JPH0361999B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of heating a structure, such as heating the bottom of a cryogenic tank.

Generally, in order to prevent freezing at the base of a low-temperature liquefied gas tank, such as an LPG tank, a heater is inserted into the bottom of the base to lower the temperature at the bottom of the tank to 0°C.
Freezing was prevented by maintaining the temperature above.

1 to 3 show examples of heating at the base of a low-temperature liquefied gas tank. Heaters 3 are arranged in parallel or radially on the base 2, and power is supplied from outside the tank. Therefore, at the outer periphery of the tank foundation, the heater was passed through a concrete foundation (ring wall) 12 with a width of approximately 2 m to lead the heater outside and connect it to the power supply line.

By the way, the outer peripheral foundation is hardly affected by the low-temperature liquid in the tank, and is kept at a relatively high temperature by the influence of the outside air, so that heating is often unnecessary.

However, it is difficult to reduce the amount of heating in the ring wall passage section with the resistance wire heater that has been commonly used in the past. If forced to do so, there is a method of using a conductor with low resistance for the passing portion, but it is difficult to modify each of the many heaters of different lengths inserted at the bottom of the tank.

On the other hand, if a self-regulating heater as shown in FIG. However, the temperature maintained at the bottom of the tank is about 0 to 5℃, and the temperature at the surrounding base is about 5 to 15℃, and although the temperature difference between the two is small and the amount of heating in the surrounding area is slightly smaller, The difference was small and it had to be said that the effect was small from an energy conservation perspective.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for heating a structure using a self-controlling heater, which solves the above-mentioned problems, reduces power consumption in parts of the structure to be heated that do not require heating, and enables efficient heating. be.

That is, in the method of heating a structure provided by the present invention, a heat insulating layer is applied to a part of a self-regulating heater having a positive temperature coefficient of resistance characteristic in the longitudinal direction so as to cover the entire circumference of the heater part. The purpose of the present invention is to lower the output of the heater more actively than other heater parts, and to position the low-output heater part provided with the heat insulating layer in a part of the heated structure that does not require heating.

Such a heat insulating layer becomes an outer covering with high thermal resistance,
By forcibly shifting the operating characteristics (positive resistance temperature coefficient characteristics) of a self-regulating heater, the internal temperature of the heater is raised due to the insulation effect even when the surrounding temperature is low, thereby controlling heat generation.

The self-control type heater is also called a PTC heater, and its structure and operation are made from crystalline plastic mixed with dispersed conductive powder such as carbon black, as shown in Figure 5a and b. Two conductors 13, 13 are embedded in a band-shaped resistor, and when electricity is applied to the resistor using the two conductors 13, 13 as electrodes, the plastic expands thermally and the degree of dispersion of the conductive powder changes. As the conductor becomes larger, the resistance between the conductors increases, and at a certain temperature it becomes a non-conductor (insulator) and no current can flow through it, and after that it repeats conduction and non-conduction to keep the temperature constant. . In other words, it has its own thermostat function.

Embodiments of the present invention will be described below with reference to FIGS. 6 and 7.

Figures 6a and 6b are perspective and cross-sectional views of a self-regulating heater partially fitted with insulation.

As is clear from the figure, the self-regulating heater 21
A layer of heat insulating material, that is, a heat insulating layer 18, is provided around the entire circumference of a portion in the length direction.

The internal structure of the self-controlling heater 21 is the same as that of the self-controlling heater shown in FIGS. 5a and 5b.
14 is a band-shaped resistor in the form of a bridge between two conductors 13, 13, and an insulator layer 15, a metal braid layer 16, and a protective coating 17 are sequentially applied on the circumference of the resistor.

FIG. 7 is a diagram showing the relationship between ambient temperature and output characteristics of a self-regulating heater, where the curve 19 is the output of a self-regulating heater without a heat insulating layer on the surface, and the curve 20 is the entire circumference. shows the output of a self-regulating heater with a heat insulating layer.

