Note: Descriptions are shown in the official language in which they were submitted.
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Description
HEAT TRANSFER UNIT FOR HEATING SYSTEMS
AND SURFACES AND RAILWAY POINT HEATER
[0001] The invention relates to a heat exchanger unit for
heating systems and surfaces, and to a track switch heater
having a heat exchanger unit.
[0002] Document EP 1 529 880 Al and WO 2005/045134 Al relate
to a thermal ground probe which delivers heat directly to
traffic facilities, the heat flow being conducted via at
least one heat pipe from the heat source via a transport zone
and, in order to provide a supply to a plurality of heat
sinks, being split up in the transport zone, long before
reaching the heat sinks, in such a way that each is split
into one or two heat flows in order to ensure a uniform
distribution or a distribution according to the respective
power demands of the connected heat sinks. The division of
the heat flows from one pipe to two is restricted in that the
sum of the cross sections of the two pipes after the
distribution must be equal to the cross section before the
distribution; that is to say the cross section of the pipe
which is closer to the probe is approximately equal in size
to the sum of the cross sections of the two distribution
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pipes. Here, the cross sections of the distribution pipes are
proportional to the ratio of the power demands of the heat
sinks connected downstream.
[0003] As a heat exchanger, a plate is provided to which up to
three heat pipes are fastened longitudinally with respect to
the rail body, but are not integrated. Said pipes are
therefore not an independent heat exchanger, but rather are
fastened to heat distribution plates in a heat-conducting
fashion.
[0004] The targeted division of a gas flow in the transport
zone requires that the calculated geometrical dimensions of
the distribution pipes be adhered to very precisely, and it is
difficult for those geometrical dimensions to be realized
during on-site assembly. No weld or solder seams should
project into the interior space of the pipe, nor should any
burrs protrude into said interior space, since such seams or
burrs hinder the gas flow and the condensate flow. The
division of a large heat flow from the probe into a plurality
of relatively small flows by means of a further interposed
heat exchanger, as proposed in EP ]. 529 880 Al, is associated
with temperature losses, which would not necessarily be
advantageous if a small temperature difference is present.
The reference to capillary pipes in document EP 1 529 880 Al,
which utilize a capillary effect in some arbitrary way,
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cannot be regarded as being equivalent to pipes of small
diameter at least in connection with the use of CO2, since at
such small diameters, the pressure drop in the pipe with the
length of up to 5 in specified in EP 1 529 880 Al is so high
that gas transport no longer takes place. It is in fact prior
art for pipes with a capillary internal structure and
diameters of 10 mm to be used to generate a backward flow of
condensate in the horizontal, or even counter to a slight
gradient up to a length of 5 m. With a smooth internal
structure and a diameter which does not generate a pressure
drop, a backward flow of a condensate is not physically
possible.
[0005] The heating of traffic signs using geothermal heat,
as is known from DE 40 36 729 Al, requires only very small
heat quantities and can be realized in a relatively simple
manner. A significant difference with respect to the
invention proposed here is the power ranges, which are
higher here by factors of 20 to several hundred; such an
increase in power is not possible using the method described
in DE 40 36 729 Al. Of equal significance for the lack of
comparability is the fact that said document involves
preventing decreased visibility caused by frost. A further
fundamental difference lies in the fact that, in a traffic
sign, only vertical distances must be overcome in the
distribution of heat, and only vertical surfaces need be
thawed. Here, gravity causes the thawed
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precipitation, snow, sleet or frost to slide down the traffic
sign. The heated traffic sign is duly a heat pipe
application, but the realization of a multi-duct heat
exchanger is designed explicitly for water/glycol mixtures.
The proposed design having a so-called heat pipe has only one
pipe with a plate, which is fastened thereto and which
conducts heat as a heat sink.
[0006] Already widespread, and known for example from DE 43
25 002 Al, are devices for heating track switch parts by
means of electric heating elements which are arranged locally
and which are intended to ensure that the track switch can be
operated even at temperatures below the freezing point.
[0007] An object of this invention is to develop a heat
exchanger unit which is adapted to the specific demands of an
application and constitutes an efficient and economical
solution.
[0009] The invention comprises a heat exchanger unit for
heating systems and surfaces, which heat exchanger unit can
be connected at least to a thermal ground probe, which is
operated with
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a multi-phase working medium, as a heat source and to a
component to be heated, the heat exchanger unit comprising at
least one heat exchanger and transport lines for the working
medium. According to the invention, for the transfer of the
latent heat originating from the heat source to the component
to be heated, at least one gas-tight heat exchanger is
formed, in a modular fashion, with a multiplicity of directly
adjacent mini-ducts in a laminar arrangement, the mini-ducts
being connected to at least one supply duct, and having a
diameter of 0.3 to 6 mm.
[0010] That diameter of the mini-ducts which is provided as a
lower limit is distinct from the dimensions of micro-ducts,
for which the literature specifies a diameter of < 0.3 mm. In
the literature, a dimension of a mini-duct is often specified
as being in the range between 0.3 mm and 3 mm diameter. In
the case of relatively large surfaces to be heated, the
diameters of the mini-ducts in this context may even be up to
6 mm. Even at such diameters, the ducts are integrated into
the component to be heated; the component to be heated
therefore is itself the heat exchanger.
[0011] Two variants of heat exchangers are possible: the
parallel flow principle and the counterflow principle.
[012] For both principles, at a temperature of the
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working medium of "rC in the heat exchanger, the desired
specific power range of the heat exchanger unit lies between
0.9 and 4 kW/m.'.
[0013] To increase the size of the duct surface and therefore
of the heat transfer area between the gas and the heat
exchanger, it is possible for a plurality of layers of ducts
to be arranged one above the other while maintaining a
minimum spacing of the ducts with respect to one another,
which is required for mechanical reasons (strength). With
said spacing, it is also possible for an even faster heating
response to be obtained.
