Tube/fin block for a heat exchanger and manufacturing process therefor

A tube/fin block for a heat exchanger has several tubes through which a heat transfer fluid can flow arranged side-by-side along a transverse direction of the block. Corrugated-fin complexes are inserted between respective adjacent tubes and are connected with the adjacent tubes. At least one of the corrugated fin-complexes is a double corrugated-fin complex with two corrugated-fin units arranged side-by-side in the transverse direction of the block. A particular manufacturing process for the tube/fin block is utilized. A heat insulation device is provided between the two corrugated fin units. A non-solderable spacer plate can be inserted between the two corrugated fin units and pulled out after the tube/fin block is soldered together so that a heat-insulating gap is formed. A plastic strip can be inserted into the heat-insulating gap as required. The block is appropriate for use, for example, in condensers and evaporators of motor vehicle air conditioners.

This application claims the priority of Application No. 197 29 239.9, filed 
in Germany on Jul. 9, 1997. 
BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates to a particular tube/fin block construction for a 
heat exchanger having several tubes arranged side-by-side along a 
transverse direction of the block and through which a heat transfer fluid 
can flow. Corrugated-fin complexes are inserted between adjacent tubes and 
are connected with the adjacent tubes. At least one of the corrugated 
fin-complexes is a double corrugated-fin complex with two corrugated-fin 
units arranged side-by-side in the transverse direction of the block. The 
invention also relates to a process for manufacturing such a tube/fin 
block. Heat exchangers with such a tube/fin block are used, for example, 
as condensers and evaporators in motor vehicle air conditioners and may 
have the form, for example, of flat-tube heat exchangers in a 
serpentine-type construction. 
In German Patent Application No. 196 49 129.0, a flat-tube heat exchanger 
having a tube/fin block of the initially mentioned type is described in 
which double corrugated-fin complexes are inserted between respective 
adjacent tubes and which the two corrugated-fin units of the double 
corrugated-fin complexes, which are arranged side-by-side in the 
transverse direction of the block, are separated from one another by a 
massive continuous separating plate. The two corrugated-fin units, on one 
side, are soldered to the separating plate and, on the other side, are 
soldered to the respective adjoining flat tubes. A sufficient distance is 
to be created by the double corrugated-fin complexes between two adjacent 
flat tubes respectively in order to twist the flat tube ends by 90.degree. 
without hindering one another and permit inserting them into a pertaining 
distributing or collecting tube. 
A heat exchanger disclosed in German Published Patent Application DE 195 36 
116 A1 has a tube/fin block of the initially mentioned type which is 
divided into two areas in which a massive supporting metal plate instead 
of one of several parallel linear flat tubes is provided. A respective 
division of the lateral distributing and collecting tubes corresponds to 
this division of the tube/fin block. The purpose of this measure consists 
of integrating two separate heat transfer fluid circulating systems in the 
heat exchanger, for example, for implementing an integrated condenser--oil 
cooler unit for a motor vehicle. 
SUMMARY OF THE INVENTION 
The present invention addresses the technical problem of providing a 
tube/fin block of the initially mentioned type in which measures are taken 
for the thermal decoupling of at least two adjacent tubes as well as the 
technical problem of providing a manufacturing process for such a tube/fin 
block. 
The invention solves these problems by providing a tube/fin block of the 
initially mentioned type which has a heat insulation device provided 
between the two corrugated-fin units of the double corrugated-fin complex 
as well as by providing a manufacturing process for manufacturing such a 
tube/fin block including the operations or steps of constructing the 
tube/fin block from tubes and corrugated-fin complexes, carrying out a 
soldering process with the constructed tube/fin block for brazing the 
tubes to the corrugated-fin complexes, and removing a spacer plate from 
the soldered tube/fin block to form a heat-insulating air gap between two 
corrugated-fin units of a double corrugated-fin complex. The process may 
further include inserting a plastic strip into the heat-insulating air gap 
formed by removal of the spacer plate. 
In preferred embodiments of the tube/fin block according to the invention, 
a heat insulation device is provided between the two corrugated-fin units 
of the at least one double fin complex. As a result, heat transfer between 
the two corrugated-fin units can be prevented or at least reduced to a 
desired degree. Correspondingly, the two tubes spaced from one another by 
this double corrugated-fin complex are thermally decoupled. This is 
expedient, for example, for a heat exchanger in a serpentine-type 
construction in which an inlet-side section of serpentine-type tubing is 
situated opposite an outlet-side section of adjacent serpentine-type 
tubing. A double corrugated-fin complex with the heat insulation device 
inserted between the two tubing sections prevents or reduces an 
undesirable heat transfer between these two tubing sections, which 
normally have different temperatures during operation. 
