DETERMINATION OF HEAT AND MASS-TRANSFER COEFFICIENTS IN THIN-LAYER DRYING OF GRAIN

Five models simulating the process of simultaneous heat and mass transfer in the drying of a layer of barley are formulated. By using the inverse method, the transfer coefficients for all five models are estimated from measured values of instantaneous surface temperature and average moisture content. A finite element method is used to solve the nonlinear coupled system of two partial differential equations modeling the drying process. It is concluded that the mass transfer coefficient is 1.08 x 10(-6) ms-1 for all five models, and that this number is much smaller than that calculated from the Lewis relation. The heat transfer coefficient is found to vary from 43 to 59 Wm-2 K-1, depending on the form of the drying model.