U.S. patent application number 12/306425 was filed with the patent office on 2009-11-26 for capillary pumped diphasic fluid loop passive thermal control device with thermal capacitor.
This patent application is currently assigned to Astrium Sas. Invention is credited to Christophe Figus.
Application Number | 20090288801 12/306425 |
Document ID | / |
Family ID | 37762221 |
Filed Date | 2009-11-26 |
United States Patent
Application |
20090288801 |
Kind Code |
A1 |
Figus; Christophe |
November 26, 2009 |
Capillary Pumped Diphasic Fluid Loop Passive Thermal Control Device
with Thermal Capacitor
Abstract
The thermal control device comprises at least one capillary
pumped diphasic fluid loop, comprising, in a known manner, an
evaporator extracting the heat from a so-called hot source and
connected via a vapour pipe to a condenser in which the
condensation of the fluid vapour releases thermal energy
transmitted to a so-called cold source, the condenser being
connected via a liquid pipe to the evaporator, and the device
moreover comprises at least one thermal capacitor in permanent heat
exchange relationship with liquid phase fluid in said at least one
diphasic fluid loop. Use in particular with space vehicles such as
satellites.
Inventors: |
Figus; Christophe; (Dremil
Lafage, FR) |
Correspondence
Address: |
MILLER, MATTHIAS & HULL
ONE NORTH FRANKLIN STREET, SUITE 2350
CHICAGO
IL
60606
US
|
Assignee: |
Astrium Sas
Paris
FR
|
Family ID: |
37762221 |
Appl. No.: |
12/306425 |
Filed: |
June 26, 2007 |
PCT Filed: |
June 26, 2007 |
PCT NO: |
PCT/FR2007/051526 |
371 Date: |
December 23, 2008 |
Current U.S.
Class: |
165/47 ;
165/104.26 |
Current CPC
Class: |
F28F 13/00 20130101;
B64G 1/506 20130101; F28F 2013/008 20130101; F28D 15/043 20130101;
F28D 15/06 20130101; Y02E 60/14 20130101; Y02E 60/145 20130101;
F28D 20/02 20130101 |
Class at
Publication: |
165/47 ;
165/104.26 |
International
Class: |
F24H 9/00 20060101
F24H009/00; F28D 15/00 20060101 F28D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2006 |
FR |
0605832 |
Claims
1. A closed circuit fluid coolant circulation thermal control
device, capable of transferring heat from at least one so-called
hot source to at least one so-called cold source, and comprising at
least one capillary pumped diphasic fluid loop, which comprises an
evaporator, intended to be placed in heat exchange relationship
with said at least one hot source and supplied, through a
microporous mass, connected to a liquid state diphasic fluid
reserve, with liquid diphasic fluid intended to be vaporized in the
said evaporator, connected by a vapour pipe to a condenser,
intended to be placed in heat exchange relationship with said at
least one cold source, to which heat is transmitted by the
condensation in said condenser of vapour phase fluid into liquid
phase fluid, which is returned to said evaporator by a liquid pipe
connecting said condenser to said evaporator, wherein the device
also comprises at least one thermal capacitor, in permanent heat
exchange relationship with liquid phase fluid in said at least one
diphasic fluid loop.
2. The thermal control device according to claim 1, wherein said at
least one thermal capacitor comprises at least one thermal inertia
mass.
3. The thermal control device according to claim 1 wherein said at
least one thermal capacitor comprises at least one mass of at least
one phase change material.
4. The thermal control device according to claim 3, wherein said at
least one phase change material is a liquid-gas phase change
diphasic fluid.
5. The thermal control device according to claim 3, wherein said at
least one phase change material is a solid-liquid phase change
material.
6. The thermal control device according to claim 3 wherein said at
least one phase change material is selected to adjust an operating
range of said at least one diphasic fluid loop and said hot
source.
7. The thermal control device according to claim 3 wherein said at
least one phase change material is selected so that the control
device operates as a thermal switch, stopping the operation of said
at least one diphasic fluid loop under given temperature conditions
of at least one of said cold source and hot source.
8. The thermal control device according to claim 1 wherein said at
least one thermal capacitor is in heat exchange relationship
principally with at least a part of said liquid pipe of said at
least one diphasic fluid loop.
