JPS6053789A - Sealing of operating liquid for heat pipe - Google Patents

Abstract

PURPOSE:To contrive the mass production of high-performance heat pipe by a method wherein a sodium sealing line, provided with a cold trap and an im purities densitometer in parallel to a dosing hopper in a loop and utilizing helium gas as cover gas, is treated by on-line treatment. CONSTITUTION:Air in a heat pipe container 1 is discharged by an exhausting device 29 by opening a valve 35 and is preheated to 350 deg.C or higher. Then, the valves 25, 26 are opened to circulate solium in the loop through the heat pipe and effect a perfect flushing whereby wetting property between a wick is improved and a pretreatment is unnecessitated. After finishing the flushing, the valve 34 is opened for a short period of time, a connecting pipeline to a dosing pod 27 is filled with sodium, the valve 32 is opened slightly to pour the sodium into the pad 27 until a continuous level meter 28 detects a level, the valves 25, 31 are closed and the valve 32 is fully opened. Under this condition, the exhausting device 29 is started to extract the gas in the pod, then, the sodium in the heat pipe moves into the pod 27 and the moving amount thereof is known by the level meter 28. There processes are treated by an on-line treatment and thereby mass-producing the high-performace heat pipes.

Description

[Detailed description of the invention] The present invention relates to a method for sealing a working fluid into a heat pipe.

More specifically, the present invention relates to a method for sealing a working fluid into a heat pipe using an alkaline earth metal as the working fluid.

When manufacturing a heat pipe as a sealed container using alkaline earth metals (sodium, potassium, etc.), impurities should be removed as much as possible from the alkaline earth metal as the filled fluid (working fluid) in order to improve performance and durability. With a few exceptions,
It is necessary to vacuum seal the non-condensable gas with sufficient degassing.

FIG. 1 shows a schematic diagram of a typical heat pipe. Structurally, a heat pipe consists of a multilayer mesh 2 called a wick attached to the inner wall of a metal container 1.
This container 1 is filled with an appropriate amount of alkaline earth metal such as IJium, and finally sealed in a high vacuum. For enclosing, etc., an enclosing pipe 3 is usually attached, and after the end of this enclosing pipe is crimped and clamped, it is sealed and welded. Alkaline earth metals are chemically extremely active and are oxidized almost instantly when they come into contact with air. Therefore, if impurities such as oxides are mixed in, the durability of the heat pipe will be greatly impaired, so the entire sealing operation must be performed in an inert gas atmosphere.

Conventionally, as a method for enclosing an alkaline earth metal in a heat pipe, taking sodium as an example, the following procedure is often used.

That is, first, commercially available solid sodium is placed in a glove box surrounded by inert gas, and the already oxidized film inside the glove box is carefully cut with a knife or the like to extract the relatively pure sodium inside. This solid sodium is placed inside a heat pipe that has already been cleaned, and the temperature is slightly raised, then a vacuum is drawn, a sinter is applied, and the enclosed pipe is finally clamped. However, this method has the following drawbacks.

(a) All work is done inside the glove box, which is time consuming and inefficient.

(b) The purity of commercially available solid sodium itself is not very high.

(C) The heat pipe is cleaned before inserting sodium, but some solid impurities, adsorbed gas, etc. remain after normal degreasing, pickling, etc., and these become sources of impurities. The wettability is reduced and the liquid reflux performance due to the capillary force of the wick, which is important for heat pipe performance, deteriorates.

(d) When evacuation is performed using a vacuum pump, unless a special pump is used, there is a high possibility that oil vapor from the vacuum pump will diffuse back into the heat pipe and become a new impurity in the heat pipe. In addition, in order to perform sufficient deaeration, it is necessary to draw the vacuum for a considerable period of time, and the more successful the deaeration is, the more contaminated it becomes.

In order to eliminate the above drawbacks (a) and (b), vacuum distillation, which is used in conventional working fluids other than alkali metals,
Application of condensed packing method is considered, but (c) and (,
The problem of i) still remains, and with difficult-to-handle materials such as alkali metals, this work may become dangerous and complicated, presenting new problems.