[0014] For the counterflow principle: the ratio of the cross
sections of the feeding distributor pipes to the overall
cross section of the respectively connected ducts should be
selected to be between 0.1 and 0.25 depending on the power
requirement of the surface to be heated and the selected duct
cross sections. The sum of the cross sections of the mini-
ducts is accordingly significantly greater than that of an
associated distributor pipe. The mini-ducts conventionally
have a smooth inner wall in order to permit effective gas and
liquid flow.
[0015] It is possible to specify a minimum diameter on the
capillary side of 0.3 mm, and a maximum diameter in the case
of aluminum heat exchangers, for reasons of strength and
economy (excessively high wall thicknesses), of 5 mm. The
minimum diameter therefore also should not be
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undersized, to avoid hindering the return flow of the liquid
working medium by the inflowing gas. Intermittent behavior of
the medium may occur even with a diameter of 1 mm and at high
power.
[0016] On the distributor side, the maximum diameter should
not exceed 20 mm. The Product Safety Act sets limits on
production monitoring, and demands frequent safety checks,
for significantly greater diameters. The Act takes the upper
of limit values from the product of pressure and volume of a
reservoir. Furthermore, the wall thicknesses then become
uneconomically thick.
[0017] When using CO, the dimensions of the distributor
pipes and the mini-ducts at power levels required for such
applications (< 2 kW per m and distributor pipe) are
substantially non-critical. The high enthalpy content of CO
entails a low flow speed. A metallic heat exchanger, on
account of its good thermal conductivity, is effective at
dissipating the latent heat of the gas, as a result of which
a suction effect, is generated which even permits unequal
capillary tube cross sections without suffering critical
power losses.
[0016] If the power requirements are increased
disproportionately in relation to the cross section of the
ducts, a build-up of condensate can occur, wherein the
outflowing condensate hinders the inflow of gaseous medium,
resulting in power-reducing, intermittent behavior of the
heat transfer.
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[0019] For the parallel flow principle, the cross sections
of the distributor pipes and ducts can be smaller.
[0020] Modules of 25 W to 200 W have been proposed for use
in track switch heaters. The dimensions are coordinated with
the type of track switch and the required snow-melting
power, and may encompass heating of the slide chairs.
[0021] Here, the invention is based on the notion of
specifying a heat exchanger unit for utilizing, collecting
and distributing low-temperature heat that preferably
originates from a thermal ground probe, the heat exchanger
unit being operated with a liquid-gaseous (multi-phase)
working medium. As a suitable heat source, it is preferable
to use the latent heat of a working medium even where there
is only a slight temperature gradient between the phase
change point of the working medium and the freezing point of
water, with it being possible to maximize the power which
can be transmitted to the heat sink, and to significantly
improve efficiency.
[0022] The heat exchanger is designed such that preferably
geothermal heat at a low temperature is used for heating and
temperature control in such a way that, even with the small
temperature differences between the working medium and the
heat sink, such as are present if the temperature level of
the working medium is not raised by any interposed heat
pump, it is possible for a large
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quantity of heat to be transferred over a limited area; that
is to say a high energy density is obtained.
[0023] It can be expected that up to 95% of the heat
extracted from the probe is not utilized for melting snow or
ice, but rather that considerable heat quantities are
dissipated by convection at temperatures below 10'C and by
radiation into the open air.
[0024] It is therefore desirable to control the extraction
of heat from the heat source, minimizing the uncontrolled
extraction of heat. This is provided by means of the
configuration of the surface and/or the material selected
for the heat exchanger.
[0025] It is additionally possible for the flow of the
working medium to be reduced or even interrupted by means of
temperature-dependent regulation. This is preferably achieved
by providing, at a position which is protected from wind and
radiation, a temperature-controlled actuator that raises the
heat exchanger at one side, or raises the feed pipe by a
small amount, in such a way that the return flow of the
medium is interrupted.
[0026] One significant innovation of the invention over
known solutions relates to improvements in the efficiency of
the core components, particularly with regard to the
distribution of heat, which improvements may also be used in
other applications and even permit effective low-
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temperature utilization in said applications for the first
time. With the invention, the efficiency of previous known
solutions is surpassed with regard to power, material use
and economy. Furthermore, additional system components are
proposed, such as for example the integration of heat
accumulators and additional heat sources, or an additional
integration of heat accumulators into the heat exchanger
itself.
(0027] Microstructure heat exchangers differ from other
heat exchangers by their high power density. It is
preferable, depending on the required power and the
resulting overall duct cross section which is defined by
the overall duct length and the duct cross section, for
approximately 100 ducts to be arranged per 10 centimeters
width of the exchanger. The heat exchanger operates with
only a small temperature difference and around the
condensation point of the working medium, with the
operating points of the two fluid phases lying close to one
of their phase change points. In particular, the
combination of a microstructure heat exchanger according to
the invention in connection with the utilization of
geothermal heat offers particular advantages, with regard
to system integration, operational reliability and freedom
from maintenance.
[0028] The heat exchanger unit is particularly useful for
heating traffic surfaces, traffic infrastructure and
traffic facilities. More specifically, the heat exchanger
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unit is particularly suitable for railroad equipment, such
as for track switches and also for railroad crossing
segments or platform segments designed as heat exchangers
and similar units designed as heat exchangers, since the
invention can be operated without additional pumps driven by
external energy and without moving parts. The heat
exchangers can be connected, preferably in a releasable and
nondestructive fashion, to one or more supply lines.
[0029] For heating traffic facilities, such as railroad track
switches, and for the clearance of snow and ice and other
applications for increasing safety in high-risk regions such
as platform edges, railroad crossings or grade crossings, it
is therefore possible to dispense with the use of electric
heating, means or other means for reducing the melting point
of the snow, for example.
[0030] Furthermore, it is possible to minimize the flow
losses and pressure losses in the heat exchanger resulting
from the mutual hindrance of the gas phase and the condensate
returning to the heat source.
[0031] The particular advantage is that the heat exchanger
unit according to the invention has a level of efficiency,
with regard to heat utilization, material use and economy,
which surpasses that of the present state of the art. The
efficiency with regard to the utilization of heat results
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from the optimized dissipation of the heat flowing out across
a temperature gradient.
