The objective of this work was to determine how various types of tea dryer
would perform with different levels of inputs. Three dryer types were commo
nly found in practice, two others are not generally used and one type is un
known in practice. Simulation models for each type were constructed from a
thin-layer drying model. The information gained from the simulations showed
which type of dryer was more efficient at heat and air utilization. Graphs
of the moisture content of the product discharged from the dryer show whic
h variables need to be controlled most tightly in practice, and which varia
bles might be successfully manipulated by a control system. This study has
implications not only for the control of various dryer types, but for the p
hysical design of the dryers. The multi-stage fluid bed dryer with re-circu
lation is found to have the best combination of characteristics, and is the
type increasingly used in industry. (C) 2000 Silsoe Research Institute.