JPH01200588A - Electric resistance heater with surface radiation - Google Patents

Abstract

PURPOSE:To enhance the heat utilization effect by forming a heat radiating surface consisting of metal wires in a certain length arranged at a constant spacing, and giving directionality to the heat radiation. CONSTITUTION:In such a way as half fitted in and half exposed to the atmosphere, a surface-shaped heat emitting member 1 is installed in a support 2 consisting of a heat insulating substance in a thickness of A so that the heat radiating surface will be convex or concave. This surface-shaped heat emitting member 1 has a heat radiating surface in an arbitrary form, e.g., a semi-circular, and the heat generated is released from an opening window O' to outside the device through direct radiation. The heat emitting member 1 is folded zigzag at certain lengths and arranged at a constant pitch P. This permits the heat to be radiated with directionality to provide good heating efficiency, and heat emitting wires can well be maintained without requiring heating of the support 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric resistance heater using a metal heating wire, and the heat utilization effect is significantly improved.

The heating element of a conventional heating element has a volumetric structure, as seen in the Co11-like heating element, so the heat radiation from the heating element lacks directionality, making it difficult to utilize heat. It is difficult to improve the effectiveness, and a lot of heat is wasted.

In the present invention, by making the heating element planarly elliptical, it is possible to impart directionality to the heat radiation, thereby significantly improving the effectiveness of heat utilization.

Conventional electric resistance heaters using metal heating wires are made by winding a round wire into a Co11 shape for small ones, and for larger ones by bending a banded wire in a zigzag shape flatly. The heating element is mounted on a heat insulating refractory support having a partially open groove or horizontal hole depending on the shape of the heating element.

As an example, if a Co11-shaped heating element using a round wire is used, Figure 1 (cross-sectional view) and Figure 2 (front view) are shown.
It is as follows.

As an example of the present invention, the case where the heat radiation surface is semicircular and the heating element using a round wire is shown in FIG. 3 (cross-sectional view) and FIG. 4 (front view). In the case of a body, Fig. 5 (cross-sectional view), Fig. 6 (front view), and Fig. 7 (overhead view) are cut along the line x-x' of Fig. 5 and Fig. 6. It is shown here (looking down from the direction).

In Figures 1 to 7, the Co11 radius (inner diameter) of the heating element and the radius (inner diameter) of the semicircular heat radiation surface are both R, and in the case of a round wire, the wire diameter is 2r, and the band wire ( Width W Thickness t
), the values of W and t were determined so as to satisfy wXt==πr2.

The common symbol numbers in each figure are: 1 indicates the heating element, 2 indicates the support made of heat insulating refractory material, 3 indicates the heat radiation window, and A indicates the thickness of the test heat generator, all of which have the same value.

O10' and ○~ are the opening dimensions of the heat radiation window, respectively.
Since the following relationship holds true, the amount of heat radiation from the heating element is also determined according to this relational expression.

0'Aya 0''> O---------= fl)
T, T' and T'' indicate the temperature of the heating wire in contact with the support during constant current operation.

T1' and T1'' indicate the internal temperature of the heat generator (which may be considered as the temperature inside the furnace) during constant current operation.

In each cross-sectional view, the dotted portions on the support body portion indicate comparable high temperature regions of the support body around the heating element.

In each front view, the shaded part of the heat generation line indicates that the amount of heat generated there is radiated directly to the outside of the device through the open window. This portion will be referred to as the direct heat radiation area of the heating element.

Since the heating wires used in the heating element exemplified above are of the same quality and have the same cross-sectional area, the electrical resistance per unit length is also the same, so the conventional Co11-shaped heating element and the surface heating radial valve heating element of the present invention The description will proceed assuming that both heating elements, which are formed with an inner diameter R and a pitch P, have the same electrical resistance value per unit pitch.

Based on the above, we will conduct a comparative study between the conventional product and the product of the present invention.

First, let's talk about direct heat radiation.

Direct heat radiation is conventional, Co11-like heat generation #- (Fig. 1,
In the case of 50% of the front heat generating surface (see Figure 2), the remaining part serves as a heat source for heating the Co11 itself and the support around it, so the temperature of these parts is
Since the temperature on the inner surface of the heater (which can be considered as the furnace temperature) is considerably higher, damage to the heating wire is accelerated.

