Development of design charts for tunnel dryers

Abstract

A dryer simulation model, comprising a material model and an equipment model, has been developed for the drying of food products in a tunnel dryer. The material model, which deals with the drying kinetics of the product, is based on the receding evaporation front phenomenon while the equipment model describes the dynamics of the dryer. The overall model takes into account the shrinkage of the product. Simulation results of the transient moisture content show good agreement with experimental results for two dryers of different drying capacity. We present a design chart relating air temperature and humidity to the required energy for drying and dryer length, which shows an appreciable effect of setting low humidity for low temperature drying. A reduction in dryer energy consumption and chamber size is obtained under this condition. Multi-stage drying is introduced for situations where saturation of the air is likely to occur in the drying chamber. © 1997 by John Wiley & Sons, Ltd.