DE1953501A1 - Starting up heat transfer tubes with solid filling - Google Patents

Abstract

To overcome the difficulties in starting up conventional heat transfer tubes with a normally solid filling (Na), at least one secondary heat transfer tube, of smaller enthalpy, but spanning thermally at least most of the length of the main tube, is attached parallel to the main tube. The secondary tube(s) consist preferably of several tubes in series, with all ends in thermal contact with the main tube. Heat transfer is just sufficient to melt the main transfer medium at operating temperature. The secondary tube may be a cavity in the wall, or centrally fitted inside the main tube. If several series are used, joints are preferably staggered.

Description

3721/68 d / XIII / 1557

Nentanwäta

DipL-kg. Rkiwrd Müller-Bömer KpL-log. Hons-Heinrkh Wey

Berlin-Dahlem, Podbielskiallea 63

Berlin, October 20, 1969

EUROPEAN ATOMIC COMMUNITY (EURATOM)

Patent application

Arrangement for stabilizing the temperature of a heated surface

The invention relates to stabilizing the temperature of a heated one Flat, for example, the temperature of the cesium reservoir in one thermionic converter.

In order to stabilize the temperature of a heated surface against changing environmental conditions, the use of a so-called. Heat pipe proposed. This means a hermetically sealed vessel in which there is a heat transfer medium is in a natural evaporation and condensation cycle. This heat pipe was used to stabilize the temperature of the heating zone

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According to the proposal mentioned, an inert gas plug is provided in the tube, the volume of which changes with the vapor pressure of the heat transfer medium. If the amount of heat absorbed by the heating zone increases, then the vapor pressure of the heat transfer medium also increases, and the inert gas plug, which is located in the cooling zone of the heat pipe, is compressed. Because the inert gas has a significantly poorer thermal conductivity possesses as the heat transfer medium, increases thus the area of the heat pipe wall that is effective for heat radiation. It has also already been proposed to have a central displacement body in the border area between the heat transfer medium and the inert gas plug to be built in in order to improve the level characteristics in the sense of a larger change in the effective radiation area a given change in vapor pressure.

This previously proposed arrangement suffers from the fact that the The temperature of the inert gas plug has a strong influence on the control accuracy; this in particular because of the temperature difference between the temperature surrounding the heat pipe and the temperature of the inert gas plug is only slight and the heat pipe walls act as good heat conductors. When using such arrangements in the area In addition to radioactive radiation, the gamma heat generated in the Warmer tube wall is developed. Prevent this interference a real stabilization of the temperature in the heating zone of the heat pipe, because they also act on the position of the boundary zone between the Daapf of the heat transfer medium and the inert gas plug.

The invention avoids these disadvantages. Dia invention there is an arrangement for stabilizing the temperature of a

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heated surface, for example the temperature of the cesium re-reservoir in a thermionic converter, with the help of a heat pipe, in which an inert gas plug floats in the area remote from the heating zone, the volume of which changes with the vapor pressure of the heat transfer medium and the area of the heat pipe arrangement that is effective for heat radiation limited, in that the part of the heat pipe in which the Inert gas plug floats, is well thermally coupled to the heating zone of a secondary heat pipe.

In a preferred embodiment of the invention, the heating zone of the secondary heat ä tube is slipped over the pot-shaped part of the first heat pipe in which the Inertgaspfropfen floats. An inert gas plug is preferably also provided in the secondary heating tube.

The stabilizing effect can be further increased by displacement bodies in the first or the secondary heat pipe or also by a third pipe which is connected to the secondary heat pipe in the same way as this is connected to the first. Preferably, the displacement bodies are mechanically and thermally to the heating zone of the well coupled opposite wall of the heat pipe, because the temperature of this ä wall than the more stable the adjacent thereto or of the opposed walls. In order to keep the gamma heating of these displacement bodies low, it is advantageous to design them as hollow, empty containers, the wall thickness of which is selected according to the operating pressure.

The invention, the temperature of the inert gas plug in the first heat pipe largely decoupled from environmental influences. This practically depends on the position of the boundary between steam and inert gas

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only depends on the amount of heat that comes from the heating zone of this first Heat pipe is added.

The invention is explained in more detail below with the aid of FIGS. 1 to 3 on the basis of some embodiments.

Show it:

FIG. 1 shows a schematic sectional illustration of a first arrangement according to the invention;

FIG. 2 shows a further arrangement according to the invention with a displacement body ;

FIG. 3 shows a further arrangement according to the invention with two displacement bodies;

Figure * f shows a beeteh of three heat pipes according to the invention Arrangement and

Figure 5 is a detailed sectional view relating to the suspension of a Sinker.