9. The thermal control device according to claim 1 wherein said at
least one thermal capacitor is in heat exchange relationship
principally with said liquid fluid reserve of said at least one
diphasic fluid loop.
10. The thermal control device according to claim 9, wherein said
at least one thermal capacitor is in direct contact with said
evaporator of said at least one diphasic fluid loop.
11. The thermal control device according to claim 9, wherein said
at least one thermal capacitor is remote relative to said
evaporator of said at least one diphasic fluid loop, and in heat
exchange relationship with said evaporator by means of at least one
of a heat pipe and an intermediate heat transfer loop.
12. The thermal control device according to claim 1 wherein said at
least one thermal capacitor is fixed to or in a housing of said
evaporator, which contains said liquid fluid reserve and said
microporous mass of said at least one diphasic fluid loop, and
close to a liquid fluid intake, originating from said corresponding
liquid pipe, in said housing, on a side of said housing opposite a
hot face of said evaporator, forming an interface with one of said
hot source an intermediate heat transfer loop and a heat pipe, and
close to a vapour fluid outlet communicating with said
corresponding vapour pipe.
13. The thermal control device according to claim 12, wherein at
least one spring, for example helical, pushes against a base of
said housing adjacent to said thermal capacitor to push back said
microporous mass towards said hot face of said evaporator said
spring being arranged in said liquid fluid reserve.
14. The thermal control device according to claim 12 wherein said
housing of said evaporator is equipped with a liquid fluid intake
tube originating from said liquid pipe and a vapour fluid outlet
tube communicating with said vapour pipe, and contains said
microporous mass separating, in said housing, a fluid liquid
reserve space, which communicates with said intake tube, from an
evaporation space, which communicates with said outlet tube, and
which is enclosed by said hot face arranged as a heat conducting
interface plate with said hot source to be cooled.
15. The thermal control device according to claim 1 for the
temperature control of said hot source comprising at least one
piece of dissipating equipment on a spaceship, with heat transfer
to said cold source that is a heat sink comprising at least one
radiator of said spaceship.
16. The thermal control device according to claim 4, wherein said
liquid-gas phase change diphasic fluid is identical to the fluid in
said at least one diphasic fluid loop.
17. The thermal control device according to claim 4, wherein said
liquid-gas phase change diphasic fluid is different from the
diphasic fluid in said loop.
Description
[0001] The present invention relates to a purely passive thermal
control device, based on at least one fluid circulation heat
transfer loop used for cooling sources dissipating thermal
energy.
[0002] More specifically, the invention relates to a closed circuit
fluid coolant circulation thermal control device, capable of
transferring heat from at least one so-called hot source to at
least one so-called cold source, and comprising at least one
capillary pumped diphasic fluid loop.
[0003] According to the state of the art, such a loop, commonly
known as a LHP (Loop Heat Pipe) is a heat transfer loop that
comprises an evaporator, intended to be placed in heat exchange
relationship with at least one so-called hot source, in order to
extract heat from said hot source, and which is supplied, through a
microporous mass connected to a reserve of diphasic fluid in liquid
state, with liquid diphasic fluid intended to be vaporised in the
evaporator. The evaporator is connected by a vapour pipe to a
condenser, intended to be placed in heat exchange relationship with
at least one so-called cold source, and thus intended to release
the heat extracted from the hot source to the so-called cold
source, to which the heat is transmitted by the condensation in the
condenser of vapour phase fluid to liquid phase fluid, which is
returned to the evaporator by a liquid pipe connecting the
condenser to the evaporator.
[0004] Thus, the evaporator and the condenser are connected by
looped piping in which a diphasic fluid circulates in a liquid
state in the cold part of the loop or liquid pipe, and in a gaseous
state in the hot part of the loop, or vapour pipe.
[0005] In this type of loop, the fluid is pumped by capillarity
(capillary loop), by means of the microporous mass connected to the
liquid state fluid reserve and ensures pumping of the liquid fluid
into the evaporator by capillarity. Thus, the liquid fluid present
in the evaporator reserve evaporates on contact with the hot
source, and the gas thus created is discharged to the condenser, in
heat exchange relationship with the cold source, and in which the
gas condenses and returns in a liquid state to the evaporator to
create a heat transfer cycle.
