The feasibility of cool storage using dimethyl-sulfoxide as a phase change material (PCM) in a rectangular enclosure was investigated. The temperature distribution in the PCM and the inlet and outlet temperatures of the flowing air were measured with time. The two-dimensional unsteady heat conduction equation was solved numerically to predict the temperature distribution in both phases of the PCM. The effect of the latent heat of melting was included by using an effective heat capacity that includes the latent heat. The agreement was good between the model prediction and the experimentally measured temperatures for both the PCM side and the air side. The experimental results indicate that, for nearly 5 h of heat discharge (cool storage), the corresponding time for heat charge was only 2.5 h, due to the effect of convection in the PCM.