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).

Description

FIELD OF THE INVENTION

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The present invention is oriented to such object.

SUMMARY OF THE INVENTION

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.

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.

Another object of the invention is to provide an apparatus to perform the above-mentioned method.

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.

With the method and loop heat pipe of the invention, the thermal conductivity of the loop heat pipe is increased.

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

The features, objects and advantages of the invention will become apparent by reading this description in conjunction with the accompanying drawing, in which:

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.

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.

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.

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.

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.

FIG. 3 shows the compared results of thermal conductance values in several thermal control devices.

DETAILED DESCRIPTION OF THE INVENTION

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.

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.

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).

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.

The high thermal conductance reference value depends on the thermal control device characteristics, such as dimensions, conditions of operation and design.

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° C. (hot environment) without any thermal electrical cooler. For 37° 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° 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.

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.

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).

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° C., the temperature inside the computer box being 35° C., for example. The processor in the computer box, attached to the evaporator saddle 60 has for example a temperature of 50° C. The condenser 30 has 30° 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° C., for example), which means that it is overcooled 5° 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).

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° 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° 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° 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).

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.

FIGS. 2a, 2b and 2c comprise the following representations:

• • a, a′: start of the vapour channel in the evaporator 10
  • b, b′: start of the vapour transport line 40
  • c, c′; start of condenser 30
  • d, d′: start of condensation in condenser 30
  • e, e′: end of condensation in condenser 30
  • f, f′-110: exit of condenser 30
  • g, g′-120: end of liquid transport line 50
  • g″: end of liquid transport line 50 in the inlet of thermal electrical cooler 90 in hot environment with thermal electrical cooler operating
  • g′″: end of liquid transport line 50 in hot environment with thermal electrical cooler 90 operating on compensation chamber 20
  • h, h′: inner surface of primary wick in evaporator 10/compensation chamber 20
  • i, i′: outer surface of primary wick in evaporator 10

The main part of the heat load applied to the loop heat pipe goes to the evaporator 10 (Q_ev) and is transferred by the loop heat pipe to the condenser 30, where heat is removed as heat of condensation (Q_c) and heat of subcooling (Q_sc). Some small part of the heat load applied is parasitic heat (Q_hi), which goes from the evaporator 10 to the compensation chamber 20.

The subcooling that liquid obtains in the condenser 10 is the following: Q_ef=g c(t_e−t_f), where g is the mass flow rate, c is the specific heat of liquid, (t_e−t_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.

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.

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′_sc=Q_h′g′=g c(T_e′−T_f′). In hot environment, due to the heating of the liquid transport fine 50 from T_f to T_g, liquid loses its subcooling corresponding to the temperature difference (T_g−T_f), so the heat leak from the ambient environment to the liquid transport line 50 is Q_II=Q_gf=g c(T_g−T_f). Thus, the available subcooling is only: Q_sc=Q_gh=g c(T_e−T_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_a>T_a′).

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_II is compensated by removing heat Q_tec with the thermal electrical cooler 90.

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.

Temperature difference of loop heat pipe is considered as difference between mean temperatures of evaporator saddle 60 and condenser 30 (T_ev−T_cond). Temperature of evaporator saddle is in some extend higher than temperature of beginning of vapour line and temperature T_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_e in the diagram.

Thermal conductance of loop heat pipe corresponds to its temperature difference: C=P/(T_ev−T_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_b−T_e) is loop heat pipe temperature difference for hot case and (T_b′−T_e′) for vacuum or for hot case with thermal electrical cooler. And thermal conductance are C=P/(T_b−T_e) and C′=P/(T_b′−T_e′) correspondently.

When the thermal electrical cooler 90 operates, the temperature difference of the loop heat pipe becomes lower (T_b′−T_e′<T_b−T_e) and therefore conductance becomes bigger C′>C.

As a general definition, hot environment is an environment where t_amb>t_f and therefore t_g>t_f that leads to the lost of subcooling.

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.

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.

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.

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.

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.

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.

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).