Development of Heat and Heat Retention in the Solar Green House Dryer

Solar greenhouse drying is a method of removing moisture from the food material in which drying medium is solar energy which is easily available and low in cost for farmers. The solar energy is decreases in the monsoon months in comparison to non-monsoon months. The decrease in the solar energy results in lower temperatures in the solar greenhouse dryer. The aluminium foil which has 88% reflectivity and black mulch sheet which is best absorber and emitter of heat radiation were used to increase the heat in the solar green house dryer. Different orientations of aluminium foil and black mulch sheet were used. By using both aluminium foil and black mulch sheet, the following treatments were experimented: T1 (control – without modifications), T2 (black mulch sheet on the floor), T3 (combination of aluminium foil on southern wall and black mulch sheet on the floor), T4 (aluminium foil on southern wall), T5 (aluminium foil on three sides of the dryer), T6 (combination of aluminium foil on three sides and black mulch sheet on the floor), T7 (combination of alternate strips of aluminium foil on two opposite sides, aluminium foil on southern wall and black mulch sheet on the floor) and T8 (alternate strips of aluminium foil on two opposite sides and aluminium foil on southern wall). The parameters viz; temperature and relative humidity were recorded in both solar green house dryer and ambient conditions. According to the results, treatment T7 was shown best results in terms of maximum temperature difference and maximum relative humidity difference. Treatment T7 exhibited maximum temperature difference between inside and outside the dryer of 19.5 °C and also maximum relative humidity difference between outside and inside the dryer of 31%.