U.S. patent application number 13/020514 was filed with the patent office on 2012-08-09 for thermal control device.
This patent application is currently assigned to Iberica del Espacio, S.A.. Invention is credited to Andrei KULAKOV, Donatas Mishkinis, Alejandro Torres Sepulveda.
Application Number | 20120198859 13/020514 |
Document ID | / |
Family ID | 46599728 |
Filed Date | 2012-08-09 |
United States Patent
Application |
20120198859 |
Kind Code |
A1 |
Sepulveda; Alejandro Torres ;
et al. |
August 9, 2012 |
THERMAL CONTROL DEVICE
Abstract
The invention refers to a thermal control device for controlling
the temperature of a heat source by means of transferring heat from
the heat source to the ambient environment, through the circulation
of a fluid in the device, said device comprising an evaporator (10)
collecting heat from the heat source, a condenser (30) rejecting
heat to the ambient environment, a compensation chamber (20), and
liquid (50) and vapor (40) transport lines connecting the
evaporator (10) and the condenser (30), the fluid flowing through
said transport lines (40, 50), the device further comprising a
thermal electrical cooler (90), the thermal electrical cooler (90)
further comprising a thermal saddle (80) attached to the cold side
of the thermal electrical cooler (90), and a thermal radiator (100)
attached to the hot side of the thermal electrical cooler (90),
such that heat is rejected to the ambient environment directly
through the thermal radiator (100), when the thermal control device
operates in a hot environment, the ambient temperature surrounding
the liquid transport line (50) being higher than the temperature of
liquid in the exit (110) of the condenser (30).
Inventors: |
Sepulveda; Alejandro Torres;
(Madrid, ES) ; Mishkinis; Donatas; (Madrid,
ES) ; KULAKOV; Andrei; (Madrid, ES) |
Assignee: |
Iberica del Espacio, S.A.,
|
Family ID: |
46599728 |
Appl. No.: |
13/020514 |
Filed: |
February 3, 2011 |
Current U.S.
Class: |
62/3.1 |
Current CPC
Class: |
F28D 15/0275 20130101;
F28D 15/04 20130101; F25B 21/02 20130101; H01L 2924/0002 20130101;
F28D 15/0266 20130101; H01L 2924/0002 20130101; H01L 2924/00
20130101; H01L 23/38 20130101; H01L 23/427 20130101 |
Class at
Publication: |
62/3.1 |
International
Class: |
F25B 21/00 20060101
F25B021/00 |
Claims
1. Thermal control device for controlling the temperature of a heat
source by means of transferring heat from the heat source to the
ambient environment, through the circulation of a fluid in the
device, said device comprising an evaporator (10) collecting heat
from the heat source, a condenser (30) rejecting heat to the
ambient environment, a compensation chamber (20), and liquid (50)
and vapor (40) transport lines connecting the evaporator (10) and
the condenser (30), the fluid flowing through said transport lines
(40, 50), characterized in that the device further comprises a
thermal electrical cooler (90), the thermal electrical cooler (90)
further comprising a thermal saddle (80) attached to the cold side
of the thermal electrical cooler (90), and a thermal radiator (100)
attached to the hot side of the thermal electrical cooler (90),
such that heat is rejected to the ambient environment directly
through the thermal radiator (100), when the thermal control device
operates in a hot environment, the ambient temperature surrounding
the liquid transport line (50) being higher than the temperature of
liquid in the exit (110) of the condenser (30).
2. Thermal control device according to claim 1, wherein the thermal
electrical cooler (90) is located in the liquid transport line (50)
close to the compensation chamber (20).
3. Thermal control device according to claim 1, wherein the thermal
electrical cooler (90) is located on the compensation chamber
(20).
4. Thermal control device according to claim 2, wherein the thermal
saddle (80) comprises a metallic rectangular plate with an orifice
inside it for the liquid transport line (50).
5. Thermal control device according to claim 3, wherein the thermal
saddle (80) comprises a rectangular plate having one flat side for
being attached to the thermal electrical cooler (90), and a
cylindrical opposite side for attaching the thermal electrical
cooler (90) to the compensation chamber (20) with the same diameter
as it.
6. Thermal control device according to claim 4, wherein the thermal
saddle (80) is made of a metal having a high thermal
conductance.
