Strip heaters are usually flat, straight and similar in shape to a ruler, but they are often finned for fuller heat radiation when they are used to heat air. They can also be used to heat tubes, pipes and nozzles, in which case they can be designed as circular bands that clamp around cylindrical objects.
Strip heaters must be bolted or clamped onto a surface, so they often feature holes, notches, clamps or bolts; many strip heater manufacturers offer custom-shaped strip heaters to fit unique applications. A few of strip heaters’ common applications include providing heat for cylinders, platens, process machines, moisture protection, thawing, baking, drying ovens, food processing, control cabinets, acrylic extrusions and space heaters.
Strip heaters may be used individually or in groups to provide melting, drying or air heating. Strip heaters can also be used in the formation and shaping of plastics. In plastic extrusion, strip heaters can be used to assist in the plasticization of raw plastic stock while it is processed in a conveyance channel. They are also used to heat plastics in advance of bending processes.
Strip heaters generate heat by transforming electrical energy into thermal energy. The process of conversion between electrical energy and thermal energy is called Joule heating.
An electrical current can be loosely defined as an excited stream of electrons. When those excited electrons collide with the atomic ions of the conductive medium, in this case the strip heater, those ions start to vibrate. Heat is one of the noticeable expressions of that vibration. The vibration of the ions of the conductor eventually is transmitted to any surrounding surfaces or atmospheric particles.
The greater the surface area of the conductive surface, the more opportunities for atomic collisions to occur. It is for this reason that strip heaters used to heat air are finned; every extra inch of conductive surface is another opportunity to create collisions.
Mica, mineral and ceramic materials are used to insulate strip heaters, and the main, outer strip heater construction materials are steel, stainless steel and nickel alloys. Mineral insulated strip heaters can reach the highest temperatures when paired with stainless steel, reaching up to 1400ºF; mica and ceramic heaters reach temperatures between 700º-1200ºF. Strip heaters are characterized by their rugged construction, easy installation and relatively low cost.