Note: Descriptions are shown in the official language in which they were submitted.
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This invention i9 directed to an apparatus for transferring
heat between two locations at a different temperature. More
particularly, the invention is directed to heat transfer apparatus
comprised of a closed tube filled with a suitable heat transfer fluid
which evaporates at the location with a higher temperature (hot zone)
and condenses at the location with a lower temperature (cold æone).
The condensate can continuously be returned to the hot zone through
the tube,
The interior space of such a vacuum-tight closed system has
a heat transfer fluid which is partly present in liquid form and partly
as saturated vapor, with the heat transfer fluid evaporating in the hot
zone and flowing to the cold zone, where it condenses and thereby
releases its heat of evaporation, If the cold zone lies above the hot
zone, the condensate will flow back into the hot zone on account of
gravity and such devices for returning are called heat siphon~. If
the condensate is returned by the use of capillary forces, the devic
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is called a heat ~ube. The heat transfer fluid is circulated by means
of the temperature difference between the hot zone and the cold zone,
which is frequently very small. The higher vapor pressure which
prevails in the hot zone provides a pressure gradient which drives
the vapor to the cold zone. An essential advantage of these heat
transfer devices is that their effective heat conductivity is o~,ders
of magnitude higher than that of the best metallic conductors. In
addition, such devices are easy to handle, easy to assemble, and
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maintenance-free, and heat can be transferred counter to
gravity. Such heat transfer devices, however, must first be
evacuated, subsequently filled with a predetermined quantity of
heat transfer fluid, and then closed vacuum tight.
The present invention is based on the task of
providing a heat transfer apparatus of the heat siphon or heat
pipe type which for a given transfer ability is much more
easily fabricated. This task is solved with a device of the
type mentioned in the introduction, by providing a sealed,
evacuated pipe, which includes a heat transfer fluid, which
is shaped along its length such that it traverses the hot and
cold zones several times. By using the evacuated and filled
pipes of great length, and by giving them the claimed form,
several mutually connected heat siphons or heat pipes are
created. It has been unexpectedly found that neighboring heat
pipes or heat siphons do not dry out as a result of the
condensation zone of the neighboring tube or siphon, which
is still carrying liquid, expanding into the region that is in
danger of drying out. As a consequ_nce, this region is also
filled with liquid and a stable state is thus reached.
It is to be understood that the term "hot zone"
as used herein refers to the zone in which the heat transfer
fluid in the pipe is heated and the term "cold zone" as used
herein refers to the zone in which the heat transfer fluid
is cooled.
It is especially advantageous to wind the tube in
a spiraling or serpentine shape in that such an arrangement
results in a device which transfers large quantities of heat
in a very narrow space. This effect is still further enhanced
if several tubular sections, designed with a
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serpentine shape, are arranged above one another, According to
a urther aspect of the invention, the ~be is designed as a drawn, /~
seamless, soft-annealed, thin-walled copper tube, In accordance
with another aspect, the tube is a corrugated metal tube with a
welded seam along its length. The soft-annealed, thin-walled copper
tube as well as the corrugated metal tube with a welding seam along
its length are flexible, so that they can be wound in nearly any
desired shape. Because of its good thermal conductivity, copper
provides good heat transfer in both the hot and cold zones. The
tube could also be formed of aluminum or stainless steel. The
design with the corrugated tube has the further advantage that the
surface is enlarged in the area of the hot zone and cooling zone,
respectively. A particularly good effect is achieved if the portions
of the tube which form the hot zone lie at a lower level than the
IS portions of the tube which form the cold zone, In this case, no
further special steps need to be taken to return the condensate, since
the condensate flows back to the hot zone by gravity, Nevertheless,
for some applications it may be advantageous to arrange capillaries
in the interior of the tube in order to transport the condensate to
the hot zone, whereby it is possible to transport the condensate
against gravity, Another advantage results from the fact that the
capillaries distribute the condensate uniformly over the entire region
of the hot zone, and consequently the effectiveness of the system can
be increased,
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In accordance with one embodiment, the device is capable
of being used to exchange heat between the transfer fluid and massive
components, for example, electronic components, such as thyristors
and the like. In accordance with such embodiment, in the area of the
hot zone and/or the cold zone of the apparatus, there is provided a
connector member formed of a material having good heat conductivity,
such as copper, which is in contact with the individual windings of the
tube which are in the area of the hot or cold zone. One or more
units or devices which are to be heated or cooled by the apparatus
are in heat conducting contact with the connectirg member. The heat
exchange device of this embodiment significantly improves the ability
to heat or cool such massive components. ~or example, in the case
where the components are to be cooled, the connecting member
interconnects the windings of the tube in the area of the hot zone and
the heat released from the components is uniformly distributed over
the windings of the tube in the hot zone.
