JPS6152359B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a device for preventing freezing of foundation concrete in which a tank for low-temperature liquids such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG) is installed. .

Conventional technology Among tanks for storing low-temperature liquids such as LNG and LPG, a large industrial tank 1 is usually constructed by pouring insulating concrete 3 such as perlite concrete on a foundation concrete 2, and placing the insulating concrete 3 on top of the insulating concrete 3. However, since the insulation effect of the insulating concrete 3 is not necessarily sufficient, the foundation concrete 2 may be cooled by the low temperature liquid in the tank 1, and as a result, the foundation concrete 2 may freeze. If such a situation occurs, the strength of the foundation concrete 2 may decrease or cracks may appear in the foundation concrete 2, and as a result, there is a risk that the tank 1 itself may sink unevenly.
Conventionally, as shown in FIGS. 1 and 2, an electric heater 5 inserted into a protective pipe 4 is buried in the foundation concrete 2, and the electric heater 5 is energized to generate heat, thereby improving the foundation concrete 2. The temperature is kept at around 5℃ to prevent it from freezing.

Problems to be Solved by the Invention However, since the electric heater 5 itself does not have an explosion-proof structure, especially in the case of the foundation of the tank 1 containing a flammable liquid such as LNG or LPG, nitrogen may be added to the pipe 4. The electric heater must be filled with an inert gas such as gas and have an explosion-proof structure, which not only complicates the structure but also creates a space between the electric heater 5 and the foundation concrete 2. There was a problem that the total thermal resistance between 5 and the foundation concrete 2 increased, and the heat transfer coefficient deteriorated. Furthermore, since the surface area of the electric heater 5 itself is small, if the pipe 4 is made thicker to increase the heat transfer area to the foundation concrete 2, the space interposed between the electric heater 5 and the foundation concrete 2 will become even wider. Therefore, there is a problem that the heat transfer efficiency further deteriorates, and if the pipe 4 is made thinner to solve this problem, the heat transfer area becomes narrower, resulting in the problem of having to increase the number of pipes installed. . Furthermore, the temperature of each part of the electric heater 5 in its length direction is not necessarily uniform, so localized low-temperature and high-temperature areas occur, which increases the internal stress of the foundation concrete 2 and, in the worst case, There was a risk that this would encourage the occurrence of cracks and damage in the foundation concrete 2.

This invention was made to solve the above-mentioned problems, and is a foundation for a low-temperature liquid tank that has a simple overall structure, can be made explosion-proof, and can evenly heat and insulate the entire foundation of the tank. The purpose of this invention is to provide an antifreeze device.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention provides a working fluid within an annular hollow section formed by an outer tube and an inner tube inserted into the inner tube along the central axis. A heat pipe with a hollow double-tube structure, which is made by enclosing a heat pipe and a heat pipe, is buried in the foundation concrete in which a low-temperature liquid tank is installed, and a heat source is provided inside the inner pipe along the axial direction and over almost the entire length. It is characterized by the fact that it has been inserted.

Function In this invention, heat for heating and insulating the foundation concrete is provided by a heat source inserted over almost the entire length inside the inner pipe, and the heat evaporates the working fluid within the heat pipe. Therefore, as a heat pipe, the temperature on the inner tube side is high and the temperature on the outer tube side is low, so the working fluid vapor flows radially from the outer circumferential surface of the inner tube, radiates heat and liquefies on the inner surface of the outer tube. . As a result, heat is transferred as latent heat of the working fluid, heating and keeping the foundation concrete warm. In this case, the heat source is long, the flow distance of the working fluid is short, and the heat pipe has a property of almost uniform temperature throughout, so that the foundation concrete is uniformly heated and kept warm.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 3 to 6.

FIG. 3 is a schematic cross-sectional view showing one embodiment of the present invention, and FIG.
are installed on the foundation concrete 12 with the insulation concrete 11 in between. The foundation concrete 12 is formed into a short cylindrical shape with a diameter larger than that of the tank 10, and a plurality of heat pipes 13 are installed inside it, more precisely on the upper side, with one end exposed to the outside of the foundation concrete 12. They are buried horizontally so that they are parallel to each other. These heat pipes 13 have a hollow double tube structure as shown in FIG. By attaching the heat pipe 13c to the outer circumferential surface of the outer tube 13a and the inner circumferential surface of the outer tube 13b, and filling a highly electrically insulating working fluid between the inner and outer tubes 13a and 13b, a heat pipe can be installed here. It was formed. Therefore, in each heat pipe 13, the inner pipe 13a side becomes a heating part (evaporation part), and the outer pipe 1 directly contacts the foundation concrete 12.
The 3b side serves as a heat dissipation section (condensation section).