[0006] In such a loop, capillarity is used as the driving pressure,
and the liquid-vapour phase change is used as a means of
transporting energy.
[0007] The liquid fluid reserve, situated close to the hot source,
generally on the rear face of the evaporator, is used to supply the
loop with liquid according to the operating temperature or
operating power.
[0008] One limitation of this type of capillary evaporator heat
transfer loop arises from the fact that, when the external
conditions significantly reduce the temperature of the cold source,
or the temperature of the hot source, or both temperatures at once,
without the temperature of the hot source becoming lower than the
temperature of the cold source, the operation of such a loop
according to the state of the art results in, in all cases, a
further reduction of the temperature of the hot source, possibly
below its normal operating range. In this case, and as is known in
the state of the art, heaters are used to control the temperature
of the hot source or the cold source, such heaters being installed
in most cases in contact with said sources or on the wall of a tank
associated with the evaporator containing the liquid diphasic fluid
reserve. However, the use of heaters has the drawback of consuming
electricity, which is always available in limited quantities and at
very high cost on board space vehicles, in particular satellites.
In some cases, furthermore, the use of heaters requires active
control by temperature sensors, installed in particular on the
aforementioned sources or the aforementioned tank, as well as a
unit to control the heaters and process the signals from the
temperature sensors, which makes the thermal control device more
complex and more costly.
[0009] The aim of the present invention is to overcome these
limitations, and to propose a capillary pumped diphasic fluid loop
thermal control device of the type set out above, that better meets
the various practical demands than the devices known in the state
of the art and, in particular, provides other advantages, which
will become apparent from the description below.
[0010] The idea behind the invention is based on the addition, to
at least one loop as set out above, of at least one thermal
capacitor which, during nominal operation of the thermal control
device, when said loop receives thermal power to transport,
accumulates heat by means of a thermal flux passing from the hot
source through the liquid state diphasic fluid present in or near
the evaporator, whilst the loop, in nominal operation, discharges
the majority of the thermal power it receives to the condenser and
the cold source, and which, when the thermal power to be dissipated
decreases or reaches zero, or the temperature of the cold source
decreases, releases thermal energy to the loop, in such a way that
it is possible to control, or even stop, the operation of said
loop, in a completely passive manner.
[0011] To this end, the invention proposes a thermal control device
of the type set out above, comprising at least one capillary pumped
diphasic fluid loop as also set out above, and which is
characterised in that it also comprises at least one thermal
capacitor, in permanent heat exchange relationship with liquid
phase fluid in said at least one diphasic fluid loop.
[0012] In a first embodiment, said at least one thermal capacitor
can comprise at least one thermal inertia mass, preferably large,
in order to store substantial thermal power during nominal
operation of the device, when the loop receives thermal power to
transport, and in order to be able to release this stored thermal
power to the loop, when the thermal power to be dissipated
decreases or reaches zero, or when the temperature of the cold
source decreases.
[0013] Such a device can also advantageously be used to store the
energy dissipated in the inertia mass when the so-called cold
source is temporarily hotter than the so-called hot source, and to
release this energy when the so-called cold source once again
becomes colder than the so-called hot source. The device thus
allows for the so-called hot source to be kept at a temperature
hotter than the average temperature of the environment, but colder
than the extreme temperatures of the environment.
[0014] However, advantageously, and according to a second
embodiment, said at least one thermal capacitor comprises at least
one mass of at least one phase change material. In this case, the
phase change material has, by absorption of the latent phase change
heat, a large thermal storage capacity that improves the control
capability of the thermal control device.
[0015] At least one phase change material can also be a liquid-gas
phase change diphasic fluid, such diphasic fluid being able to be
identical to the fluid in said at least one diphasic fluid loop of
the control device, or different from the diphasic fluid in such
loop. Advantageously however, at least one phase change material is
a solid-liquid phase change material, which facilitates the
production of the additional thermal capacitor and its
incorporation into the evaporator on the diphasic fluid loop, and
which also offers the advantage of facilitating the selection of
the phase change material(s) of the additional thermal capacitor(s)
to adjust the operating range of the corresponding diphasic fluid
loop and the hot source.
