A Model for Indian Standard Kiln Drying Schedules for Timber Based on Diffusion Theory of Drying

Regressions of the form t-t_w + 5 = a/u_m + bU_m akin to the equation of the drying schedUle derived from the diffusion theory of drying, could be fitted to Indian Standard schedules I to VII of IS: 1141-1973 with high degree of correlation, indicating that these empirically evolved schedules by and large conform to the diffusion theory of drying. Values of the drying intensity parameter β derived from constants 'a' for the different schedules were found to be strongly correlated to the group mean basic density of the species falling under different schedules : β = .5954 + .5787 (1/ρ)- .1055 (lρ)². It was Indicated that in general heavier timbers would call for milder drying schedules, though significant deviations from this trend should be expected in case of individual species on account of differences in physical properties other than basic density that influence moisture movement and drying degrade.