3. Utilities

In order to vaporize the liquid impregnating the moist product, a heat supply and vapour removal are essential. The three conventional modes of heat transfer – convection, conduction and radiation – can be used, either alone or simultaneously. Although less common, induction heating is also used in the textile and paper industries.

Convective and contact dryers use a heat transfer fluid. In contact dryers, the sole function of the heat transfer fluid is to transfer heat, while agitation (if required) is mechanical and vapors are evacuated by sweeping at atmospheric pressure or by vacuum suction. In convective dryers, the vapors from the vaporized liquid are evacuated by the heat transfer fluid, which is usually also used to agitate the product, as in fluidized-bed dryers, or to transport it, as in pneumatic dryers...

Radiation or induction...