JPH10122775A - Variable conductance heat pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent thermal diode characteristics by forming a gas reservoir at a condensing portion side and a low heat conductive portion between an evaporating portion and the condensing portion in a container for containing working liquid and noncondensible gas therein in a variable conductance type heat pipe. SOLUTION: The variable conductance heat pipe 11 is used, for example, to control temperature of a reaction container of a chemical plant. Working liquid and noncondensible gas are contained in the container. And, its evaporating portion 32 side is contained in the reaction container 8. Meanwhile, a condensing portion 42 side is disposed out of the container 8, and a gas reservoir 52 is provided at its end. The pipe 11 has a low heat conductive portion 62 is provided across a borderline between the container 8 and its outside. This portion 62 designates a portion in which axial heat conductivity is sufficiently lowered as compared with those of portions 32 and 42, and is formed by providing a portion formed of titanium alloy having low thermal conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat pipe having a variable conductance.

[0002]

2. Description of the Related Art The technology of applying a heat pipe to a heat radiation mechanism has been practically used for a long time. In the case of a normal heat pipe, the heat transfer amount is determined by the temperature difference between the evaporating part (the side to be heated, that is, the side to be radiated) of the heat pipe and the condensing part. However, depending on the object to be radiated, there is a case in which the temperature is maintained at a certain temperature and the heat is radiated when the temperature is exceeded. For example, it is used in a chemical plant including a certain type of reactor, a chemical battery or a fuel cell, or a device related to nuclear power generation. In such a case, it is inconvenient if the operation is started due to the temperature difference between the evaporating section and the condensing section of the heat pipe. Therefore, it is conceivable to apply a variable conductance heat pipe having a variable conductance instead of a normal heat pipe.

[0003] Variable conductance heat pipes are heat pipes that do not operate substantially until a certain temperature is reached. As such heat pipes, those applying a shape memory alloy, heat pipes mixed with non-condensable gas, and the like are known. The latter case is generally used because of its advantages such as a relatively simple structure and a relatively wide range of application temperature. Originally, this kind of variable conductance heat pipe has been developed as a heat transport device for space, but recently, its use on the ground, such as the above-mentioned battery application and chemical plant, is also increasing. .

A conventional variable conductance heat pipe mixed with a non-condensable gas is enclosed inside the heat pipe in such a manner that when the working fluid in the heat pipe starts to evaporate, the working fluid is pushed by the evaporating flow of the working fluid. The non-condensable gas is pushed toward the condensing section. The interface between the non-condensable gas and the evaporating flow of the working fluid
If it does not reach the condensing section, the condensation of the working fluid vapor does not start. Therefore, the heat pipe does not operate. still,
The operation of the heat pipe is not strictly occurring because of some diffusion at the interface. Practically, this generally means that the heat pipe has not been activated.

[0005] If the temperature is increased, the interface between the non-condensable gas and the evaporating flow of the working fluid moves to the condensing section side. This is because the temperature dependency on the saturation pressure of the working fluid is extremely large as compared with the non-condensable gas. When the interface moves toward the condensing section and reaches a part of the condensing section, the condensation of the working fluid vapor starts. The result is a heat pipe that is virtually inactive up to a certain temperature.

[0006]

