In this paper we present a new model for thermodynamic analysis, in terms of exergy, of a drying process. Exergy efficiencies are derived as functions of heat and mass transfer parameters. An illustrative example is considered to verify the present model and to illustrate the applicability of the model to actual drying processes at different drying air temperatures, specific exergies of drying air, exergy differences of inlet and outlet products, product weights, moisture contents of drying air, and humidity ratios of drying air. As a result, this work is intended not only to demonstrate the usefulness of exergy analysis in thermodynamic assessments of drying processes, but also to provide insights into their performances and efficiencies. It is believed that the present model should be useful to people seeking (i) to optimize the design of drying systems and their components and (ii) to identify appropriate applications and optimal configurations for drying systems. (C) 2003 Elsevier Ltd. All rights reserved.