower surface configurations of the heat
transfer section 11 may be asymmetric so as to provide the
different configurations from each other. Determination of use of
which type of the heat transfer section configuration depends upon
conditions of heat exchange as actually applied.
[0044] The flange 12 is composed of flat portions 12a, which are
disposed continuously along two sides of the periphery of a
rectangular shape and bulge portions 12b continuously extending
from the heat transfer section 11 along the other two sides. When
the plates are placed in parallel one upon another, the adjacent
two plates come into contact with each other at their flat portions
and bulge portions. In such a state, the non-contact portions of
these two plates define openings, which communicate with gap
portions 30, 40 formed between the plates.
[0045] When the heat exchange plates 10 are placed in parallel one
upon another, there are provided alternately, between the heat
transfer sections 11 thereof, the first gap portions 30 through
which the first heat exchange fluid flows and the second gap
portions 40 through which the second heat exchange fluid flows. A
set of the heat exchange plates 10 thus stacked is provided on the
opposite longer sides thereof with the first openings 31 for
causing the first heat exchange fluid to flow in and from the first
gap portions 30, on the one hand, and on the opposite shorter sides
thereof with the second openings 41 for causing the second heat
exchange fluid to flow in and from the second gap portions 40, on
the other hand. The positions of the first and second openings 31,
41 may be optionally set by changing the positional relationship
between the flat portions 12a and the projections 12b of the flange
12. After joining the plates at the flanges 12, the first and
second gap portions are completely separated from each other in a
water-tight manner except for the first and second openings 31,
41.
[0046] The cover plate 18 serves as an outer shell of the heat
exchanger and is made of a metallic thick plate having a sufficient
strength.
[0047] The cooling plate 19 is made of a thick plate so as to
provide a hollow portion through which cooling water serving as a
cooling medium flows and a sufficient strength preventing
deformation thereof. The cooling plate 19 serves as a guide member
which is fastened by bolts 19a to prevent deformation and deviation
of the heat exchange plates 10.
[0048] Now, description will be given below of manufacturing steps
of the heat exchanger manufacturing method of the first embodiment
of the present invention. On the assumption that the heat exchange
plates 10 are made of titanium and in previous steps prior to the
manufacturing steps as mentioned above, the titanium thin plates
are subjected to a press-forming process utilizing a press forming
device, and the heat exchange plates thus press-formed are
transferred to stages for the manufacturing steps as mentioned
above. The recess portions on the lower surface of the plate, which
correspond to the projections 13 on the upper surface thereof, has
the same shape as that of the recesses 14 on the upper surface of
the plate, and the projections portions on the lower surface of the
plate, which correspond to the recesses 14 on the upper surface
thereof, has the same shape as that of the projections 13 on the
upper surface of the plate.
[0049] First, the heat exchange plate 10 is placed on the other
heat exchange plate 10 with the upper surfaces thereof brought into
contact with each other to prepare a first-stage combination of
plates. Then, the other pair of heat exchange plates 10 are placed
on the opposite sides of the basic combination of plates with the
lower surfaces thereof brought into contact with each other to
prepare a second-stage combination of plates. The, further other
pair of heat exchange plates 10 are placed on the opposite sides of
the second-stage combination of plates with the upper surfaces
thereof brought into contact with each other to prepare a
third-stage combination of plates. Such a combination step is
repeated. In such steps, the heat exchange plate 10 to be stacked
for example in the third-stage combination step is placed on the
other heat exchange plate 10 as already placed in accordance with
the second-stage combination step so that the inner surface of the
heat exchange plate 10 in the third-stage combination step face the
outer surface of the heat exchange plate 10 in the second-stage
combination step and the latter is positioned upside down, but the
inner surface of the heat exchange plate 10 in the third-stage
combination step face the inner surface of the heat exchange plate
10 in the first-stage combination step and these plates have the
same configuration orientation. A predetermined number of plates
are stacked while placing the alternate plates upside down and
turning them inside out.
