ABSTRACT
Since impingement yields very high heat or mass transfer rates, it is a popular system for convective drying when rapid drying or small equipment is desired. An impingement dryer system should be chosen only if the product is in a form that is amenable to being subjected to a multiplicity of hot jets directed normally onto one or both of its surfaces. Design of impingement dryers is both simplified and aggravated by the excessive number of design variables or parameters that can be specified or chosen arbitrarily; at least a dozen of these are important and have been studied systematically in recent literature. The effects of crossflow, movement of the impingement target, large temperature differences, high drying rate, and artificial turbulence are among the most important to be considered in the design of impingement dryers. For rapidly moving impingement surfaces it is likely that an optimum angle of impingement may exist.
