JPH06323767A - High temperature heat pipe safety device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a safe use of a high temperature heat pipe using an alkali metal as a working fluid, and a safety device of a high temperature heat pipe that enables further high temperature use. [Structure] A high temperature heat pipe 1 and a reaction container 4 for converting a working fluid 11 made of an alkali metal of the heat pipe 1 into a stable alcoholate are communicated with each other through a communication pipe 2, and in the communication pipe 2, The communication pipe 2 is normally shut off, but a rupture disk 3 that ruptures by the action of a pressure equal to or higher than a predetermined pressure and connects the reaction container 4 and the heat pipe 1 is provided. Further, the reaction container 4 is provided with a pressure release valve 5 for suppressing the internal pressure thereof within a predetermined value. When the inside of the heat pipe 1 becomes abnormally high in pressure, the rupture disk 3 bursts and the working fluid 11 therein flows out into the reaction vessel 4, where it is converted into alcoholate which is a stable substance. Therefore, it is possible to prevent the alkali metal from being released to the outside as it is.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high temperature heat pipe safety device using an alkali metal such as sodium as a working fluid.

[0002]

2. Description of the Related Art Sodium (Na) has a boiling point of 889.
Since it is as high as ℃, the sodium heat pipe using Na as a working fluid is widely used as a high temperature heat exchange means such as high temperature waste heat recovery device, Stirling engine, solar heat collector, high temperature soaking furnace, nuclear power etc. Is becoming available.

In this case, Na reacts with water and causes a severe oxidation reaction with water in the air. Therefore, even if the heat pipe should be damaged, the heat pipe should be kept to a minimum to prevent an accident. Has some safety considerations. For example, in the case where the closed container is made of SUS316L, the design upper limit temperature is suppressed to about 800 ° C., and consideration is given to always suppress the vapor pressure of Na in the heat pipe to a negative pressure. . Also,
In the case where the closed container is made of Inconel 600 (Ni-based heat-resistant alloy), the design upper limit temperature is suppressed to about 1000 ° C., and even if the vapor pressure of Na in the heat pipe is higher than the atmospheric pressure, at most. Consideration is given so as to keep the pressure as low as 2-3 atm.

[0004]

However, in recent years 1
There is a growing demand for sodium heat pipes used in the high temperature range of over 000 ° C, and materials such as SUS316L and Inconel 600, which are relatively low-priced and easily available, are not enough for the sealed container. Is happening. Therefore, tungsten (W), molybdenum (M
o), tantalum (Ta), ceramics, etc. have to be studied as materials for closed containers, and along with the problems of high cost and long delivery of heat pipes, various design conditions must be examined. , It was not easy to make such a heat pipe.

Further, particularly in a high temperature heat pipe using Na as a working fluid, which is used in a Stirling engine,
Helium (He), which is the operating gas of this engine, is used as the object to be heated, and the tube in which this He flows under high pressure is contained in the closed container. Therefore, the operating temperature of this heat pipe is below the boiling point of Na. Even if the temperature is high, if the tube is broken in the heat pipe closed container, the pressure in the heat pipe closed container will rise to several tens of atmospheres. For this reason, there is a possibility that the hermetically sealed container of the heat pipe may be damaged and the working fluid Na may be explosively scattered to the outside to cause a serious accident.

The above problem similarly occurs in a high temperature heat pipe using an alkali metal such as lithium (Li) or potassium (K) as a working fluid.

The present invention has been made in view of the above circumstances, and it is safe to use a high temperature heat pipe using an alkali metal as a working fluid, and a high temperature heat pipe safety device that can easily use a higher temperature. The purpose is to provide.

[0008]

In order to achieve the above-mentioned object, the present invention provides a reaction vessel which reacts with a working fluid composed of an alkali metal in a high temperature heat pipe to convert it into a stable alcoholate, and this reaction vessel. And a communication pipe that communicates with the heat pipe, a rupture disk that normally shuts off the communication pipe and ruptures by the action of a pressure equal to or higher than a predetermined pressure to communicate the reaction container with the heat pipe, and the reaction container And a pressure release valve for suppressing the internal pressure of the device within a predetermined value.

