Flexible Heaters and Multiple Heating Zones

Flexible heaters are suitable for a wide range of uses that require variable heating options. While providing optimal heat transfer, they also offer the right temperature for products like foodservice, medical devices, sensors, instrument panels, and electronics.

We are accustomed to thinking of heaters in standard shapes like square, round, and rectangular. However, customized flexible heaters are available in a wide variety of shapes that have the requisite shape to wrap around specific objects like inserts and pipes. They may also have different temperature zones for applications that generate their own heat in some places while requiring heating in others.

Designers make flexible heaters from polyimide and silicone rubber, and their size depends on the resistive element necessary. For very thin flexible heaters, etched foil heaters are the most suitable, and both polyimide and silicone materials can use them. Etched foil heaters are also suitable for smaller flexible heaters, as they can be as small as 1-inch square, or as large as 18 x 24 inches for silicone rubber, and 10 x 70 inches for polyimide. For larger sizes, designers prefer wire-wound resistive elements.

If necessary, designers can make flexible heaters in odd and non-symmetrical shapes as well. However, the specific needs of the application almost always define the shape, requiring laser cutters and mechanical equipment for creating the outline of the desired shape. Recent developments ensure that internal cutouts are also possible, such as in rectangular, square, circular, and other shapes, without sacrificing the reliability and heating capacity of the flexible heater.

Etched foil elements allow quick thermal transfers and faster warmups for heaters made from both polyimide and silicone rubber. However, wire wound heaters are notably slower, and there may be a delay in heat transfer when the heater element is wire-wound. Wire wound heaters are not suitable for polyimide heaters.

Some applications do not require heating equally throughout the surface. For instance, some electronic circuitry may create its own heat, protecting itself from external or internal temperature changes. Such applications do not require additional heating. However, outside this protected zone, the rest of the circuitry may require suitable temperature control for proper operation. Engineers provide suitable heating with cut-outs along the heater material. Flexible heaters with multiple heating zones are the answer for applications that require heating but at different temperatures.

Flexible heaters made from polyimide or silicone rubber are the most suitable for such applications. Multiple zone heating is necessary if some part of the electronics requires heating at a certain temperature, while another part needs raising to a different temperature.

Making heaters with multiple heating zones requires designers to place different heating elements at suitable places, with separate controls for these zones. However, other simpler options are also available, requiring one heater and a single controller. One of the options involves using elements with variable widths.

The width of the conductor of foil etched heaters impacts the watt density in specific areas of the flexible heater. When the width of the conductor is low, its resistance increases resulting in lowering the thermal output at that zone, creating multiple heating zones.