RU1833969C - Explosion-proof electric heater - Google Patents

Abstract

Usage: in the electric power industry and heat engineering in explosive atmospheres. SUMMARY OF THE INVENTION; the heater contains a U-shaped heating element in the chamber and a thermal safety element adjacent to it of the same shape. The connection of these elements with the temperature controller and the power supply cut-off unit allows to increase the control of overheating of the heater surface. 5 il.

Description

The invention relates to electric power and heat engineering and can be used in explosive atmospheres.

The purpose of the invention is to increase operational reliability by controlling overheating of the surface of the heater and shorting the heating coil to the housing.

For this purpose, a thermosafety element is additionally introduced into the chamber with the liquid coolant, made in the form of a U-shaped tube filled with periclase with a copper conductor inside and a low-melting insert, connected in series with the heating element and adjacent to its surface in the area with the low-melting insert.

In FIG. 1 shows a general view of the device with a breakout, in FIG. 2 is a plan view of FIG. 3-thermal safety device; in FIG. 4 - electric circuit of an electric heater; in FIG. 5 is a top view of a thermal safety device.

The device consists of a heat exchange chamber 1 filled with a liquid intermediate coolant, and a control chamber 2 containing a power supply disconnecting unit and isolated from the chamber 1. In the chamber 1, there is a tubular resistive heating element 3 in the form of a U-shaped tube, which is in close contact in its upper part with the surface of the thermosafety element 4, also U-shaped, the thermosensitive element 5 of the thermostat of the power supply cut-off block of the heating element, installed throughout no heating element.

In the chamber 2, at the outgoing ends of the tubular resistive heater 3 and the thermofuse element 4, there are electric contacts 6, and of the thermally sensitive element 5 there is a switching device 7 of the thermostat, all elements being connected in series with the supply electric cable (Fig. 4).

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In FIG. 1, in the place of the excavation, the design of the thermal safety element 4 is shown, which consists of a tubular sheath 8, inside which a copper conductor 9 is placed, in the middle of the length of which s the zone of interaction with the heating element, a piece of a flat tape 10 of fusible material is mounted (Fig. 3) . The internal cavity of the thermal safety element 4 is filled with periclase 11. The place of the joint 12 between the low-melting tape 10 and the copper conductor 9 is thickened.

For better contact between the surface of the tube 8 of the thermofuse element and the surface of the heating element, the diameter of the tube of the thermofuse device should be larger than the diameter of the heater element, and at the bend on the outside of the tubular shell 8 there is a profile with a diameter equal to the diameter of the tube of the heating element 3 to a depth of 1 / 4 diameters.

The cross-section of the copper conductor 9 is determined by calculation, depending on the current and power of the heater so that it does not heat up when current flows.

Similarly, a cross section of a fusible insert 10 having the shape of a flat strip is selected in order to increase the heating area from an external heat source,

The melting temperature of the insert 10 is selected depending on the specified conditions, taking into account corrections for losses and errors.

The heater operates as follows ..

When electric energy enters the contacts 6 of the heating element 3, the surface of the latter begins to heat up, heating the liquid heat carrier with which the heat exchange chamber 1 is filled. The liquid, heated to a temperature close to the boiling point, maintains a predetermined temperature for heating the surface of the electric heater.

In emergency situations, for example, if the liquid for some reason flows out of the heat exchange chamber 1, the heating element 3 heats up

norms, which can lead to overheating and destruction of the heater shell.

However, when a certain temperature is reached in the chamber 1, the thermosensitive element will react and the contacts of the switching device 7 of the thermoregulator will open, disconnecting the power supply from the heating element 3.

In the case of, for example, closing a heating coil to a housing or a malfunctioning temperature regulator (5, 7), a thermal safety device 4, i.e. when heating the surface of the heating element 3 above the permissible

temperature, there is a rapid heating of the flat fusible insert 10, which melts and the power supply circuit of the heating element 3 is opened.

In the event of a thermal fuse activation, the heater cannot be restored and needs to be replaced.

Thus, the proposed heater can be used in explosive atmospheres, increases reliability, providing protection against explosion in any emergency situations by disconnecting the power supply from the faulty heater.

Fo rmula of the invention

An explosion-proof electric heater containing a housing with two chambers, in one of which a power supply cut-off unit is located, and in the other filled with a liquid intermediate heat carrier, there is a tubular resistive heating element and a thermosensitive element of the temperature regulator of the heating element power supply cut-off unit installed

along its entire length, characterized in that, in order to increase operational reliability by controlling overheating of the surface of the heater and shorting the heating coil to the housing,

a chamber with a liquid coolant is additionally introduced a thermal safety element made in the form of a U-shaped tube filled with periclase with a copper conductor located inside and

fusible insert, connected in series with the heating element and adjacent to its surface in the area with fusible insert.

FIG. 2

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