[0032] In a preferred embodiment of the invention, the mini-
ducts may be arranged, in the case of a particularly high
heat requirement, in a plurality of planes. To be able, with
the small temperature difference, to transfer a heat quantity
which is required for the intended purpose, the heat transfer
area on the side of the working medium must be maximized. The
heat exchanger is formed in one plane, or in a plurality of
planes depending on the energy requirement, of a plurality of
parallel-running ducts, but preferably comprises 2 to 100
ducts per 10 centimeters of width of the heat exchanger and
per plane. The duct diameter preferably lies between 0.5 mm
and 5 mm. In this way, the transfer area from the working
medium to the heat exchanger, and therefore the possible
energy density, is maximized. At the same time, however, the
external surface area must be kept as small as possible in
order to minimize the radiation losses to the environment.
The material selected for the heat exchanger should have good
conductivity and a high level of corrosion resistance.
[0033] In this way, the heat exchanger may take the form of
a microstructure so-called plate-type heat exchanger which,
using the micro-channel principle, is optimized according to
the chosen working medium (preferably CO;), and the
application.
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[0034] When using CO2 as a working medium, a configuration of
the inflow conditions, as is known in heat exchangers, is
only necessary in the case of extreme power demands, since
with simple branching of the ducts from the distributor
pipe, the temperature difference in the heat exchanger with
respect to optimum inflow conditions is only a few tenths of .
a degree. The design from figure 1 or figure 3 is adequate.
Flaring of the capillary pipes is not necessary with CO2 even
in counterflow heat exchangers if said minimum diameters of
the ducts are provided and the power does not exceed an
output power of 5 kW/Hr.
[0035] It is advantageously possible, in order to improve
the return flow of the condensate in counterflow heat
exchangers, for the closed "ends" of the ducts to be curved
upward. In this way, the condensate from said region is
provided with an impetus, which improves the overall return
flow. This is particularly advantageous with relatively long
ducts, such as may be provided in platform edge heaters or
railroad crossing heaters.
(00361 It is possible for the upper apex line of a mini-duct
to run in both a rising and falling manner in sections
proceeding from the inlet point of the gaseous component of
the working medium. The transport mechanism of the gaseous
medium is based on pressure gradients which are generated by
= the reduction in the volume of the gaseous working medium as
a result of
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condensation. The flow of the gaseous medium is basically
independent of the spatial guidance of the ducts.
[0037] Furthermore, it is advantageously possible for the
upper apex line of a mini-duct to rise proceeding from the
inlet point of the gaseous component of the working medium.
In this way, the gaseous component of the working medium in
the mini-duct is directed more effectively.
[0038] Furthermore, the lower apex line of a mini-duct or of
a duct section may advantageously be inclined in the
direction of the outlet point of the liquid component of the
working medium. This ensures an improved outflow of
condensate, since the return flow of the liquid working
medium is effected primarily by gravity. To reliably
discharge the condensate, the ducts should generally have an
inclination in the flow direction which is sufficient but
nevertheless as slight as possible, and a cross section
suitable for the fluid being used. Due to its very low
viscosity, very small inclinations and cross sections may be
selected if the working medium is CO2.
[0039] In a preferred refinement of the invention, a mini-
duct may widen along the longitudinal axis. This may also
take place conically. If a heat exchanger using a gaseous
working medium is installed horizontally or approximately
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horizontally and use is made predominantly of the stored
latent heat, the return flow of the condensate may not be
sufficiently assisted and further disruptive influences must
be eliminated. As one measure for improving the return flow,
it is proposed that the heat exchanger be designed such that
at least the inflow of the gas into the heat exchanger
hinders the return flow of the condensate as little as
possible.
[0040] In one preferred embodiment, the feed duct may taper
along the longitudinal axis in the flow direction of the
gaseous fluid. This may take place conically. Such a cross-
sectional narrowing is possible because, as a result of the
distribution between the individual mini-ducts, gaseous
working medium is constantly extracted from a supply duct in
the flow direction.
[0041] The discharge duct may advantageously widen along the
longitudinal axis in the flow direction of the fluid. Such a
cross-sectional widening is possible because liquid working
medium is constantly passing from the individual mini-ducts
into the discharge ducts in the flow direction.
(0042] it is advantageously possible for the feed duct and
discharge duct to be formed on one side of the mini-ducts as
a supply duct, or for the feed duct and discharge duct to be
arranged spaced apart from one another. It is
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possible in this way for the length and efficiency of the
feed line or discharge line paths to be optimized according
to the structural requirements of a specific application.
[0043] Where the feed and discharge ducts are located at
different sides, there is practically no mutual hindrance,
since the gas flow runs above the outflowing condensate in
the mini-duct and in the same direction.
[0044] It is also possible for the condensate return flow to
be arranged in the profile of a duct. In this case, the
cross-section increases up to the outlet. The gradient angle
of the upper envelope line with respect to the horizontal is
positive over the entire length, being aligned upward in the
flow direction. The angle of the lower envelope line is
negative up to the outlet, being directed downward, following
gravity, in the flow direction. In this design, the gradient
angle of the section from the outlet to the closed end may be
formed with a different, preferably greater gradient. This
accelerates the returning condensate and introduces kinetic
energy so the condensate more easily overcomes any horizontal
sections in the profile.
[0045] As a result of the arrangement of the outlet and
inlet - the outlet is situated in any case lower than the
inlet - gas is prevented from escaping without having
dissipated its latent heat. At the same
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time, the outflowing condensate blocks any possible
undesired inflow of gas at the outlet side. Furthermore,
this arrangement allows the return to extend back in
parallel in a separate pipe, separated from the gas flow,
into the probe pipe expediently no further than up to the
boundary between the transport and heat absorption zones.
[0046] If the entire heat exchanger is installed with a
slight inclination, then it should be ensured that the
installation inclination and the inclination of the ducts at
least do not fully compensate one another, but rather
supplement one another to the greatest possible extent.