According to further features of preferred embodiments of the invention, 
the heat insulation device is formed by a perforated separating plate. 
Since its openings have no, or at least no significant, heat conductivity 
but do have a heat insulating effect, the heat conductivity of the 
perforated separating plate is clearly reduced in comparison to a massive 
separating plate. The larger the surface proportion of the openings, the 
higher the heat-insulating effect of the perforated separating plate. 
According to further features of preferred embodiments of the invention, 
the heat insulation device is formed by a profiled separating plate which 
is provided with punctiform or linear projections, such as beads, on one 
or both of its sides. This results in an at most line-type contact of the 
two corrugated-fin units of the double corrugated-fin complex with a 
correspondingly low heat conductivity. 
According to additional features of preferred embodiments of the invention, 
the heat insulation device is formed by a separating metal plate which is 
provided, at least on one side, with a heat-insulating coating which 
prevents a noticeable heat transfer through the separating metal plate. 
Since, as a result of the heat-insulating coating, brazing of the 
separating metal plate to the adjoining corrugated-fin units may not be 
possible, according to a further development of the invention, the 
separating metal plate may be provided with position securing devices 
which secure it with respect to a moving-out of the tube/fin block. 
According to yet further features of preferred embodiments of the 
invention, the heat insulation device is formed by a heat-insulating air 
gap. Such a tube/fin block can advantageously be produced by a process 
including the particular steps or operations of constructing the tube/fin 
block from tubes and corrugated-fin complexes carrying out a brazing 
process with the constructed tube/fin block for brazing the tubes to the 
corrugated-fin complexes, and removing a spacer plate from the soldered 
tube/fin block to form a heat-insulating air gap between the two 
corrugated-fin units of the double corrugated-fin complex. The two 
corrugated-fin units of a respective end plate may adjoin the air gap or, 
as an alternative, may be situated directly opposite each other by way of 
the air gap. Particularly in the latter case, it is advantageous, as a 
further development of the invention, to manufacture the corrugated-fins 
of a non-solder-plated material and, for manufacturing the tube/fin block, 
to provide the tubes with solder by a brazing operation. 
In further developments of the invention, the heat insulation device is 
formed by a plastic strip having a low heat conductivity which largely 
prevents a heat transfer between the two adjoining corrugated-fin units. 
Such a tube/fin block can be produced, for example, by a process including 
the operations of removing a spacer plate from the soldered tube/fin block 
to form the heat-insulating air gap, and inserting a plastic strip into 
the heat-insulating air gap formed by the removal of the spacer plate 
which is advantageous in that the plastic strip does not have to be 
resistant to the temperatures used during the brazing process because it 
is inserted after the soldering process. 
According to further features of preferred embodiments of the invention, at 
least one of the two corrugated-fin units of the double corrugated-fin 
complex is provided, on its side facing the air gap or the plastic strip, 
with a metal end plate, which is advantageous particularly for pulling-out 
a spacer plate inserted for the brazing process and possibly for inserting 
the plastic strip. 
In further developments of preferred embodiments of the invention, the heat 
insulation device is formed of a nonwoven ceramic element or mineral fiber 
material. Such a nonwoven element also has a desired low heat 
conductivity. In a further development of this measure, the nonwoven 
element is accommodated in a U-shaped separating metal plate with flanks 
which act as metal end plates of the adjoining corrugated-fin units. In 
its bending edge area, the separating metal plate has a perforated 
construction in order to prevent a significant heat transfer between the 
two flanks of the separating metal plate over the bending edge area. 
Finally, according to further features of the invention, the heat 
insulation device is formed by two metal end plates which, only by way of 
projections provided on one or both of the mutually opposite metal end 
plate sides, rest against one another in a punctiform or linear manner 
while, on an exterior side, the plates are connected with the respective 
adjoining corrugated-fin unit. By the at most linear contacting of the two 
metal end plates, a noticeable heat transfer between the latter is 
avoided. 