The basic principle of the invention will now be explained with reference to FIG . The surface 1 to be stabilized is the heating surface of a first heat pipe 2. The heat supply is indicated by arrows 3 in the area of the heating zone. The heat pipe 2 consists of a high-temperature-resistant material, the interior of which is covered in the longitudinal direction by capillary channels, not shown in the figure, a metal is used as the heat transfer medium, which is in vapor form at the normal operating temperature in the heating zone, while it condenses in the KUhlecoe opposite the heating zone. Outside the metal vapor space * f is located

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another Inertgaspfropfen 5 in the heat pipe, and that due to the entrainment in the vapor of the heat transfer medium

in the top, i.e. the heating zone

Area. The horizontal boundary layer between the two is through one line 6 indicated; the limit, however, is in truth as a transitional area to understand. Especially on the wall of the heat pipe, the boundary is fluid due to the high heat conduction in the wall. Because the inert gas is a much worse heat conductor than steam, the line 6 also means a temperature jump and a limitation for the Heat flow and heat radiation effective heat pipe area.

In the vicinity of the line 6, another heat pipe 7 is slipped over the outside of the heat pipe 2, the outwardly directed wall surfaces of which act as heat radiators. The direction of the radiated heat is indicated by arrows 8. So DJs secondary Wärmeröhre7 acts as a cooler for the first heat pipe 2, with the result that the line 6, hochschifbtj in the drawn Laga but then practically stuck during heating initially surprising there with increasing Wärmeaufuhr. Since the inert gas plug is completely enclosed by the second heat pipe and its temperature hardly changes, a significantly higher stabilizing effect for the temperature of the surface 1 can be expected compared to previously proposed arrangements.

This effect can be increased even further in an arrangement according to FIG. 2 , in which the same reference symbols are used for the same parts. The only difference to Figure 1 is a displacement body 9 in the first heat pipe 2, specifically in the area of the line 6. This displacement body is known to achieve a larger change in the approximately wall surface for a given change in volume of the inert gas plug ^

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The stabilization of the temperature of the surface can be improved even further by an arrangement according to FIG. 3 again with the same reference symbols for the same parts. In contrast to the last-mentioned arrangement, an inert gas plug 10 is also provided in the secondary heat pipe 7 so that the secondary heat pipe also has a boundary line 11 that changes with the heat flow. Here, too, the change characteristics are preferably sensibly influenced by a displacement body.

One can stabilize now by further Kaekadenschaltungen further heat pipes even higher drive "but should have three heat pipes beyond cascade only limited practical value, given the effort that this is necessary." Line arrangement with three heat pipes shows the Fi gur k. here, then, only the third heat pipe 13 radiates essentially the heat. with verhäitnismäseig little effort, the stabilization effect can be increased when mechanical displacement body and especially thermally e ~ n the area which it couples enclosing heat pipe, which has the most stable temperature behavior. This is always the opposite of the heating surface 14. in figure 5 such a coupling is schematically illustrated, as may occur in one or in all the heat pipes. a metal block 15 of good thermal conductivity material forms the bridge zwiechen the wall lA · and the displacement body l6. From this figure is also to ercehen that

the displacement body is preferably hollow with a wall thickness which just withstands the maximum operating pressure. In this way, the gamma-ray heating of the displacement body plays the least possible role in the temperature of the inert gas plug. The mechanical stability of the displacement body can be further improved by structural struts (not shown).

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Claims (1)

- 7 - 3721/68 d / XIII / 1357 195350Ί Claims / 1.! Arrangement for stabilizing the temperature of a heated surface, for example the temperature of the cesium reservoir in a thermionic converter, with the help of a so-called heat pipe, i.e. a hermetically sealed vessel in which there is a heat transfer medium in a natural evaporation and condensation cycle wherein in the remote heating zone region of the heat pipe floats a Inertgaspfropfen whose volume varies with the vapor pressure of the heat carrier medium and which is effective for the heat radiation surface of the Wärmeröhrenwandung limited, thereby featuring g e that the part of thermodynamics (2), which the Inertgaspf ^ opfen (5) floats, is well thermally coupled to the heating zone of a secondary heat pipe (7). 2. Arrangement according to claim 1, characterized in that the heating zone of the secondary heat pipe (7) is placed in a pot-shaped manner over the part of the first heat pipe (2) in which the inert gas plug (5) floats. 3. Arrangement according to claim 1 or 2, characterized in that an inert gas plug (10) is also provided in the secondary heat pipe (7) (Fig. 3). k. Arrangement according to Claim 3, characterized in that the part of the secondary heat pipe (7) in which the inert gas plug (10) floats is well thermally coupled to the heating zone of a tertiary heat pipe (13). 009825/1189 -8th- - 8 - '3721/68 d / XIII / 1357 5. Arrangement according to one of the preceding claims, characterized in that the heat pipe interior has a greatly reduced effective cross section due to a central displacement body (9, 12, 16) in the border area between the vapor of the heat transfer medium and the inert gas. 6. Arrangement according to claim 5, characterized in that the displacement body is mechanically and thermally well coupled to the wall of the heat pipe opposite the heating zone (Hg, 5). 7. An arrangement according to claim 6, characterized in _t that the displacement body (9, 18 »16) is a hollow, empty container, the Wändetärke is selected in accordance with the operations just pressure. 009825/1 1 89