What is Electrical Heating Unit?
The conversion of electrical energy to heat energy is known as electric heating. The heating system that converts the electrical energy to heat energy for various application is called electrical heating unit. Electricity is employed as the firing mechanism in electric heating systems, which transforms electric current to heat. Electric heaters have heating elements in the form of electric resistors.
Electric coils or strips can be employed in a variety of designs to supply heat, such as convectors in or on the walls, under windows, or as baseboard radiation in part or all of a room. In both private homes and public buildings, the use of electricity for heating is becoming more common.
Heating is essential and efficient for both industrial and residential applications. Glass molding, insulator baking, welding, copper enameling, and metal melting, among other activities, all require heating. Heating is essential in the home for cooking, water warmth (water heaters), induction heaters, and room heaters in the winter, pressing clothes, and many other functions.
Process of Electric Heating Unit
The electrical heating method has a fairly simple functioning concept. The heating elements of the heating coil all have resistance. As a result of the Joule's effect, heat is produced when an electric current flows through the heating element or resistors.
The amount of heat produced is determined by the resistance, the amplitude of the current flow, and the duration of the flowing current. If the resistance is greater and the other variables remain constant, the heat generation will be greater. Similarly, if the current flow is greater and all other values remain constant, the heat production will be greater. Similarly, if the time period is longer and the other values are smaller, the heat generation will be greater.
Type of Electric Heating Unit
(a) Power Frequency Heating
Electrical power is used to heat any substance directly in this process. Again, there are two types of power frequency heating.
(b) Resistance Heating
Direct and indirect resistance heating are two types of resistance heating.
(i) Direct Resistance Heating
Figure shows schematic installation diagram of Direct Resistance Heating. The current flows directly through the substance to be heated while using direct resistance heating. Charge refers to the material that will be heated in an electric heating system. The system's efficiency is quite great because the charge itself provides a conduit for passing current and heat is generated in the charge. Resistance welding and electrode boilers are two common instances of direct resistance heating.
(ii) Indirect Resistance Heating
A current is sent via a resistive device, which heats up due to ohmic loss. Following that, the heat is delivered to the substance that has to be heated. Electrical cooking heater ovens, immersion water heaters, and metal heat treatment equipment all use indirect resistance electric heating.
(c) Arc Heating
An electric arc furnace is a furnace that uses an electric arc to heat material. The arc can be used to obtain extremely high temperatures. Arcs can form between two electrodes with a large enough potential difference or between one electrode and the charge itself. The charge itself behaves like the other electrode in the second scenario.
(i) Direct Arc Heating
A direct arc furnace is an electric furnace that produces an arc between the electrode and the charge.
The installation of direct electric arc furnace is shown in the diagram. Refractory material is used to line the furnace's chamber. The arc is formed when an electrode and a charge come into contact. Graphite or carbon electrodes are projected from the furnace's top, and a three-phase power supply is provided.
The charge allows the electricity to travel through them. Because the arc is in direct contact with the charge, direct electric arc furnaces can achieve the maximum temperatures. The arc will cause automatic stirring as it passes through the charge.
(ii) Indirect Arc Heating
The indirect-arc furnace is an electric furnace that produces an arc between two electrodes and transfers the heat generated by the arc to the charge.
The installation of an indirect arc furnace is shown in the diagram. Between the two electrodes in this furnace, an arc is formed. Radiation is used to transfer the heat produced to the charge. The temperature is lower than it would be in a direct arc furnace. As a result, indirect arc furnaces are ideal for melting non-ferrous metals such as brass, copper, zinc, and other non-ferrous metals with lower melting points.
(d) High Frequency Heating
It can be classified as
- Induction Heating
- Dielectric Heating
(i) Induction Heating
Induction heating has two types
- Direct Induction Heating
- Indirect Induction Heating
Direct Induction Heating
The current is induced in the charge itself during direct induction heating as a result of changing current nearby. Heat is produced in the charge itself due to the charge's inherent resistance. Direct induction electric heating is exemplified by the induction furnace and the eddy current heaters.
Indirect Induction Heating
The current induced in the heating elements of the furnace by mutual induction of the source coil heats them up in this technique. Radiation and convection then transmit this heat to the charge. Metal melting is the primary use for indirect induction ovens.
(ii) Dielectric Heating
It is quite difficult to heat an installation material such as wood, ceramic, or plastic in a consistent manner. Here, dielectric capacitive heating at high frequencies is used. High-frequency current can travel through dielectric material connected between two electrodes, which acts as a capacitor. As current goes through the capacitor, the dielectric material warms up in a homogeneous manner. Although the system's efficiency is only around 50%, the dielectric heating frequency ranges from 10 to 50 kHz.
Advantages of Electric heating unit
- Economical
- Cleanliness
- Flue Gases are not Present
- Controllability
- Automatic Security
- Upper Temperature Limit
- Requirements for Special Heating
- High Utilization Efficiency
- Efficient
Context and Applications
The use of electricity for heating is required for Domestic, Industrial and Other Applications.
In each of the expert exams for undergraduate and graduate publications, this topic is mainly taught in:
- Bachelor of Technology in Electrical Engineering
- Masters of Technology in Electrical Engineering
Related Concepts
- Electrical Heating System
- Electrical Arc Furnace
- Types of Electrical Heating Unit
- Electrical Resistance Heating Unit
- Infrared Heating
- Electrical Heaters
- Electrical Gas Heaters
- Gas Cylinder Heaters
Common Mistakes
- Leaving the heat running when No one in home.
- Leaving windows unlocked.
- Neglecting System Maintenance.
- Setting the temperature too Low during night.
Practice Problems
Q1. The conversion of electrical energy to heat energy is known as …………...
A. Mechanical Energy
B. Electric heating
C. Kinetic energy
D. None
Answer: B
Explanation: The conversion of electrical energy to heat energy is known as electric heating.
Q2. Electricity is passed through an element and transformed to heat in the resistance kind of heating, is known as …………..
A. Resistance Heating
B. Furnace Heating
C. Boiler Heating
D. Electrical Gas Heaters
Answer: A
Explanation: Electricity is passed through an element and transformed to heat in the resistance kind of heating is known as Resistance Heating.
Q3. What are the types of Resistance heating?
A. Direct Heating
B. Indirect Heating
C. Both A and B
D. None
Answer: C
Explanation: Both are types of Resistance Heating.
Q4. What are the types of high frequency heating?
A. Induction Heating
B. Dielectric Heating
C. Infrared Heating
D. All of the above
Answer: D
Explanation: All are the types of high frequency heating.
Q5. A ………………. is an electric furnace that produces an arc between the electrode and the charge.
A. Direct Arc Furnace
B. Indirect Arc Furnace
C. Indirect Resistance heating
D. Direct Resistance Heating
Answer: A
Explanation: A direct arc furnace is an electric furnace that produces an arc between the electrode and the charge.
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