[0050] During combining the heat exchange plates 10 together, a
spacer 16 that is made of material, which does not diffusion-bond
to the heat exchange plates under diffusion bonding conditions of
the heat exchange plates, is placed in a space between the flat
portion 12a of the flange 12 of the heat exchange plate 10 and the
flat portion 12a of the flange 12 of the adjacent heat exchange
plate 10 to apply a uniform pressure to the opposing surfaces of
the flat portions 12a of the heat exchange plates 10, even when
increase in a temperature of the plates during the diffusion
bonding puts the flat portions 12a of the plates in an annealing
condition, thus causing unfavorable deformation of the flat
portions 12a of the plates. Therefore, an appropriate contact state
of the flat portions 12a of the adjacent plates can be ensured to
cause the diffusion bonding to appropriately progress. The spacers
may be inserted into the spaces between the flat portions of the
heat exchange plates 10, after completion of the combining steps of
the plates 10.
[0051] In the adjacent heat exchange plates 10 thus stacked, the
flanges 12 come into contact with each other at the flat portions
12a or the bulge portions 12b, and the projections 13 on the heat
transfer sections 11 of the adjacent heat exchange plates 10 come
into contact with each other. Such a contact state of the heat
exchange plates 10 causes the heat exchange plates 10 to be placed
apart from each other by a predetermined distance, excepting the
contact areas.
[0052] In the heat exchange plates 10 thus stacked, a gap between
the heat transfer sections 11 of the upper surfaces of the adjacent
heat exchange plates 10 serves as the first gap portion 30 and a
gap between the bulge portions 12b of the flange 12 at the edge of
the longitudinal side (i.e., the respective short side) serves as
the first opening 31 communicating with the above-mentioned first
gap portion 30 (see FIG. 1).
[0053] In the heat exchange plates 10 thus stacked, a gap between
the heat transfer sections 11 of the lower surfaces of the adjacent
heat exchange plates 10 serves as the second gap portion 40 and a
gap (in which the spacer 16 is placed) between the flat portions
12a of the flange 12 at the edge of the transverse side (i.e., the
respective long side) serves as the second opening 41 communicating
with the above-mentioned second gap portion 40 (see FIG. 1).
[0054] After a predetermined number of the heat exchange plates 10
is stacked into a plate assembly 17, the cover plate 18 is placed
on each end of the plate assembly 17 in the stacking direction, and
the cooling plate 19 is placed on the outer surface of the
respective cover plate 18. The cooling plates 19 are fastened
together with the use of bolts 19a and nuts 19b. A relatively weak
pressing force (a maintaining force) is applied to the plates in
the direction of the normal to the plates, thus maintaining
parallelism thereof. The pressing force is set as a smaller
pressure (in case of titanium, about 0.5 MPa) to an extent that
plastic deformation does not occur even when the temperature of the
heat exchange plate 10, which has once been subjected to the press
formation process, increases to a predetermined temperature at
which diffusion bonding peculiar to the material of the plate
occurs (in case of titanium, from about 800.degree. C. to about
900.degree. C.). Accordingly, the diffusion bonding causes no
damage to the press-formed shape of the heat exchange plate 10. The
pressure applied to the plate is adjusted by tightening torque of
the bolts 19a and the nuts 19b.
[0055] In addition, a conduit 19c having a tubular shape is
connected to each of the cooling plate 19 so that the cooling water
flows therein. The heat exchange plate 10, which is placed on the
one end side in the stacking direction of the heat exchange plates,
and the cover plate 18, which comes into contact with this heat
exchange plate 10 are connected to one of the terminals of an
electric power supply (not shown), and the heat exchange plate 10,
which is placed on the other end side in the stacking direction of
the heat exchange plates, and the cover plate 18, which comes into
contact with this heat exchange plate 10 are connected to the other
of the terminals of an electric power supply so that electric
current can be applied to all the heat exchange plates 10 through
their contact areas. The heat exchange plates 10 and the other
components attached thereto are received in a diffusion bonding
vessel 60, which can provide a vacuum state in which air is removed
from an internal space that can be separated from an open air, or a
low pressure state in which only an inner gas atmosphere exists.