Advantageous constructions of preferred embodiments of the invention are 
illustrated in the drawings and will be described. Other objects, 
advantages and novel features of the present invention will also become 
apparent from the following detailed description of the invention when 
considered in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As a cutout, FIG. 1 illustrates a tube/fin block for a multi-flow heat 
exchanger in a serpentine-type construction which contains several 
serpentine-type tubings 1a, 1b and corrugated-fin complexes 2 between two 
adjacent linear serpentine-type tubing sections respectively. For reasons 
of simplicity, the center section of the tube/fin block is illustrated in 
a shortened fashion in FIG. 1. The corrugated-fin complexes 2 are used, on 
the one hand, for mechanically stabilizing the tube/fin block and, on the 
other hand, for increasing the heat transfer between a heat transfer fluid 
guided through the serpentine-type tubings 1a, 1b and a medium which is 
guided away perpendicularly to the plane of the drawing of FIG. 1 on the 
exterior side of the tube over the tube/fin block. 
Two serpentine-type tubings respectively of the several serpentine-type 
tubings 1a, 1b which are arranged side-by-side in a row along the 
transverse direction S of the block are situated opposite one another by 
connection sections 1c, 1d which lead on opposite sides out of the 
tube/fin block and into an assigned distributor or collector which is not 
shown. This means that, of the mutually opposite connection sections 1c, 
1d of adjacent serpentine-type tubings 1a, 1b, one forms an inlet-side 
tubing section and the other forms an outlet-side tubing section. However, 
during operation of the heat exchanger, a heat transfer fluid which 
normally flows through these sections 1c, 1d varies in temperature 
because, depending on the function of the heat exchanger, the heat 
transfer fluid absorbs or delivers heat while it flows through the 
parallel serpentine-type tubings. Correspondingly, a heat transport 
between the two connection-side tube sections 1c, 1b of adjacent 
serpentine-type tubings 1a, 1b is undesirable because such heat transport 
reduces the efficiency of the heat exchanger. 
In order to prevent this undesirable heat transport or at least reduce it 
to an acceptable degree, one thermally decoupling double corrugated-fin 
complex 2a respectively is provided between the opposite connection-side 
tube sections 1c, 1d of adjacent serpentine-type tubings 1a, 1b, while 
between the individual linear tubing sections within each serpentine-type 
tubing 1a, 1b, a conventional single corrugated-fin unit 2b is inserted. 
The thermally decoupling double corrugated-fin complex 2a consists of two 
corrugated-fin units 2c, 2d, which are arranged side-by-side in the 
transverse direction S of the block, and of a flat heat insulation device 
3 which is situated between the corrugated-fin units 2c, 2d. In the 
following, various advantageous implementations of this heat insulation 
device 3, which causes the thermal decoupling function of the double 
corrugated-fin complex 2a, will be explained in detail. 
In the example of FIG. 2, the heat insulation device is formed by a 
separating metal plate 3a which is provided with circular openings 4. 
Like, for example, the serpentine-type tubings 1a, 1b, the separating 
metal plate 3a consists of aluminum. As a result, the separating metal 
plate 3a can be soldered to the two adjoining corrugated-fin units 2c, 2d 
in the same brazing process in which the corrugated-fin complexes 2, which 
are also manufactured of aluminum, are soldered to the serpentine-type 
tubings 1a, 1b. In the area of the openings 4, the heat transfer degree 
between the two corrugated tube units 2c, 2d of the double corrugated-fin 
complex 2a is virtually negligible or at least sufficiently low. The 
larger the surface proportion of the openings 4, the higher the thermally 
decoupling effect of the perforated separating metal plate 3a. With the 
secondary prerequisite that a residual separating metal plate surface 
remains which is capable of transmitting the pressing required for the 
brazing, the surface proportion of the openings 4 is selected to be as 
large as possible. 
Instead of the separating metal plate 3a of FIG. 2 provided with circular 
openings 4, other separating metal plates with modified hole patterns can 
be used as heat insulation devices. Thus, FIG. 3 illustrates another 
thermally decoupling, perforated separating metal plate 3b made of 
aluminum which is provided with a hole pattern of various rectangular 
openings 5a, 5b. As another alternative, the use of perforated sheets is 
considered. In all cases, in contrast to a massive continuous separating 
metal plate made of aluminum, the hole pattern results in a significant 
reduction of the heat conductivity and therefore in considerable thermal 
decoupling of the adjoining corrugated-fin units 2c and 2d of the double 
corrugated-fin complex 2a and consequently of the tubing sections 1c, 1d 
of the tube/fin block which are spaced from one another by this double 
corrugated-fin complex 2a. As an alternative to a perforated separating 
metal plate, the use of a profiled separating metal plate which is 
provided on one or both sides with punctiform or linear projections is 
conceivable; such a construction results in only a punctiform or linear 
contact of the two corrugated-fin units with a correspondingly low heat 
transfer capability. 
