What Are Electric Heating Elements

Electric heating elements, which come in a wide variety of shapes, sizes and materials, are used throughout the heat treat industry when high temperatures, maximum power and heavy-duty cycles are required. They can be found in a ribbon, rod or coil form and made from alloys like nickel-chromium, iron chromium-aluminum or refractory metals.

Variations

Whenever electricity passes through anything that has a certain amount of resistance it produces heat. The amount of heat that is produced is dependent on how much electricity is used and the amount of resistance involved.

Unlike gas heating elements that emit fumes and smoke which pollute the atmosphere, electric heating is clean and safe. There is no smoke, flue gases or pollutants which makes it a popular choice for modern homes and businesses.

Flexible heater solutions come in a variety of shapes and sizes to suit different applications. There are two predominant configurations – wire-wound elements and etched foil elements. Both types have their own benefits but it’s important to choose a reliable supplier to ensure the best results. You can control each individual radiator in your home with an electric heating system so you only use energy for the rooms that you need to warm up. This reduces your energy consumption and bills, as well as your carbon footprint.

Materials

Electric heating elements are made from a variety of heat conducting materials. Some are metals such as nichrome, while others are more sophisticated and use platinum or molybdenum. Some types reach very high temperatures such as those used in industrial iron smelts.

The basic function of a heating element is to convert electrical energy into heat energy through the process known as Joule heating. This occurs when electric current passes through the element and encounters resistance which in turn produces heat. The amount of heat produced depends on the magnitude of the electric current and the level of resistance.

Most electric heating elements are made of nichrome, an alloy of nickel and chromium in wire, ribbon or strip form. This material is ideal for use in heating elements because it has relatively high resistance and forms an adherent layer of chromium oxide when heated for the first time. This prevents the material from breaking or burning out.

Design

Since many different kinds of electrically conductive materials can be used to make electric heating elements, there are many configurations that can be made. These are not just in terms of shape; they can also be in how the element is designed to function.

One important aspect is the watt density of the element (power dissipated per unit area). Too high and the element can burn out prematurely and cause damage to the furnace.

Choosing the right watt density for a particular application can be determined by solving equations where 'r' is the resistance of the element wire material, 'l' is the length of the wire and 'd' is its diameter. It is also essential to choose the right lead configuration. It must be fastened to the actual element conductor with care so as not to compromise the integrity of the insulation. For instance, using a self-sticking tape should be avoided as this can break down into carbon based compounds which could contaminate the conductor.

Applications

A heating element must be matched to the process in which it will operate. The target operating temperature, watt density and power supply are critical to selecting the proper heater for a given application. The watt density must be sufficient to provide heat transfer without exceeding the rated temperature of the process fluid. It must also be selected within the design voltage of the power supply.

Graphite heaters, for example, reach high temperatures and are used in vacuum furnaces. They are not brittle and can withstand repeated cycles of heating and cooling but will oxidize over time.

Other types of electric heaters include industrial, duct, cartridge-style and space heaters. The designs of these heaters vary depending on the intended application. They may be straight or formed into coils, open or closed. Closed coils, for instance, have a sheath to keep the elements and process medium from touching which reduces risks of fire, burns or electrocution.