The process of heat energy transmitted from a high temperature source to that at a lower temperature is basically heat transfer. Heat transfer is of three types –
- Convection – through a gas or fluid
- Conduction – by direct contact between two objects
- Radiation or Infrared – through invisible electromagnetic waves
In radiation, heat energy is transferred through infrared, microwave, radio wave and ultra violet rays. The electromagnetic waves can be near, medium or far depending on the wavelength of heat transmission.
Among the many important aspects of infrared is the ability to transmit energy in the 5 to 12 micron wavelength range which is seen as the most effective. There are several types of infrared rod elements in the 'far' category that are in use.
- Ceramic – these are by far the most common infrared rod elements and are quite similar in appearance to metal infrared elements. Some manufacturers of metal roads coat them in a ceramic layer to ensure better infrared emission quality.
- Ceramic filled glass tubes – in this type, a metal filament is placed within a glass tube that is packed with lava dust or sand which is then heated by the metal filament to emit infrared at required wavelength. However, two factors go against this – a) localization of heat emission and b) fragility of the glass tube.
- Metal – various types of metals like stainless steel and alloy are used in this element. This also emits highly localized heat which can be very uncomfortable for heating at close range within an enclosed space.
The ceramic infrared rod elements are used for temperatures up to 1000°C, which are reached in under a minute, making it ideal for usage in applications that require high outputs.
Infrared Rods are also used in the medical field for highly complex treatment procedures.