JPH0245799B2 - HIITOPAIPUHENOSADOEKIFUNYUHOHO - Google Patents

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 of sealing a working fluid into a heat pipe using an alkali liquid metal as the working fluid.

Alkaline liquid metals (sodium, potassium, etc.)
When manufacturing a heat pipe as a sealed container using a heat pipe, in order to improve performance and durability, it is necessary to remove impurities as much as possible from the alkaline liquid metal used as the sealed liquid (working fluid), and to thoroughly degas non-condensable gases. It is necessary to vacuum-seal the product in a vacuum state. FIG. 1 shows a schematic diagram of a typical heat pipe. Structurally, the heat pipe is made up of a multilayer mesh 2 called a heat pipe that is tightly attached to the inner wall of a metal container 1.The container 1 is filled with an appropriate amount of alkaline liquid metal such as sodium, and is eventually heated to a high temperature. sealed in 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 liquid 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.

Conventionally, as a method for sealing an alkaline liquid metal into 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 after raising the temperature slightly, it is evacuated and the enclosed pipe is finally clamped. However, this method has the following drawbacks.

(a) All work is done inside a 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 this not only becomes a source of impurities, but also causes leakage of liquid. This leads to a decrease in the heat pipe performance, and the liquid reflux performance due to capillary force, which is important for heat pipe performance, deteriorates.

(d) When vacuuming with a vacuum pump, unless a special pump is used, there is a high possibility that the 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 contamination it becomes.

In order to eliminate the above drawbacks (a) and (b), it is possible to apply vacuum distillation and condensation filling methods used for conventional working fluids other than alkali metals, but (c) and (d) Not only do these problems still remain, but with difficult-to-handle materials such as alkali metals, this work can be dangerous and complicated, creating 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 in the direction of arrow 10, is cooled and condensed within container 1, and is thereby able to be filled with sodium. . When filling is completed, the enclosing pipe 3 is clamped and the heat pipe 1 is removed from the joint 11. At this time, unless the temperature is carefully controlled, 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 fully deaerates an extremely pure alkaline liquid metal and seals it in a heat pipe, improves its wettability to the heat pipe, and furthermore enables efficient filling of hydraulic fluid in a relatively short period of time. The purpose is to provide a method.

That is, the present invention provides a method for filling a heat pipe with a working fluid using an alkali liquid metal loop in which a heat pipe container with a built-in heat pipe is filled with an alkali liquid metal. A measuring pot is installed in parallel in the container, and using helium gas as a cover gas above the free liquid level, the loop is used as a sealing line to connect one of the sealing pipes of the heat pipe container and the non-gas of the measuring pot. The present invention relates to a method of filling a working fluid into a heat pipe, which is characterized by connecting the supply side to a vacuum evacuation device and performing on-line processing.

According to the method of the present invention, an alkaline liquid metal heat pipe with excellent durability and performance can be manufactured on an industrial scale. And the method of the present invention
It can be widely applied to the production of heat pipes using alkaline liquid metals and various heat transfer devices that apply these high-temperature heat pipes.

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

(a) The heat pipe is installed in a circulating liquid metal loop equipped with a cold trap and other equipment to capture impurities in the liquid metal.

(b) Turn on all heat pipe flushing, degassing, and vacuum sealing operations in the liquid metal loop.
The point is that it is a method that can be implemented on a line.

(c) Parallel metering pots were used to prevent contamination of the inside of the heat pipe even if oil vapor back-diffused during evacuation.

(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.

(e) By using He gas as a cover gas for the liquid metal loop, the degassing of free gas in the liquid metal in the loop is promoted, and the amount of noncondensable gas brought into the heat pipe is extremely small.

(f) As a pre-treatment to improve the leakage of the wick, the liquid metal itself is flushed as described in (b), eliminating the need to dispose of the pre-treatment agent.

(g) Because it is filled online in the liquid metal loop, it requires less complicated work and can be done efficiently, and if heat pipes are installed in parallel, large-scale processing is possible.

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 then the valve 15 is closed. In this way, a closed loop circulated by the electromagnetic pump 16 is formed. A heater 17 and a cooler 18 are usually installed to adjust the temperature of the sodium in the loop. In addition, the flow rate in the loop is measured by a flow meter 19.
Further, 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). 13 is a cold trap that removes sodium impurities in the system, and 21 is an expansion tank that absorbs 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 of developing fast breeder reactors;
Although it is a difficult fluid to handle, thanks to many years of experience, we have operating technology that allows us to easily obtain sodium of high purity (oxygen concentration: around 1 ppm). 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 loop with helium gas as the cover gas. It is characterized by

The details of the heat pipe filling line 23 are described in the fourth section.
As shown in the figure. In FIG. 4, the heat pipe container 1 is connected to the sodium loop via joints 24 at both ends of the enclosing pipe 3. Furthermore, bellows-sealed gate valves 25 and 26 are installed above and below the heat pipe container 1. A measuring pot 27 is installed in parallel to the heat pipe container 1, and a continuous indicator type liquid level gauge 28 is provided in this pot. Reference numeral 29 is a high vacuum evacuation device, which can suck the gas in the measuring pot 27.
This also serves as a device that can pressurize gas by switching valves or the like. 30 is a cooling section leading to the exhaust device 29, where the gas is cooled. It also serves as a condensation trap for sodium vapor. Sodium valves 31-35 are arranged as shown. Further, the heat pipe itself is also connected to the exhaust system 29 through a line such as 36.