An example of the apparatus for the above-mentioned vacuum distillation and condensation method is shown in FIG.

In the figure, 1 is a heat pipe container, 6 is sodium for injection, and with valves 8 and 9 open, it is evacuated by a high vacuum exhaust pump 5, and a heater 12 attached to the wall of the container 7 is used. Heat and evaporate sodium 6.

The generated steam moves as shown by arrow 10 and reaches container 1.
It is cooled and condensed within the tank, allowing it to be filled with sodium. If the temperature is not carefully controlled when the filling is complete, condensation will occur in pipes other than the heat pipe 1, making it difficult to ascertain the true amount of sodium sealed in the heat pipe 1.

The present invention enables the highly pure alkaline earth metal to be fully degassed and sealed in the heat pipe, has good wettability to the wick, and can be filled with hydraulic fluid efficiently in a relatively short time. The purpose is to provide a method that can be used.

That is, the present invention provides a method for sealing a working fluid into a heat pipe using an alkaline earth metal loop in which a heat pipe container with a built-in wick is filled with an alkaline earth metal, in which a cold trap and an impurity concentration meter are installed in the alkaline earth metal loop. A measuring pot is installed in parallel to the container, and helium gas is used as a cover gas above the free liquid level, and the loop is used as a sealing line for on-line processing. Related to liquid filling method.

According to the method of the present invention, alkaline earth metal heat pipes with excellent durability and performance can be manufactured on an industrial scale. The method of the present invention can be widely applied to the production of heat pipes using alkaline earth metals and various heat transfer devices to which this high-temperature heat pipe is applied.

Next, the features of the present invention will be listed.

(a) A heat pipe is installed in a circulating liquid metal loop equipped with a cold trap, which is a device for capturing impurities in the liquid metal.

(b) The method allows all of the flushing, degassing, and vacuum sealing operations of the pipe in the liquid metal loop to be performed online.

(Q) Parallel liability pots were used as a method to prevent the inside of the heat pipe from being contaminated even if there was back diffusion of oil vapor during vacuuming.

(d) By using the parallel measuring pots mentioned above, it is possible to grasp the amount of working fluid filled into the heat pipe and the degree of vacuum inside.

(,) The use of He gas as a cover gas for the liquid metal loop promotes the degassing of free gas in the liquid metal in the loop, thereby extremely minimizing the amount of noncondensable gas carried into the heat pipe.

(f) As a pre-treatment to improve the wettability of the wick (b)
) The method uses 7 lashings of the liquid metal itself, eliminating the need for pretreatment agents.

(b)) For on-line filling in the liquid metal loop,
It requires less complicated work and can be done efficiently, and by installing heat pipes in parallel, it is possible to process large quantities.

The present invention will be explained below with reference to the drawings.

FIG. 3 shows a typical circulating liquid metal (hereinafter a sodium loop is shown as a specific example) loop with a cold trap 13.

Sodium is filled into the loop by pressure feeding from the storage tank 14, and its vent valve 15 is closed. In this way, a closed loop in which the electromagnetic pump 16 circulates is formed. A heater 17 and a cooler 18 are usually installed to adjust the temperature of sodium in the loop. Further, the flow rate in the loop is measured by a flow meter 19, and the purity of sodium in the loop is measured by an impurity concentration meter (oxygen concentration meter, etc.) 20.

Furthermore, the temperature of each part within the loop is monitored by a thermocouple (not shown). 16 is a cold trap for removing sodium impurities in the system; 21 is an expansion tank for absorbing the thermal expansion of sodium; , an inert gas is applied as a cover gas to prevent further contamination of sodium. Here, 22 is this cover gas supply system.

Such a sodium loop is well known in the technical field that develops fast breeder reactors, and although it is a difficult fluid to handle, with the accumulation of many years of experience, it is easy to create high-purity (oxygen concentration around 1 ppm) sodium loop. Possesses driving skills that will allow you to: On the other hand, in the existing sodium loop, argon gas is used as the cover gas, but in the present invention, a heat pipe filling line 23 of an online processing method is installed in the sodium loose with helium gas as the cover gas. It is characterized by

Details of the heat pipe filling line 23 are shown in FIG. In FIG. 4, the heat pipe container 1 is loosely connected to the enclosed pipe 3 via joints 24 at both ends thereof.