The heat transfer ability of the device can be increased,
particularly in the case of a wound corrugated tube, by providing the
connecting member with a recess for each winding of the tube which
is matched to and in heat transfer contact with the corrugation.
For example, it is possible to produce recesses in the connecting
member by means of machine-tooling, or by casting the connecting
member with such recesses. The windings can be connected to the
connecting member through a layer of solder with good heat
conductivity; e.g., a solder with a copper-silver base.
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In accordance with another aspect of the invention, the tube iB
a wound tube having individual windings thereof, in either the hot or
cold zone, interconnected through a vertically disposed connecting
member. In accordance with this aspect, each of the individual
windings includes a portion which is inclined with respect to horizontal
so that heat transfer fluid condensate flows back into the hot zone
by gravity. The direction of inclination is dependent upon whether
the individual windings are connected by the connecting member in the
area of the hot or cold zone, The vertical arrangemer~t is particularly
advantageous wherein the heat transfer fluid in the tube at the cold
zone is cooled by a gas ~connecting member at hot zone) in that
convection is increased by the upward flow of the heated gas. The
individual windings are spaced from each other to permit gas to
flow all around such windings.
In accordance with another embodiment, the windings or bends
of the tube in the area of the hot and/or cold zone are surrounded by
a liquid tight vessel, with the medium which is to be heated or cooled
by the heat exchange apparatus flowing through such vessel,
In accordance with another aspect, a heat exchanger unit can
be provided by providing as a unit the heat transfer tube with the
individual windings or bends thereof extending into a vessel through
openings therein, with such windings or bends being connected to
the walls at the openings; e.g., by soldering. In this manner, the
vessel can be connected in fluid flow communication with a circulating
2 5 system having a medium which is to be heated or cooled, with such
medium being heated or cooled by flow through the veEsel in heat
transfer contact with the individual windings of the tube within the
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vessel. Such a unit can be used, for example, with particular advantage as a
cooling system for motor vehicles in that there is a weight saving of up to 5
kg, and reliability is increased since the cooling loop itself can remain tight
even if the heat tube is destroyed. Such a unit in accordance with the invention
can be employed with every type of cooling system which employs a liquid coolant,
including, for example, in addition to motor vehicles, rail-bound vehicles,
stationary cooling systems, such as engines, dry cooling towers at power
plants, etc.
Another preferred application is to obtain heat from the ground or from the
air. In contrast to cooling systems, the medium to be heated, for example the
working medium of a heat pump system, is conducted through the vessel and in
heat transfer contact with the windings of the tube. The portion of the windings
outside the vessel can be in the ground, in ground water-or in the open air. It
is particularly advantageous to use a corrugated tube in that its increased sur-
face per unit length improves the heat exchange, and for many cases, the flexi-
bility resulting from the corrugations can also be advantageous.
Thus, in accordance with the present teachings, a heat transfer apparatus
is provided for use in exchanging heat from a hot zone to a cold zone, the
apparatus comprising a plurality of pipe sections each having a first end portion
extending into the hot zone and a second end portion extending into the cold zone,
each of the pipe sections being at least partially filled with a heat transfer
media which is readily vaporized while in the hot end portion and condensed while
in the second end portion whereby the heat transfer media constantly moves as a
vapor from the hot zone to the cold zone and as the condensate from the cold zone
to the hot zone between the first and second portions of the plurality of pipe
sections. The improvement which is provided in such apparatus comprises the
plurality of pipe sections being formed from a single, transversely corrugated,
thin wall metal tube length wound in a spiral or serpentine shape and having a
its opposite ends closed pressure-tight, and the first end portion of each of
the plurality of pipe sections being positioned at a lower level than the second
end portion of the pipe section.
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The invention will be further described with respect to the accompanying
drawings wherein:
Figure 1 is a simplified isometric view of an embodiment of the heat
transfer device of the present invention;
Figure 2 is a simplified eleyational view of another embodiment of the
heat transfer device of the present invention;
Figure 3 is a simplified isometric view of a further embodiment of the
heat transfer device of the present invention; and
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Figure 4 is a simplified isometric view of still another
embodiment of the heat transfer device of the present invention,
The figures show heat transfer devices which include a metal
tubelO wound in the shape of a helix ~Figure 1) or wound in a
serpentine fashion ~Figure 2), The tube 10 is advantageously fabricated
from a copper band, whose walls are e. g., O. 3 mm thick. In a
continuous operating process, this band is formed into an open seam
tube, welded along its length, and subsequently corrugated. But the
possibility also exists of using a seamless drawn copper tube for the
tube 10. AMer being finally drawn, this tube is soft-annealed and is
consequently quite flexible.