[0047] If the individual ducts of the heat exchanger are of
slightly conical design, a design having both ports (i.e. the
gas inlet and condensate outlet) on the same side and one
having the ports on different sides, will differ. If both
ports are on one side, then the widened end is situated at
the port side, with the gradient angle of the longitudinal
axis of the pipe, measured from the port side with respect to
the horizontal, being greater than that of the upper pipe
envelope line but smaller than that of the lower pipe
envelope line, which should be less than 0. If the ports are
situated at different sides, then the widened side of the
pipe is situated on the side of the condensate outlet,
wherein the gradient angle of the upper pipe envelope line
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with respect to the horizontal, measured from the gas inlet
side, should be at least greater than O. The gradient of the
longitudinal axis with respect to the horizontal should be
negative. The gradient angle need not remain constant over
the length of the ducts and may be adapted for the
installation conditions.
[0048] In both embodiments, the port for the gas supply is
situated higher than that of the condensate outlet. In the
embodiment with the ports on one side, the hindrance of the
flows is minimized, since the gas flow runs above the
condensate return flow.
[0049] In one preferred embodiment of the invention, a layer
which inhibits the transfer of heat may be at least partially
arranged between the working medium and the outer surface of
the heat exchanger. An aluminum heat exchanger may possibly
have too high a degree of thermal conductivity, such that
under some conditions, the thermal probe dissipates too much
heat. With a thin insulating layer, the thermal conductivity
along the path from the fluid to the heat exchanger surface
may be reduced by virtually any desired order of magnitude.
The heat exchanger and its parts, such as transport lines,
may be provided with an insulating layer which such that the
region below the heat exchanger as viewed in the
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flow direction is not heated, and the probe is not
subjected to unnecessary loading.
[0050] Furthermore, it may be advantageous to form the mini-
ducts transporting the working medium into a housing,
wherein the heat conductance values of the materials of the
two assemblies - duct system and housing - may differ. Here,
the production of the distribution and of the ducts composed
of plastic is correspondingly cost-effective.
[0051] In one preferred embodiment of the invention, a heat
accumulator may be integrated into at least one heat
exchanger and/or at least one transport line for the return
flow of the liquid working medium to the heat source. In this
way, ambient heat or heat from solar radiation is stored and
introduced into the circuit of the working medium.
[0052] In one preferred refinement of the invention, a return
transport line may be arranged from the heat accumulator to
the heat exchanger for the gaseous working medium formed as a
result of the absorption of heat in the heat accumulator.
[0053] Here, one advantage is the reduction in the
extraction of heat from the heat source, or the
regeneration of said heat. A further reduction in the
extraction of heat from the thermal ground probe and the
improvement of the regeneration of said heat may be
obtained in this way. By
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utilizing ambient heat, and in particular heat from solar
radiation, the temperature of the working medium at the
heat sink may be temporarily increased to such an extent
that the circulation of the working medium and the
extraction of heat from the ground are interrupted for a
period of time. A reduction in the operating duration of a
thermal ground probe as a primary heat source allows the
thermal ground probe to be designed more cost-effectively.
If sufficient installation space is available, the
accumulator may also be formed with silica gel or zeolite
as accumulator material.
[0054] In one preferred embodiment, an auxiliary heater may
be integrated as a further heat source. In this way, the
heat exchanger unit is designed for an extreme extraction of
heat.
[0055] The upper side of a heat exchanger may advantageously
be installed so as to be at least slightly inclined with
respect to the horizontal. If the heat exchanger is installed
in a horizontal or virtually horizontal position and for the
purpose of thawing frozen precipitate, the surface should be
designed so as to ensure reliable drainage of the thawed
precipitate. This measure also serves to reduce the undesired
dissipation of heat to the environment.
[0056] Standing water on the heat exchanger would, on
account of its high heat storage capacity, absorb
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considerable amounts of power, rendering said power useless.
In contrast, if water, melted snow or melted ice is
prevented from remaining on the surface in any more than a
thin film of moisture, then thermal power is no longer
extracted from the heat source for the further melting or
heating of the melt water, such that only a significantly
lower thermal power is extracted as a result of an air flow
or radiation. The surface is therefore preferably designed
such that the snow or sleet which falls thereon is
immediately at least partially melted and the melt water
flows off from the surface as a result of at least a slight
gravitational component, preferably from a slightly oblique
plane which runs parallel to the pipes conducting the
working medium. For the use of the heat exchanger in track
switch heaters, a material is selected which has good
thermal conductivity, preferably a metal with a smooth
surface, for example aluminum, which at the same time has
very small heat dissipation values. These measures allow
more heat than is necessary for clearing snow and ice to be
extracted from the heat exchanger only by convection, such
as a cold air flow, and as a result of the pure radiation
losses, for example to the cold environment. The radiation
and convection losses are however kept to the lowest
possible level as a result of the minimization of the heat
exchanger surface and the material selection.
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[0057] In one preferred embodiment of the invention, a
thermal ground probe which is fixedly installed in the ground
can be isolated from vibration by means of an elastic
connecting element. If a heat exchanger is exposed to
vibration and shock loading, for example in transportation
equipment, particularly if the working medium is gaseous and
used under a high working pressure (approximately 40 bar if
CO2 is used), the heat exchanger must be vibrationally
insulated from a related thermal ground probe, and must
withstand the high pressure over a long period of time. Here,
the working pressure may be monitored by means of a pressure
or temperature display.
[0058] Since it must be possible to carry out maintenance
repair and replacement work on the traffic facilities and
traffic surfaces, it is preferable that the elastic element
be removable in a non-destructive fashion, for example, to
separate the heat exchanger from the thermal ground probe and
replace it in the event of damage or during maintenance work
in the surroundings of the heat exchanger. Since the heat
exchanger is not necessarily rigidly connected to the surface
or equipment to be heated, it is also possible for the
elastic fastening of the heat exchanger to act as a
vibrational insulator.
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[0059] If the heat exchanger is not the surface or system to
be heated but rather must be fixedly connected thereto, it is
proposed, in order to improve the transfer of heat by means
of the use of thermally conductive pastes, that the contact
pressure of the heat exchanger against the heat sink be
increased by means of a screw connection or that a metallic
connection be provided, for example by soldering.
