Mathematical Drying Model of Drying System
In the model of this work, development of the mathematical
drying model was based on a near-equilibrium
drying model similar to some previously published
works[7,9,13] and the crumb rubber bed was composed of
series of thin layers. For a given thin layer, the energy
equation is derived based on the first law of thermodynamics
by assuming that heat loss is very small and can
be negligible. Thus, the temperatures of hot air and crumb
rubber at each thin-layer bed are in thermal equilibrium at
a small time interval. The major assumption was that there
exists thermal equilibrium between grain and drying air
and the outlet drying air condition from the first thin layer
is used as the input drying air condition for the next layer
and the same calculation procedure is made for all thin
layers with advancing time step. In addition, the moisture
is transferred by liquid diffusion and the shrinkage is
negligible during drying. The main equations of the model
are listed as follows