[0016] Another advantage is that the phase change material(s) of
the thermal capacitor(s) can be selected in such a way that the
control device operates as a thermal switch, stopping the operation
of said at least one diphasic fluid loop under given temperature
conditions of the cold source and/or the hot source.
[0017] In any event, the thermal control device according to the
invention allows for heat transfer between the thermal capacitor(s)
and the liquid fluid reserve of said at least one diphasic fluid
transfer loop, said at least one thermal capacitor being in heat
exchange relationship principally with at least part of the liquid
pipe of said at least one diphasic fluid loop, or, advantageously,
said at least one thermal capacitor being in heat exchange
relationship principally with said liquid fluid reserve of said at
least one diphasic fluid loop.
[0018] This heat transfer between the thermal capacitor and the
liquid fluid reserve of the transfer loop, either in the evaporator
or in the liquid circulation piping, can take place directly, by
conduction, in which case it is advantageous that said at least one
thermal capacitor is in direct contact with the evaporator of said
at least one diphasic fluid loop.
[0019] However, this heat transfer can also take place indirectly,
in such a way that the thermal capacitor is remote from the liquid
fluid reserve of the evaporator, in which case said thermal
capacitor is in heat exchange relationship with said evaporator
through at least one heat pipe and/or at least one intermediate
heat transfer loop.
[0020] According to an embodiment that is advantageously simple to
implement, said at least one thermal capacitor is fixed to or in a
housing of said evaporator, which contains said liquid fluid
reserve and said microporous mass of said at least one diphasic
fluid loop, and close to a liquid fluid intake, originating from
said corresponding liquid pipe, into said housing, on the side of
the housing opposite a hot face of said evaporator, forming an
interface with said hot source or intermediate heat transfer loop
or with said heat pipe, and close to a vapour fluid outlet into
said corresponding vapour pipe.
[0021] Advantageously in this case, to improve the cooperation
between the evaporator and the microporous mass, at least one
spring, preferably helical, pushing against a base of said housing
adjacent to said thermal capacitor to push back said microporous
mass towards said hot face of said evaporator, is arranged in said
liquid fluid reserve.
[0022] To facilitate the production of the diphasic fluid loop,
said housing of said evaporator is advantageously equipped with a
liquid fluid intake tube originating from said liquid pipe and a
vapour fluid outlet tube to said vapour pipe, and contains said
microporous mass separating, in said housing, a fluid liquid
reserve space, which communicates with said intake tube, from an
evaporation space, which communicates with said outlet tube, and
enclosed by said hot face arranged as a heat conducting interface
plate with said hot source to be cooled.
[0023] Thus, during the operation of said at least one diphasic
fluid loop of the thermal control device according to the
invention, said at least one associated thermal capacitor will
store some of the energy provided by the hot source, beyond a
certain temperature (evaporating or melting temperature) when
advantageously a phase change material (liquid-vapour or
solid-liquid respectively) acts as a thermal capacitor. In the
event that the temperature of the hot source drops, possibly below
a temperature threshold (condensing or solidification temperature)
if a phase change material (liquid-gas or solid-liquid
respectively) acts as a thermal capacitor, this thermal capacitor
returns all or part of the thermal energy stored to the fluid
reserve with which it is in heat exchange relationship. A first
effect is that the liquid diphasic fluid circulating in the loop or
contained in the evaporator of this loop is thus heated. A second
effect is that the thermal performance of the transfer loop, which
is very sensitive to the temperature of the fluid in liquid state,
is reduced in a completely passive manner. Such a diphasic fluid
loop transports almost all of the thermal energy by phase change of
the fluid, and requires in order to operate a few kilogram calories
to keep the fluid circulating from the condenser to the evaporator
in a liquid state. The heating of this liquid, according to the
invention, by at least one additional thermal capacitor, allows for
the heat transfer performance of the loop to be very significantly
altered, and the loop thus operates as a thermal controller
(non-zero thermal performance, low transfer) or even as a thermal
switch (zero thermal performance, no transfer).
