A mathematical model has been proposed to simulate unsteady state simultaneous heat and mass transfer in an aggregative fluidized bed of porous particles. An implicit finite difference method is being used to solve the partial differential equations describing the model. A computer program is written for solving the model and by using this program the effect of mass transfer on heat transfer has been studied by comparing two examples in a fluidized bed of silica-gel particles. In the first example the simultaneous heat and mass transfer is considered by measuring the rate of gas drying and also rate of heat transfer between gas and solid particles. In the second example heat transfer without mass transfer is considered by measuring heat exchange between gas and solid particles. For testing the proposed model the experimental results obtained by a pilot scaled fluidized bed were compared with those predicted by the model. A good agreement has been observed between the results.