7. Thermal control device according to claim 6, wherein the thermal
saddle (80) is made of aluminum.
8. Thermal control device according to claim 1, wherein the thermal
electrical cooler (90) comprises a hot plate and a cold plate,
having different electrical polarity.
9. Thermal control device according to claim 1, wherein the thermal
electrical cooler (90) further comprises a fan to facilitate heat
rejection.
10. Method to increase thermal conductivity of a thermal control
device according to claim 1 working in a hot environment, the
ambient temperature surrounding the liquid transport line (50)
being higher than the temperature of liquid in the exit (110) of
the condenser (30), wherein the method comprises the steps of
cooling of the thermal control device by means of the thermal
electrical cooler (90), and removing heat, obtained by liquid
inside of the liquid transport line (50) or by compensation chamber
(20) from the hot environment, by means of the thermal electrical
cooler (90) from the liquid transport line (50) or compensation
chamber (20), and heat released by the thermal electrical cooler
(90) itself, this heat being directly rejected to the ambient
environment outside the thermal control device and hot
environment.
11. Method according to claim 10, wherein the cooling of the
thermal control device is made in the liquid transport line (50)
close to the compensation chamber (20).
12. Method according to claim 10, wherein the cooling of the
thermal control device is made in the compensation chamber (20).
Description
FIELD OF THE INVENTION
[0001] The present invention relates to improvements in a thermal
control device, in particular to a method for increasing the
thermal conductance of a thermal control device and to an apparatus
to perform such method.
BACKGROUND OF THE INVENTION
[0002] At present, thermal control of electronics and computer
equipment is the key element of proper operation of these kind of
equipments. The most commonly known thermal devices used for
controlling thermal loads in electronics are the so called two
phase heat transfer loops, which are also known in engineering
practice as loop heat pipes.
[0003] The purpose of these known loop heat pipes is to transfer
heat between a heat source (for instance, an electronic element)
and a heat sink (for instance, a radiator). A loop heat pipe is a
closed, hermetically sealed circuit, which is partially filled by a
working fluid, which is called heat carrier. Known loop heat pipes
operate in the saturation curve of the working fluid, such that the
two phases (vapour and liquid) of this fluid are always present in
the circuit.
[0004] Known loop heat pipes usually comprise at least five
elements: an evaporator, a compensation chamber, a vapour transport
line, a condenser and a liquid transport line. These systems can
also comprise a pressure regulating valve, which provides
temperature control to loop heat pipes. In order to provide a
constant circulation of the working liquid in the circuit capillary
porous wicks are used.
[0005] Also, some known loop heat pipes comprise a thermal
electrical cooler, which provides a performance improvement of the
thermal control device, providing the possibility of temperature
control and start-up facilitation. A thermal electrical cooler is a
device comprising a hot side and a cold side, having different
temperatures, which creates a heat flux between said two sides,
which makes it possible to cool or to heat certain parts of loop
heat pipes.
[0006] It is known from WO 01/33153 a thermal electrical cooler
improving the start-up ability of the loop heat pipe. In this
document, the thermal electrical cooler is located attached on one
side to the compensation chamber, with its other side being
attached to the heat pipe, transferring heat to the evaporator.
Therefore, with the help of the thermal electrical cooler, heat is
removed from the compensation chamber of the loop heat pipe, being
transferred to a localized position in the evaporator. This
provides vaporization in the evaporator wick and creates a
temperature difference between the compensation chamber and the
evaporator, which facilitates the start-up of the loop heat
pipe.
[0007] Also, it is known from document U.S. Pat. No. 7,111,394, a
thermal electrical cooler device providing performance improvement
of the loop heat pipe comprising said device. This thermal
electrical cooler provides the possibility of reducing parasitic
heat leak from the evaporator to the compensation chamber in the
loop heat pipe, also providing temperature control of the loop heat
pipe. Document RU 2117893 describes the application of a thermal
electrical cooler for increasing reliability of the loop heat pipe
operation at transient regimes. Document SU 1834470 provides an
example of an application of a thermal electrical cooler for loop
heat pipes comprising a bypass valve: the object of this invention
is providing the possibility of switching thermal electrical cooler
and bypass valve operation.
