Dehumidifier is one of the essential components in liquid desiccant air-conditioning system, whose hourly performance is required to predict the annual energy consumption of the system. Model complexity and the required amount of computer time usually do not permit the use of models based on a differential element. In order to estimate the hour-by-hour performance of dehumidifier, a simplified approach is proposed in the present study, in which enthalpy and moisture effectiveness are adopted as indexes to describe the heat and mass transfer performances of the dehumidifier. Empirical correlations of enthalpy and moisture effectiveness are expressed by enthalpy difference, moisture difference, air and desiccant flow rate, based on corresponding experimental results. Empirical correlations are given for a cross-flow packed dehumidifier, the average absolute differences between the calculated values and the experimental findings are 6.3% and 6.0% for enthalpy effectiveness and moisture effectiveness, respectively, with discrepancies mainly within 20%. Good agreements are also shown for counter-flow dehumidifiers available in literatures. (c) 2005 Elsevier Ltd. All rights reserved.