U.S. patent number 3,823,457 [Application Number 05/337,953] was granted by the patent office on 1974-07-16 for method of fabricating a heat exchanger having two separate passageways therein.
This patent grant is currently assigned to U.S. Philips Corporation. Invention is credited to Adrianus Pieter Van De Mosselaer, Johannes Van Esdonk, Jan Leedert Melse, Adrianus Petrus Severijns, Frans Adrianus Staas.
United States Patent |
3,823,457 |
Staas , et al. |
July 16, 1974 |
METHOD OF FABRICATING A HEAT EXCHANGER HAVING TWO SEPARATE
PASSAGEWAYS THEREIN
Abstract
A method of manufacturing a heat exchanger for exchanging heat
between helium flows in a temperature range below 2K, comprising
two end plates having inlet and outlet apertures, and a stack of
very thin foils arranged between the end plates with passageways
that extend transverse to the planes of the foils and separate
ducts in the planes of the foils which communicate with the
passageways. During manufacture the foils are attached with
supports provided between foils, which supports are removed by
means of a rinsing liquid after the foils have been soldered to
each other.
Inventors: |
Staas; Frans Adrianus
(Emmasingel, Eindhoven, NL), Melse; Jan Leedert
(Emmasingel, Eindhoven, NL), Esdonk; Johannes Van
(Emmasingel, Eindhoven, NL), Severijns; Adrianus
Petrus (Emmasingel, Eindhoven, NL), De Mosselaer;
Adrianus Pieter Van (Emmasingel, Eindhoven, NL) |
Assignee: |
U.S. Philips Corporation (New
York, NY)
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Family
ID: |
19815574 |
Appl.
No.: |
05/337,953 |
Filed: |
March 5, 1973 |
Foreign Application Priority Data
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Mar 11, 1972 [NL] |
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7203268 |
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Current U.S.
Class: |
29/890.039;
165/166; 29/423; 165/167 |
Current CPC
Class: |
F28D
9/0075 (20130101); F25J 5/002 (20130101); F28F
3/083 (20130101); Y10T 29/49366 (20150115); F28F
2260/02 (20130101); Y10T 29/4981 (20150115); F25J
2290/42 (20130101); F25J 2215/30 (20130101); F25J
2290/44 (20130101) |
Current International
Class: |
F28D
9/00 (20060101); F28F 3/08 (20060101); F25J
3/00 (20060101); B21d 053/02 (); B23p 015/26 () |
Field of
Search: |
;165/167,166
;29/157.3D,423 ;113/118D |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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991,096 |
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Oct 1951 |
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FR |
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1,501,669 |
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Dec 1969 |
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DT |
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1,593,206 |
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Jul 1970 |
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FR |
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Primary Examiner: Lanham; Charles W.
Assistant Examiner: Reiley; D. C.
Attorney, Agent or Firm: Trifari; Frank R.
Claims
What is claimed is:
1. A method of manufacturing a heat exchanger through which fluid
can flow in forward and rearward directions comprising the steps of
stacking alternately thin metal sheets of thickness in the range of
2-10.mu. and thick metal sheets of thickness in the range
40-100.mu., said thick sheets having apertures therein which with
said adjacent thin sheets define ducts extending generally parallel
to the planes of said sheets with height of the ducts equal to the
thickness of said thick sheets, said ducts being forward flow ducts
spaced alternately, and rearward flow ducts situated intermediate
each two forward-flow ducts, said thick and thin sheets having
further apertures that are aligned along axes transverse to said
planes of the sheets to define at least two separate passageways
for said forward and rearward flows respectively, said forward flow
passageway and duct being in communication, and said rearward flow
passageway and duct being in communication, placing in each of said
ducts and between and contacting the adjacent thin sheets a support
having thickness substantially the same as that of said thick
sheet, each support being a material that is etchable by an etching
solvent that will not dissolve said metal sheets, pressing said
sheets together in the direction of said axes, heat treating said
pressed stack of sheets to bond together said sheets by soldering,
etching away said supports by rinsing same with said etching
solvent.
2. A method of manufacturing a heat exchanger through which fluid
can flow in forward and rearward directions comprising the steps of
stacking alternately thin metal sheets of thickness in the range of
2-10.mu. and thick metal sheets of thickness in the range of
40-100.mu., said thick sheets having apertures therein which with
said adjacent thin sheets define ducts extending generally parallel
to the planes of said sheets with height of the ducts equal to the
thickness of said thick sheets, said ducts being forward flow ducts
spaced alternately, and rearward flow ducts situated intermediate
each two forward-flow ducts, said thick and thin sheets having
further apertures that are aligned along axes transverse to said
planes of the sheets to define at least two separate passageways
for said forward and rearward flows respectively, said forward flow
passageway and duct being in communication, and said rearward flow
passageway and duct being in communication, placing in each of said
ducts and between and contacting the adjacent thin sheets a support
having thickness substantially the same as that of said thick
sheet, each support being a material that is etchable by an etching
solvent that will not dissolve said metal sheets, pressing said
sheets together in the direction of said axes, heat treating said
pressed stack of sheets to bond together said sheets by diffusion,
and etching away said supports by rinsing same with said etching
solvent.
