Performance evaluation of forced convection desiccant bed solar dryer integrated with sensible heat storage material

This paper reports a new type of forced convection indirect type solar dryer setup fabricated in Nagpur, India and its performance was studied. The main objective of the present study was to incorporate new drying technology and develop a solar dryer that could function effectively for few more extra hours even after the sunset. Thus a forced convection indirect type solar dryer integrated with heat storage material (Gravel) & desiccant beds (Silica Gel) was developed. In forced convection solar dryer with heat storage material, the grapes were dried from an initial moisture content of 80% to the final moisture content of 20% in about 78 hours, while it took only about 57 hours in the forced convection solar dryer with heat storage and desiccant beds to reach the required moisture content. Due to the use of heat storage material, the temperatures inside the solar dryer remains 3-5°C higher than the ambient temperature even during off sunshine hours. Also, the heat storage regulates the temperature of the collector outlet during uneven climatic conditions. The maximum temperature attainedby air inside the dryer cabinet was 78°C. The desiccant beds can be regenerated in about 5 hours during a normal day and removes the moisture from the products even during the night. The air flow rate in both the cases was maintained at 0.026 kg/s. The quality of the grapes obtained from the solar dryer was excellent with proper coloring and taste as compared to those dried directly under the sun.