A compact desiccant-evaporative HMX (heat and mass exchanger) has been proposed by combining the benefits of the regenerative indirect evaporative cooling and the liquid desiccant dehumidification. In this design, the compact HMX was able to cool and dehumidify the product air simultaneously in a single unit. A computational model has been developed and validated using experimental data. The model displayed good agreement with the experimental findings with maximum discrepancy of 8%. The heat and mass transfer behavior was theoretically investigated to illustrate the detailed air treatment performance of the HMX. Simulations were performed to study the effect of several key parameters on the HMX's performance. Due to the effect of pre-cooling and pre-dehumidification, the working air showed improved cooling potential in the working channel. Consequently, the temperature of the product air could be reduced below the dew-point temperature of intake air. Simulation results showed that the outlet temperature of the product air was affected by the working-to-intake air flow rate ratio and the dimensionless channel length, while the outlet humidity ratio of the product air was influenced by the length of the liquid desiccant film and the dimensionless channel length. (C) 2015 Elsevier Ltd. All rights reserved.