[0008] However, the purpose of the application of the thermal
electrical cooler in loop heat pipes in the above-mentioned
documents does not include the problem related to the existing need
of increasing loop heat pipe thermal conductance by means of
compensating parasitic heat leak between the ambient environment
and the liquid line in the loop heat pipe.
[0009] In the operation of a loop heat pipe contour, when vapour of
the working fluid reaches the condenser, it condenses along a
certain length of the condenser with the consequent liquid
formation; this liquid continues to flow inside the cooled
condenser along the rest of its length, which makes that this
liquid is therefore cooled down below the saturation temperature of
the fluid. This phenomenon is called subcooling, and helps to
compensate the parasitic heat leak from the evaporator to the
compensation chamber. However, in hot environment operation, for
example operating inside a computer box, when the environment
temperature inside the box is higher than the temperature of the
liquid phase of the working fluid in the exit of the condenser,
this liquid looses its subcooling, so an additional subcooling is
thus needed.
[0010] In most of the known applications, the thermal electrical
cooler is attached to the compensation chamber in the loop heat
pipe, having thermal contact with the evaporator. In some other
applications, the thermal electrical cooler is attached to the
evaporator, having thermal contact with the compensation chamber in
the loop heat pipe. In all these known applications, the thermal
electrical cooler provides redistribution of heat between the
compensation chamber and the evaporator, and heat transferred by
the thermal electrical cooler (including heat generated by the
thermal electrical cooler itself) goes though the contour of the
loop heat pipe, being further rejected in the condenser of the loop
heat pipe. Therefore, an additional area of the condenser in the
loop heat pipe is needed for such configuration, which increases
the mass of the loop heat pipe.
[0011] Thus, a method to increase the thermal conductance of a loop
heat pipe in hot environment (for example inside hot boxes with
electronic equipment or in computer cabinets) without increasing
the condenser and without the need of transferring additional heat
by the loop heat pipe is needed.
[0012] The present invention is oriented to such object.
SUMMARY OF THE INVENTION
[0013] The present invention is oriented to provide a method for
increasing the thermal conductance of a thermal control device,
particularly a loop heat pipe controlling thermal loads in an
electronic equipment, and to an apparatus to perform such
method.
[0014] An object of the present invention is to provide a method
for increasing the performance of a loop heat pipe in hot
environment in particular increasing its thermal conductivity.
[0015] Another object of the invention is to provide an apparatus
to perform the above-mentioned method.
[0016] According to the invention, a loop heat pipe with increased
thermal conductance is provided, comprising an evaporator, a vapour
transport line, a condenser embedded into a radiator in order to
increase the area of heat rejection, a liquid transport line and a
thermal electrical cooler. The thermal electrical cooler of the
loop heat pipe of the invention is either attached in its cold side
to the liquid transport line of the loop heat pipe close to the
compensation chamber, or it is attached in its cold side onto the
compensation chamber, the hot side of the thermal electrical cooler
being attached to a radiator, such that heat is rejected to the
ambient environment. In this way, the increase in the loop heat
pipe thermal conductance in hot environment is achieved by cooling
the liquid transport line of the loop heat pipe close to the
compensation chamber with the help of the thermal electrical
cooler, in order to compensate the lost of sub-cooling that occurs
when the loop heat pipe is operating in hot environment. Heat
removed from the liquid transport line, effected by the thermal
electrical cooler, as well as heat released by the thermal
electrical cooler itself, are rejected to the ambient environment
outside the loop heat pipe.
[0017] With the method and loop heat pipe of the invention, the
thermal conductivity of the loop heat pipe is increased.
[0018] Other features and advantages of the present invention will
be disclosed in the following detailed description of illustrative
embodiments of its object in relation to the figure attached.
DESCRIPTION OF THE DRAWINGS
[0019] The features, objects and advantages of the invention will
become apparent by reading this description in conjunction with the
accompanying drawing, in which:
[0020] FIG. 1a shows a schematic view of a loop heat pipe having
increased thermal conductivity, controlling the temperature of a
heat source, according to a first embodiment of the invention.
[0021] FIG. 1b shows a schematic view of a loop heat pipe having
increased thermal conductivity, controlling the temperature of a
heat source, according to a second embodiment of the invention.