Then, the inner space of the vessel is separated from the open air,
and pressure in the vessel is reduced to remove air from the inner
space thereof and each gap portions between the plates to provide
the vacuum state or an inert gas such as argon gas is supplied into
the inner space of the vessel during the pressure reducing
operation to substitute the inert gas for the air, while
maintaining a communicating condition of the above-mentioned
conduit 19c with the open air and a connecting condition of the
plates with feeding wires 15 of the electric power source.
[0056] When the electric power source is turned on in such a state
to apply an electric current through the feeding wires 15 to the
stacked plates, Joule heat is generated directly from the plates
themselves to provide an electric current application-heating state
in which the plates are heated. The temperature of the contact
areas including the projections 13, which projects from the plates,
is increased to reach the predetermined temperature (in case of
titanium, from about 800.degree. C. to about 900.degree. C.) at
which the diffusion bonding occurs. The plates, which come into
contact with each other by a predetermined pressure caused by the
bolts and nuts, are kept at the above-mentioned temperature for
about one hour, to diffusion-bond the contact areas of the plates
into a united body. The plates come into contact with each other at
the small areas including the projections 13, etc., during the
diffusion bonding operation. As a result, contact pressure between
the plates is relatively high to provide an appropriate contact
state of the plates, thus permitting progress of the diffusion
bonding at the contact areas of the plates, without causing any
problems.
[0057] A force required to plastically deform the plates is
gradually decreased, and in other words, the plates becomes apt to
be plastically deformable, along with temperature increase of the
plates prior to the diffusion bonding. However, the pressure by
which the plates as stacked and fastened are pressed each other is
set to be small to an extent that the plates are not plastically
deformed, even when the plates are placed at the predetermined
temperature at which the diffusion bonding occurs. Therefore, there
is no variation in shape of the plates and an appropriate contact
state in which the adjacent plates come into contact with each
other can be maintained.
[0058] After completion of the diffusion bonding of the heat
exchange plates 10 at the contact areas thereof, the heating step
by applying the electric current is stopped, and the cooling water
is supplied into the hollow portions of the cooling plates 19 to
cool rapidly the heat exchange plates 10 as bonded, from the
outside thereof. After the temperature of the plates decreases to a
temperature which has no influence on characteristic properties of
the plates, even when they come into contact with air, the internal
space and the gap portions between the plates are restored from the
vacuum state or the low pressure state to the original state prior
to the pressure reducing operation. Then, the united plate assembly
17 composed of the heat exchange plates 10 is taken out from the
diffusion bonding vessel 60. All the spacers 16 are removed from
the spaces between the flat portions 12a of the flange 12 of the
plates. The manufacturing steps are completed in this manner.
[0059] In the united plate assembly 17 into which the heat exchange
plates 10 are combined together by the diffusion bonding process,
the plates are integrally connected with each other at the edges of
the plates and the contact areas of the projections 13 of the heat
transfer section 11, excepting the openings 31, 41, through the
diffusion bonding process, thus providing an extremely high bonding
strength of the plates 10. It is therefore possible to make heat
exchange between the first and second heat exchange fluids without
causing deformation of the plates 10, even when the heat exchange
fluids having a high pressure are used or there is a large
difference in pressure between the first and second heat exchange
fluids.
[0060] According to the first embodiment of the present invention,
the heat exchange plates 10 are placed one upon another and the
minimum pressure is applied to the stacked plates 10 only in the
stacking direction, to ensure a contact state at positions where
the adjacent plates should come into contact with each other, and
the stacked plates are put in the temperature condition and the
atmospheric condition under which the diffusion bonding of metal of
which the plates are made, appropriately progresses, to bond the
adjacent plates together at a plurality of contact portions thereof
by the diffusion bonding. It is therefore possible to manufacture
the heat exchanger in which the stacked plates 10 are combined
firmly together not only at the peripheral edges of the plates, but
also at a large number of contact portions thereof, by using normal
heat exchange plates obtained by a press-forming process, without
impairment of the press-formed shapes of the plates. Accordingly, a
pressure proof strength for each part of the heat exchanger can be
substantially enhanced to permit increase in pressure of the heat
exchange fluid as introduced or increase in difference in pressure
between the heat exchange fluids, thus making it possible to set
appropriate conditions under which an effective heat exchange is
made. A high performance heat exchanger can therefore be
provided.
