DE2350980A1 - Gas-stabilised capillary-structure heating tube - with connecting-duct from gas reservoir having openings near cooling and heating zones - Google Patents

Abstract

The heating-tube relies on transfer of the latent vaporisation heat of a fluid heat-conductor, with fluid phase passing from cooling zone to heating zone through a capillary structure inside a variable-size chamber gas-filled by thermic, mechanical or hydraulic action. The connecting duct passing through the chamber, and the gas reservoir from which it leads off, are pref. clad with an inner capillary structure, these and the capillary structure in the chamber being interconnected. The annular space between the duct and an enclosing sheath, which opens into chamber and reservoir, may also be filled by a linked capillary structure. More accurate operative temperature stabilisation can be effected, regardless of the direction of flow.

Description

Applicant

Institute for Nuclear Technology and Energy Conversion e. V. 7 Stuttgart SO - Holderbuschweg 52

Heat transfer device

The invention relates to a heat transfer device in the form of a closed chamber in which a partly liquid, partly vaporous Heat transfer medium circulates while passing through an evaporation-condensation process, wherein the transport of the liquid phase of the heat carrier from the cooling zone to the heating zone

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takes place by means of a capillary structure arranged inside the chamber and wherein the Chamber and a gas reservoir connected with it a certain amount of a Contains control gas generated by thermal / mechanical or hydraulic action fills a variable in its size space in the chamber.

Such heat transfer devices are in the relevant technical literature generally referred to as heat pipes, in particular as gas-stabilized heat pipes. you Heat transport is based on the transfer of the latent heat of vaporization from one to the Working temperature of the heat pipe matched liquid heat transfer medium. Used in a heating zone If heat is supplied to the designated area of the heat pipe, then liquid vaporizes here out of the capillary structure, flows into the colder area known as the cooling zone

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of the heat pipe and is reflected there, releasing its heat of condensation. The condensate is transported back from the cooling to the heating zone through the capillary structure, so that the circuit of the heat carrier closes. To generate the for the steam flow required pressure drop, only a minimal temperature difference is required between Heating and cooling zone, since the saturation state that is always present within the heat pipe even small temperature differences cause a relatively large change in pressure. at In practical use, a constant internal or operating temperature over the entire Length of the active heat pipe zone can be assumed.

Usually, the cooling system (cooling surface and coolant temperature) remains during operation of a heat pipe unchanged, so that there is a strong dependency between the amount of heat transferred and the operating temperature of the

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Sets the heat pipe. To stabilize the operating temperature, it is known / the cooling surface of the heat pipe in proportion to the amount of heat transferred by adding an im Control gas located inside the heat pipe takes up a more or less large part of the cooling zone fills out and removes this part of the heat transfer circuit. The control gas, in general a noble gas, can by various external influences to the desired extent are introduced into the cooling zone, so that depending on the amount of heat transferred the active cooling surface of the heat pipe can be influenced in terms of constant operating temperature can. A dispersion of the gas buffer over the entire length of the heat pipe is in the operating state through the constant to the hot zone Heat transfer steam flowing through the cooling zone is excluded.

Practical embodiments of such temperature-stabilized Heat pipes can be found in the

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sentence "Temperature stabilization with heat pipes with changing heat flows" by K.R, Schutt, Commission of the European Communities, EUR 4634 d.

In the practical application of such known systems, difficulties arise as soon as the direction of heat flow is to be reversed. The cooling zone takes the place of the previous heating zone and the gas buffer to control the moves accordingly Cooling surface at the other end of the heat pipe. The gas reservoir with its regulating mechanism remains in place, however, because it is rigidly connected to the heat pipe. In this State is only a regulation in the sense of adding gas, i.e. reducing the cooling surface possible, since the heat transfer vapor flow automatically to the gas supplied Cooling zone and thus blows into the gas buffer. A regulation in the opposite sense, so one Gas extraction to enlarge the cooling surface separates

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because the gas reservoir is now adjacent to the heating zone and possibly heat transfer steam could withdraw, which would lead to the immediate burn out of the heat pipe.