3. A method according to claim 1 wherein each of said supports
comprises a frame extending along and spaced inward from the edge
of said aperture that defines the corresponding duct.
4. A method according to claim 1, comprising the further steps of
forming said thick and thin sheets of metal which have
predetermined area by providing on a substrate a first layer of
lacquer covering zones where said passageway apertures are to be
located in a thin sheet, then electrochemically forming upon said
substrate a first layer of copper to a maximum thickness of 5.mu.
covering an area equal to said sheet area and defining a first thin
sheet, then providing a second layer of lacquer on said first thin
sheet in a zone where said duct aperture is to be located in a
thick sheet, then electrochemically forming upon said first thin
sheet a second layer of copper to a thickness in the range of 40 to
100.mu. thick defining a first thick sheet, repeating these steps
alternatingly, until the desired number of thick and thin sheets
are formed, and then dissolving all the lacquer layers.
5. A method according to claim 1 wherein said thin sheets have
thickness of approximately 2.mu. and said thick sheets have
thickness of approximately 40.mu..
Description
BACKGROUND OF THE INVENTION
The invention relates to a method of manufacturing a heat exchanger
which is suitable for the exchange of heat between two helium flows
in the temperature range below 2K. Two end plates are provided with
an inlet aperture for one of the flows and an outlet aperture for
the other helium flow. A stack of further plates are arranged
between said end plates, the stack comprising four through ducts
which extend transverse to the plate direction and which
communicate two by two with the apertures in the end plates and
which further bound a number of separated parallel ducts which
extend mainly in the plate direction and which alternately
communicate with two of the through ducts.
A heat exchanger of the kind set forth is known from German
Offenlegungsschrift 1,501,669. This known heat exchanger is
intended for cooling highly viscous media such as curds.
Consequently, the heat exchanger is of substantial proportions and
its construction is very robust.
The heat exchanger relating to the method according to the present
invention is intended for exchanging heat between two helium flows
at temperatures below 2K. At these very low temperatures, the
exchange of heat is effected mainly by the exchange of phonons
(quantized atom vibrations). Because the acoustic velocities in the
helium and in the metal wall differ considerably, the refractive
index for phonons in helium is much larger than that in the metal
wall. For the passage of phonons from helium to the wall, this
gives rise to substantial reflection. The heat exchange between
helium and the metal wall is very poor due to the occurrence of
this surface resistance. In order to obtain adequate heat exchange
at these low temperatures, use was made thus far of heat exchangers
having very large surfaces. For example, heat exchangers are known
for this purpose which consist of a copper block containing two
chambers which are filled with copper balls which are sintered to
each other. These chambers are connected in the helium flows which
have to exchange heat.
These heat exchangers are not very satisfactory in view of their
large dimensions which give rise to long refrigeration times of the
refrigerators in which they are used.
SUMMARY OF THE NEW INVENTION
The method according to the invention has for its object to provide
a heat exchanger offering a substantially better exchange of heat,
extremely low flow resistance and small volume. To this end, the
method is characterized in that the stack of plates is formed by a
number of very thin metal foils which are proportioned such that
the thickness of the separating walls between the ducts is 2-10
.mu., the thickness dimension of the ducts being between 40.mu. and
100.mu.. A support having the same thickness dimension as the
parallel ducts is provided during the stacking of the foils, at
least at the area where each of the parallel ducts communicates
with a through duct, this support being made of a metal which can
be selectively removed at a later stage by means of a rinsing
liquid which does not attack the foils. Subsequently the end plates
are firmly pressed against the stack of foils and the assembly is
subjected to a thermal treatment during which the foils are
connected to each other by soldering or diffusion. Then the heat
exchanger thus formed is rinsed with the said rinsing liquid and
the supports are removed.
In a heat exchanger manufactured by the method according to the
invention, use is made of foils which have a very small thickness
but which are nevertheless vacuum tight. With the very small
thickness dimension of the separating wall (2-10.mu.), the phonons
can now readily penetrate through this separating wall as a result
of two effects, i.e., the phonon tunnel effect and the free-path
length effect. Thanks to these effects a striking improvement of
the exchanging of heat is achieved. Furthermore, the heat exchanger
thus obtained has a small volume and a low flow resistance.
A difficulty encountered in the manufacture is the vacuum-tight
connection of the foils. This connection can be obtained by
soldering, in which case the foils must be provided with a layer of
solder, or by diffusion. In both cases the foils must be firmly
pressed against each other. At the areas where the parallel ducts
communicate with the passage, this pressing against each other
cannot be adequately realized and at these areas leaks occur
because of insufficient pressing.
This problem is eliminated in the invention by providing a support,
in at least these areas, which ensures the transfer of force. This
support is made of a metal which can be etched away at a later
stage by means of a rinsing liquid, without the foils being
attacked. In this manner very good adhesion of the foils is
achieved.
However, if the foils are soldered to each other, sometimes a
problem arises in that the solder flows along the support, so that
clogging occurs with the result that the rinsing liquid cannot flow
through.
