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In this paper a mathematical model for simulation of natural convection in a solar dryer which consists of solar collector, drying enclosure and the chimney has been investigated. The temperatures along the solar collector as well as drying enclosure were obtained by numerical solution of intercoupled momentum and energy equations. The variation of the air temperature in the collector and across the drying enclosure is incorporated in the prediction of the thermal buoyancy effect. The results show that with in creasing the collector length the air temperature at the exit of collector is increased. The latter decreased while the chimney height increased. It is found that the mass flow rate of air is described by collector length and chimney height. The air temperature along the dryer enclosure has been measured and is compared with numerical solution results. The agreement between experimental and numerical results are quite satisfactory.