Self-regulating heat pipes without a gas reservoir that can be influenced from the outside are also known. Depending on the amount of heat transferred, your gas buffer is pushed back more or less far into the cooling zone, since
Change the pressure and temperature of the heat transfer medium according to the applied heating power. A change in the vapor pressure and
thus the working temperature is assumed, so that with this arrangement no complete stabilization of the heat pipe temperature can be achieved.

The object of the present invention is therefore to provide a heat transfer device of the type mentioned at the beginning Kind to improve so that regardless of the direction of the heat flow a stabilization the operating temperature with high accuracy

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is borrowed. In particular, an essential side effect of gas buffering, namely the and switching off a heat pipe by filling the entire cooling zone with control gas can be effected regardless of the operating direction of the heat pipe.

Starting from a heat transfer device in the form of a closed chamber in which a partly liquid, partly vaporous heat transfer medium undergoing an evaporation-condensation process circulates, the transport of the liquid phase of the heat carrier from the cooling zone to the heating zone by means of an im Capillary structure arranged inside the chamber takes place and the chamber and one with it in Connected gas reservoir contains a certain amount of a control gas, which by thermal, mechanical or hydraulic action a changeable space in its size Fills chamber, this object is according to the invention solved in that one of the gas reservoir

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outgoing connecting line crosses the chamber and in the area of the cooling and heating zones is provided with openings.

Through this connecting line, the gas reservoir is available even if the heating and heating circuits are interchanged Cooling zones always have a direct connection with the cooling zone and can act as a gas buffer there build up or influence an already existing gas buffer in the desired sense. It is true that the solution according to the invention requires that the gas reservoir also in each case with the heating zone communicates. However, this does not have any adverse effects, since the control gas, independently, in which zone of the heat pipe chamber it is added, always from the heat transfer vapor is transported to the cooling zone. The heat pipe concept according to the invention thus allows all control functions of a gas cushion, namely temperature stabilization or to use heat flow control or shutdown of a heat pipe, no matter

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whether the heat must be transferred in one direction or the other.

Is closed with abrupt changes in the volume of the control gas in the heat pipe chamber calculate, if the gas buffer is reduced, there is a risk that parts of the heat transfer vapor entrained and fed to the gas reservoir. To the resulting To counteract a shortage of heat transfer medium in the active circuit, it is advantageous to that the connecting line and the gas reservoir are lined along their inner walls with a capillary structure and that both capillary structures are in communication with each other and with the capillary structure in the chamber. Will the filling of the Heat transfer device including the gas reservoir and the connecting line dimensioned so that that all capillary structures are saturated with heat transfer fluid, so is ensures that any heat transfer medium entrained in the reservoir is returned to the active one

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Heat pipe chamber is sucked back and the The amount of heat transfer medium remains constant.

It is particularly advantageous if the capillary structures the connecting line and the gas reservoir are coarser than the capillary structure in the heat pipe chamber. This means that if the height level is different, between the individual elements avoided that about the gas reservoir at the expense of Heat pipe chamber soaked with liquid.

The gas reservoir can theoretically be accommodated directly in the heat pipe chamber itself However, it is to rule out a mutual temperature influence expedient that the chamber and the gas reservoir have a certain distance from one another and that the connecting line from one at its ends into the chamber on the one hand and in the gas reservoir on the other hand opening jacket is surrounded and that the annular space between the jacket and the connecting cable

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is filled with capillary structure that corresponds to the structures in the chamber and in the reservoir connected is. The flowing back into the heat pipe chamber is through the annulus Liquid has a considerable flow cross-section with correspondingly low friction losses offered so that the liquid even with larger distances between gas reservoir and chamber can certainly be sucked back into the latter.

Further details and features of the invention emerge from the following description of an embodiment based on a drawing,

Figure 1 shows a heat pipe with a separate gas reservoir.

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A heat pipe chamber 1 running along its inner wall is clad with a capillary structure 2, is via a spacer tube 3 with a Gas reservoir 4, which in turn is lined with a capillary structure 5, in connection. Inside the spacer tube 3 there is a braided or fabric-like structure 6 of relatively coarse porosity, which establishes a capillary connection between the two structures 2 and 5. Along her A connecting line 7 traverses the structure 6 along its longitudinal axis. The line 7 starts from the gas reservoir 4, extends over almost the entire length of the heat pipe chamber 1 and is held at its end by guides 8. In the area of the two ends of the heat pipe chamber, the connecting line 7 is provided with openings 9 and 10, respectively. A thin layer of capillary structure 13 is arranged in its interior.