[0024] The thermal control device according to the invention is
appropriate for a number of applications. Particular mention can be
made of applications on board spacecraft, when such a spacecraft is
subject to large thermal variations in its operating range, for
example between phases in which it is directly lit by the sun, and
phases of eclipse or in which it is no longer directly exposed to
solar radiation.
[0025] On this type of spacecraft, the thermal power of the
on-board dissipating equipment, in particular the electronic
equipment, is dissipated, as known in the state of the art, by
radiation by means of radiators in contact with the cold space, the
size of these radiators being defined by the hot thermal
environment of the spacecraft. In eclipse phase, for cold
situations, and according to the state of the art, the radiators or
dissipating equipment can be heated by means of heaters.
[0026] A further subject of the invention is therefore the
application of a thermal control device specific to the invention,
and as defined above, to the temperature control of a hot source,
comprising at least one item of dissipating equipment on a
spaceship, such as a satellite, with heat transfer to a cold source
that is a heat sink comprising at least one radiator of said
spaceship.
[0027] Further characteristics and advantages of the invention will
become apparent from the non-limitative description given below of
an embodiment described with reference to the attached drawings, in
which:
[0028] FIG. 1 is a partial view, part cross-section and part side
elevation, of a thermal control device according to the invention,
in the end part of its capillary pumped diphasic fluid loop which
comprises the evaporator and a thermal capacitor specific to the
invention,
[0029] FIG. 2a is a diagrammatic side elevation view of the thermal
control device partly shown in FIG. 1, connecting a hot source to a
cold source, to explain the operating principle of the diphasic
fluid loop of the device, in the configuration in which the hot
source is to be cooled, and
[0030] FIG. 2b is an analogous view to FIG. 2a to explain the
operating principle of said loop when it is stopped.
[0031] The example of a purely passive thermal control device (or
thermal controller) shown in FIGS. 1 to 2b comprises a single
capillary pumped diphasic fluid loop, labelled 1 as a whole,
inserted as a coolant circulation heat transfer loop between a
so-called hot source A to be cooled, for example an item of heat
dissipating electronic equipment on board a satellite, and a
so-called cold source B, in this example a radiator supported on an
external face of the satellite, the carrying structure of which is
diagrammatically labelled S.
[0032] The loop 1 essentially comprises, at its two ends, an
evaporator labelled 2 as a whole, which extracts heat from the
dissipating equipment A during operation, and a condenser 3 that
releases the heat to the radiator B. The loop 1 also comprises a
first fluid pipe 4 connecting the outlet 5 of the evaporator 2 to
the intake 6 of the condenser 3, and through which the evaporator 2
supplies the condenser 3 with vapour phase diphasic fluid (for
example ammonia with the formula NH.sub.3), for which reason the
pipe 4 is known as the vapour pipe, and a second fluid pipe 7
connecting the outlet 8 of the condenser 3 to the intake 9 of the
evaporator 2, through which the condenser 3 supplies the evaporator
2 with liquid phase diphasic fluid, for which reason the pipe 7 is
known as the liquid pipe.
[0033] The evaporator 2 is able to absorb heat extracted from the
dissipating equipment A by evaporation of the diphasic fluid
circulating in the loop 1, the gaseous fluid leaving the evaporator
2 being transferred by the vapour pipe 4 to the condenser 3, which
is able to release and discharge the heat to the radiator B by
condensation of the vaporised fluid, the fluid in liquid state then
returning by the liquid pipe 7 to the evaporator 2, in such a way
as to thus form a fluid heat transfer loop.
[0034] As shown in FIG. 1, the evaporator 2 comprises a metal
housing 10, equipped with a liquid fluid intake tube 9 originating
from the liquid pipe 7, and a vapour fluid outlet pipe 5 to the
vapour pipe 4, and the housing 10 contains a microporous mass 11
that separates, inside the housing 10, a liquid fluid reserve space
12 into which the intake tube 9 opens, from an evaporation space
13, which communicates with the outlet tube 5, and which is
enclosed, on the opposite side to the microporous mass 11, by a hot
face 14 of the evaporator 2, this hot face being kept a small
distance away from the mass 11 by a mesh structure forming a
spacer, and made up of a thick heat-conducting plate closing the
housing 10 at one end and forming an interface plate with the
dissipating equipment A to be cooled during operation, and by which
plate 14 the evaporator 2 is held fixed against this equipment
A.
