JPH01186582A - Gas heating heater - Google Patents

Abstract

PURPOSE:To prolong the life of a heating heater by giving variations in the thickness of a heating wire, and reducing the difference of temperatures between the heating wire and gas of a high temperature part. CONSTITUTION:A gas heating heater is formed with heating wires 1a, 1b, 1c, and 1d seriesly connected to be admitted in a heat resistant tube. Individual diameters d1, d2, d3, and d4 of the wires 1a-1d are formed so as to gradually become larger at the distance from d1 of the entrance side to d4 of the exit side. The larger the diameter of a heating wire, the smaller the resistant value of the heating wire, and the smaller the heating value. The difference of temperatures, between the gas heated to high temperatures at the vicinity of the exit and the heating wire at the vicinity of the exit, is kept smaller com pared to the case where the heating tube from the entrance to the exit has the same diameter by the diameter variation of the heating wire. This makes it possible to prolong the life of a heating wire.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a gas-heated heater, and more particularly to a gas-heated heater that heats gas while passing it from one side of the cylindrical heater to the other.

(Prior Art) Conventionally, electric gas heating heaters for obtaining high-temperature gas for use in metal melting and resin baking, for example, are shown in Figure 3.
As shown in Fig. 4, a heating wire 1 is used as a heating element, the heating wire is bent, and the surface of the heating wire is coated with alumina or the like to prevent electrical contact between adjacent wires.
As shown in FIG. 5, it is housed in a heat-resistant insulating tube 2.

Note that 3 indicates a heat-resistant insulating rod inserted through the center of the winding of the heating wire 1.

This type of gas heater is simply made by bending one heating wire as shown in Figures 3 and 4, so power is applied to heating wire 1 and gas flows from the inlet to the outlet of the heater. When heating gas, as shown in Figure 6, the temperature of the heating wire 1 near the inlet of the heater is low, and the temperature of the heating wire 1 near the exit increases accordingly, resulting in a shortened lifespan. Ta.

In addition, in Fig. 6, the temperature difference between the temperature of the heating wire 1 and the gas is not constant, and the difference increases from 01 to 02 as you get closer to the exit. This is because the heat transfer coefficient becomes smaller, and the curve is drawn because the amount of heat dissipated to the outside of the heater increases as the temperature increases.

Also, if it is necessary to raise the temperature of the gas higher, it is necessary to increase the electric capacity of the heating wire accordingly, but in this case, the temperature difference between the gas temperature and the heating wire becomes larger and larger.
On the other hand, since there is a limit to the heat resistance temperature of the heating wire, there is a limit under certain dimensions.

(Object of the Invention) The object of the present invention is to provide a gas heating heater that extends the life of the gas heating heater by varying the thickness of the heating wire and reducing the difference between the temperature of the heating wire and the gas in the high temperature section. is to obtain.

(Structure of the Invention) The gas heating heater of the present invention has a heating wire formed by connecting a plurality of heating wire elements of different diameters in series, and a gas inlet at one end of the heating wire that is inserted inside the heating wire. and a heat-resistant tube having a gas outlet at the other end.

(Example of the invention) The present invention will be explained in detail below with reference to the drawings.

In the present invention, the diameter d gradually increases as shown in FIG.
Fig. 3 shows heating line elements 1a to 1d in which 1 to d4 are large.
After bending as shown in Figure 4, the wires are connected in series by welding, etc., and the diameter of the heating wire increases as it approaches the outlet of the heater.

The gas heating heater of the present invention has a heating wire element 1 near the inlet.
Since a is thin, the resistance value per unit length is large, and therefore the capacitance density (W/
cnf) becomes larger, the temperature of the gas can be further increased. On the other hand, near the exit, the capacity is low, and in addition, the wire diameter is large, so the surface area per unit length is large, so the capacity density is smaller, the temperature difference with the gas is smaller, and the temperature between the heating wire and the gas is As shown in Figure 2, the maximum temperature of the heating wire can be significantly lowered compared to conventional heaters, allowing a larger capacity to be set and increasing the gas temperature. The gas heater can be made more compact or have a longer lifespan.

According to the experimental example, the temperature of the air at 5 ON-of/h was increased to 20°C using a heater made of a single heating wire with a diameter of 21°C.
When heating from ℃ to 800℃, the temperature of the heating wire near the outlet reached 1100℃, but starting from the inlet,
Diameter 1.8mm, 2mm, 2.3mm, 2.6mm
In the heater in which the heating wire 1 was formed using the heating wire element, the maximum temperature of the heating wire reached only 910° C. under the same conditions.

The heating wire 1 can similarly obtain arbitrary temperature characteristics by connecting heating wire elements of arbitrary different thicknesses in series in an arbitrary order.

(Effects of the Invention) As described above, the gas heating heater of the present invention has the great advantage of having a long life and being able to raise the gas temperature, or easily obtain arbitrary temperature characteristics.

[Brief explanation of the drawing]

Figure 1 is an explanatory cross-sectional view of the gas heating heater of the present invention, Figure 2 is an explanatory sectional view of the gas heating heater of the present invention;
The figure is a diagram showing the relationship between the heating wire of a gas heating heater and the gas temperature, Figure 3 is a front view of the heating wire in a wound state, Figure 4 is a side view thereof, and Figure 5 is a diagram of a conventional gas heating heater. The explanatory cross-sectional view, FIG. 6, is a diagram showing the relationship between the heat generation line of the gas heater and the gas temperature. 1... Heat generating line, 1a to 1d... Heat generating line element, 2...
・Heat-resistant insulated tube, 3...Heat-resistant insulated rod. $3 @ Meal 4 @

Claims (1)

[Claims] A heating wire formed by connecting a plurality of heating wire elements with different diameters in series, and a heat-resistant tube having a gas inlet at one end and a gas outlet at the other end through which the heating wire is inserted. A gas heating heater characterized by comprising: