ng made of spheroidal cast iron steel ENGJS GGGK B4-FV-23B Bevel-helical gearbox B4

Flender/Flender Gear Units/Bevel-helical gearbox B4

ystems is generally based on the mode of heat transfer to the material (.., conduction, convection, and radiation). The conduction mode of drying, 1 Das and Chakraverty also termed nonadiabatic, or indirect mode of drying, is accomplished by direct contact of the product with heated surface or heated particles. In convection drying, the air isheated to the desired level of temperature and is used as medium of convective heattransfer. In the radiation-heating mode, the material being dried absorbs energy from somesource that emits electromagnetic radiation. This absorbed energy is converted to heat that vaporizes the water molecules inside the food material. Ideally, all these modes of heat transfer act together; it is the quantitative proportional contribution of heat transferthat determines the mode of heat transfer occurring during drying of material. 3 CONDUCTION DRYING When heat for drying ows from the surface of the retaining wall to the wet solid, this phenomenon is known as conduction drying. This mode of drying is generally more appro-priate for very wet solids. Conduction drying of materials can also be accomplished bydirect contact with the heated particles. 3.1 Drying by Direct Contact with Heated Surface The materials to be dried are placed over heated bed (stationary, vibratory, or moving) that supplies heat for vaporization of moisture. The evolved vapor is removed under subat- mospheric pressure (vacuum), or by stream of gas that acts as carrier of moisture. In spite of high thermal efciency compared with convective dryer (, conduction dryersare expensive to build and to operate. Consequently, these are commercially used onlyfor low temperature and an atmosphere of low-level oxygen for drying of valuable materi- als that are essentially thermolabile and easily oxidizable. In this category, the most important one is the steam-tube rotary dryer that can handle free-owing granular materials, such as cereal grains or the like. It consists of acyl