[0009]

If the pressure inside the heat pipe rises above a certain level for some reason, the rupture disc will burst and
The working fluid inside flows out to the reaction vessel side, and the pressure in the heat pipe is lowered. Then, in this reaction vessel, the working fluid made of alkali metal that has flowed into this reaction vessel is changed to alcoholate, which is a stable substance, and when the pressure in this reaction vessel rises above a predetermined value, the pressure release valve opens, and this reaction The pressure in the container is suppressed below a predetermined value. In this case, even if alkali metal is released from the reaction vessel,
Since this is a stable alcoholate, this alkali metal does not react violently with moisture in the air.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a cross-sectional view of a heat pipe and a safety device attached to the heat pipe.

In the figure, reference numeral 1 is a high temperature heat pipe in which Na as a working fluid 11 is enclosed in a long and narrow hermetically sealed container 10, and the heat pipe 1 has a condenser portion 1a whose front end portion is inclined upward. And the rear end side is the evaporating portion 1b which is inclined downward.

Here, the heat pipe 1 is a vacuum degassed closed container 10 in which a fluid (Na in this case) which evaporates and condenses in a target temperature range is enclosed as a working fluid 11, and an evaporation part 1b. The working fluid 11 is vaporized by the heat absorption at, and this vapor is moved to the condenser section 1a,
By condensing this in the condensing part 1a, the heat is released to the outside. In this case, the working fluid 11 is recirculated from the condensing section 1a to the evaporating section 1b by the action of gravity, but a wick is provided in the closed container
The liquid may be refluxed by the capillary force of this wick.

On the tip side of the evaporating section 1b of the heat pipe 1, a connecting tube 2, a rupture disk 3 and a reaction vessel 4 are provided.
A safety device 6 for the heat pipe 1 including a pressure release valve 5 is attached. Each device of the safety device 6 is made of a material having heat resistance equal to or higher than that of the heat pipe 1.

The connecting pipe 2 is a thin pipe which connects the heat pipe 1 and the reaction vessel 4 to each other, and reacts with the upwardly inclined portion 2a extending from the tip of the evaporation portion 1b of the heat pipe 1 along the longitudinal direction of the heat pipe 1. It is composed of a descending portion 2b that descends to the container 4 side. Then, the upwardly inclined portion 2a of the connecting pipe 2
Flange 2 with a rupture disc 3 sandwiched inside
c is formed, and the rupture disc 3 in the flange portion 2c blocks the heat pipe 1 of the connecting pipe 2 from the reaction vessel 4. When the pressure inside the heat pipe 1 rises above a predetermined pressure for some reason, the rupture disc 3 ruptures at the center portion thereof to make the heat pipe 1 and the reaction container 4 communicate with each other, and to close the heat pipe 1 closed container 10 It is intended to prevent the destruction of. Therefore, the burst pressure of the rupture disc 3 is, for example, the heat pipe 1
It is set below the design pressure of the closed container 10.

Further, the reaction vessel 4 has therein a liquid alcohol (for example, methanol) 4a which reacts with Na which is the working fluid 11 of the heat pipe 1 to convert it into stable sodium alcoholate. The pressure release valve 5 is attached to the upper side of the reaction container 4 and releases the gas in the reaction container 4 to the outside to prevent pressurization of the reaction container 4. The reaction vessel 4 and the connecting pipe 2 between the rupture disc 3 and the reaction vessel 4 are filled with an inert gas G such as argon gas that does not react with Na.

Next, the safety device 6 for the heat pipe 1
The operation of will be described. The closed container 10 of the heat pipe 1 is made of, for example, Inconel 600, the design temperature thereof is, for example, 1000 ° C., and the design pressure thereof is, for example, 3 atm.
1 has a vapor pressure of 1-2 in its normal operating state.
It shall not exceed the atm. Also,
In this case, the burst pressure of the rupture disc 3 is also 3 atm.
Is set to.

For example, when the evaporation portion 1b of the heat pipe 1 is heated to 1000 ° C. or more due to some abnormality and the vapor pressure of the working fluid 11 in the hermetically sealed container 10 rises to 3 atm or more, the rupture disk 3 is ruptured and hermetically sealed. The working fluid 11 in the container 10 passes through the connecting pipe 2 and the inert gas G
The inside flows out into the reaction container 4. And this reaction container 4
In the inside, Na which is the working fluid 11 reacts like 2Na + 2CH ₃ OH → 2CH ₃ ONa + H ₂ (1) and is converted into sodium alcoholate (CH ₃ ONa) which is a stable substance.