By applying the heat insulating layer 18 all around the circumference, the thermal resistance of the covering part increases, so even when the ambient temperature is low, the inside is heated and the internal temperature control is activated, resulting in a decrease in output. As can be seen from this phenomenon, at the outer foundation, where the temperature is higher than the lower interior of the low-temperature tank,
Even with an untreated self-regulating heater, the output is slightly lower than that of an internal one, but by providing a heat insulating layer to cover the entire circumference, the effect of the low output is made even greater, and the output is significantly reduced. I can do it.
Therefore, by locating the heater portion provided with the heat insulating layer 18 in a portion that passes through a portion that does not require heating, it is possible to significantly suppress the heating of the portion that does not require heating.

Note that the heat insulating layer 18 can be easily formed by wrapping a material that increases thermal resistance, such as foamed rubber or foamed polyethylene, around the self-regulating heater and applying a heat-shrinkable tube to the outside thereof.

For example, in a liquefied propane gas tank, if the foundation diameter is about 50 m and the width of the outer foundation is 2 m, the heating power amount is 30 W/m ² , and the 7th
A self-regulating heater with operating characteristics as shown in numeral 19 in the figure is used, and a heat insulating layer with a thickness of 2.5 mm is applied around the entire circumference to create a self-regulating heater with operating characteristics as shown in numeral 20. Suppose we did. This heater operates at an ambient temperature of approximately 40°C, and has a smaller output of 26 W/m compared to the untreated heater's output of 26 W/m.
If applied to a length of m, it will save 3.5kw.
The total heating amount of the conventional foundation was 58.9kw, which is a saving of 5.9%, and the outer foundation was 9.0kw, which is a saving of 39%.

In the above embodiment, the heating target is the bottom part of the tank as the heated structure, but it is not limited to this, for example,
When performing heating that has non-heating parts during power supply, in order to prevent unnecessary heating, it is necessary to insulate the entire circumference of a part of the self-regulating heater in the lengthwise direction to achieve the intended purpose. can be achieved. In other words, when melting snow from steel, cross members,
When heating only the diagonal members of a structure made up of diagonal members, unnecessary power consumption can be reduced by providing a heat insulating layer to the heater portion added to the cross member portion.

As explained above, according to the method for heating a structure using a self-regulating heater according to the present invention, when installing the heater in the structure to be heated, it is possible to apply a heat insulating layer to the heater in the final step. It is easy to install, and conventional self-control heaters can be used for heater production, contributing to improved economic efficiency.

In addition, since only a local coating is required, the self-control type heater can be handled without impairing its characteristics, and the heating effect on the heated structure is assumed to be due to the original output of the self-control type heater. It is possible to reduce wastage of quantity and is truly useful as a long-term energy saving measure.

[Brief explanation of drawings]

Figure 1 is a side view showing how to heat the base of the low-temperature liquefied gas tank, Figure 2 is an enlarged sectional view of section A in the same figure, Figure 3 is a temperature distribution diagram of the base of the tank when it is not being heated, Figure 4 The figure is an example of parallel laying of the foundation heating piping system, Figures 5a and b are perspective views and sectional views respectively showing typical examples of conventional self-regulating heaters, and Figures 6a and b are the main A perspective view and a sectional view showing an example of a self-control type heater having a heat insulation layer applied to the heating method in the invention, and FIG. 7 is an output characteristic diagram of the self-control type heater and a self-control type heater provided with a heat insulation layer. . In the code, 1 is a low-temperature liquefied gas tank, 2 is a tank base, 3 is a heater, 4 is a tank bottom insulation layer, 5 is dry sand, 7 is an outer periphery foundation, 8
is a conduit for inserting a heater, 9 is a heater for heating, 10
is the base temperature, 11 is the bottom piping, 12 is the outer foundation, 13 is the conductor, 14 is the resistor, 15 is the insulator layer, 16 is the metal braid layer, 17 is the protective coating, 18
is a heat insulating layer, 19 is a self-control type heater output line, 20 is
21 is the output line of the self-control type heater provided with a heat insulating layer, and 21 is the self-control type heater (main body).

Claims (1)

[Claims] 1. A heat insulating layer is applied to a longitudinal part of a self-regulating heater having a positive resistance temperature coefficient characteristic so as to cover the entire circumference of the heater part, and the output of the heater part is lowered more actively than other heater parts. A method for heating a structure using a self-controlling heater, characterized in that the low-output heater portion provided with the heat insulating layer is located in a portion of the structure to be heated that does not require heating.