[0060] It is advantageously possible for the component to be
heated to itself be designed as a heat exchanger. In a
further advantageous refinement, the mini-ducts may be
formed at least as co-supporting elements of the component
to be heated. In the event that the heat exchanger
constitutes the component to be heated, the surface of which
cannot be formed from metal, and the radiation losses are
therefore greater than in the case of a metallic surface,
the higher thermal energy requirement must be taken into
consideration in the design of the probe. Here, for this
purpose, the metallic pipes are designed at least as co-
supporting elements of the heat exchanger.
[0061] It is advantageously possible for the heat exchanger
with its mini-ducts to be designed such that it can be tilted
with respect to the horizontal by means of a control unit.
The power losses as a result of radiation and convection can
be then counteracted by means of a temperature-controlled
circuit.
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ZL1
The inclination in the condensate return flow, preferably in
the counterflow embodiment, can then be varied such that the
condensate can no longer flow back. For this purpose, a
control element which expands or contracts in the event of a
temperature change may be arranged on the heat exchanger. In
this way, the extraction of energy from the heat source can
be controlled in a targeted fashion as a function of the
ambient temperature. This counteracts an unnecessary
extraction of heat from the heat source.
[0062] It is advantageously possible for at least one return
transport line to be raised by means of a control unit,
thereby preventing the return flow of condensate. Said
control unit may be arranged under the condensate return
line, with the aim of raising the return transport line for
example only locally in order to prevent the return flow of
the condensate and to interrupt the gas flow. Here, the heat
exchanger need not necessarily be designed to be tiltable.
[0063J In a preferred embodiment of the invention as a track
switch heater, at least one heat exchanger can be integrated
into a slide chair, in the locking crib, in the region of
the track switch tongue on the rail web and/or on the rail
base of the track switch.
[0064] The heat exchangers are installed such that, in the
simplest case, they longitudinally cover a tie crib for a
width of approximately the adjustment travel of the track
switch tongue, and lie approximately
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over half of the width of the inner rail base. If the heat
exchanger is additionally used for heating the adjacent
slide chairs, then a sufficient transfer of heat of the
required heat quantity per unit time is ensured by means of
a sufficient contact pressure against the slide chairs.
[0065] The ties of a track change their position over time
after being laid as a result of the applied load. here, the
movements in the longitudinal direction are of particular
significance because those movements change the installation
space for the heat exchanger.
[0066] It is advantageously possible for at least one heat
exchanger to be integrated in a slide chair of the track
switch. The solution according to the invention makes it
possible for a slide chair of a track switch to be heated
and also for the rail head to be heated. If it is necessary
for two or more heat exchangers receiving a working medium
from one heat source to be connected in series, the
connection must comprise an elastic element to compensate
for opposing movements without damaging the heat exchanger.
[0067] A preload is often generated by means of a
resiliently mounted connection. The preload is selected
such that a sufficient contact pressure against the
respectively delimiting slide chairs is generated in all
CA 02684030 2014-10-02
26
positions between the minimum and maximum change in position
of the ties.
[0068] For heating a slide chair in track switches, it is
important for said slide chair to be thermally connected to
a heat exchanger. Alternatively, in particular where the
demands on heating power are relatively high, slide chairs
having integral heat exchangers are proposed. Said heat
exchanger may be designed as a removable plate, or the mini-
ducts may be guided in grooves, which may be milled or
forged under or on the slide chair, for example. It is also
possible for the slide chair and heat exchanger to be formed
as one component.
[0069] It is advantageously possible for at least one heat
exchanger to be arranged in the region of the track switch
tongue on the rail web and/or on the rail foot.
[0070] To prevent the track switch tongue from possibly
becoming fixedly frozen to the stock rail, it is proposed
that heating be provided by means of the corresponding heat
exchanger with guidance on the rail web and ducts which run
in the transverse direction with respect to the rail. The
fastening of the heat exchanger and the increase in the
contact pressure by means of screws, is preferably done with
a bore through the neutral axis of the rail web. In the case
of increased heat requirements, an additional heat exchanger
may be arranged on the outer channel of the rail profile
below the rail head.
CA 02684030 2014-10-02
27
[0071] With powers of approximately 120 W per side and crib
interval, adequate melting power is provided even for
snowfall of more than 10 cm/h. It is to be assumed that up to
95% of the power output does not actually melt snow but
rather is lost to radiation and convection. Minimizing power
loss is therefore expedient and economical.
[0072] To prevent radiation and convection there, the web
and the base of the stock rail may be thermally insulated
to the outside, and the web may also be thermally insulated
to the inside if the structure of the track switch permits
this. The insulation may be fastened to the rail base and,
on the outer side, may surround an additional heat
exchanger which may be provided in the outer channel of the
rail profile.
[0073] Heat exchangers which are not intended to heat the
slide chair or the rail head are fastened with clamps to the
rail base and lie against the ties. Heat exchangers may
additionally be fastened to a tie. Said heat exchangers are
designed in terms of their dimensions such that an increase
in the tie interval will not allow the heat exchangers to
fall between the ties, while a reduction in the tie interval
will not permit the heat exchangers to be damaged by the
slide chairs. It is advantageously possible for at least one
heat exchanger to also be integrated in
CA 02684030 2014-10-02
Zb
the locking crib of the track switch and/or designed as a
cover for the locking crib.
[0074] In a further preferred embodiment of the invention as
a track switch heater, the heat exchanger unit may be
mounted on the support points on the track switch by means
of deformable elements. If the heat exchangers are used in
railroad engineering for heating track switches in order to
clear the latter of snow and ice, then the proposed
technology must be adapted to the more difficult
requirements. The heat exchangers must thus be designed such
that a change in length of the installation space does not
have an influence on function and operational reliability,
and does not damage the heat exchanger.
[0075] If the heat exchanger is designed as a component
mounted on a tie, and covers and heats approximately half of
a tie crib at both sides of said tie, the cost of
vibrational insulation and of compensation for length
variations in the installation space can be minimized.
