UNDERSTANDING INFRARED RADIANT HEATING TECHNOLOGY

August 2019

Common Applications

Plastics and Rubber

Plastifying of plastic sheets and rolls for thermoforming and vacuum forming
Preheating or vulcanizing rubber sheets
Heating glass fiber reinforced plastic during production
Curing plastisols
Laminating and plastic welding

Food

Baking and browning small bakery products
Keeping food warm
Heating processed cheeses
Packaging food products

Textiles

Setting Nylon® and Perlon® threads
Gelling PVC paste coatings on fabrics
Drying washed, dyed, and finished textile fabrics
Heat set synthetic fabrics

Paper/Pulp

Drying of paper pulp
Quick drying of gummed, sized, or lacquered paper
Drying of unprocessed and printed wallpaper
Heating papier-mâché before pressing
Adhesive activation

Miscellaneous Processes

Drying and curing of paint and powder coatings
Drying raw tobacco
Evaporation of water and solvents
Ink drying
Comfort heat for agricultural, zoological and reptilian pet applications

Note: Many applications in this field are unique and present substantially different operational parameters and characteristics. It is highly recommended that you contact our staff of knowledgeable sales engineers with specific technical questions relating to your application.

Infrared radiant heat energy can be delivered to concentrated areas at a very fast rate with individual heaters or heater arrays. Infrared energy is commonly used to heat plastics, remove moisture, cure painted finishes or heat food products. This is because plastics, organic substances and water absorb infrared energy more efficiently than other materials in industrial applications.

The efficiency of radiation heat transfer exchange between bodies depends on:

The emissivity values of the emitter (i.e. ceramic heaters).
The absorption, reflection and transmission properties associated with the receiving medium.
The relative temperature differences.
The surface characteristics.
Relative position and physical geometry.

Infrared Images

The Basics of Infrared Radiation

The three main modes of heat transfer are:

Conduction – When two bodies of different temperature are brought in contact with each other, heat energy flows from the hotter to the colder body.
Convection – Heat energy is transferred from a higher temperature region in a gas or liquid to a lower temperature region as a result of movement of masses within the fluid or gas.
Radiation – Infrared radiant energy is transported through space by electromagnetic waves without the need for a conductive media. Consequently, heat can be delivered in concentrated areas at very fast rates. Electromagnetic radiation can be further broken down into four basic categories: ultraviolet, infrared (short/medium/long wavelength), microwave, and radio frequency/induction.

Why Can’t We See Infrared Radiation?

Electromagnetic radiation is measured in wavelength “λ” or in frequency “f”. Both quantities are related by the equation λ = c ÷ f, where "c" is the speed of light (3 x 10^-8 m/s). Infrared radiation wavelengths fall outside the visible range in the electromagnetic spectrum; see adjacent figure. One micrometer, µm, is equal to 10^–6 meter.

The total radiant energy “W” in watts per square centimeter emitted by an object is found with the Stefan-Boltzmann law: W = εσT⁴, where “ε” is the emissivity factor, “σ” is the Stefan-Boltzmann constant (5.67 × 10^–12 W/cm²K⁴), and “T” is the surface temperature of the object in °K (0°C equals 273°K).

All matter emits radiant energy as a consequence of its finite temperature. Only at absolute zero (–273°C), when all molecular activity ceases, does matter stop emitting radiant energy. In solids and liquids, emission of radiant energy is considered a surface phenomenon, while for gases and certain semi-transparent solids, such as glass and salt crystals (at elevated temperature), emission is considered a volumetric phenomenon.

Infrared Wavelengths

Radiant heating is regarded by many as a technology that is complicated and difficult to work with. While radiation theory can be complicated, it is far easier to apply when given the appropriate heating devices and guidance on which device best suits your application. No matter what the application needs, Tempco has the right product to satisfy your requirements.