[0022] FIG. 2a shows the Pressure-Temperature diagram of the
working fluid in the loop heat pipe operated in vacuum and in hot
environment without thermal electrical cooler.
[0023] FIG. 2b shows the Pressure-Temperature diagram of the
working fluid in the loop heat pipe having increased thermal
conductivity, according to a first embodiment of the present
invention, as shown in FIG. 1a.
[0024] FIG. 2c shows the Pressure-Temperature diagram of the
working fluid in the loop heat pipe having increased thermal
conductivity, according to a second embodiment of the present
invention, as shown in FIG. 1b.
[0025] FIG. 3 shows the compared results of thermal conductance
values in several thermal control devices.
DETAILED DESCRIPTION OF THE INVENTION
[0026] A loop heat pipe, as shown in FIG. 1, is an effective heat
transfer or thermal control device, comprising an evaporator 10, a
compensation chamber 20, a condenser 30, a vapour transport line 40
and a liquid transport line 50 connecting them. The evaporator 10,
typically cylindrical, is located inside an evaporator saddle 60,
to which heat dissipating devices are attached. The condenser 30 is
embedded to a radiator 70, in order to increase the area of heat
rejection.
[0027] The evaporator 10 comprises inside a porous wick, and the
loop heat pipe is charged with working fluid. Part of the inner
volume of the loop heat pipe (wick, liquid transport line 50, and
the compensation chamber 20 and the condenser 30, partially) is
filled with the liquid phase of the working fluid, while part of
the inner volume of the loop heat pipe (the vapour transport line
40, partially the compensation chamber 20 and the condenser 30, as
well as vapour channels and grooves in the evaporator 10) is filled
with the vapour phase of the working fluid. The compensation
chamber 20 compensates the change in volume of liquid, which occurs
with the changing of the operating temperature and corresponding
liquid density, which therefore varies the volume of liquid.
[0028] The most part of the loop heat pipe is located inside a hot
environment in a box 130 (for example computer box), which is
separated from the ambient environment, where the condenser 30 and
the radiator 100 are located (see FIGS. 1a and 1b).
[0029] When heat is supplied to the evaporator 10 by the heat
releasing equipment or heat source, the working liquid evaporates
from the wick in the evaporator 10. Vapour goes from the evaporator
10 to the condenser 30 through the vapour transport line 40, where
it is condensed. After that, the working liquid returns to the
compensation chamber 20 and the evaporator 10 through the liquid
transport line 50, to be evaporated in the wick of the evaporator
10. The compensation chamber 20 plays a significant role in the
operation of the loop heat pipe, regulating the operational
temperature of the loop heat pipe. The thermal balance in the
compensation chamber 20 of the loop heat pipe mainly defines the
thermal conductance of the loop heat pipe. Parasitic heat leak from
the evaporator 10 to the compensation chamber 20 reduces the
thermal conductance of the loop heat pipe if this is not
compensated by returned liquid sub-cooling effected in the
condenser 30. The loop heat pipe operates near the saturation line
of the working liquid and, because part of the length of the
condenser 30 is filled with vapour and part is filled with liquid,
this liquid is overcooled below its temperature of saturation. This
sub-cooled liquid gives the opportunity to compensate parasitic
heat leak from the evaporator 10 core to the compensation chamber
20.
[0030] The high thermal conductance reference value depends on the
thermal control device characteristics, such as dimensions,
conditions of operation and design.
[0031] As to the definition of high thermal conductance, FIG. 3
shows an example of the thermal control device performance at hot
environment with and without the thermal electrical cooler
application. Curve 200 represents the results of thermal
conductance values in thermal control devices operating at ambient
environment 37.degree. C. (hot environment) without any thermal
electrical cooler. For 37.degree. C., the heat leak from hot
environment to the liquid transport line leads to decreasing the
conductance of the thermal control device. This FIG. 3 also shows
curve 300 of the thermal conductance in a thermal control device
operating at ambient environment temperature of 37.degree. C. being
provided with a thermal electrical cooler (this line corresponds
also to vacuum operation of the thermal control device without heat
exchange with ambient). Therefore, with the help of a thermal
electrical cooler, thermal conductance can be increased, as
represented by curve 300 in FIG. 3, compared to curve 200 in FIG.