Furthermore, bellows-sealed gate valves 25 and 26 are installed above and below the heat pipe container 1. A measuring bot 27 is installed in parallel to the heat pipe container 1, and a continuous indicator type liquid level gauge 28 is provided inside the pot. 2
9 is a high vacuum evacuation device, which can suck the gas inside the weighing bot 27. This also serves as a device that can pressurize the gas by switching the valve or the like. 3° is a cooling section up to the exhaust device 29, whereby the gas is cooled. It also serves as a condensation trap for sodium vapor. Sodium valves 31-35 are arranged as shown.

Also, the heat pipe itself is connected to the exhaust system 2 with a line like 36.
9 is connected.

Thus, according to the method of the present invention, the sodium loop is operated in circulation using a cold trap.

High purity sodium can be easily obtained. On the other hand, a cover gas is an example of a non-condensable gas that can be mixed into sodium, but unlike fluids such as water, for alkaline earth metals such as IJium, at normal operating temperatures (approximately 300 to 500 degrees Celsius), Gas hardly dissolves in the liquid and can be ignored.

The problem with mixed gas is the presence of free gas. This is similar to initial vacuum filling for IJ gas, and is removed by gravity separation in the expansion tank 21, but with conventional gases with high specific gravity such as argon gas, expansion The gravity separation efficiency in tank 21 is somewhat poor. On the other hand, when high-grade silver is required as in the present invention, if helium gas is used, helium is about 1/1 of argon.
Because of its specific gravity of 0, separation performance is greatly improved and almost complete deaeration can be performed. In this way, highly purified and sufficiently degassed sodium can be supplied to the heat pipe. Needless to say, purity is measured using an impurity concentration meter of 20
constantly monitored.

Next, the procedure for filling Hildpibe will be shown. valve 25.26
is in the closed state, and the heat pipe container 1 is in the joint 24
connected to the loop via.

At this time, since the inside of the heat pipe container 1 is filled with air, the valve 35 is opened and the air is expelled by the exhaust device 29. As a subsequent operation, in order to fill the heat pipe with sodium, it is necessary to preheat it, and the temperature is raised to about 350°C or higher. At this time, the sodium temperature in the loop is also approximately the same temperature. After the temperature rises, for a very short time, valve 3
5 is opened, and the exhaust device 29 is used to expel the adsorbed gas further generated due to the temperature rise to create a vacuum inside the heat pipe. After this, valve 35 is closed. This operation is carried out because if the wick in the heat pipe is dense, the free gas present in the wick may not be able to escape due to the interfacial tension with the liquid. For wicks that do not have this concern, it is sufficient to purge helium gas when installing the heat pipe, and in some cases, this vacuum process may be omitted.

The valves 25,26 are then opened, allowing the sodium in the loop to circulate into the heat pipe. At this time, valves 31.33 are open and valves 32.34 are closed. When sodium at a temperature of 350°C or higher is circulated in the heat pipe container 1, most of the impurities therein either react with the sodium or are washed away, resulting in almost complete 7 lashing. This allows flushing to be superior to any other conventional process. In addition, since the high-temperature sodium itself is made to flow through the wick, the wick and sodium become more compatible, improving wettability, and greatly increasing the liquid reflux performance of the wick, which is the lifeblood of heat pipe performance. In conventional pretreatment to improve wettability, the pretreatment agent itself remains, which becomes a new source of impurities, but there is no need to worry about this since the pretreatment is done with the heat pipe filled fluid itself. I'm exhausted.

Needless to say, all impurities removed from the heat pipe during heat pipe flushing are captured in the cold trap 15.

7. Once the lashing is complete, open the valve 34 for a very short time,
The pipe connecting the heat pipe and the metering pot 27 is filled with sodium, and the valve 34 is immediately closed. Next, valve 32 is slightly opened and sodium is introduced into metering bot 27 until continuous level gauge 28 detects the sodium level. next,
Close valves 25, 31 and fully open valve 32.