[0061] In the first embodiment as described above of the present
invention, the cooling water is supplied into the cooling plate 19
only when cooling the plates after completion of the diffusion
bonding process. However, the present invention is not limited only
to such an embodiment. In case where the electric current is
applied to the heat exchange plate 10 through the cooling plates 19
and the cover plates 18, and in other words, the electric current
is applied also to the cooling plates 19 and the cover plates 18 to
generate Joule heat therefrom, the cooling water may be supplied
into the cooling plates 19 even during application of the electric
current to the heat exchange plates 10. This makes it possible to
cool the cooling plates 19, while applying the electric current to
the plates during the diffusion bonding, to prevent variation in
shape (i.e., a warp) of the cooling plates 19 and the cover plates
18 and to maintain a proper positional relationship among the
cooling plates 19, the cover plates 18 and the plates 10 placed
between them, thus preventing adverse effects in the bonding of the
plates 10. The spacer 16 may have a hollow structure through which
a cooling water flows to cool the plates in cooperation with the
cooling plates 19.
Second Embodiment of the Present Invention
[0062] Now, the second embodiment of the present invention will be
described in detail below with reference to FIGS. 9(A) to 11(C).
FIGS. 9(A), 9(B) and 9(C) are descriptive views illustrating a
stacking state of the heat exchange plates in the heat exchanger
manufacturing method according to the second embodiment of the
present invention, FIG. 10 is a descriptive view illustrating the
inside of the vessel for bonding the plates during the diffusion
bonding process, in the heat exchanger manufacturing method
according to the second embodiment of the present invention, and
FIGS. 11(A), 11(B) and 11(C) are descriptive views illustrating the
diffusion bonding state of the plates, in the heat exchanger
manufacturing method according to the second embodiment of the
present invention.
[0063] The second embodiment of the present invention is the same
as the first embodiment of the present invention in that the
stacked heat exchange plates 20, the cover plates 28 and the
cooling plates 29 are received in the diffusion bonding vessel 60
and they are bonded together at the contact areas by the diffusion
bonding process, but the former is different from the latter in
that the united plate assembly 27, which has previously been
prepared by welding the heat exchange plates 20 at the edges
thereof, is received in the fusion bonding vessel, and a heating
step is applied to the plates in a high temperature atmosphere to
diffusion bond the plates at the contact areas of the projections
of the heat transfer sections 21, which are placed in the center of
the respective plate.
[0064] The heat exchange plate 20 has a structure in which a heat
transfer section 21 having a pattern of irregularity is formed on
the central portion of a rectangular metallic thin sheet and
flanges 22 are formed in the periphery of the plate so as to
surround the heat transfer section 21, utilizing a prescribed
press-forming device (not shown), in the same manner as the first
embodiment of the present invention. The heat transfer section 21
and the flange 22 are the same in shape and structure as those of
the first embodiment of the present invention. Description of them
is therefore omitted.
[0065] When the heat exchange plates 20 are placed in parallel one
upon another, there are provided alternately, between the heat
transfer sections 21 thereof, the first gap portions 30 through
which the first heat exchange fluid flows and the second gap
portions 40 through which the second heat exchange fluid flows. A
set of the heat exchange plates 20 thus stacked is provided on the
opposite longer sides thereof with the first openings 31 for
causing the first heat exchange fluid to flow in and from the first
gap portions 30, on the one hand, and on the opposite shorter sides
thereof with the second openings 41 for causing the second heat
exchange fluid to flow in and from the second gap portions 40, on
the other hand.
[0066] Now, description will be given below of manufacturing steps
of the heat exchanger manufacturing method of the second embodiment
of the present invention. On the assumption that in previous steps
prior to the manufacturing steps as mentioned above, the thin
plates are subjected to a press-forming process utilizing a press
forming device, and the heat exchange plates 20 thus press-formed
are transferred to stages for the manufacturing steps as mentioned
above.