In order to eliminate this problem, in a further preferred
embodiment of the invention, each of the supports to be provided is
formed by a frame which can consist of a number of parts and which
extends along the entire inner edge of the relevant parallel
duct.
It was found that such a frame completely stops the flowing of the
soldering material into the ducts, so that clogging no longer
occurs.
In a further preferred embodiment of the method according to the
invention, each of the foils is formed by growing a layer having a
thickness of less than 5 .mu. on a suitable substrate in an
electrochemical manner. The areas for the through ducts first are
covered with a lacquer, after which a further layer of lacquer is
provided on the areas where the parallel duct extends and the
through channels extend further, after which further growing of the
foils up to a thickness of between 40 .mu. and 100 .mu. takes
place.
The invention will be described in detail hereinafter with
reference to the drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exposed view of a heat exchanger.
FIG. 2 shows the heat exchanger of FIG. 1 in the operating
condition.
FIGS. 3 and 4 show how supports can be used for assembly.
FIGS. 5 and 6 diagrammatically illustrate how a foil can be
made.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 diagrammatically shows the construction of a heat exchanger.
It comprises two end pieces 1 and 2, each of which is provided with
an inlet aperture, 3 and 4, respectively, for a helium flow forward
and rearward and with an outlet aperture, 5 and 6, respectively.
Arranged between the end plates 1 and 2 is a stack 7 of copper
foils. These foils are divided into closed foils 8 having a
thickness of approximately 2 .mu., and foils 9 having a rectangular
aperture. By means of apertures 10, 11, 12 and 13, four through
ducts or passageways are obtained which communicate with the
apertures 3, 4, 5 and 6, respectively, in the end plates defining
forward flow via inlet aperture 3, passageways 10 and 13, ducts 14,
and outlet aperture 6; and rearward flow via inlet aperture 4,
passageways 11 and 12, ducts 15, and outlet aperture 5
The rectangular apertures in the foils 9 form parallel ducts 14 and
15, the ducts 14 communicating with the passageways 10 and 13, and
the ducts 15 with the passageways 11 and 14. In this manner a heat
exchanger configuration is obtained comprising a number of parallel
ducts for the one helium flow and a number of parallel ducts for
the other helium flow.
Two methods can be used to obtain adhesion of the end plates to the
foils, i.e., soldering and diffusion.
In both cases all foils must be forcibly pressed against each
other. This can be effected over the entire circumference with the
exception of the areas 16 because there three foil parts are
situated which are bound by a duct part. Consequently, at these
areas no forces can be transferred and leakage is liable to
occur.
In order to prevent such leakage, supports 20 can be provided at
the areas 18 as shown in FIG. 3 in the case of diffusion of the
foils. It is thus achieved that the foils are properly pressed
together also at the areas 16. During the relevant thermal
treatment, the foils will be properly diffused together also at
these areas.
If the foils are soldered to each other, in which case the foils 9
are provided with a layer of soldering material in advance, it is
more advantageous to construct the supports in the form of a frame
22, as shown in FIG. 4, which extends along the entire inner edge
of the relevant parallel duct. This frame offers the important
advantage that the flowing of soldering material into the duct
space is completely counteracted, so that these ducts cannot become
clogged. So as to ensure proper transfer of forces at the areas 18,
the frame 22 has such a thickened portion 23 at these areas that
only a narrow gap remains.
The supports as well as the supporting frames are made, for
example, of soft steel or aluminium, respectively, i.e., materials
which can be removed by means of an acid or a lye after completion
of diffusion or soldering, respectively. To this end, it is
important that the acid or the lye can be rinsed through, so the
supports and supporting frames may not completely block the
passage.
After completion of these operations, a heat exchanger as shown in
FIG. 2 is obtained. This heat exchanger excels by its favourable
heat exchanging properties, small volume and low flow resistance.
Furthermore, the use of the method according to the invention
ensures a very reliable and leak-free heat exchanger.
The number of parallel ducts in which the helium flows exchange
heat can be arbitrarily chosen, depending on the circulating helium
flows and the relevant temperature range. In many cases 100 or more
ducts will be used.
As was already stated in the preamble, the use of very thin
separating walls between the ducts and the resultant phonon tunnel
effect and the free-path length effect ensure a very favourable
exchanging of heat with low flow resistance and small volume.
In the stack of the heat exchanger shown in FIG. 2, two kinds of
foils are used, i.e., closed foils having a thickness of
approximately 2 .mu. and foils having an aperture and a thickness
of approximately 40 .mu.. It was found that foils can be
manufactured in which these two are combined. The manufacture
thereof is diagrammatically shown in FIGS. 5 and 6.
On a brass plate 30 layers of lacquer are first provided at the
areas 31, 32, 33 and 34. Subsequently, a copper layer 35 is
electrochemically grown to a thickness of approximately 2 .mu..
After that, a lacquer layer 36 is provided ant the copper foil is
grown further to approximately 40 .mu..
By means of these foils the number of soldered or diffused
connections between the foils is reduced to one half.
* * * * *