Thus, according to the method of the present invention, highly pure sodium can be easily obtained by circulating the sodium loop using a cold trap. On the other hand, cover gas is an example of a non-condensable gas that can be mixed into sodium, but unlike fluids such as water, alkali liquid metals such as sodium do not contain gas in the liquid at normal operating temperatures (approximately 300 to 500 degrees Celsius). hardly blends in and can be ignored. The problem with mixed gas is the presence of free gas. This can be removed by vacuum filling the initial sodium filling or by gravity separation in the expansion tank 21, but with conventional gases with high specific gravity such as argon gas, the gravity separation efficiency in the expansion tank 21 is low. Somewhat bad. On the other hand, when high deaeration is required as in the present invention, if helium gas is used, the separation performance is greatly improved because helium has a specific gravity of about 1/10 of argon, and almost complete deaeration can be achieved. Can be done.
In this way, highly purified and sufficiently degassed sodium can be supplied to the heat pipe. Needless to say, the purity is constantly monitored by the impurity concentration meter 20.

Next, the procedure for filling the heat pipe will be shown. valve 2
5 and 26 are in the closed state, the heat pipe container 1 is connected to the loop via the joint 24. 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, raising the temperature to approximately 350°C or more. At this time, the sodium temperature in the loop is also approximately the same temperature. After the temperature has been raised, the valve 35 is opened for a very short time, and the exhaust device 29 is used to expel the adsorbed gas that is further generated due to the temperature rise, creating a vacuum in the heat pipe. After this, valve 35 is closed. This operation is carried out because if the wick inside 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, so if this operation is not performed, In devices where this is not a concern, it is sufficient to purge helium gas when installing the heat pipe, and in some cases, this vacuum process may be omitted.

Next, valves 25 and 26 are opened to circulate the sodium in the loop into the heat pipe. At this time, the valves 31 and 33 are open, and the valves 32 and 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 flushing. This allows for flushing that is superior to any other conventional process. In addition, since the high-temperature sodium itself is made to flow through the wick, the compatibility between the wick and the sodium improves, the leakage is improved, and the liquid reflux performance of the wick, which is the lifeblood of heat pipe performance, is greatly improved. In conventional pretreatment to improve wettability, the pretreatment agent itself remains, which becomes a new source of impurities, but since the pretreatment is performed with the heat pipe filled fluid itself, this worry is completely eliminated. . Needless to say, all impurities removed from the heat pipe during heat pipe flushing are captured in the cold trap 13.

Once the flushing is complete, valve 34 is opened very briefly to fill the line connecting the heat pipe and metering pot 27 with sodium, and valve 34 is immediately closed. Next, the continuous liquid level gauge 2 is opened by slightly opening the valve 32.
Add sodium to measuring pot 27 until 8 detects the sodium level. Next, valves 25, 31
is closed, and the valve 32 is fully opened. As a result, the upper end side of the heat pipe container 1 is closed, forming a communicating pipe with the measuring pot 27. In this state, when the exhaust device 29 is activated and the gas inside the measuring pot 27 is drawn out, the sodium in the heat pipe moves to the measuring pot 27. In addition,
The vapor pressure of sodium at around 350℃ is quite small.
The effect on the exhaust system is small. The amount of movement is measured by the liquid level gauge 28
Therefore, 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 of 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 down, the enclosed pipe 3 is clamped, and then the heat pipe container is removed from the joint part 24. For the sodium remaining in the measuring pot 27, after closing the valve 33, the valves 32 and 34 are opened, the gas in the measuring pot is pressurized appropriately, the sodium is discharged, and preparation is made for filling the next heat pipe container with sodium.

As described above, the following effects can be obtained in the present invention.

(1) When filling heat pipes with alkaline liquid metal, it is possible to fill the heat pipe with liquid metal of a high 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,
Capable of enclosing sufficiently degassed liquid.

(4) One of the drawbacks of the conventional process of sealing alkaline liquid metal into heat pipes is vacuum evacuation.
Special equipment technology is no longer required. That is, since the inside of the parallel measuring pot is evacuated rather than the inside of the heat pipe itself being evacuated directly, 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 the liquid metal itself is pretreated by flashing, the wettability of the liquid metal is extremely good.
Greatly improves the liquid reflux performance of heat pipes.
Furthermore, there is no new contamination associated with the wettability improvement pretreatment.

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

(7) 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. Furthermore, it becomes possible to grasp purity and the like.

(8) As a total effect of the above, it becomes possible to produce an alkaline liquid metal heat pipe 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. FIG. 2 shows an example of an apparatus for vacuum distillation and condensation used in the production of heat pipes. FIG. 3 shows a schematic diagram of a circulating liquid metal loop with a cold trap according to the method of the invention, and FIG. 4 is a detailed view of the heat pipe filling line in FIG. 3.

Claims (1)

[Claims] 1. In a method of filling a heat pipe with a working fluid using an alkaline liquid metal loop in which a heat pipe container with a built-in heat pipe is filled with an alkali liquid metal, a cold trap and an impurity concentration meter are provided in the alkaline liquid metal loop, and a cold trap and an impurity concentration meter are installed in the container in parallel. A measuring pot is installed, and using helium gas as a copper gas above the free liquid level, one side of the sealing pipe of the heat pipe container and the non-gas supply side of the measuring pot are vacuum evacuated using the loop as a sealing line. A method for filling a working fluid into a heat pipe, which is characterized by connecting it to a heat pipe and performing online processing.