Mathematical Model of Air Replacement Time onAirless Drying

摘要

Airless drying actually is a modification of superheated vapor drying. This drying processworks in high temperature wind and closes drying circulation by itself. The vapor from materials ismixed with air in machine. They are heated to the inlet temperature demanded by drying and theyare still taken as the drying medium. The main characters of airless drying are fully using of thepotential heat of vapor, high heat efficiency, no pollution to environment and good drying quality. It issignificant on designing the drier and optimizing the drying technique to study the airless dryingprocess, the replacement time of original air in the drying room and to analyze the factors affectingthe air replacement time.In this paper, for conveniently analyzing and simplifying the mathematical model, severalassumptions are taken: the dry air and vapor are mixed equably at any case; the air pressure in thedrier is equal to the atmospheric pressure; taking dry ing materials as high humid materials; dryingrate is constant in the whole process; there is no moisture in the air in the dryer at the beginning ofthe test.A mathematical model to determine the air replacement time on airless drying was developed andverified. Parameters impacting the air replacement time were analyzed by using the model. Theresults showed that at higher evaporation rate, the air replacement time could be reduced. Atconstant drying rate, the air replacement time could be shortened at higher working temperature. Inorder to reduce the air replacement time, the capacity of the drying room should be reduced as smallas possible.