Experimental investigation of the performance of the solar tunnel dryer for drying aonla pulp

This article presents the critical design specifications and field performance of an improved solar tunnel dryer for drying aonla plup. The dryer consists of an ultraviolet stabilised semi-transparent polythene sheet of 200-micron thickness with loading capacity of 1 ton of aonla in a batch. Drying of aonla is mainly carried out by traditional method of sun drying, but the use of improved solar tunnel dryer has led to a considerable reduction in drying time and dried aonla of better quality in comparison to aonla dried under the sun or other solar dryer. The results, shown by plotting the variation of air temperature, moisture content, etc. indicate that the dryer performs better with chimneys, exhaust fans, north wall, as they considerably reduce the fluctuations in the drying air temperature with fluctuating solar radiation.