[0035] The microporous mass 11 thus ensures the capillary pumping
of the liquid fluid from the reserve 12 to the evaporation space
13, in which the liquid fluid thus pumped is vaporised by the heat
extracted from the dissipating equipment A through the hot face 14,
and the vaporised fluid escapes through the outlet tube 5 to the
vapour pipe 4 and the condenser 3, where it condenses and returns
through the liquid pipe 7 to the evaporator 2 to create a heat
transfer cycle.
[0036] To enhance the capillary pumping carried out by the
microporous mass 11, the latter is elastically pushed back into the
housing 10 towards the conducting plate of the hot face 14 by a
spring 15, for example helical, arranged in the liquid fluid
reserve 12 space, and held at one end against the microporous mass
11 by pushing, with its other end, against a base 16 enclosing the
liquid fluid reserve 12 and made from a good heat-conducting metal
or metal alloy.
[0037] According to the invention, a thermal capacitor 17 is
associated with the loop 1 in such a way that it is in permanent
heat exchange relationship with the liquid fluid in the reserve
12.
[0038] This is advantageously obtained, as shown in FIG. 1, by
fixing the thermal capacitor 17 in direct contact with the
evaporator 2, in such a way that the heat exchange relationship
between the liquid fluid in the reserve 12 and the thermal
capacitor 17 takes place by conduction.
[0039] However, as a variant, the thermal capacitor 17 can be
offset relative to the evaporator 2, in which case the thermal
capacitor 17 can be fixed in permanent heat exchange relationship
with part of the liquid pipe 7, and preferably with the intake tube
9, which contains fluid in liquid state, or thermally coupled to
the evaporator 2 by at least one heat pipe or at least one
intermediate heat transfer loop.
[0040] In both cases, the thermal capacitor 17 can be made up of a
large thermal inertia mass (metal block with good thermal
conductivity) fixed for example to the base 16 of the liquid fluid
reserve 12, or mounted in the housing 10 of the evaporator 2.
[0041] In the preferred embodiment, the thermal capacitor 17
comprises a tank 18, which is fixed under the base 16 and/or to the
housing 10, continuing on from the latter, of the evaporator 2, and
contains a mass of a phase change material 19, which can be a
similar, or even identical, diphasic fluid to the fluid in the loop
1, but which is preferably a solid-liquid phase change material 19.
The heat transfers between the thermal capacitor 17 and the liquid
fluid reserve 12 are thus made possible directly by conduction
through the base 16 and the housing 10.
[0042] Inevitably, there is a parasitic, but small, thermal link
between the hot source A (dissipating equipment) and the thermal
capacitor 17.
[0043] By arranging a phase change material 19 (either
solid-liquid, through use of a paraffin for example, or a
liquid-gas phase change material) as a thermal storage capacitor by
absorption of the latent phase change heat, at the rear face of the
evaporator 2, that is, on the other side of the base 16 of the
housing 10 relative to the liquid fluid reserve 12, it is possible
to use this thermal capacitor 17 to alter the performance when the
loop 1 dissipates power, as shown in FIG. 2a. In this case, the
dissipating equipment A radiates heat (radiation r1) and transfers
a principal thermal flux Q1 to the evaporator 2, from where a
thermal flux Q2 is transferred by the fluid vaporised by the
evaporator 2 and circulating in the vapour pipe 4 to the condenser
3, transferring a thermal flux Q3 to the radiator B, which radiates
this heat into cold space (radiation r2) whilst a thermal flux Q4
is transferred by the liquid fluid reserve 12 from the evaporator 2
to the thermal capacitor 17. Thus, during nominal operation, when
the loop 1 receives thermal power to transport to the condenser 3,
the phase change material 19 accumulates heat, by liquefaction or
vaporisation of the material, due to the thermal flux Q4 that
passes through the evaporator 2, whilst the loop 1, which is in
nominal operation, discharges the majority of the thermal power
through the flux Q2 to the evaporator 3 and the cold source B.