[0076] The device according to the invention for the improved
utilization of geothermal heat for heating systems at low
temperature comprises at least one of the following
improvements, providing a heat exchanger that can be used for
temperature control or for heating purposes, preferably for
heating transportation
CA 02684030 2014-10-02
29
equipment. In relation to the prior art, said device
constitutes a more efficient and more economical method.
[0077] In contrast to the known heat exchangers which
utilize geothermal heat and which are used in combination
with heat pumps and in which the heat is transferred in a
controlled fashion from a positively-driven medium to a
second positively-driven medium, it is proposed here that
the latent heat contained in a working medium may be
dissipated directly to the environment.
[0078] If the heat transfer area on the side of the working
medium is maximized, then it is possible for the required
heat quantity to be transferred even at the low temperature
difference from thermal ground probes.
[0079] In this way, the transfer surface area from the
working medium to the heat exchanger, and therefore the
possible energy density, is maximized. At the same time, the
exposed surface is kept as small as possible through a
compact design, so as to minimize the radiation losses to the
environment.
[0080] The reduction in the extraction of heat from a thermal
ground probe, which has hitherto been realized by means of
regulating or actuating elements such as valves, takes place
in a passive fashion, specifically by means of the material
selection and the configuration of the surface of the heat
exchanger.
CA 02684030 2009-10-09
[00811 Exemplary embodiments of the invention will be
explained in more detail on the basis of schematic
drawings, in which, in each case schematically:
[0082] figure 1 shows a plan view of a heat exchanger
having duct structures and the flow characteristic of the
working medium,
[0083] figure 2 shows a cross section through a heat
exchanger according to figure 1 along a mini-duct,
[0084] figure 3 shows a cross section through a further
embodiment of a heat exchanger according to figure 1 along
a mini-duct,
[0085] figure 4 shows a plan view of a further embodiment
of a heat exchanger having duct structures and the flow
characteristic of the working medium,
[0086] figure 5 shows a cross section through the heat
exchanger according to figure 4 along a mini-duct,
[0087] figure 6 shows a plan view of a further embodiment
of a heat exchanger having duct structures and the flow
characteristic of the working medium,
[0088] figure 7 shows a cross section through the heat
exchanger according to figure 6 along a mini-duct,
[0089] figure 8 shows a detailed view of the constituent
parts of a heat exchanger for forming mini-ducts,
[0090] figure 9 shows a cross section, running
perpendicular to the mini-ducts, of the heat exchanger
formed from the constituent parts in figure 8,
(00145923.DOC)
CA 02684030 2009-10-09
31
[0091] figure 10 shows a partial view of a tie interval
heater having transport lines leading from a thermal
ground probe,
[0092] figure 11 shows a partial view of a tie interval
heater having an elastic connecting element for pressure
monitoring, and branching transport lines,
[0093] figure 12 shows a partial view of :he tie interval
heater having an elastic connecting element for pressure
monitoring, and branching transpor: lines, as per figure
. 11 at a different pressure,
[0094] figure 13 shows a partial view of a further
embodiment of a slide chair heater having duct structures,
[0095] figure 14 shows a partial view of a slide chair
heater having a heat exchanger with duct structures
additionally integrated in the slide chair,
[0096] figure 15 shows a cross section through the slide
chair heater according to figure 14, perpendicular to the
mini-ducts,
[0097] figure 16 shows a partial view of a slide chair
heater having two heat exchangers which are supplied from
one heat source and which have duct structures and
branching transport lines and deformable elements,
[0098] figure 17 shows a partial view of a slide chair
heater which is of complex design with a plurality of heat
exchangers,
[0099] figure 18 shows a plan view of the duct guidance
in a heat accumulator,
00145923.DOCI
CA 02684030 2009-10-09
32
= [00100] figure 19 shows an arrangement of the individual
system elements with a heat exchanger and heat accumulator
of a heat exchanger unit,
[00101] figure 20 shows an arrangement of the individual
system elements with a heat exchanger and heat accumulator
of a heat exchanger unit in connection with a thermal
ground probe,
[00102] figure 21 shows a partial view of a locking crib
heater having duct structures,
[00103] figure 22 shows a partial view of a further
embodiment of a locking crib heater having duct
structures,
[00104] figure 23 shows a cross section through a heat
exchanger along a mini-duct which operates on the
counterflow principle,
[00105] figure 24 shows a cross section through a heat
exchanger along a mini-duct which operates on the
counterflow principle, in the working position,
[00106] figure 25 shows a cross section through a heat
exchanger along a mini-duct which operates on the
=
counterflow principle, in the standby position.
[00107] Corresponding parts are denoted by the same
reference symbols in ail the figures.
[00108] Figure 1 shows a plan view of a heat exchanger 11
having duct structures 111, 114, 115 and the flow
characteristic FG, FE' of the working medium_
00115923.DOCI
CA 02684030 2014-10-02
33
[00109] The heat exchanger 11 has, in the transverse
direction, a multiplicity of mini-ducts 111 which run parallel
to one another. The gas inflow and the condensate return flow
of the working medium take place in directly adjacent feed
ducts 114 and discharge ducts 115 which are situated on one
side of the mini-ducts 111.
[00110] Arrows denoted by FG indicate the flow direction of
the gaseous medium. Arrows denoted by FF indicate the flow
direction of the liquid medium after having dissipated heat in
the heat exchanger 11.
[00111] In the heat exchanger 11, the parallel mini-ducts 111
may of course also run obliquely or may for example be curved
in an S-shape or run in a spiral fashion.
[00112) Figure 2 shows a cross section through a heat
exchanger 11 according to figure 1 along a mini-duct 111. The
gas inflow and the condensate return flow of the working
medium take place in directly adjacent supply ducts, namely
feed ducts 114 and discharge ducts 115, which are situated on
one side of the mini-ducts 111. In this case, the mini-ducts
are formed with a constant cross section along the
longitudinal axis L. Such mini-duct arrangements are
preferably installed with a slightly inclined longitudinal
axis L, primarily to ensure the condensate return flow and
thereby improve the power.