Thereby, the upper end side of the heat pipe container 1 is closed, forming a communication pipe with the measuring bot 27. In this state, when the exhaust device 29 is activated and the gas inside the metering hot 27 is drawn out, the sodium in the heat pipe moves to the metering pot 27. Note that the vapor pressure of sodium at about 350° C. is very small, and the effect on the exhaust system is small. Since the amount of movement is measured by the liquid level gauge 28, the amount of sodium filled inside the heat pipe 1 can be determined. Furthermore, the degree of enclosed vacuum can be ascertained from the level difference with the measuring pot, and if the level difference in the exhaust device is devised, a high vacuum is not necessary. When the filling is completed in this way, the valve 26 is immediately closed, the heat pipe container 1 is cooled, the enclosing pipe 3 is clamped, and the joint part 2 is
Remove the heat pipe connector and tena from 4. Measuring pot 27
The sodium remaining in the valve 52. is removed after the valve 33 is also closed.
54 is opened, the gas in the measuring pot is appropriately pressurized, the sodium is discharged, and preparation is made for filling the next heat pipe container with sodium.

In addition to the above, the present invention provides the following effects.

(1) When filling heat pipes with alkaline earth metals, it is possible to fill liquid metals with a purity that is incomparable to conventional methods.

[2] Since impurities can be almost completely removed by flushing the heat pipe before filling it, new impurities are unlikely to be eluted into the liquid during the period of use after the heat pipe is filled with liquid.

(3) By installing a heat pipe enclosure line with a liquid metal loop using helium gas as a cover gas, a sufficiently degassed liquid can be enclosed.

(4) A special device d is used for vacuum evacuation, which was one of the drawbacks of the conventional work of enclosing alkaline earth metals into heat pipes.
Technology is no longer needed.

That is, since the inside of the parallel measuring pot is evacuated instead of directly evacuating the inside of the heat pipe itself, there is almost no fear of contamination, there is no need to create a high vacuum, and the above-mentioned cooling section 30 can be provided. In other words, there are no temperature restrictions at all. Furthermore, it is theoretically possible to grasp the degree of vacuum enclosed within the heat pipe.

(5) Since pretreatment is performed by flushing the liquid metal itself, the wettability of the wick is extremely good and the liquid reflux performance of the heat pipe is greatly improved. Furthermore, there is no new contamination associated with the wettability improvement pretreatment.

(6) By introducing a measuring pot, it becomes possible to accurately grasp the amount of filling into the heat pipe.

(Installing an on-line heat pipe encapsulation line into the liquid metal loop simplifies the process and reduces the probability of contamination because it is on-line.)
It becomes possible to understand purity, etc.

(8) As a total effect of the above, it becomes possible to produce alkaline earth metal heat pipes with excellent durability and performance on an industrial scale.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a typical conventional heat pipe. Figure 2 shows an example of a device for vacuum distillation and condensation methods used in the production of heat pipes; Figure 3 shows a schematic diagram of a circulating liquid metal loop with a cold trap according to the method of the present invention; The figure is a detailed view of the heat pipe filling line in FIG. 3. Sub-Agents 1) Meifuku Agent Ryo Hagiwara - Continued from page 1 0 Inventor Masao Kado Shin-Shidasuna Research Institute, Arai-cho, Takasago City (2-1-1 Mitsubishi Heavy Industries, Ltd. High School 407-

Claims (1)

[Claims] In a method of filling a heat pipe with a working fluid using an alkaline earth metal loop in which a heat pipe container with a built-in wick is filled with an alkaline earth metal, a cold trap and an impurity concentration meter are installed in the alkaline earth metal loop, and a cold trap and an impurity concentration meter are installed in parallel with the container. A method for filling a working fluid into a heat pipe, the method comprising: installing a measuring pot in the heat pipe, using helium gas as a cover gas above the free liquid level, and performing on-line processing using the loop as a filling line.