Physical Process Modeling-Heat Transfer Module. Furnace I

APPLICATION
These are universal type furnaces. They find wide application in age hardening, temper hardening, annealing, normalization and in heating before forging, stretching, pressing, and glazing and baking of ceramics.

CONSTRUCTION
The furnace has a welded construction of sheet and shaped steel. The heating chamber is built up of interlocked bricks and is insulated with ceramic tiles and asbestos sheets. The tiles on the bottom of the furnace form a channel into which the walking beam is driven. The heaters, installed in open channels on the bottom, vault and walls of the furnace, are coils of high quality resistance wire. The furnace door is operated up and down electromechanically by an electric motor, a reductor and a gear and chain drive. In case of power cut the door can be raised or lowered manually by cranking up the reductor. On opening the door switches limit the furnace door in the two extreme positions and cut the power supply to the heaters. The working temperature in the heating chamber is regulated and recorded by a thermocouple and a thermoregulator. The movable feeding unit is composed of a walking beam and rails.

INSTALLATION AND OPERATION
1. The furnace and the electric panel are to be furnace is delivered in a finished state. The user connects the furnace to the electric panel.
2. The furnace is to be dried carefully before initial use, after repair work or after longer stand-still period. The drying is carried out after the operating instructions.
3. The following operating precautions are to be taken:
- the furnace is not to be operated at temperatures exceeding the working temperatures indicated in the operating instructions;
- the good working order of the automatic heat regulation equipment is to be checked periodically; the connections between the heating elements are to be examined regularly for possible loosening;
- the equipment is to be grounded.

APPLICATION
The walking beam-type electric resistance box furnace has universal application. The furnace finds use in age hardening, temper hardening, annealing and normalization processes as well as in heating in forging, stretching, pressing, and glazing and baking of ceramics.

CONSTRUCTION
The furnace is a welded unit of sheet and shaped steel. The heating chamber is built up with interlocked bricks and is insulated with ceramic tiles and asbestos sheets. The coil heaters made of high quality resistance conductor are installed on the bottom, vault and walls of the furnace. The heating chamber has two heat zones and the temperature is regulated by two thermocouples and two teat regulators. The furnace door is operated automatically by means of a starting device comprising a reductor and an electric motor. In case of power cut the door is operated manually by a crank. The heaters are automatically switched off when the furnace door is opened. The stationary feeding mechanism is installed in front of the furnace. The walking beam is operated mechanically by a power drive unit. The furnace is fitted out with an electric panel where the necessary operation and control equipment is installed.

Theory Background

REGULATION OF THE TEMPERATURE

EXPERIMENT
Furnace 1

resistance furnace experiment

Measurement
thermocouple

measurement, thermocouple - experiment

Heated details

furnace beam-type detail

REGULATION OF THE TEMPERATURE

A model for analysis of the temperature field end effects in the walls of an electric resistance furnace

When dividing the wall into elementary volumes an area of the temperature values is obtained in which are placed the possible solutions for each one case. In congruence with the practically occurring phenomenon of decreased temperature in the corner elements it is possible through several computations to achieve variant of sizes determining its even distribution. The attached shows the possible area of distribution of the temperature in different materials, sizes of the elementary volumes, correspondence in the geometry of the heater, the wall and the heated body.
With the increase in the ratio length of the final size to the total length, the temperatures of the two areas tends to become equal, i.e. the graph which is located in the area determined above. This can be used for evaluation and respectively as a criterion for determining of the usable working space in which thermal field is provided with a level of unevenness assigned in advance. It is determined both by the linear sizes and by the thermo-technical parameters of the material of the layers.

APPLICATION
The furnace is used for drying and baking of parts at low temperatures.

CONSTRUCTION
The furnace is a stationary type furnace and is mounted on a concrete base. It has a metal frame of shaped steel which is coated both on the inside and the outside with sheet iron. It has glass wool insulation. Openings in the bottom and vault of the working box secure the heated air circulation. A vent in the vault regulates the air circulation. Two pull-out pans for the parts to be heat-treated are fitted in the heating chamber. Another pan on the bottom of the working box collects the melts in the healing process. A heat insulated door seals the heating chamber. The furnace door is hand-operated. Tube electric heaters produce the rated temperature in the heating chamber. A thermocouple and a thermoregulator control the working temperature automatically.