Therefore, in the anti-freeze device configured as described above, by energizing the heater wire 14 and generating heat, the working fluid in the heat pipe 13 is transferred to the inner pipe 13a.
It is heated and evaporated on the outer peripheral surface of the
The steam flows radially and radiates heat and condenses on the inner peripheral surface of the outer tube 13b, and as a result, the foundation concrete 12 is heated. Therefore, the base concrete 12 can be maintained at a predetermined temperature (for example, about 5° C.) by controlling the amount of heat generated from the heater wire 14 by controlling the current flowing through the heater wire 14 or the energization time. In addition, in order to control the current flowing through the heater wire 14 or the energization time, etc., a detection means such as a temperature measuring element may be buried in the foundation concrete 12.

Therefore, in the above antifreeze device, heat is applied from the heater wire 14 as a heat source to the inner tube 13a by convection, conduction, or thermal radiation, and the heat is transferred to the outer tube by the working fluid in the heat pipe 13. 13
carried to b. In that case, the amount of heat transported by the heat pipe 13 is extremely large, and the heat transfer resistance is substantially equal to zero. Therefore, the heat transfer resistance between the heater wire 14 and the foundation concrete 12 is equal to Although it depends on the space between the outer tube 1 and the
3b can be made wider, and as a result, the heater wire 14
It is possible to promote heat transfer between the base concrete 12 and the base concrete 12, to ensure a wide heat transfer area to the base concrete 12, and to reduce the number of heat pipes 13. In addition, as mentioned above, the heat pipe 13 has a characteristic that the entire temperature is equalized, so the entire foundation concrete 12 can be heated and kept warm almost uniformly, and as a result, the generation of high-temperature areas and low-temperature areas is prevented. As a result, generation of thermal stress within the foundation concrete 12 can be prevented. Furthermore, an inner tube 13a housing the heater wire 14
By sealing the tank 10 and using a highly electrically insulating working fluid, the entire heat pipe 13 has a so-called explosion-proof structure, so even when liquefied fuel such as LNG is stored in the tank 10, Safety can be ensured.

Note that the heat source in this invention is not limited to the heater wire 14 shown in the above embodiment, but as shown in FIG.
By supplying hot water 15 at about 0.degree. C., the hot water 15 may be used as a heat source. In that case, the inner pipe 13
The interior of the inner pipe 13a is divided into two by a partition along the axial direction, and hot water is supplied to one of the compartments and drained from the other compartment to circulate the hot water, or one end of the inner pipe 13a is connected to a hot water source. In addition, it is desirable to connect the other end to a return pipe to circulate hot water.

Effects of the Invention As is clear from the above explanation, according to the device of the present invention, a heat source is housed coaxially within a heat pipe buried in the foundation concrete, and the heat source is housed inside the heat pipe over almost its entire length. By transmitting heat to the foundation concrete via heat pipes, the foundation concrete is heated and kept warm, which not only reduces the heat transfer resistance between the heat source and the foundation concrete, but also increases the heat transfer area. Therefore, the required number of heat pipes can be reduced, and in combination with the fact that the heat source is long, almost equal to the total length of the heat pipe, the entire foundation concrete can be evenly heated and kept warm, and high temperatures can be maintained. It is possible to prevent the occurrence of low-temperature zones and low-temperature zones, and thereby prevent the generation of thermal stress within the foundation concrete.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of a conventional device, FIG. 2 is a cross-sectional view taken along the - line in FIG. 3 is a sectional view taken along the line arrow 3, FIG. 5 is a sectional view showing an example of a heat pipe used in the present invention, and FIG.
The figure is a sectional view showing another example of the heat pipe used in the present invention. 10...Tank, 12...Foundation concrete,
13...Heat pipe, 13a...Inner pipe, 13b
...outer tube, 14...heater wire, 15...hot water.

Claims (1)

[Claims] 1. A heat pipe with a hollow double-tube structure in which a working fluid and a pipe are sealed in a hollow part with an annular cross section formed by an outer pipe and an inner pipe inserted along the central axis inside the outer pipe is installed in a low-temperature liquid tank. 1. A foundation freeze prevention device for a cryogenic liquid tank, characterized in that the device is buried in foundation concrete on which the inner tube is installed, and a heat source is inserted inside the inner tube along the axial direction and along almost the entire length of the inner tube.