The overall effectiveness of a wet six-row wickless heat pipe-heat exchanger (HPHX) for tropical building HVAC systems was simulated using a computer simulation program. This computer program, utilizing Fortran source code, was developed based on the effectiveness-NTU method together with the ridge model for predicting the film condensation and uses the concept of iteration to predict the temperature distribution across the HPHX and its overall effectiveness. The effects of inclination angle and inlet evaporator relative humidity on heat transfer coefficient for the HPHX were determined using TRNSYS Type98 component. The wet HPHX effectiveness and relative humidity were also studied in this research experimentally. Copyright (C) 2002 John Wiley Sons, Ltd.