3.
[0032] If the loop heat pipe operates in vacuum, and heat exchange
between the liquid transport line 50 and the surroundings does not
exist, the temperature in the end of the liquid transport line 120
(FIGS. 1a and 1b) is the same as in the beginning of the liquid
transport line 110: liquid reaching the compensation chamber 20 has
practically the same sub-cooling as in the outlet of the condenser
30.
[0033] However, in ambient environment, due to parasitic heat leak
in liquid transport line 50, temperatures in points 110 and 120 are
different. Liquid in the liquid transport line 50 is heated if
ambient temperature is higher than liquid temperature (in this case
liquid looses its sub-cooling).
[0034] As an explanation of the operation of a loop heat pipe
controlling thermal loads in an electronic equipment, for example,
in a computer box 130 (FIGS. 1a or 1b can be used for references),
the condenser 30 with the radiator 70 are located outside the
mentioned computer box 130. A possible operational case is for
example that the ambient environment temperature is 20.degree. C.,
the temperature inside the computer box being 35.degree. C., for
example. The processor in the computer box, attached to the
evaporator saddle 60 has for example a temperature of 50.degree. C.
The condenser 30 has 30.degree. C. on the liquid/vapour interface.
Thus, liquid continues to flow along the radiator 70, this radiator
70 having ambient environment temperature. Therefore, liquid is
cooled (up to 25.degree. C., for example), which means that it is
overcooled 5.degree. C. compared the condenser 30 vapour
temperature (called "subcooling"). This subcooling helps compensate
some parasitic heat leak from the evaporator 10 to the compensation
chamber 20 (inside this assembly).
[0035] If ambient temperature inside the computer box 130 is equal
or lower than the temperature of liquid, the liquid then reaches
the compensation chamber 20, in point 120 of FIG. 1a or 1b, with
temperature 25.degree. C. or even less, so the circuit continues
working effectively. However, in a case in which the liquid is
heated more and more along its way inside the computer box 130 and
reaches, for example, a temperature of 34.degree. C. (this happens
in hot environment operation of the loop heat pipe), its subcooling
has been lost. For this reason, liquid is to be cooled to have
25.degree. C. in point 120. Therefore, in hot environment operation
of the loop heat pipe, a thermal electrical cooler 90 is needed,
when ambient temperature inside the computer box 130 is higher than
liquid temperature at the exit of the condenser 30 (point 110 in
FIGS. 1a and 1b).
[0036] In order to illustrate what has been said, FIG. 2a shows the
Pressure-Temperature curve of the working fluid and idealized
diagram of operating cycles of the loop heat pipe of the invention.
The cycle (a b c d e f g h i) in FIG. 2a represents a loop heat
pipe operating in hot environment. The other three cycles shown
represent a loop heat pipe with increased thermal conductivity:
cycle (a'b'c'd'e'f'g'h'i') in FIG. 2a corresponds to operation in
vacuum; cycle (a'b'c'd'e'f'g''g'h'i') in FIG. 2b, and cycle
(a'b'c'd'e'f'g'''h'i') in FIG. 2c, correspond to the operation in
hot environment with a thermal electrical cooler installed on the
liquid line and on the compensation chamber, respectively.
[0037] FIGS. 2a, 2b and 2c comprise the following representations:
[0038] a, a': start of the vapour channel in the evaporator 10
[0039] b, b': start of the vapour transport line 40 [0040] c, c';
start of condenser 30 [0041] d, d': start of condensation in
condenser 30 [0042] e, e': end of condensation in condenser 30
[0043] f, f'-110: exit of condenser 30 [0044] g, g'-120: end of
liquid transport line 50 [0045] g'': end of liquid transport line
50 in the inlet of thermal electrical cooler 90 in hot environment
with thermal electrical cooler operating [0046] g''': end of liquid
transport line 50 in hot environment with thermal electrical cooler
90 operating on compensation chamber 20 [0047] h, h': inner surface
of primary wick in evaporator 10/compensation chamber 20 [0048] i,
i': outer surface of primary wick in evaporator 10
[0049] The main part of the heat load applied to the loop heat pipe
goes to the evaporator 10 (Q.sub.ev) and is transferred by the loop
heat pipe to the condenser 30, where heat is removed as heat of
condensation (Q.sub.c) and heat of subcooling (Q.sub.sc). Some
small part of the heat load applied is parasitic heat (Q.sub.hi),
which goes from the evaporator 10 to the compensation chamber
20.