The mode of action is as follows:

After the entire system has been thoroughly evacuated, it is also filled via the valve 11 a certain amount of heat transfer medium

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and to control gas. The amount of heat transfer medium is such that all Capillary structures are saturated, while the amount of control gas is essentially down the temperature range in which the gas reservoir to move the gas front is driven in the heat pipe chamber. Depending on the area of application, they are used as heat transfer media for example ammonia, · water, potassium, or sodium can be used as control gas mostly helium or argon is used.

In the arrangement shown in Fig. 1, the heating zone is located on the gas reservoir oriented towards the end of the heat pipe chamber. There is thus an operating state that excludes temperature stabilization in the previously known heat pipe designs. In contrast it allows the connection line via its opening 9 also a remote To influence heat pipe lying gas buffer 12 in the desired manner.

If, for example, the aim is to stabilize the heat pipe operating temperature, for example

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because the component to be cooled should be kept at as constant a temperature as possible, so causes the slight increase in temperature of this component with increased heat build-up an external cooling of the gas reservoir by means of a control system known per se Circuit. The control gas contracts, releasing some of the information it has filled out Cooling zone free for the heat transfer circuit. This process continues until the Enlargement of the cooling surface is sufficient to bring the operating temperature back to the desired level To depress the value. With reduced heat accumulation on the component to be cooled, when it drops of its temperature below the setpoint value the temperature of the gas reservoir accordingly regulated upwards until the gas has expanded so far into the cooling zone that the remaining Cooling surface allows heat to be dissipated at the desired operating temperature.

Should the heat pipe be switched on and off , for example when it comes to the controlled extraction of heat from a storage tank, this is how it is Control gas is pressed into the heat pipe chamber until it fills the entire cooling zone.

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The condensation heat of the resulting heat transfer condensate can no longer be dissipated, and the cycle comes to a standstill.

If the heating and cooling zones are swapped, the gas cushion moves to the left end of the heat pipe chamber, and the supply and discharge of the gas takes place via the openings 10 in the obeaeen described way.

Because there is a certain diffusion of the heat carrier vapor into the control gas and thus into the gas reservoir cannot be ruled out, the additional capillary structures 5 and 6 ensure that that the person responsible for the heat transfer circuit Structure 2 does not gradually dry out.

The thin network layer 13 inside the connecting line 7 essentially has the task of To avoid droplet formation inside, so that the control gas always has a sufficient flow cross-section has available.

The inventive arrangement of the connecting line 7 with its openings 9 and 10 can

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Claims (3)

2350380 vs. - / 1. j heat transfer device in the form of a closed chamber in which a partially liquid, partially vaporous heat transfer medium while going through an evaporation-condensation process circulates, with the transport of the liquid phase of the heat carrier from the cooling zone to the heating zone takes place by means of a capillary structure arranged in the chamber interior and wherein the chamber and a gas reservoir connected to it a certain amount contains a control gas, which by thermal, mechanical or hydraulic action fills a space of the chamber of variable size, characterized in that that one emanating from the gas reservoir Ferbindungsleitung crosses the chamber and is provided with openings in the area of the cooling and heating zones. 509816/01 U 2. heat transfer device according to claim 1, characterized, that the connection line and the gas reservoir are lined along their inner walls with a capillary structure and that both capillary structures with each other and communicate with the capillary structure in the chamber. 3. Heat transfer device according to one of the preceding claims, characterized, that the chamber and the gas reservoir have a certain distance from each other and that the connection line starts from one its ends into the chamber on the one hand and into the gas reservoir on the other hand Sheath is surrounded and that the annular space between the sheath and connecting line with Capillary structure is filled in with the structures in the chamber and in the reservoir connected is. 50981 B / 0 1 U 4 »Heat transfer device according to claim and, 3 ί '- ■■ -.-- - ■. ■ - thereby gekeaazeichnefc ^ ^: " ^: -'----" - V that the KapillrsfcruJcfcur "at the blending" line uad la the "gas reservoir" is coarser than the capillary structure- in the 'chamber- »" "' - - BATH ORIGINAL «, Ο Blank page