An Equation to Compute the Heat of Evaporation of Water For Rough Rice During Drying

A semi-theoretical equation expressing the enthalpy of evaporation as a function of moisture content and temperature of rice, was derived from equilibrium moisture content (EMC) and saturated vapor pressure (ps) equations. Values of heat of eveporetion at different moisture contents and temperatures are within the range of those preaented in the literature for rough rice. It is shown that other methods widely used in the past to calculate enthalpies of eva-poration (also called heat of desorption. vaporization or desorption-vaporization) can give erroneous results depending on the form of the EMC equation used to compute values of water vapor preseure in the grain. The method presented in this paper can be applied to cereals and food products other than rice, as long as the appropriate EMC equation is selected.