[0050] The subcooling that liquid obtains in the condenser 10 is
the following: Q.sub.ef=g c(t.sub.e-t.sub.f), where g is the mass
flow rate, c is the specific heat of liquid, (t.sub.e-t.sub.f) is
the temperature difference between the end of condensation (e) and
the inlet of liquid line (f). Point (f) corresponds to point 110 of
the device.
[0051] The line (f-g) in the diagram of FIG. 2a represents the
movement of liquid in the liquid transport line 50 in hot
environment; point (g) corresponding to point 120 of the
device.
[0052] The line (f'-g') in the diagram of FIG. 2a represents the
movement of liquid in the liquid transport line 50 in vacuum, when
there is no heating. Therefore, in vacuum, the available subcooling
which can compensate heat leak from the evaporator 10 to the
compensation chamber 20 is: Q'.sub.sc=Q.sub.h'g'=g
c(T.sub.e'-T.sub.f'). In hot environment, due to the heating of the
liquid transport fine 50 from T.sub.f to T.sub.g, liquid loses its
subcooling corresponding to the temperature difference
(T.sub.g-T.sub.f), so the heat leak from the ambient environment to
the liquid transport line 50 is Q.sub.II=Q.sub.gf=g
c(T.sub.g-T.sub.f). Thus, the available subcooling is only:
Q.sub.sc=Q.sub.gh=g c(T.sub.e-T.sub.g). In hot environment,
compared to vacuum conditions, the lost of subcooling of the loop
heat pipe leads to increasing the temperature of the compensation
chamber 20, that, in turn, leads to increasing the evaporator
temperature (T.sub.a>T.sub.a').
[0053] When the thermal electrical cooler 90 is installed on the
liquid line 50 according to FIG. 1a, the cycle (a b c d e f g h i)
is transformed into cycle (a'b'c'd'e'f'g''g'h'i') in FIG. 2b. Point
g in the diagram moves to point g'. Because heat leak from the
evaporator 10 to the compensation chamber 20 can be compensated
more completely, point h moves to point h' (temperature of
compensation chamber 20 is decreased) and point a moves to point a'
together with corresponding lines. As a result, heating of the
liquid line 50 is represented by line (f'-g'') and cooling of the
liquid line 50 by the thermal electrical cooler 90 is shown as line
(g''-g'). Heat applied from hot environment to the liquid line 50
Q.sub.II is compensated by removing heat Q.sub.tec with the thermal
electrical cooler 90.
[0054] When the thermal electrical cooler 90 is installed onto the
compensation chamber 20 according to FIG. 1b, point h moves to
point h' and cycle (a b c d e f g h i) is transformed into cycle
(a'b'c'd'e'f'g'''h'i') in FIG. 2c. In this case, heat from hot
environment to the liquid line 50 and the lost of subcooling are
compensated by the thermal electrical cooler 90 in the compensation
chamber 20 directly.
[0055] Temperature difference of loop heat pipe is considered as
difference between mean temperatures of evaporator saddle 60 and
condenser 30 (T.sub.ev-T.sub.cond). Temperature of evaporator
saddle is in some extend higher than temperature of beginning of
vapour line and temperature T.sub.b in the diagram with acceptable
precision can be considered as mean evaporator temperature. Mean
temperature of condenser depends, in principle of operational
conditions, and it can be considered corresponding to T.sub.e in
the diagram.
[0056] Thermal conductance of loop heat pipe corresponds to its
temperature difference: C=P/(T.sub.ev-T.sub.cond), where C is
thermal conductance and P--heat load. The less the temperature
difference, the higher is thermal conductance of a loop heat pipe.
Therefore (T.sub.b-T.sub.e) is loop heat pipe temperature
difference for hot case and (T.sub.b'-T.sub.e') for vacuum or for
hot case with thermal electrical cooler. And thermal conductance
are C=P/(T.sub.b-T.sub.e) and C'=P/(T.sub.b'-T.sub.e')
correspondently.