[00113] Figure 3 shows a cross section through a further
embodiment of a heat exchanger 11 according to figure 1
CA 02684030 2014-10-02
34
along a mini-duct 111. In this case, the upper apex line OS
of the mini-duct 111 rises slightly proceeding from the
feed duct 114 for conducting the gaseous component of the
working medium. The lower apex line US is inclined in the
direction of the discharge duct 115 for discharging the
liquid component of the working medium. In this case, the
normally preferred inclination of the longitudinal axis L
of the mini-ducts 111 is already integrated in the heat
exchanger 11 itself.
[00114] Figure 4 shows a plan view of a further embodiment
of a heat exchanger 11 having duct structures 111, 114, 115
and the flow directions FG, FF of the working medium.
[00115] The associated cross section through the heat
exchanger 11 according to figure 4 along a mini-duct 111 is
shown in figure 5. In said embodiment, the supply ducts,
namely feed duct 114 and the discharge duct 115, are
situated on opposite sides of the mini-ducts 111. The
profile of a mini-duct 111 again has an upper apex line OS
which rises continuously from the inlet point 112 of the
gaseous component of the working medium. The lower apex line
US, in contrast, is inclined in the direction of the outlet
point 113 of the liquid component of the working medium.
[00116] Figure 6 shows a plan view of a further embodiment
of a heat exchanger 11 having duct structures 111, 114, 115
and the flow directions FG, FF of the working medium. In
this embodiment, the discharge duct 115 divides
CA 02684030 2014-10-02
the mini-ducts 111, which run parallel to one another, into
two halves.
[00117] Figure 7 shows a cross section through the heat
exchanger 11 according to Figure 6 along a mini-duct 111.
Here, the upper apex line OS of the mini-duct 111 rises
continuously from the feed duct 114 for conducting the
gaseous component of the working medium. The lower apex line
US is inclined, in its partial sections, in the direction of
the discharge duct 115 for discharging the liquid component
of the working medium.
[00118] Figure 8 shows a detailed view of the constituent
parts of a heat exchanger 11 for forming mini-ducts 111. The
heat exchanger 11 is composed of an upper shell 116 and a
lower shell 118, between which a punched corrugated plate
117 is arranged to form the mini-ducts 111. The heat
exchanger may also be produced in one piece from an extruded
profile.
[00119] The described multi-part configuration of the heat
exchanger 11 may also be utilized in the application such
that, for example, the upper shell 116 or lower shell 118
individually may be integrally connected to the component to
be heated. In this case, the final assembly of the heat
exchanger 11 is then carried out on site. This single-piece
configuration serves to ensure a minimum heat transfer
resistance from the heat exchanger to the component to be
heated.
CA 02684030 2014-10-02
36
[00120] Figure 9 shows a cross section, running
perpendicular to the mini-ducts 111, of the heat exchanger
111 formed from the constituent parts in figure 8. Here, the
upper shell 116 and the lower shell 118 are joined together
with the corrugated plate 117. The corrugated plate 117 is
connected to the upper shell 116 and lower shell 118 in a
pressure-tight manner and is in good thermally conductive
contact with the housing formed from the lower shell 118 and
upper shell 116.
[00121] Figure 10 shows a partial view of a tie crib heater
having a thermal ground probe 21 and transport lines 12. In
figure 10, the transport lines 12 are guided along the side
surfaces of the tie 37 to the rail 38. In figure 10B, the
transport lines 12 are arranged along one side surface of
the tie 37.
[00122] Figures 11 A and B show a partial view of a tie crib
heater having an elastic connecting element 14 for pressure
monitoring, and branching transport lines 12. The transport
lines 12 are guided partially over the outer region of the
tie 37 and, in the further profile, toward the side surface
and under the rail 38. The connecting element 14 is designed
as an integrated pressure display which signals a possible
pressure drop in the system, which manifests itself in a
change in length of the elastic connecting element 14.
Figures 12 A and B show a partial view of a further
embodiment of the tie crib heater having an elastic
connecting element 14 for
CA 02684030 2014-10-02
37
pressure monitoring, and branching transport lines 12 which
are arranged on one side surface of the tie 37.
[00123j The functional reliability of the hear exchanger,
which depends on the operating pressure is monitored by
means of a pressure display which is integrated into the
elastic element of the vibration isolation arrangement.
Said elastic element is a corrugated pipe which is
arranged in the transport zone so as to be visible
adjacent to the end of the tie. If the operating pressure
in the pipe is adequate, the corrugated pipe is extended;
if the operating pressure falls as a result of damage,
then the corrugated pipe is shortened. The damage is
therefore evident from viewing the corrugated pipe, or the
damage may be signaled by means of an electrical contact
which is triggered when the corrugated pipe is shortened.
A comparison of figures 11 A and B and of figures 12 A and
B shows the effect of the pressure-dependent change in
length, which is indicated by the elastic connecting
element 14. The pressure display may also be provided by
virtue, for example, of a pressurized supply pipe being
composed of elastic material, which sags in the event of a
significant pressure drop.
(00124] Figure 13 shows a partial view of a further
embodiment of a track switch and slide chair heater having
duct structures 111, ].14, 115. The heating takes place by
means of outer ducts 111 which are guided around the slide
chair 31 and which are arranged on the tie 37. The
CA 02684030 2014-10-02
38
individual ducts 111 may also have different cross sections
in order to provide a uniform distribution of the gaseous
working medium. The heat exchanger 11 runs parallel to the
rail 38 so as to also heat the latter in partial sections.
[00125] Figure 14 shows a partial view of a track switch and
slide chair heater additionally having a heat exchanger 11
with duct structures 111 integrated in the slide chair. The
heat exchanger 11 again runs parallel to the rail 38 so as to
also heat the latter in sections. The slide chair 31 has, at
the top in the center on the tie 37, a cutout into which are
formed additional grooves for holding mini-ducts 111.
[00126] As can be seen from figure 15 in a cross section
through the slide chair heater according to figure 14
perpendicular to the mini-ducts, an additional plate is
placed as an upper shell 116 into the cutout in shell 119,
which upper shell 116 absorbs the pressure forces originating
from the track switch tongue. The slide chair 31 is itself
designed, in effect, as a heat exchanger 11.
