Facts at your Fingertips: Convection versus Conduction Drying in Industry

Adjustment and control of moisture levels in solid materials is a critical aspect in the manufacture of many chemical products. Drying can be defined as the vaporization and removal of water or other liquids from a solution, suspension, or other solid-liquid mixture to form a dry solid. A complicated process involving simultaneous heat and mass transfer, accompanied by physicochemical transformations, industrial drying is often accomplished through one or more of four broad mechanisms, including the following: direct drying (convection); indirect or contact drying (conduction); radiant drying; and dielectric or microwave drying. This one-page reference focuses on the differences between convection and conduction drying. Conduction (contact drying) Contact drying involves an indirect method for removing liquid from a solid material by applying heat. In contact drying, the heat-transfer medium is separated from the material to be dried by a metal wall. Heat transfer to the product occurs predominantly by conduction through metal walls and impellers. Mixing is required to ensure contact between material surface and the heat-transfer surface. Heat-transfer fluids are often steam, hot water, or a heated oil [1]. Conduction drying can…