Questions and Answers on Flexible Heaters
What are flexible heaters?
Heaters that are flexible in nature can be wrapped or formed and attached to surfaces to be heated. Conforming to the surface the flexible heating elements provide more contact surface area for efficient transfer of heat to the surfaces.
The heating elements are bonded inside a protective conductive layer of insulating material heat transfer material. This material, usually silicone rubber-based, protects the metallic resistive elements from damage and electrical conduction to surfaces. The resistive elements can be wire or etched foil for flexibility.
Where are these flexible electric heaters used?
Electric car battery heating is becoming one of the major uses to flexible electric heaters. Solid-state batteries using metallic lithium anodes must be kept at an elevated temperature of 140 degrees F during charging. The batteries or battery compartment must have heating elements to maintain these high temperatures for prolonged periods during charging.
The nylon reinforced silicone rubber heaters are used in industrial applications. Attached to surfaces that require heating such as food industries, pipes, drums, valves, batteries, communications equipment, medical equipment, even aerospace applications.
The heaters come in large sizes at 120 -240 V for heating of 55-gallon drums to very small 2 x 2 inch 12 V sizes for inside cars, trucks, farm & construction equipment, trains, and planes.
Batteries for electrical equipment come in all shapes and sizes. Very small batteries, as well as large battery arrays used in electrical vehicles, need protection from freezing. The capability of these flexible heaters to be manufactured in very small customized shapes and sizes is a huge advantage compared to traditional flexible wire heaters.
What are the advantages of etched foil heating elements?
The etched foil resistive element is very thin compared to wire resistive elements. For comparison, the aluminum foil used in everyday applications is from .0005 - .00025 inches in thickness. That thickness of foil or other alloy is etched chemically to provide the custom patterns used for a flexible heater.
The thinness and exactly repeatable patterns of the foil provide consistency in watt density from one etched foil heater to another. The foil patterns can be custom designed to allow for punching or drilling of the silicone heater for attaching to molding around specific heating applications.
Why is silicone rubber used for flexible heaters?
Silicone rubber has several advantages making it an excellent solution to protect the electrical heating elements from damage, a wide temperature range, and superior heat transfer properties. It is also lightweight and flexible.
Silicone rubber has good resistance to weather & aging, fungus & bacteria, acetone, alcohol, formic acid, brake fluid, acetic acid, greases, hydrochloric, and sulfuric acid at 10% concentrations, and other industrial chemicals. It also has good steam resistance up to 266 degrees F. Most of all it is durable to abrasion and pressure.
Using silicone rubber around the resistive elements adds little to the overall thickness of the heaters which is a very desirable characteristic for electronic circuits, medical equipment, and aerospace applications.
The melting temperature of silicone exceeds the max continuous operating temperature of most heaters around 180 degrees C. Silicone actually doesn’t burn until 450 degrees C.
How is the heat generated in a flexible electric heater?
Resistive wire or etched foil is used to generate heat inside a flexible heater. Wire, either in multiple strands or single cables have been used traditionally but are being replaced by etched foil. The etched foil allows for thinner diameters and more consistent placement throughout the heaters. The consistent placement allows for more even heating in the small devices.
Different alloys and thicknesses are used in each to create the right power output for each device. The etched foil also allows for repeatable manufacturing of custom sizes and shapes.
As with any resistive heater, the power output or wattage depends on the total resistance of the circuit and the voltage applied. The high power density of the etched foil for a square inch of the heating surface makes them highly desirable for use in small spaces requiring high heat.
The heating elements come with cable or lead wires bonded to the resistive elements for attachment to the electrical control circuit. Larger heaters such as 55-gallon drum band heaters come with built-in thermostats and electrical cords with plugs.
Do I need a temperature controller for an etched foil heater?
The need for temperature controllers is dependent on the application. It is possible to size the flexible heater such that it maintains continuous heat to the surface materials without needing temperature sensors or controllers.
Some applications may need a temperature sensor to turn off the heater after warming up the material or surface. Yet others may require constant control over the temperature. It is best to check with our experienced engineers on your application for the correct monitors or controls.
Can I get help selecting the right kind of etched foil silicone heater?
Please request a quotation or investigate our other heating options for your specifications and application. Call 1-864-607-9047 and talk to an engineer, not a salesperson. Leverage our experience and knowledge to help you make the right decision on the best heater.