[0067] The heat exchange plate 20 is placed on the other heat
exchange plate 20, which has been prepared through the same steps
for the former plate, with the former plate placed upside down and
turned inside out. These plates come into contact with each other
not only at the flat portions 22a of the flanges 22 thereof, but
also at the projections on their heat transfer sections 21, thus
providing a predetermined gap between them, except for these
contact areas. These two heat exchange plates 20 thus stacked are
welded together at parts of the flat portions 22a of the flanges 22
to prepare a pair of welded plates 26. A gap between these two heat
exchange plates 20 of which the pair of welded plates 26 is
composed serves as the first gap portion 30, and another gap
between the bulge portions 22b of the flanges 22 of the plate on
the shorter sides thereof serves as the first opening 31, which
communicates with the above-mentioned first gap portion 30.
[0068] The pair of welded plates 26 is placed on the other pair of
welded plates 26, which has been prepared through the same steps
for the former, so that these pairs of welded plates 26 come into
contact with each other not only at the bulge portions 22b of the
flanges 22 of the heat exchange plates 20, but also at the
projections of the heat transfer sections 21, and these pairs of
welded plates 26 are apart from each other by a predetermined
distance at the other areas than the contact areas.
[0069] These stacked pairs of welded plates 26 are welded together
at the edges of the bulge portions 22b of the adjacent heat
exchange plates 20 into a united body. In such a united body of the
welded plates 26, a gap between the pair of welded plates 26 and
the other pair of welded plates 26 serves as the second gap portion
40, and a gap between the flat portions 22a of the flanges 22,
which are not brought into contact with each other, serves as the
second opening 41, which communicates with the above-mentioned
second gap portion 40. The same step of welding the two pairs of
the welded plates 26 is repeated for a required pairs of the welded
plates 26 to prepare a united plate assembly 27.
[0070] After completion of preparing the united plate assembly 27,
the cover plate 28 is placed on each end of the plate assembly 27
in the stacking direction, and the cooling plate 29 is placed on
the outer surface of the respective cover plate 28. The cooling
plates 29 are fastened together with the use of bolts and nuts. A
relatively weak pressing force (a maintaining force) is applied to
the plates in the direction of the normal to the plates, thus
maintaining parallelism thereof.
[0071] In addition, a conduit 29c having a tubular shape is
connected to each of the cooling plate 29 so that the cooling water
flows therein. Conduits 71, 72 for pressure reduction/increase and
gas supply/discharge for the first gap portions 30 and the second
gap portions 40 are connected to the first opening 31 and the
second opening 41. The united plate assembly 27 and the other
components attached thereto are received in a diffusion bonding
vessel 60, which can provide a vacuum state or a low pressure state
in the same manner as the first embodiment of the present
invention. Then, the inner space of the vessel is separated from
the open air, and pressure in the vessel is reduced to remove air
from the inner space thereof to provide the vacuum state or an
inert gas such as argon gas is supplied into the inner space of the
vessel during the pressure reducing operation to substitute the
inert gas for the air, while maintaining a communicating condition
of the above-mentioned conduit with the open air. At the same time,
air is removed from each gap portions between the plates to provide
the vacuum state or an inert gas such as argon gas is supplied into
the gap portions between the plates to substitute the inert gas for
the air through the above-mentioned conduits.
[0072] Then, the inert gas having a high temperature and a
predetermined pressure is supplied into the second gap portions 40
through the second openings 41 and the conduit 72, while
maintaining the vacuum state or the low pressure state in the first
gap portions 30, so that the pressure in the second gap portion 40
is higher than the first gap portion 30 by about 20-100 kPa. In
such a state, the temperature of the plates defining the first gap
portion 30 is increased and pressure is applied to these plates to
generate a force, which causes these plates to come close to each
other (see FIG. 11(A)). The plates are firmly held so that the
contact areas of the projections of the heat transfer sections 21
of the plates, which areas are located in the first gap portion 30,
is kept at the pressure of 2 to 5 MPa in this manner and the
temperature thereof is increased to the predetermined temperature
(in case of titanium, from about 800.degree. C. to about
900.degree. C.) at which the diffusion bonding occurs. Such a
temperature is kept for a predetermined period of time to
diffusion-bond the contact areas of the plates.
