Experimental Investigations on Thermal Storage in a Solar Dryer

S. Krishnan, B. Sivaraman


Thermal energy storage for solar dryer has recently attracted increasing interest as the availability of solar energy is intermittent. The effectiveness of thermal energy storage using Phase Change Material (PCM) in solar dryer application was investigated in this work. A solar cabinet dryer having 3 evenly spaced trays that provide maximum heat flow with drying area of 0.5 m2(each)that caters to a family was constructed and its performance evaluated. The experiments were done on the dryer with and without thermal storage for 3 days each during the month of April when the sunshine remains considerable in Annamalai Nagar located at 11.39° N Latitude and 79.69° E Longitude. The temperature at different vital locations was recorded from 10 a.m. onwards until the cabinet temperature fell to that of the atmosphere. The mass flow rate of air during experimentation varied between 0.001-0.003 kg/s. A paraffin (n-docosane)-kerosene composite of 12.5 kg and 2:1 mass ratio was used for thermal storage in the dryer. The PCM was filled in 20 numbers of 20 mm diameter aluminum tubes having 500 mm length and 100 aluminum cans of 150 ml capacity (excluding space for phase change). The results were analysed for the variation of thermal absorption and storage based on air velocity, temperature gradient, and solar intensity. The cabinet temperature remained 25-30°C higher than that of atmosphere during mid-day.  The peak heat gain fell by 18% on the days of experimentation with thermal storage due to the heat conducted by PCM pipes. On an average, the thermal efficiency of the system with thermal storage improves by 50 % of its efficiency without thermal storage unit. It was found that the dryer with thermal storage can sustain the required temperature for 3 hours after  sunshine hours and then it falls gradually. 


n-docosane; paraffin; phase change material; solar cabinet dryer; thermal energy storage

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