[0057] When the thermal electrical cooler 90 operates, the
temperature difference of the loop heat pipe becomes lower
(T.sub.b'-T.sub.e'<T.sub.b-T.sub.e) and therefore conductance
becomes bigger C'>C.
[0058] As a general definition, hot environment is an environment
where t.sub.amb>t.sub.f and therefore t.sub.g>t.sub.f that
leads to the lost of subcooling.
[0059] The method according to the invention for increasing the
thermal conductivity of the loop heat pipe working in hot
environment conditions consists of cooling the liquid transport
line 50 in the end 120 in order to provide the same or lower
temperature of liquid in the end 120 as in the beginning 110 of the
liquid transport line 50. The heat obtained from the cooling of
liquid in the liquid transport line 50 in ambient environment is
removed back to the ambient.
[0060] The above-referred situation is very frequent in terrestrial
applications of the loop heat pipe, for example when the loop heat
pipe is used for cooling a computer equipment inside a computer
case.
[0061] The system able to operate the method for increasing the
thermal conductivity of the loop heat pipe working in hot
environment conditions according to the invention, as it has been
described, is a loop heat pipe comprising a thermal electrical
cooler 90, usually known as TEC or also as Peltier element as main
element. One side (cold part) of the thermal electrical cooler 90
is attached to a special thermal saddle 80 installed in the end
part of the tube of the liquid transport line 50 or on the
compensation chamber 20, this thermal saddle 80 being preferably
metallic. The thermal saddle 80 in the thermal electrical cooler 90
plays the role of an auxiliary interface element between the tube
of the liquid transport line 50 or the compensation chamber 20 and
the thermal electrical cooler 90: the tube of the liquid transport
line 50 or the tube of the compensation chamber 20 is cylindrical
and the thermal electrical cooler is usually flat; therefore, in
order to effectively remove heat from all the perimeter of the tube
of the liquid transport line 50 we need to have a metallic surface
surrounding the tube in the liquid transport line 50, being in
contact with it. Preferably, this thermal saddle 80 comprises a
metallic, preferably made of aluminum, rectangular plate having an
orifice inside of it for the tube of the liquid transport line 50
(embodiment of FIG. 1a). The thermal saddle 80 for the installation
of the thermal electrical cooler 90 onto the compensation chamber
20 (in the case of FIG. 1b) comprises a rectangular plate having
one flat side for being attached to the thermal electrical cooler
90, and a cylindrical opposite side for attaching the thermal
electrical cooler 90 to the compensation chamber 20 with the same
diameter as it.
[0062] The other side (hot part) of the thermal electrical cooler
90 is attached to a thermal radiator 100 with extended surface,
rejecting heat to the ambient environment. The thermal radiator 100
can have the same design as those used in computer processors.
Besides, a fan (not shown) can be used to facilitate the heat
rejection in the thermal electrical cooler 90. Therefore, the
thermal electrical cooler 90 collects heat from the liquid in the
liquid transport line 50 and transfers it to the ambient
environment. In order to increase the thermal conductivity of the
loop heat pipe, normal electrical polarity is used in the two parts
of the thermal electrical cooler 90, so that the cold part in the
thermal electrical cooler 90 is colder than the hot plate, and heat
is then transferred from the liquid to the ambient environment.
[0063] According to the invention, the thermal balance of the
thermal electrical cooler 90 and its coupling to the rest of the
loop heat pipe is different from other applications of known
thermal electrical coolers in loop heat pipes. In known
applications, heat obtained or rejected to the ambient environment,
together with heat produced by the thermal electrical cooler
itself, is redistributed amongst the elements of the loop heat
pipe, being further transferred to the condenser of the loop heat
pipe, where heat is finally rejected. Therefore, these loop heat
pipes have to transfer more heat along its loop, which makes that
some elements are to be over-dimensioned. However, in the method
proposed by the invention, heat is rejected directly from the end
120 of the liquid transport line 50 or from the compensation
chamber 20 to the ambient environment.
[0064] Although the present invention has been fully described in
connection with preferred embodiments, it is evident that
modifications may be introduced within the scope thereof, not
considering this as limited by these embodiments, but by the
contents of the following claims.
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