Rotary dryers are widely utilized for drying granular materials through direct contact with hot gas. Developing a one-dimensional mathematical model for such a dryer requires the application of principles from thermodynamics, heat transfer, and mass transfer. In this study, the rotary dryer was segmented transversally into small control volumes, with fixed dimensions throughout the drying process. Heat and mass balance equations were applied to each control volume, and the system was solved using MATLAB Simulink. The model provided detailed insights into the material temperature, drying air temperature, material moisture content, and the relative humidity of the drying air at various axial locations. The results were validated using an industrial coir pith drying rotary dryer developed by the National Engineering Research and Development Centre (NERDC). The simulation yielded an R2 value above 0.8, demonstrating its reliability for optimizing processing parameters and improving industrial rotary drying processes to enhance product quality and production rates.