[0044] On the other hand, if the loop 1 is no longer operating to
transport power, as described above with reference to FIG. 2a, but
in temperature gradient mode (see FIG. 2b), that is, when the
thermal power to be dissipated by the equipment A decreases until
it reaches zero, or the temperature of the cold source B drops,
tests have shown that it is sufficient to keep the liquid fluid
reserve 12 of the evaporator 2 hotter than the hot face 14 of this
evaporator 2, in order to completely cancel out the operation of
the loop 1. This is obtained by the fact that the phase change
material 19 releases thermal energy through the flux Q5 to the
liquid fluid reserve 12 of the evaporator 2, by condensation or
solidification of the phase change material 19, so that by this
means, it is possible to control and even stop the operation of the
capillary pumped diphasic fluid loop 1, in a completely passive
manner.
[0045] In this case, no thermal flux is transported by the loop 1,
and the evaporator 2 heats the equipment A that radiates towards
the inside of the satellite (radiation r.sub.3).
[0046] A thermal switch is thus created with appropriate sizing of
the thermal capacitor 17 (by adjustment of the mass (and nature) of
the phase change material 19) and it is thus possible to
regulate/control the loop 1 over a very long period, all the more
because the heat accumulation of the phase change material 19 of a
thermal capacitor 17 mounted directly on the liquid fluid reserve
12 of a loop 1 is much faster than its thermal energy release.
[0047] To restart the loop 1, all that is required is either to
restart the operation of the dissipating equipment A, so that there
is thermal power to be dissipated again, or for the temperature of
the cold source B to increase again.
[0048] The use of a capillary transfer loop 1 the evaporator 2 of
which is fitted with a thermal capacitor 17 based on the use of a
phase change material 19 according to the invention allows, on the
one hand, for efficient transfer of the thermal energy from the
equipment A to the radiator B when the temperature of the equipment
A is greater than the melting temperature of the material 19, in
the case of a solid-liquid phase change material 19, whilst also
heating the thermal capacitor 17 by means of the parasitic thermal
flux passing through the evaporator 2. When the temperature of the
equipment A drops below a certain threshold, defined by the
solidification temperature of the phase change material 19, the
thermal capacitor 17 releases heat to the liquid reserve 12 of the
capillary loop 1, which has the effect of heating the cold liquid
coming from the condenser 3, and reducing the thermal performance
of the transfer loop 1, in such a way that the equipment A will be
kept passively within a limited temperature range preventing
efficient heat transfer from the equipment A to the radiator B
during this phase.
[0049] Mention can also be made of the application of the device to
the passive temperature control of equipment A with variable heat
dissipation (the cold source B being at a temperature assumed to be
approximately constant). In this case, the use of the device
according to the invention allows in the same way for the
temperature variation range of the equipment A to be significantly
reduced, in a completely passive manner. In this case, the thermal
capacitor 17 absorbs some of the excess high-power energy, thus
allowing for good heat transfer with the cold source B (strong
coupling), and releases this energy to the liquid circulating to
the low-power evaporator 2, allowing for low heat transfer to the
condenser 3, and thus the low-power radiator B (weak coupling).
[0050] In a very general application, the device according to the
invention is applied to a system subject to operating and
environmental constraints such that, at the same time, the
dissipation of the hot source A and the external thermal flux
received by the cold source B vary. In all cases, the use of the
device according to the invention allows for the passive limitation
of the temperature excursions of the hot source A, by filtering the
thermal interference of each end of the transfer loop, at the
evaporator 2 and the condenser 3.
[0051] In all of these examples of applications, it must be noted
that the thermal control takes place in a completely passive
manner, without the use of a thermistor, thermostat, heater, data
acquisition and processing equipment, or any type of active or
semi-active thermal control system using one or more of these
elements.
[0052] Generally, it is possible to alter the behaviour of this
thermal controller, by thermally insulating the thermal capacitor
17 from the environment and the transfer loop 1 to a greater or
lesser extent, or through the selection of the phase change
material 19. The controller can thus be adjusted according to the
operating temperature range.
* * * * *