[0073] After completion of the diffusion bonding of the contact
areas of the projections, which are placed in the first gap portion
30, the gas in the second gap portion 40 is removed through the
second opening 41 and the conduit 72 to put the second gap portion
40 in a vacuum state or a low pressure state. Then, the inert gas
having a high temperature and a predetermined pressure is supplied
into the first gap portions 30 through the first openings 31 and
the conduit 71 so that the pressure in the first gap portion 30 is
higher than the second gap portion 40. In such a state, the
temperature of the plates defining the second gap portion 40 is
increased and pressure is applied to these plates to generate a
force, which causes these plates to come close to each other (see
FIG. 11(B)). The plates are firmly held so that the contact areas
of the projections of the heat transfer sections 21 of the plates,
which areas are located in the second gap portion 40, is kept at
the pressure in the same manner as the case of bonding of the
contact areas of the projections in the second gap portion 40 and
the temperature thereof is increased to the predetermined
temperature. Such a temperature is kept for a predetermined period
of time to diffusion-bond the contact areas of the plates.
[0074] After completion of the diffusion bonding of the heat
exchange plates 20, the high temperature gas is removed and the
inner space of the vessel and the gap portions are put in the
vacuum or low pressure state and a non-heating state, and the
cooling water is supplied into the hollow portions of the cooling
plates 29 to cool rapidly the united plate assembly 27 from the
outside thereof. After the temperature of the plates decreases to a
temperature which has no influence on characteristic properties of
the plates, even when they come into contact with air, the internal
space and the gap portions between the plates are restored from the
vacuum state or the low pressure state to the original state prior
to the pressure reducing operation. Then, the united plate assembly
27 is taken out from the diffusion bonding vessel 60. The
manufacturing steps are completed in this manner.
[0075] In the united plate assembly 27 into which the heat exchange
plates 20 are combined together by the diffusion bonding process,
the plates are integrally connected with each other, not only at
the edges as welded of the plates, but also at the contact areas of
the projections 13 of the heat transfer section 11, excepting the
openings 31, 41, through the diffusion bonding process, thus
providing an extremely high bonding strength of the plates 20 in
the same manner as the first embodiment of the present invention.
It is therefore possible to make heat exchange between the first
and second heat exchange fluids without causing deformation of the
plates 20, even when the heat exchange fluids having a high
pressure are used or there is a large difference in pressure
between the first and second heat exchange fluids.
[0076] According to the second embodiment of the present invention,
the stacked heat exchange plates 20 are previously welded at the
peripheral edges of the plates to prepare a welded assembly and
then the welded assembly are bonded together by diffusion bonding
at portions thereof, which are brought into contact with each other
and have not been bonded together. The plates can therefore be
previously combined into the welded assembly, prior to the
diffusion bonding, to ensure an appropriate stacking state of the
plates so that the welded assembly can be easily handled. This step
may be applied as a subsequent step in the conventional method of
manufacturing a heat exchanger in which only peripheral edges of
plates are welded together, thus enabling the plates as combined in
accordance with the conventional method of a heat exchanger to be
more firmly combined together. Therefore, a pressure proof strength
can be substantially enhanced to permit to introduce a high
pressure heat exchange fluid into a gap between the adjacent
plates. As a result, a heat exchange efficiency can be improved in
accordance with various types of heat exchange conditions.
[0077] In the second embodiment as described above of the present
invention, the heat exchange plates 20 are welded together at the
edges thereof, prior to the diffusion bonding process. However, the
present invention is not limited only to such an embodiment. The
heat exchange plates may be bonded by a brazing process utilizing a
brazing metal having a melting point, which is higher than the
maximum temperature to which the plates reach in the fusion bonding
vessel 60 during the fusion bonding process, in place of the
above-mentioned welding process.
