Solid desiccant air dehumidifier system is widely being used to supply dry air for many industrial processes. As humid atmospheric air flows through the system, the water vapor in the air is adsorbed by the desiccant material, resulting in dry air leaving the system. The performance of the system is usually determined through experimental work. However, this practice is often complex to carry as it requires precise measuring instruments, time consuming and it can be labor intensive too. A numerical solution has become a preferred choice to determine the performance of the system. The goal of this work is to determine the moisture removal capacity (MRC), thermal effectiveness (ϵth) and dehumidification effectiveness (ϵDW) of a solid desiccant wheel of an air dehumidifier system by a validated numerical method. A representative two-dimensional model of the air channel was developed and meshed using triangular elements. Flow simulations were carried out under a transient condition. The numerical model was validated by comparing the simulation results at the outlet of the air channel with similar results of experimental data obtained from the literature. The relative errors were found to be about 1.05% for air temperature and 8% for air humidity, indicating that the numerical model has a good capability of estimating the desiccant material performance. It was also found that the MRC, ϵDW and ϵth are about 22 g/s, 76% and 43% respectively.