AN EXPERIMENTAL AND NUMERICAL STUDY OF HEAT-TRANSFER IN A SIMULATED COLLECTOR FOR A SOLAR DRYER

Indirect passive solar crop dryers have the potential to considerably reduce the losses that presently occur during drying of some crops in many parts of the ''developing'' world. The performance so far achieve d with such dryers has, however, not proved to be very satisfactory. I f this performance is to be improved it is necessary to have an accura te computer model of such dryers to assist in their design. An importa nt element is any dryer model is an accurate equation for the convecti ve heat transfer in the collector. To assist in the development of suc h an equation, an experimental and numerical study of the collector he at transfer has been undertaken. In the experimental study, the collec tor was simulated by a Im long by lm wide channel with a gap of 4 cm b etween the upper and lower surfaces. The lower surface of the channel consisted of an aluminium plate with an electrical heating element, si mulating the solar heating, bonded to its lower surface. Air was blown through this channel at a measured rate and the temperature profiles at various points along the channel were measured using a shielded the rmocouple probe. Local heat transfer rates were then determined from t hese measured temperature profiles. In the numerical study, the parabo lic forms of the governing equations were solved by a forward-marching finite difference procedure.