STUDY OF THE FOOD CROP DRYING PROCESS BY USING PHASE CHANGE MATERIAL(PCM) SOLAR COLLECTOR MASTER OF SCIENCE IN ENERGY TECHNOLOGY

Abstract

Solar dryers are a sustainable and cost-effective alternative to traditional drying methods for various food items. The basic components of a solar dryer include a solar collector, a hot air circulation system, and a drying chamber. The solar collector absorbs and converts solar radiation into thermal energy, which is used to heat the air that circulates through the drying chamber. Three types of solar collectors have been used in this research experimental solar crop dryer. They are Copper plate, Aluminum plate and Galvanized iron sheet coated with black paint for maximizing solar heat absorption. The size of three plates are 1m2 and thickness is 1mm. Three types of food crops potato, normal paddy and boil paddy (each 500gm) were dried in solar dryer and in open sun at the same time. The product dries faster in solar dryer when Copper plate uses as a solar collector. This happens due to the thermal conductivity of copper plates is higher than aluminum and galvanized iron sheet. Open sun drying took 1.5 hours longer to dry than using the experimental solar dryer. The air circulation system helps to distribute the heated air evenly around the food material, promoting efficient drying. The solar dryer was operated at four air velocity 1.8m/s, 2.2m/s, 2.5m/s and 2.7 m/s. Crops dry faster at 2.5 m/s velocity because they can absorb better moisture. At 2.5 m/s air velocity in the experimental solar dryer dry potato, normal paddy and boil paddy (each 500gm) take drying time of 1.5 hours,1.5 hours and 1 hour which is shorter drying time than open sun drying. Paraffin waxes are used as a phase change material(PCM) (100gm/m2,200gm/m2, 300gm/m2 and 400 gm/m2) in this research experiment. When 300 gm/m2 phase change material (PCM) is used as a heat storage medium then it took the least drying time than other amounts of phase change material (PCM). Experimental solar dryer using 300gm/m2 PCM as heat storage in copper plate collector, potato, normal paddy and boil paddy (each 500 gm) take drying time 2 hours ,2 hours and 1.5 hours respectively which is shorter drying time than open sun drying. The maximum collector efficiency of copper plate solar collector and with PCM were found 21% and 25% respectively which is higher than aluminum plate solar collector (18%) and with PCM (21%) respectively. The highest drying efficiency with copper plate solar collector and with PCM were determined to be 8.5% and 14.4%, respectively, which is greater than aluminum plate solar collector (7%) and with PCM (12.9%) respectively. The co-relation among the drying chamber temperature, absorber plate temperature, and solar intensity is (Fdct) = 36.49229+0.012944tAPT -0.05424 Si and the co-relation v among drying time, amount of PCM, air velocity and drying chamber temperature(0C) is (Fdt)=7.9375-0.008125WPCM+2.51Av+0.3125Tdtem. Proximate analysis (Moisture, Protein, Crude Fiber (CF), Crude Fat (EF), Ash) is done to check the quality of the product. The value of proximate analysis was found to be better in dryer than open sun. Pearson’s Correlation coefficient was found within the range (0.76-0.98) for all cases. PCM-based solar dryers use materials that can store and release large amounts of thermal heat energy during the phase change, providing a stable and consistent drying temperature and humidity even in variable weather conditions. Additionally, PCM can be used to store excess thermal heat energy generated during peak sunlight hours, which can be released later to maintain the drying temperature during periods of low sunlight.