In the variable conductance heat pipe, heat is not substantially transferred by the working fluid until a certain temperature. However, since the heat conduction phenomenon via the container that constitutes the heat pipe is occurring,
Even at a stage where heat transfer by the hydraulic fluid is not substantially performed, heat transfer is performed. However, for example, in equipment such as a chemical reaction furnace, during operation, the heat radiation mechanism is operated so as not to exceed a certain temperature, but on the contrary, there may be a case where it is desired to control so as not to fall below a certain temperature. Alternatively, there is a case where it is desired to suppress the temperature of the reaction furnace from lowering via the installed heat pipe after the operation is stopped. In addition, there is a demand that, for example, depending on the type of battery, it is desired to maintain a certain temperature, but to prevent an excessive rise in temperature. In such a case, it is desired to reduce the heat transfer as much as possible at the stage where the heat transfer by the working fluid is not substantially performed. Excellent thermal diode characteristics such that the ratio of the maximum heat transfer amount (the maximum value of the heat transfer amount by the heat pipe) to the heat transfer amount at the stage where the heat transfer by the hydraulic fluid is not substantially performed is as large as possible. There was a need for a variable conductance heat pipe.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a variable conductance heat pipe having excellent thermal diode characteristics. That is, the variable conductance heat pipe of the present invention has a container, a working fluid and a non-condensable gas contained in the container, and the container has a gas reservoir on the side of the condenser, A low heat conduction portion having a lower heat conduction than the condensation portion and the evaporation portion is formed between the first and second portions. One of the embodiments of the present invention has a container, a working fluid and a non-condensable gas contained in the container, wherein the container has a gas reservoir formed on a condensing portion side, Is a variable conductance heat pipe having a portion having a small material cross-sectional area between the evaporating section and the condensing section.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a conceptual diagram for explaining a variable conductance heat pipe. A predetermined amount of hydraulic fluid is contained in the container 2 of the variable conductance heat pipe 1. The container 2 also contains a predetermined amount of a non-condensable gas. The non-condensable gas refers to a gas that does not condense under the normal use condition of the variable conductance heat pipe 1. Generally, the boiling point of the working fluid in the container 2 is affected by the pressure in the container 1. When the temperature of the evaporating section (heat absorbing section) 3 is lower than the boiling point, it is naturally considered that the working fluid does not substantially evaporate (strictly speaking, in terms of thermodynamic and statistical mechanics, the working fluid is Some evaporation and condensation have occurred).

When the evaporating section 3 is heated and its temperature becomes equal to or higher than the boiling point of the working fluid, the working fluid evaporates and its vapor moves to the condensing section 4. However, the vapor cannot substantially reach the condensing section 4 due to the non-condensable gas. (Strictly speaking, since there is a diffusing action, some of the vapor particles are slightly condensed to the condensing section 4. After all, heat transfer by evaporation and condensation of the working fluid has not been performed.

When the evaporating section 3 is further heated, the interface between the working liquid vapor and the non-condensable gas is further pushed toward the condensing section 4 due to an increase in the evaporating pressure of the working liquid. When the temperature of the evaporator 3 rises to some extent, the interface reaches the condenser 4, but the temperature of the evaporator 3 at this time is referred to as a predetermined temperature TL. The interface between the working fluid vapor and the non-condensable gas strictly has some diffusion phenomena, etc. It does not point to the border.

In the present invention, a gas reservoir 5 is provided as shown in FIG. Usually, the gas reservoir 5 is provided on the opposite side of the evaporator 3 with respect to the condenser 4. When the pressure of the working fluid vapor increases, the non-condensable gas passes over the condensing section 4 and reaches the gas storage section 5.
However, if the volume of the gas reservoir 5 is large enough, substantially all of the non-condensable gas will eventually be contained in the gas reservoir 5 (it goes without saying that However, diffusion phenomena always exist, but that is not a problem here). In this case, the vapor of the hydraulic fluid occupies the condensing section 4, and as a result, the vapor of the hydraulic fluid is sufficiently condensed.

However, the gas reservoir 5 is partially formed,
It does not matter if it overlaps. In other words, the non-condensable gas to be sealed may be increased to such an extent that it cannot be accommodated in the gas reservoir 5.

As described above, the variable conductance heat pipe 1 does not operate as a heat pipe when the temperature of the evaporator 3 is lower than the predetermined temperature TL, but operates when the temperature is higher than the predetermined temperature TL. Even when the temperature of the evaporator 3 is lower than TL, the above-described diffusion phenomenon between the working fluid and the non-condensable gas occurs. In addition, there is transportation of heat by heat conduction via the container 2.

As the heating of the evaporating section 3 is advanced, the non-condensable gas will eventually be sufficiently pushed into the gas storage section 5 to maximize the heat transport amount of the heat pipe. It is referred to here as quantity QH. The temperature at this time is referred to as a maximum temperature TH. Assuming that the heat transport amount at the predetermined temperature TL is described as QL, the value of QH / QL is one of the standards of the thermal diode characteristics. To increase this value,
It is necessary to make QL as small as possible.

In the present invention, a low heat conducting section 6 is provided in a portion between the evaporating section 3 and the condensing section 4 of the container 2. By doing so, QL can be reduced. Here, the low heat conducting part 6
The term refers to a portion in which the thermal conductivity in the axial direction is sufficiently lower than that of the evaporating unit 3 and the condensing unit 4. The axial direction is a direction from the evaporating section 3 to the condensing section 4. For example, as shown in the conceptual diagram of FIG.
And a portion formed of a titanium alloy 61 having low thermal conductivity. The portion of the titanium alloy 61 has sufficiently higher thermal resistance than the copper material 71. Although a titanium alloy is taken as an example of a material having low thermal conductivity, other metal materials or non-metal materials may be used. Alternatively, the thickness of the low thermal conductive portion 6 may be reduced to reduce the cross-sectional area, or a combination of these may be used.