FIG. 4 is a lateral view in the direction of arrow D of FIG. 1 and 
illustrates another possible configuration of the thermally decoupling 
double corrugated-fin complex 2a. In this example, between the two 
corrugated-fin units 2c, 2d of the double corrugated-fin complex 2a, which 
is situated between the two connection-side tubing sections 1c, 1d of 
adjacent serpentine-type tubings, a separating metal sheet 3c of aluminum 
is inserted as a heat insulation device which is provided on both sides 
with a heat-insulating ceramic coating, for example, of aluminum nitrite. 
The coating can be applied, for example, by a plasma spraying or 
vaporizing process. The two-sided ceramic coating causes the thermal 
decoupling of the two adjoining corrugated-fin units 2c, 2d. Since the 
coating material is not solderable, the coated separating metal plate 3c 
is not connected by the brazing process for the tube/fin block with the 
adjoining corrugated-fin units 2c, 2d. In order to nevertheless prevent a 
sliding-out of the separating metal plate 3c, the separating metal plate 
3c is manufactured with a slightly larger width than the corrugated-fin 
units 2c, 2d and, on the resulting side edges which protrude on both 
sides, is bent to form holding tabs 6a, 6b, of which, on each side, at 
least one rests against one corrugated-fin unit and at least one other 
rests against the other adjoining corrugated-fin unit. 
In a view which corresponds essentially to that of FIG. 4, FIG. 5 
illustrates another possible configuration of a thermally decoupling 
double corrugated-fin complex between the two adjacent tubing sections 1c, 
1d. In this configuration, the mutually facing sides of the two 
corrugated-fin units 2c, 2d of the double corrugated-fin complex are 
provided with respective soldered-on metal end plates 7, 8, and the two 
metal end plates 7, 8 are spaced from one another in order to define 
either a heat-insulating air gap 11 or a space within which a 
heat-insulating plastic strip 9 may be inserted. This, in turn, causes the 
desired thermal decoupling of the two corrugated-fin units 2c, 2d. 
For manufacturing the tube/fin block with this type of a thermally 
decoupling double corrugated-fin complex, the tube/fin block is 
constructed first, in which case the respective metal end plate 7, 8 is 
arranged on the two mutually opposite sides of the corrugated-fin units 
2c, 2d of the double corrugated-fin complex, and a metal spacer plate 10 
made of a non-solderable material, for example, of special steel or of a 
ceramically coated strip material, is inserted between the two metal end 
plates 7, 8. When special steel is used for the metal spacer plate 10, the 
latter is provided with a coating, for example, made of chalk or graphite, 
which cannot be wetted by the solder which is used in the subsequent 
brazing process. Then the constructed tube/fin block is subjected to a 
brazing process in order to solder the corrugated-fin complexes to the 
tubes, in which case the two metal end plates 7, 8 are simultaneously 
soldered to the respective corrugated fin unit 2c, 2d of the double 
corrugated-fin complex. The metal spacer plate 10, which is resistant to 
the brazing process temperatures, during the brazing process, is not 
connected with the adjoining metal end plates 7, 8 and can therefore be 
laterally pulled out in the direction illustrated by the arrow after the 
brazing process. The heat-insulating plastic strip 9 can now be inserted 
in the resulting gap 11 laterally between the two metal end plates 7, 8 as 
the heat insulation device. The plastic strip 9 acts simultaneously as an 
air closing strip, which is desirable for some applications. Therefore, in 
this manufacturing process, the material of the plastic strip 9 must not 
be designed with respect to a resistance to the temperature during the 
brazing process, but can be selected specifically to provide a high heat 
insulation capacity. 
As an alternative to inserting the plastic strip 9 illustrated in FIG. 5, 
as required, the gap 11 may remain between the two metal end plates 7, 8 
after it is created by the pulling-out of the metal spacer plate 10. The 
gap 11 will then act as a heat-insulating air gap between the two 
adjoining corrugated-fin units 2c, 2d. As another alternative, the metal 
end plates 7, 8 can be eliminated. The tube/fin block will then be 
soldered together without using the metal end plates. For this purpose, 
for example, the corrugated fins may consist of non-solder-plated material 
and the tubes may be provided with solder. 