A certain length is separated from the finished tube length and
;~ is closed pressure-tight at both ends by means of the caps 12. One
of the caps 12 has a tube stud (not shown), to which a vacuum pump
can be connected for evacuation of the tube. After evacuation, the
heat transfer fluid is introduced and the tube stud is closed pressure-
tight. The tube 10 can be wound either before evacuation and filling
or else it can also be wound afterwards.
In the embodiments shown in Figures I and 2, the hot zone 13
is in the lower region, while the cold zone 14 is located in the upper
region, so that the condensate is returned to the hot zone 13 by
gravity .
When the wound tube 10 is filled, no special provision must
be made for filling each individual winding with heat transfer fluid
in that after start-up, the fluid distributes itself uniformly among
the individual windings. With the embodiments shown, all the lower
regions form the hot zone 13, while all the upper regions form the
cold zone 14. By means of the invention, a tube 10, prepared
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as a heat siphon or heat tube, has successully been made into a
large number of neighboring heat siphons or heat tubes, which
considerably reduces costs and greatly multiplies the efficiency of the
heat tube or heat siphon. It has been unexpectedly found that a tube
S winding cannot dry out since, in this case, the condensation zone of
neighboring windings extends into the region of the winding that is
threatening to dry out, whereby the condensate again flows into this
winding .
Obviously the invention is not limited to the heat siphons shown
in the embodiments, but is just as well applicable to heat transfer
systems which work according to the principle of the heat tube, i.e.,
in which the condensate is returned by capillary forces. For this
application, however, it is necessary to insert a capillary system into
the interior of the tube, for example in the form of a plastic network.
Figure 3 shows a heat transfer device comprised of a corrugated
copper tube 10 wound in the form of a spiral or helix. The corrugated
copper tube 10 as previously described is evacuated, filled with a
heat transfer fluid according to a precise dosage, and closed vacuum-
tight. A connecting member 15, made of copper, is soldered to
the outside of the tube parallel to the axis of the helix, with the
member 15 including recesses 16 for each winding. So that condensate
can return to the hot zone 13 by gravity, the individual windings of
the corrugated copper tube 10 are aligned at an angle oC to the long
axis of the connecting member 15, where ~ is less than 9oo. Heat
generators 17, for example electronic components like thyristors, can
be affixed in heat transfer contact with member 15 whereby the heat
released therefrom is transferred through the connecting member 15
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and attached tube windings to the heat transfer fluid within the windings.
The heat transfer fluid, in liquid form situated in the area of
the hot zone 13 is evaporated by the heat energy that is transferred
through the connecting member 15 and windings. As a result of the
pressure differential, the evaporated fluid flows into the cold zone 14,
where it condenses, and flows back to the hot zone 13 through the
inclined portion of the windings. Cooling in the region of the cold zone
14 which is effected by a gas, such as air. can be increased by forced
convection, for example by a ventilator ~not shown).
It is to be understood that the connecting member 15 could be
connected to the windings in the area of cold zone 14, in which case
the inclined portion of the windings would extend in the opposite
direction .
The heat transfer device in accordance with the embodiment of
Figure 3 could also be employed in a manner such that two heat
transfer devices are connected together through their respective
connecting members 15 in heat transfer contact with each other. In
such case, the heat connecting member 15 of one device is in the
area of the cold zone thereof, and the heat connecting member 15 of
the second device is in the area of the hot zone thereof.
The heat transfer device of Figure 3 can also be employed by
connecting two or more of such devices through connecting member
15 to an element which is to be heated or cooled. For example, two
or more of such devices can be connected in heat transfer contact
with the outside wall of a vessel or tube through which a medium to
be heated or cooled flows.
A further embodiment is shown in Figure 4, wherein the metal
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tube 10 is formed into a serpentine structure, as shown. The
windings 18 of the tube 10, are introduced through openings into a
container l9, for example, a tube shaped container, and the windings
18 are tightly soldered to the wall of the container 19. For example,
the medium to be cooled, possibly water in an automobile engine,
can be introduced into and withdrawn from the container 19, through
connecting openings 21 and 22. The heat transferred from the medium
being cooled to the heat transfer fluid in the windings 18 of tube 10
within container l9 evaporates the fluid which flows into the cold zone
14, outside of vessel l9 wherein the fluid is cooled and condensed by
a gas, such as air, which is caused to flow in heat transfer contact
with the portion of the windings in cold zone 14.
A similar device may be used with stationary installations,
where the required air circulation is taken care of either by ventilators
or by a cooling tower. Depending on the design, the windings can
be arranged approximately horizontally to or on both sides of container
.; 19
Alternatively, the device can be used to heat a fluid in container
19, in which case the container 19 will be connected to the top portion
of the windings in cold zone 14.
Numerous modifications and variations of the present invention
are possible in light of the above teachings and, therefore, within
the scope of the appended claims the invention may be practiced
otherwise than as particularLy described.
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