The material of the container 2 other than the low heat conducting portion 6, the type of the working fluid, and the like are the same as those of the conventional variable conductance heat pipe. Specifically, the material of the container 2 is preferably a copper material or the like, and the working fluid is typically water or the like.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on embodiments. FIG. 3 is a conceptual diagram illustrating an embodiment of the present invention. The variable conductance heat pipe 11 of the present invention can be used for controlling the temperature of a reaction vessel or the like of a chemical plant, for example. It is assumed that an efficient reaction is realized when the degree is about the same. If the temperature exceeds 280 ° C., unnecessary thermal decomposition occurs. Therefore, it is desired to control the temperature in the reaction vessel 8 to 250 to 280 ° C. Although the reaction vessel 8 is provided with a heating device (not shown), it also generates heat due to the reaction. In this case, the reaction vessel 8 is heated to 250 ° C., and thereafter the reaction vessel 8 has a large reaction heat, and particularly the heating apparatus. The reaction shall be maintained without heating.

The evaporator 32 of the variable conductance heat pipe 11 of the present invention is accommodated in the reaction vessel 8.
The condensing section 42 is located outside the reaction vessel 8, and a gas reservoir 52 is provided at the tip thereof. The length of the gas reservoir 52 is 300 mm, and the length of the variable conductance heat pipe 11
Is about 2 m long.

The variable conductance heat pipe 11 is
The gas reservoir 52 has an outer diameter of 34 mm and a wall thickness of 1.65 mm.
The thickness is 3 mm and the thickness is 1.2 mm. The material is stainless steel, and three layers of phosphor bronze mesh are inserted into the inner wall except for the gas reservoir 52. The working fluid is naphthalene and the non-condensable gas is xenon. This variable conductance heat pipe 11
It is designed such that 50 ° C. is a predetermined temperature (TL) and 275 ° C. is a maximum temperature (TH). Therefore, the evaporator 32
When the temperature exceeds 250 ° C., heat transfer by the working fluid is substantially started, and the heat transfer amount rapidly increases.

The low heat conducting portion 62 is located across the boundary between the inside and outside of the reaction vessel 8. FIG. 4 is a partially enlarged schematic view of the low heat conducting portion 62. The outer diameter is 16.1 m by external cutting.
m. The thickness is 0.6 mm.

Now, a heating device (not shown) provided in the reaction vessel 8 was started, and a reaction in the reaction vessel 8 was started by a rise in temperature. This reaction is properly realized in a temperature range of 250 to 280 ° C, but after heating to about 250 ° C, the temperature rises even if the heating device is stopped by the heat of reaction. However, if the variable conductance heat pipe 11 having a predetermined performance and heat dissipation is attached, the cooling can be performed so that the temperature does not exceed 280 ° C. On the other hand, when the temperature of the evaporator 32 is lower than 250 ° C., the heat transfer by the working fluid is substantially stopped, so that unnecessary cooling can be prevented. Thus, control of the temperature range of 250 to 280 ° C. was performed efficiently.

Comparative Example 1 The same as Example 1 of the present invention except that the low heat conducting portion 62 was not provided. In the variable conductance heat pipe of Comparative Example 1, similarly to that of Example 1 of the present invention, when the evaporating section is heated to 250 ° C. or higher, heat transfer by the working fluid is substantially started, and the heat transfer amount rapidly increases. I have.

In each of the variable conductance heat pipes of Example 1 of the present invention and Comparative Example 1, heat transport by the working fluid is substantially started when the evaporator temperature rises to 250 ° C. or higher, and the heat transport amount rapidly increases. On the other hand, when the temperature is lower than 250 ° C., the heat transfer by the hydraulic fluid is substantially stopped. However, the temperature range to be controlled is 250-2.
When the temperature is 80 ° C. and lower than 250 ° C., it is desired to suppress the heat radiation by the variable conductance heat pipe as much as possible. Comparing the variable conductance heat pipes of Inventive Example 1 and Comparative Example 1, when the temperature was less than 250 ° C., Inventive Example 1 had a heat transport amount (radiation amount) of about 48% as compared with that of Comparative Example 1. That is, in FIG. 1, the variable conductance heat pipe 1 of the present invention is
It can be seen that unnecessary cooling when the temperature of the evaporating section 32 was lower than 250 ° C. was prevented.

