where T
w
is temperature of the drum surface (8C), T
is
temperature of evaporating surface (8C), L is latent heat
(kJ/kg H
O), and h is an overall heat transfer coefficient
(W m
22
2
8C
21
). The value of h varies between 200 and
2,000 (W m
22
8C
21
), depending on the type and the
thickness of the film being dried.
evp