In a cutout-type lateral view corresponding to FIG. 1, FIG. 6 illustrates 
another configuration of a thermally decoupling double corrugated-fin 
complex between the two adjacent tubing sections 1c, 1d. In this example, 
a nonwoven element 12 made of a heat-insulating material, for example, of 
a ceramic material or of a mineral fiber material, is inserted as the heat 
insulating device between the two corrugated-fin units 2c, 2d of the 
double corrugated-fin complex. The nonwoven element prevents a mutual 
interlocking of the two adjoining corrugated-fin units 2c, 2d and absorbs 
excess solder of the corrugated-fin units 2c, 2d during the brazing 
process without being soldered to them. As an alternative to leaving the 
nonwoven element 12 as the heat insulation device, the nonwoven element 12 
may be pulled out after the brazing process, after which the resulting gap 
between the two corrugated-fin units 2c, 2d will then act as a 
heat-insulating air gap. 
FIGS. 7 and 8 illustrate another configuration of the thermally decoupling 
double corrugated-fin complex for the tube/fin block of FIG. 1. In this 
example, a U-shaped solderable separating metal sheet 13 is inserted 
between the two corrugated-fin units 2c, 2d of the double corrugated-fin 
complex. A nonwoven element 14 made of a heat-insulating material is 
inserted into the interior of the separating metal plate 13. By its flanks 
13a, 13b, the U-shaped separating metal plate 13 is soldered on its 
exterior side to the respectively adjoining corrugated-fin unit 2c, 2d. In 
its bending edge area 13c, the separating metal plate 13 is provided with 
openings 16 which are situated side-by-side in a row and which are spaced 
from one another by narrow webs 15, as illustrated more clearly by FIG. 8. 
Because of the heat-insulating nonwoven element 14 and the heat-insulating 
openings 16 in the separating metal plate bending edge area 13c, no 
noticeable heat transfer takes place between the two separating metal 
plate flanks 13a, 13b and thus between the adjoining corrugated-fin units 
2c, 2d, which, in turn, ensures the thermally decoupling effect of the 
double corrugated-fin complex. As required, the two free end edges of the 
U-shaped separating metal plate 13, instead of, as illustrated, ending 
open, may be folded over while leaving a heat-insulating air gap, so that 
the nonwoven element 14 is securely enclosed against removal. 
FIG. 9 is a view corresponding to FIG. 7 and shows another implementation 
of the thermally decoupling double corrugated-fin complex. In this 
example, the two corrugated-fin units 2c, 2d of the double corrugated-fin 
complex are respectively provided on their mutually opposite sides with 
one metal end plate 17, 18. Both metal end plates 17, 18 have *punctiform, 
or as an alternative, linear beads, as a result of which corresponding 
punctiform or linear protrusions 19, 20 are formed on the mutually 
opposite metal end plate sides. The protrusions 19, 20 of both metal end 
plates 17, 18 are situated at corresponding points so that the two metal 
end plates 17, 18 rest against one another with an only punctiform or at 
most linear contact in the areas of the protrusions 19, 20. The at most 
linear contact between the two metal end plates 17, 18 permits at most 
only a slight heat transfer; no significant heat transfer takes place in 
the air gap area situated between these end plates. On the whole, the two 
metal end plates 17, 18, which at most have linear contacts, therefore act 
as a heat insulating device which is sufficient for causing the desired 
thermal decoupling between the corrugated-fin units 2c, 2d of the double 
corrugated-fin complex. 
According to the invention, heat insulation between two adjacent tubes of a 
tube/fin block is provided at respective desired points by inserting a 
respective thermally decoupling double corrugated-fin complex. It is to be 
understood that double corrugated-fin complexes, equipped in this manner 
with a heat insulation device, can be used not only for heat exchangers 
with serpentine-type constructions as shown but also for heat exchangers 
of other construction types and whenever there is a demand for thermal 
decoupling of adjacent tubes of tube/fin heat exchanger blocks. 
The foregoing disclosure has been set forth merely to illustrate the 
invention and is not intended to be limiting. Since modifications of the 
disclosed embodiments incorporating the spirit and substance of the 
invention may occur to persons skilled in the art, the invention should 
construed to include everything within the scope of the appended claims 
and equivalents thereof.