As described above, the variable conductance heat pipe of Example 1 of the present invention has better thermal diode characteristics than that of Comparative Example 1. Therefore, it can be seen that the present invention is a variable conductance heat pipe that is more suitable for the heat radiation mechanism when it is desired to control the temperature within a predetermined temperature range. As a method of reducing the cross-sectional area of the material of the low heat conduction portion and the low heat conduction portion, a method of reducing the thickness is practical and desirable.

Second Embodiment of the Invention FIG. 2 is a conceptual diagram. The variable conductance heat pipe 10 is a thermosiphon type heat pipe having a length of about 1 m, and uses water as a working fluid and argon as a non-condensable gas. The material of the container is copper material 71 and titanium alloy 61 (Ti-6Al-4V) except for the gas reservoir 51.
It is formed with. The part of the titanium alloy 61 functions as a low heat conducting part, and its length is 20 mm. Except for the gas reservoir 51, the container had an outer diameter of 19.1 mm and an inner diameter of 16.7 mm. Phosphor bronze having a mesh number of 150 was inserted into the inner wall along the tube wall and arranged. The gas reservoir 51 has an outer diameter of 3
4 mm, inner diameter 31.7 mm. The copper material 71 and the titanium alloy 61 were joined by brazing. The thermal conductivity of the material constituting the copper material 71 is 390 W / mK, and that of the titanium alloy 61 is 8 W / mK.

Comparative Example 2 The same as Example 2 of the present invention except that the titanium alloy 61 was made of the same material as the copper material 71.

In the variable conductance heat pipes of Example 2 of the present invention and Comparative Example 2, the predetermined temperature (TL) can be adjusted by adjusting the amount of non-condensable gas charged. The amount of heat transported at a temperature lower than the predetermined temperature (TL), that is, at the stage where the heat transport by the working fluid was not substantially performed, was compared between the inventive example 2 and the comparative example 2. As a result, the inventive example 2 was compared with the comparative example 2.
The heat transport amount was about 1/6 of that of. Therefore,
The variable conductance heat pipe 10 of Example 2 of the present invention
The thermal diode characteristics are superior to those of Comparative Example 2. The variable conductance heat pipe 10 of the present invention
Is a heat pipe suitable for a heat radiation mechanism when it is desired to control the temperature within a predetermined temperature range.

As described above, the variable conductance heat pipe according to the present invention has excellent thermal diode characteristics and is suitable for a heat radiation mechanism for controlling a predetermined temperature range. As the material of the container, stainless steel and copper are shown in the above-described example, but other materials, such as Al, can also be used. Further, the titanium alloy is used as an example of the material having a large thermal resistance as the low heat conductive portion, but other metal materials and nonmetal materials can be applied. Although not described in the embodiments, as a method of forming the low heat conductive portion, a method of reducing the cross-sectional area of the material and a method of using a different material may be used in combination.

[0029]

The variable conductance heat pipe according to the present invention realizes excellent thermal diode characteristics.
The present invention can be suitably applied to a heat radiating mechanism for controlling to a predetermined temperature.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a variable conductance heat pipe of the present invention.

FIG. 2 is a conceptual diagram illustrating a variable conductance heat pipe of the present invention.

FIG. 3 is a conceptual diagram illustrating an embodiment of the present invention.

FIG. 4 is a partially enlarged conceptual diagram illustrating an embodiment of the present invention.

[Explanation of symbols]

 1, 10, 11 Variable conductance heat pipe 2 Container 3, 31, 32 Evaporation unit 4, 41, 42 Condensing unit 5, 51, 52 Gas storage unit 6, 62 Low heat conduction unit 61 Titanium alloy 71 Copper material 8 Reaction vessel 91, 92 fins

Claims (2)

[Claims] 1. A container comprising: a container; a working fluid and a non-condensable gas accommodated in the container; wherein the container has a gas reservoir on the condenser side (radiation side); A variable conductance heat pipe in which a low heat conduction part having a lower heat conduction than the condensation part and the evaporation part is formed. 2. A container comprising: a container; a working fluid and a non-condensable gas accommodated in the container; wherein the container has a gas reservoir on the side of a condensing section; A variable conductance heat pipe with a small section of material between the section and the section.