Heat plays an important role in everyday life. All heating requirements in domestic purposes such as cooking, room heater, immersion water heaters, and electric toasters and also in industrial purposes such as welding, melting of metals, tempering, hardening, and drying can be met easily by electric heating over the other forms of conventional heating.
Heat also can be produced by passing the current through material to be heated. This is called electric heating. There are various methods of heating a material but electric heating is considered far superior as compared to the other heating methods such as produced by coal, oil, and natural gas.
Electric Heating Methods
Various electric heating method as per their working principle.Like,
Resistance Heating
Direct resistance heating:- In this method, the electric current is made to pass through the substance to be heated. This principle of heating is employed in electrode boiler.
Indirect resistance heating:- In this method, the electric current is pass through a high resistance heating element, so heat is developed, heat is transferred to charge which is to be heated from the heating element by convection or radiation. This method of heating is employed in immersion water heaters.
Electric Oven:- Ovens are used to cook the food for domestic purpose and treatment of metals in industries. In electric oven current flows through the metallic elements to heat up the element and in turn the enclosed space and cook food.
Induction Heating
when a coil is wound on a magnetic Core and is given supply then magnetic field is produced. If this field changes its magnitude, an EMF is produced and if circuit is closed then current will flows. Transformer is an example of low frequency induction heating.
If ac current flow through the coil wound on a core, the magnetic flux linking with the core changes hence an EMF induced in the core. As core provides a closed path, eddy current starts flowing through the core. Now if the substance to be heated is used as core then the substance can be heated by flowing this eddy current. This is the principle of induction heating/furnaces.
Electric arc heating
Heat is produced with the help of electric arc by using Electric arc furnace. Electric Arc Furnace means an extremely hot enclosed chamber, where heat is produced by means of electrical supply provided to the Carbon/Graphite electrodes for melting certain metals such as scrap steel without changing the properties of the scrap metal.
Electric arc is produced between the electrodes if a sufficiently high voltage is applied across an air gap between electrodes, the air becomes ionized and start conducting in the form of arc and produced heat.
The electric arc heating furnace are of following two types. 1. Direct Arc Furnace 2. Indirect Arc Furnace
Infrared heating
In this method of heating, the heat energy is transferred from source (incandescent lamp) and focused upon the body to be heated up in the form of electromagnetic radiations. Normally, this method is used for drying clothes in the textile industry and to dry the wet paints on an object.
This is also called as Radiant heating. In this heating element is made of tungsten which also operates at 2500 ° C and at this temperature, the element emits sufficient infra red (IR) radiations. This temperature is higher than the resistance heating.
Microwave heating
In RF Heating or Microwave Heating the material is subjected to an electromagnetic wave that causes the molecules in the material to oscillate, thereby generating heat. This phenomenon has applications ranging from microwave ovens, through therapeutic medical treatment, to material processing in the manufacturing industry.
Microwave heating, uses electromagnetic energy in the frequency range 300-3000 MHz and is used to heat many dielectric materials. Microwave heating is used industrial, scientific and medical applications, for frequencies between 915 and 2450 MHz. Domestic microwave ovens uses a frequency of at 2450 MHz. The way in which a material will be heated by microwaves depends on its Shape, size, dielectric constant, nature of the microwave equipment used.
Microwave radiation is best known for heating food in the kitchen, in recent years it has found new application in many industrial process such as those involving melting, smelting, drying and joining.
Heating by microwave radiation constitutes highly coupled nonlinear problem giving rise to new and unexpected physical behavior the best know of which is the appearance of “hot spots”.
Solar Heating
Solar heating is the most readily available source of energy. It does not belong to anyone and therefore, it is free. It is also the most important of the non-conventional sources of energy because it is non-polluting and therefore, helps in lessening the greenhouse effect.
Heat from the sun in the form of radiation passes through the atmosphere where most of it is absorbed by the Earth.Some infrared radiation (heat) is reflected back into space.Greenhouse gases act as heat trap also known as atmosphere glass, trapping some of this infrared radiation (heat) return back to the earth to forms more heat on earth’s surface.
Without greenhouse gases or glass, the average temperature on Earth would be 60 ° F and life on Earth would look very different than it does today. Just like greenhouse effect we use heat collector to collect heat which comes sun.Solar heat is used for many purpose like solar water heater, solar furnace, solar cooker etc.
Advantages of Electric heating
Economical:- Electric heating equipment is cheaper, they do not require much skilled persons, therefore maintenance cost is less.
Cleanliness:- Since dust and ash are completely eliminated in the electric heating, it keeps surroundings clean or ash free.
Pollution Free:- As there are no flue gases in the electric heating, Therefore it is pollution free.
Ease of control:- In this heating temperature can be controlled and regulated accurately either manually or automatically as per requirement.
Uniform Heating:- With electric heating, the substance can be heated uniformly, throughout whether the material conducting or non-conducting.
High Efficiency:- In non-electric heating, only 30–60% of heat is utilized but in electric heating 80–100% of heat can be successfully utilized. Therefore, overall efficiency of electric heating is very high.
Automatic protection:- Protection against over current and over heating can be provided by using the automatic control devices.
Heating of non-conducting materials:- The heat developed in the non-conducting materials such as wood and porcelain is possible only through the electric heating.
Better working conditions:- No irritating noise is produced with electric heating and also radiating losses are low.
Less floor area:- Due to the compactness of electric furnace, floor area required is less.
High temperature:- High temperature can be obtained by the electric heating except the ability of the material to withstand the heat.
Safety:- The electric heating is quite safe.