In this case, as shown in the reaction formula (1), since the hydrogen gas (H ₂ ) is generated, the pressure in the reaction container 4 rises, but the pressure in the reaction container 4 is equal to that of the pressure release valve 5. When the pressure becomes higher than the set pressure, the pressure relief valve 5 opens, and this pressure relief valve 5
Internal H ₂ and Na are released to the outside via the. However,
Even in this case, since all Na in the reaction vessel 4 is changed to sodium alcoholate which is a stable substance,
This Na does not subsequently react explosively with water (water in the air, etc.).

In addition, for example, when the heat pipe 1 is such as to contain a tube in which He is flowed in order to heat the high pressure He that is the working fluid of the Stirling engine, for some reason If this tube is broken by this, the high pressure He in this tube will leak into the closed container 10 of the heat pipe 1. For this reason, the pressure inside the closed container 10 of the heat pipe 1 rises above the design pressure.
The rupture disk 3 ruptures before rupture, and He leaked into the closed container 10 and Na in the closed container 10 flow out to the reaction container 4 side through the connecting pipe 2. And N
a is changed to sodium alcoholate, which is a stable substance in the reaction vessel 4, and when the pressure in the reaction vessel 4 rises above a predetermined value, the pressure release valve 5 opens and the pressure in the reaction vessel 4 is maintained at a constant value. To be done. Even in this case, Na is not released to the outside of the reaction vessel 4 as it is, so that Na does not explosively react with water.

As described above, even if the heat pipe 1 is a sodium heat pipe for high temperature using Na as the working fluid, the heat pipe 1 prevents the closed container 10 from being broken, and the closed container is Since the safety device 6 for converting Na flowing out from 10 into a stable substance is attached, even if an abnormal state occurs in the heat pipe 1, an accident can be prevented in advance.

Further, by attaching a safety device 6 to the heat pipe 1, the heat pipe 1 using this Na is used.
The design temperature and design pressure of SUS can be raised to the limit of the conditions of materials used, and it is relatively inexpensive and easily available.
By using materials such as 316L and Inconel 600, it is possible to easily provide the heat pipe 1 that is used at a higher temperature than the conventional one.

In the above embodiment, the working fluid 11 contains Na.
I explained about the high temperature heat pipe using
Even in a high temperature heat pipe that uses another alkali metal such as lithium (Li) or potassium (K) as the working fluid 11, Li and K react violently with water. Therefore, a similar safety device to this heat pipe 1 is used. If it is attached, the same effect can be obtained.

[0023]

As is apparent from the above description, according to the present invention, the high temperature heat pipe in which the working fluid is made of alkali metal, the reaction vessel, the connecting pipe, the rupture disc, and the pressure release valve are provided. Since the safety device having the above is attached, the safe use of such a heat pipe and the use at higher temperature can be easily performed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a safety device according to an embodiment of the present invention and a heat pipe including the same.

[Explanation of symbols]

1 ... Heat pipe, 3 ... Rupture disc, 4 ...
Reaction container, 5 ... Pressure release valve, 6 ... Safety device, 11 ... Working fluid.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masahiko Ito 1-5-1 Kiba, Koto-ku, Tokyo Fujikura Ltd. (72) Inventor Yuuji Saito 1-5-1 Kiba, Koto-ku, Tokyo Stock Association Company Fujikura (72) Inventor Fumiaki Aoyama 1-5-1 Kiba, Koto-ku, Tokyo Stock Company Fujikura

Claims (1)

[Claims] 1. A reaction vessel for reacting with a working fluid composed of an alkali metal of a high temperature heat pipe to convert it into a stable alcoholate, a connecting pipe for connecting the reaction vessel and the heat pipe, and this connecting pipe for normal use. And a rupture disk that ruptures by the action of a pressure equal to or higher than a predetermined pressure to connect the reaction container and the heat pipe, and a pressure release valve that suppresses the internal pressure of the reaction container within a predetermined value. Safety device for high temperature heat pipe.