In the case of the surface heat radiation type valve heating element of the present invention, it is from about 90% of the heat generating surface, and although the amount of heat generated is the same as that of the conventional product, the amount of heat radiation increases. The temperature of the heating element is lower than that of the conventional product, and especially in the case of a band wire, the amount of heat radiation further increases, so the difference from the furnace temperature becomes even smaller. If this is shown by the temperature symbol in the figure, it will be as follows.

T>T'>T″ −−−−−−−−−−−−121 In other words, the product of the present invention has a large amount of direct heat radiation, so the heating time of the furnace is shortened with the same electric power. At the same time, the heating element is operated at a lower temperature, so the life of the heating wire is extended.

Next, consider the accumulation of heat in the heat generator.

As can be easily seen by comparing FIG. 1 and FIG. 3, in the case of the Co11-like heating element, the contact area with the support is 2, compared to the heating element of the present invention. Since the amount of heat will be about twice as high, the high temperature area that will occur around it will not only be proportional to that, but also, as mentioned above, the temperature will also be higher, so it is thought that the amount of accumulated heat will be about three times as much. It will be done.

The above can be summarized in the following three points.

1) The heating element of the present invention emits a large amount of direct heat.

2) The heating element of the present invention has a small temperature difference from the furnace temperature.

3) The heating element of the present invention reduces the amount of heat accumulated in the furnace body.

These three points are the basis of the heating element of the present invention, and by applying them, the practical effects described below will be produced, so we believe that they will greatly contribute to thermal processing work. .

a) Furnace temperature can be controlled more accurately.

b) The temperature of the furnace can be raised and cooled more quickly.

C) The furnace can be kept at a higher temperature.

d) Longer the life of the heating wire.

Furthermore, as shown in FIG. 7, in the heat generator of the present invention, each line segment constituting the heat generating element is partially housed in the support body through a protruding barrier indicated by 2f, so that each line segment The position of
Since it is fixed, there is no short circuit between the lines or movement of the entire heating element, and it can withstand long-term operation at high temperatures.

[Brief explanation of the drawing]

FIGS. 1 and 2 are a sectional view and a front view of a part of a conventional heating element using a Co11-shaped heating element. FIGS. 3 and 4 are a sectional view and a front view of a portion of the heat generator of the present invention when using a round wire. FIGS. 5 and 6 are a sectional view and a front view of a portion of the heat generator of the present invention when a band wire is used. FIG. 7 is an overhead view of the cross section taken along the line xx' in FIG. 5 as seen in the direction of the arrow. In each figure, 1 is a heating element, 2 is a support made of a heat insulating refractory, 3 is a heat radiation window, and A is the thickness of the heating element. R
represents the inner diameter of Co11, 2r represents the diameter of the round wire, and W and t represent the width and thickness of the band wire. 0, O' and O'' respectively indicate the opening dimensions of the heat radiation window. 2' in Fig. 7 shows a state in which a part of the support body protrudes into the line segment. T, T' and T'' indicate the temperature of the heating wire in contact with the support during constant current operation. T, , T,', and T1'' indicate the internal temperature of the heat generator (which can be considered as the temperature inside the furnace) during constant current operation. Patent applicant Sato Measurement 1 Indication of the case Patent application No. 025021 of 1988 2 Title of the invention Surface heat radiation type electric resistance heater 3 Person making the amendment Relationship to the case Patent applicant 4 Date of amendment order April 26, 1988 5 Target of correction: All drawings

Claims (2)

[Claims] (1) Metal heating wire (round wire or band wire) in a zigzag shape,
When performing folding and bending with the same length, the line array (the line portions of the folded sections that make up the line array are called line segments) has an arbitrary shape called a heat radiation surface. Surface heat radiation type electric resistance heating using a heating element made of line segments arranged at approximately equal intervals on a surface such as a semicircular surface, semielliptical surface, parabolic surface, or U-shaped surface. vessel. (2) The heating element shown in item (1) is
096053, 59-102376 and 61-1704
By using the support made of heat insulating refractories and its installation method as shown in 61, the heat radiation surface becomes a concave or convex surface, and the line segment of the heat radiation surface partially envelops into the support.
A surface radiant electric resistance heater mounted so that it is partially exposed in the air.