This paper describes the application of the Effectiveness (ε)-NTU method of heat exchanger design, a well established and relatively simple design procedure, to packed beds where simultaneous heat and mass transfer processes occur. The method, also used for cooling tower design, is extended easily to packed bed liquid desiccant dehumidifiers. Computations indicate that at the operating ranges normally encountered in dehumidifiers, the ε-NTU method yields results that are in consonance with those obtained using more rigorous and well established but time consuming methods. The model also compares satisfactorily with the limited experimental data available.