Introduction:
Heat is required for both industrial and domestic purposes. Heat is required in industries for melting metals, molding glass, enameling copper, baking insulators and welding etc. Domestic purposes require heat for cooking, heating water, heating rooms in winter, pressing clothes and more.
All those heating purposes can be fulfilled by electricity. Electric heating has some advantages.
Electric heating is dirt-free so cleaning requires minimal effort.
Electric heating is free of flue gases so there is no need for an exhaust system to generate heat.
Temperature control can be done very easily.
Electric heating system is economical as compared to other conventional heating systems available in the industry. Both installation cost and running costs are quite low.
Automatic protection against any abnormality in heating system can easily be provided in electric heating system.
The efficiency of the system is significantly higher than other equivalent heating systems.
Electric heating system is noise free.
The system starts up much faster than other heating systems.
Types of Electric Heating:
Power Frequency Heating:
In this method, electrical power is used directly to heat any substance. Power frequency heating is again divided into two types.
Resistance Heating:
Arc Heating:
Obstruction warming can be immediate opposition warming, circuitous opposition warming.
Direct Resistance Heating:
In direct resistance heating systems, current flows directly through the material being heated. In an electric heating system, the substance to be heated is called charge. Since the charge here provides the path for the current and heat is generated in the charge, the efficiency of the system is quite high. Popular examples of direct resistance heating are resistance welding and electrode boilers.
Indirect Resistance Heating:
In this method, electric current is passed through a resistive element where heat is generated due to ohmic loss. This heat is then transferred to the substance to be heated. Popular examples of indirect resistance electric heating are immersion water heaters, electric cooking heaters, ovens, and heat treatment systems for metals.
Arc Heating:
Exceptionally high temperatures can be gotten from the curve. A bend can frame either between two terminals of adequate likely distinction or between a cathode and the actual charge. In any case, the actual charge acts like the other terminal.
Indirect Arc Heating:
In an electric furnace where an arc is generated between two electrodes and the heat generated in the arc is transferred to the charge, it is called an indirect arc furnace.
Direct Arc Heating:
In an electric furnace, where an arc occurs between the electrode and the charge, it is called a direct arc furnace.
High Frequency Heating:
This sort of electric warming can be ordered as
- Dielectric Heating.
- Infrared Heating.
- Induction Heating.
 1. Dielectric Heating:
Installation materials such as wood, ceramic and plastic etc. are very difficult to heat evenly. High frequency dielectric capacitive heating is used here. The dielectric material connected between the two electrodes acts as a capacitor, and high frequency current can pass through the capacitor. Current through the capacitor produces uniform heating in the dielectric material. The applied frequency in dielectric heating is very high in the range of 10 to 50 kHz, but the system efficiency is about 50% lower.
2. Infrared Heating:
This is the most wasteful technique for electric warming. It is likewise the most straightforward type of electric warming. Here electromagnetic radiation from a brilliant light is centered around a surface for warming. Drying the weed painted surface of an object is generally utilized.
3. Induction Heating:
Induction Heating is of two types:
- Direct Induction Heating.
- Indirect Induction Heating.
Direct Induction Heating:
In direct induction heating, the current is induced in the charge itself due to close switching. Due to the inherent resistance of the charge, heat is generated in the charge itself. Induction furnaces and eddy current heaters are two well-known examples of direct induction electric heating.
Indirect Induction Heating:
In this method, the heating elements of the furnace are heated by the current induced in them by mutual induction of the source coil. This heat is then transferred to charge by radiation and convection. Indirect induction furnaces are mainly used for melting metals.
