Vacuum contact drying of monohydrate lactose and potassium chloride packed beds were experimentally investigated and numerically simulated. The classical "vaporization front" model was improved to correctly represent the experimental drying rate data. The main model modification consisted of introducing linear variation in solvent content at the vaporization front as opposed to classical modeling where this parameter was assumed constant. The new model, as applied to the falling rate drying period, involved only one fitting parameter. The validation experiments were conducted with a laboratory vacuum contact dryer. (C) 2006 Elsevier B.V. All rights reserved.