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Difference between Induction Heating and Dielectric Heating
Heating is a process of increasing the temperature of a body at an acceptable level by using thermal energy. The mechanism involved in heating is generally referred as a heating system.
When the process of heating is performed by using the electric current, i.e. the electric current is converted into heat energy by employing a suitable mechanism is called the electric heating. The principle behind the electric heating is the heating effect of electric current which states that when an electric current flows through a conducting medium, the medium resists the flow of this current which results in the rise in temperature of the medium, i.e. the heating of the medium.
Today, different methods of electric heating are available like resistance heating, induction heating, arc heating, dielectric heating, etc.
Let's start with the basics of induction heating and dielectric heating so it becomes easier to understand the differences between them.
What is Induction Heating?
The type of electric heating in which heating a body is done by means of electromagnetic induction is known as induction heating.
In Induction Heating, a device called induction heater is used which consists of an electromagnet and an oscillator. The oscillator generates an alternating current (AC) of high frequency, which is passed through the coil of electromagnet.
The changing magnetic field produced by the electromagnet is allowed to link with the object to be heated. This changing magnetic field causes the induction of electric current (called Eddy current) in the body of the object. When this induced current flows through the object, the material of the object resists the current flow and heat it as per the Joule’s law of heating.
The one of the most important feature of the induction heating is that it generates the heat inside the object body itself. Which results in less heat loss and rapid heating of the object. Further, it does not require any external contact which may cause contamination issues.
The frequency of AC supply for induction heating depends on the material of object, size of object, coupling and penetration depth, etc. The induction heating is used in industries for surface hardening, melting, brazing, soldering, etc.
What is Dielectric Heating?
The process of heating in which a high-frequency alternating electric field or radio waves or microwave radiations are used to heat the dielectric materials is known as dielectric heating. The dielectric heating is also known as electronic heating, radio frequency (R.F.) heating, high frequency heating and diathermy.
The dielectric heating is mainly used for heating of insulators like wood, plastics and ceramics, etc. which cannot be heated easily and uniformly by the other methods of heating. The frequency of the input supply required for dielectric heating typically ranging from 10 MHz to 15 MHz and the applied voltage is about 20 kV.
The working principle of the dielectric heating is same as that of an electrostatic capacitor, i.e. electrostatic induction. When an AC supply of high frequency is applied across two conducting plates, then the dipoles of insulating material placed between the plates will change their alignment after each half cycle of AC supply. During this process, some amount of energy is wasted due to interatomic friction in the dielectric material. This loss of energy is known as dielectric loss. Therefore, the heat is produced in the dielectric material and is used for heating applications.
Difference between Induction Heating and Dielectric Heating
The following table highlights all the noticeable differences between induction heating and dielectric heating −
| Basis of Difference | Induction Heating | Dielectric Heating |
|---|---|---|
| Definition | The type of electric heating in which heating a body is done by means of electromagnetic induction is known as induction heating. | The type of electric heating in which a high-frequency alternating electric field is used to heat the dielectric materials is known as dielectric heating. |
| Principle of operation | The working of the induction heating is based on the principle electromagnetic induction. | The working of dielectric heating is based on the principle of electrostatic induction. |
| Frequency of AC supply used | The frequency of AC supply employed in induction heating is medium, usually ranging from 100 kHz to 500 kHz. | The high frequency AC supply is used in the dielectric heating. The typical frequency range is 10 MHz to 50 MHz. |
| Cause of heating | In case of induction heating, the eddy currents induced in the object due to electromagnetic induction are the main cause of production of heat. | The interatomic friction in the dielectric material is the cause of production of heat in case of dielectric heating. |
| Area of heat production | In the induction heating, the heat is produced on the surface of body. | In the dielectric heating, the heat is produced inside the material. |
| Types | There are two types of induction heating namely ‘direct induction heating’ and ‘indirect induction heating’. | There is no such further classification of dielectric heating. |
| Material to be heated | Induction heating used for heating of conducting materials such as metals. | Dielectric heating is used for heating of insulating and dielectric materials like wood, plastic, etc. |
| Cost of heating equipment | The heating equipment used for induction heating are relatively less costly | The heating equipment used for dielectric heating is expensive. |
| Heat distribution in body | In case of induction heating, the heat distribution is non-uniform. | Dielectric heating heats the body uniformly. |
| Applications | The applications of induction heating are in surface hardening, soldering, brazing, annealing, etc. | The applications of dielectric heating involves drying of wood, food processing, cooking and baking, gluing, etc. |
Conclusion
Induction Heating and Dielectric Heating are both categorized as high-frequency electric heating, and both are extensively used in several industrial heating applications.
The most significant difference between these two types of heating is that Induction Heating is used for heating the conducting materials like metals, whereas Dielectric Heating is used for heating of insulating materials like wood, plastic, etc.
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