[00127] Figure 16 shows a partial view of a track switch and
slide chair heater =having two heat exchangers 11, which are
supplied from one heat source, with duct structures 111, 114,
115 and branching transport lines 12. The arrangement of two
heat exchangers, which are fed from one probe pipe, with
longitudinally running ducts also has a deformable element 36
on the slide chair 31 for length
CA 02684030 2014-10-02
39
compensation of the installation space in the tie interval.
The transport line 12 has a slightly bulged shape at the base
side for the improved separation of the gas phase and of the
condensate by the lower condensate duct.
[00128] Figure 17 shows a partial view of a track switch and
slide chair heater which is of complex design and has a
plurality of heat exchangers 11 fastened to the tie or to the
slide chair. The figure illustrates a juxtaposed arrangement
of heat exchangers 11 with mini-ducts running longitudinally
with respect to the rail 38. Said mini-ducts may also be
arranged transversely with respect to the rail. The ties of a
rail and the slide chairs change their positions over time
after having been laid on account of the applied load.
Therefore, in each case two heat exchangers 11 are arranged in
pairs on one slide chair 31, with a certain gap remaining
between the two heat exchangers 11 for length expansion. The
working medium is supplied from a probe pipe (not shown) to
the heat exchangers 11 which are arranged in series, with the
heat exchangers 11 being supplied from branching transport
lines 12. In this case, the feed and return transport lines
are realized by one pipe.
[00129] Figure 18 shows a plan view of the duct guidance in a
heat accumulator 13. Here, said heat accumulator 13 is for
example a latent heat accumulator from which the
CA 02684030 2009-10-09
condensate flowing back from the heat sink absorbs the
heat contained in the heat accumulator, evaporates and
flows to the heat sink - the heat exchanger 11 - again
without heat having to be extracted from the thermal
ground probe as a source. In the lower-lying section plane
A, one possible arrangement of zones of accumulator
material which run parallel to one another is illustrated.
[00130] In order that the return-flowing gas and the
condensate running in the opposite direction influence one
another only to a small extent, the ducts are widened in
the direction of the gas flow, preferably horizontally.
The ducts preferably have, corresponding to the heat which
can be absorbed in the heat source, a plurality of outlets
situated in the profile of the condensate flow, through
which outlets the gas escapes from the duct and flows back
to the heat exchanger. The heat accumulator 13 may be
split into a plurality of regions. Therefore, the heat in
the respective region is extracted parallel thereto. If
the heat source is cooled in the first section, then the
condensate here is no longer evaporated, but rather passes
into the second region, absorbs the heat from said second
region, evaporates and flows back through the next outlet
to the heat sink. The processes are similar in the further
regions. The separation into a plurality of regions has
the advantage that the gas does not flow in the opposite
direction to the condensate over the entire pipe length in
(00145923.Doc)
CA 02684030 2014-10-02
41
the heat source, and the two phases thus hinder one another
only to a small extent.
[00131] Figure 19 shows an arrangement of the individual
system elements with a heat exchanger 11 and heat accumulator
13 of a heat exchanger unit. The arrangement of the system
elements has the connection of the heat exchanger 11 and of
the heat accumulator 13 via the transport lines 12 with
elastic connecting elements 14. The flow directions of the
working medium through the system are also shown.
[00132] Figure 20 shows the arrangement of the individual
system elements with a heat exchanger 11 and heat accumulator
13 of a heat exchanger unit 1 in connection with a thermal
ground probe 21 as a heat source 2. For illustration, the
flow directions of the working medium through the system are
shown flowing through feed transport lines 121 and return
transport lines 122.
[00133] Figures 21 and 22 show an arrangement of the heat
exchanger 11 for a locking crib heater of a track switch 3.
The locking crib 35 is covered by a heat exchanger 11 so as
to minimize the infiltration of snow or ice. A further heat
exchanger which prevents freezing of the melt water may be
arranged on the base of the locking crib, and the water may
be discharged in this way.
[00134] Figure 23 shows a cross section through a heat
exchanger 11 along a mini-duct 11]. which operates on the
counterflow principle. To improve the return flow of the
condensate in a virtually horizontally arranged heat
CA 02684030 2014-10-02
42
exchanger, the closed end is turned upward in the counterflow
embodiment. The feed 114 and discharge 115 ducts are formed as
a unitary supply duct.
[00135] Figures 24 and 25 show a cross section through a heat
exchanger 11, having a tilting mechanism 4, along a mini-duct
111 which operates on the counterflow principle. In figure 24,
the duct is tilted in the working position. The inclination
allows the liquid working medium to flow out to the heat
source unhindered. In contrast, in figure 25, the heat
exchanger 11 is in a standby position. The mini-ducts 111 of
the heat exchanger 11 are inclined by the tilting mechanism in
such a way that the condensed working medium can no longer
flow back the heat source. The extraction of energy from the
heat source can then be more precisely controlled.
CA 02684030 2014-10-02
43
List of reference symbols
1 Heat exchanger unit
11 Heat exchanger
111 Mini-ducts
112 Inlet point
113 Outlet point
114 Feed duct, supply duct
115 Discharge duct, supply duct
116 Upper shell
118 Lower shell
117 Corrugated plate
119 Shell
12 Transport lines
121 Feed transport line
122 Return transport line
13 Heat accumulator
14 Connecting element
2 Heat source
21 Thermal ground probe
22 Auxiliary heater
3 Component to be heated; track switch
31 Slide chair
32 Track switch tongue
33 Rail web
34 Rail base
CA 02684030 2009-10-09
44
35 = locking crib
36 Deformable elements
37 Tie
38 Rail
4 Tilting mechanism, control unit
OS Upper apex line of a mini-duct
US Lower apex line of a mini-duct
Longitudinal axis of a mini-duct
FG Flow direction of gaseous medium
7r Flow direction of liquid medium
, =
A Lower section plane
=
(00145923_DOCI
