The heating method of resistance heating has wide application such as treatment of metals(annealing,hardening etc,) drying and baking of potteries,stoving of enamelled ware and commercial and domestic cooking. Temperature upto 1273K can be achieved by this method.
There are two types of Resistance Heating:
a) Direct Resistance Heating:- In this method the material or charge to be heated is taken as a resistance and current is passed through it. the charge may be in the form f powder, pieces or a liquid. Two electrodes are immersed in the charge and connected to the supply in case of availaibility of three phase supply. This method has high efficiency. Heat temperature control is not possible in this method.This method is used in salt bath furnance and in the eectrode boiler of heating.
b) Indirect Resistance Heating:- In this method the current is passed through a wire or other high resistance material forming a heating element.The heat produced is directly proportional to the core losses. The heat is transffered by conduction ,convection,radiation processes. if heat is transffered by conduction the resistor must be in contact with the charge. An enclosure known as heating chamber is required for transfer by radiation and convection.
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