[0078] In the above-described first and second embodiments of the
present invention for manufacturing the heat exchanger, the heat
exchange plates 10, 20 having no holes are used as the plate to be
stacked into the united plate assembly, so as to be adapted to the
heat exchanger structure in which the openings 31, 41 for supply
and discharge for the heat exchange fluids are placed at the
peripheral portions of the plates. However, the present invention
is not limited only to such an embodiment. Plates each of which has
holes through which the heat exchange fluids flow in the same
manner as the conventional plates for a usual plate-type heat
exchanger that are placed one upon another through gasket members
may be used as the heat exchange plates to be stacked. In this
case, when the projections, which serve as the contact areas of the
adjacent plates, are provided in a place continuously surrounding
the hole in which there is a difficulty in welding the plate
through the conventional welding process, the plates are
fusion-bonded appropriately at the above-mentioned place in a
water-tight manner. The fusion-bonded areas provide such a
water-tight property to permit formation of a part of the fluid
passage. Therefore, the heat exchanger can be manufactured without
causing any problems.
[0079] In the above-described first embodiment of the present
invention for manufacturing the heat exchanger, the plates are
heated by applying the electric current thereto to diffusion-bond
all the contact areas of the plates, and in the above-described
second embodiment of the present invention for manufacturing the
heat exchanger, a high temperature gas is used to heat the plates,
in order to diffusion-bond the plates, which have been temporarily
welded at the peripheral edges thereof. However, the present
invention is not limited only to such embodiments. The other
heating process such as a high temperature gas heating, than the
electric current application-heating may be applied in order to
diffusion-bond all the contact areas of the plates, or the other
heating process such as an electric current application-heating,
than the high temperature gas heating may be applied in order to
diffusion-bond the plates, which have been temporarily welded at
the peripheral edges thereof.
[0080] In the above-described first and second embodiments of the
present invention for manufacturing the heat exchanger, the stacked
heat exchange plates 10, 20 are received in the diffusion bonding
vessel 60 having the internal space, which can be separated from an
open air, the internal space of the diffusion bonding vessel 60 is
kept in the vacuum state in which air is removed from the internal
space or the low pressure state in which only an inner gas
atmosphere exists, and then the diffusion bonding process is
carried out. However, the present invention is not limited only to
such embodiments. The method of the present invention may comprise
the steps of placing the heat exchange plates 50 as combined, in a
vessel 80 having a thin metallic bellows, which is flexibly
deformable in the stacking direction of the plates, applying the
pressing force to the plates in the stacking direction thereof,
discharging a gas in the vessel through air inlet and outlet
portions; closing the air inlet and outlet portions to keep an
inside of the vessel 80 in the vacuum state or the low pressure
state, and then carrying out the diffusion bonding process. In this
case, it is possible to put, along with the deformation of the
vessel 80, the space surrounding the contact portions of the plates
in the vacuum or low pressure state, thus enhancing reliability of
the diffusion bonding and providing an improved contact of the
plates. In addition, it is possible to reduce load of a pump for
discharging the gas in the vessel 80 to provide the vacuum state or
the low pressure state, thus permitting the use of a pump having a
low output and a low cost and reducing the manufacturing costs
required for the diffusion bonding process. The method of the
present invention may comprise the steps of disposing cooling
plates 39, to which the tubular conduits 39c are connected to flow
the cooling water therein, on the outside of the vessel 80 in the
same manner as the first embodiment of the present invention,
providing feeding wires 35, in a water-tight manner, which are
connected to the plates placed on the opposite ends sides of the
stacked plates 50 in the stacking direction thereof to apply an
electric current to the plates 50, putting the inside of the vessel
80 in the vacuum or low pressure state, applying the electric
current to the plates through the feeding wires 35 to heat them,
thus causing the diffusion bonding. After completion of the
diffusion bonding, the heating step by applying the electric
current is stopped, and the cooling water is supplied into the
hollow portions of the cooling plates 39 to cool rapidly the heat
exchange plates 50 as bonded, from the outside thereof through the
vessel 80.
[0081] In case where the cooling plates 39 are disposed on the
upper and lower sides of the heat exchange plates 50 in the
vertically stacking direction, the upper cooling plate 39 may be
used as a pressing member for applying a pressing force to the
stacked heat exchange plates 50 in the vessel 80. The stacking
direction of the plates when carrying out the diffusion bonding is
not limited only to such a vertical direction. The diffusion
bonding may be carried out in a state the heat exchange plates 50
are stacked in the horizontal direction.
* * * * *