Design, development and optimization of baffles and corrugated type solar air collectors for drying applications

Agriculture has a vital role in the Pakistan's economy. For value addition and to overcome the food security problem crops are dried to increase their shelf life. Drying is an energy intensive process. Now a day there has been a growing trend in adapting solar air heaters for purpose of drying. Solar energy is used by the solar air heaters to heat air and then this heated air is used in many applications requiring moderate to low temperature. In Pakistan mean global irradiation ranges between 200-250Wm-2 per day. It is equal to 1.500-3,000 sunshine hours. Pakistan is receiving on an average 5.3 kWh m-2 per day. To harness this solar energy potential two laboratory scale solar air collectors baffle and corrugated type were designed, developed and evaluated in this study. Performances of the collectors were analyzed by measuring different parameters under different environmental conditions. For the optimization of the collectors to simulation was carried out by using computational Fluid dynamics model. First of all simulation of both the collectors on Solid Works were carried out and there was net difference of 7.05 degree C at outlet was measured. The average outlet temperature of baffle collector at air velocity of 5m/s, 8m/s and 11.5 m/s was observed as 57.13 degree C, 70.91 degree C and 70.23 degree C respectively and mean temperature difference between inlet and outlet was observed as 20.06 degree C, 32.06 degree C and 31.97 degree C respectively. The average outlet temperature of corrugated solar collector at air velocity of 5m/s, 8m/s and 11.5 m/s was observed as 64.87 degree C, 66.45 degree C and 63.98 degree C respectively and mean temperature difference between inlet and outlet was observed as 27.81 degree C, 27.60 degree C and 25.73 degree C respectively. It was also depicted from the results that efficiency of the collector has a direct relation with the velocity of air passing through the collector. The mean efficiency of baffle collector at air velocity of 5m/s, 8m/s and 11.5m/s was observed as 32.71%, 35.97% and 62.86% respectively and the mean efficiency at same flow rate in corrugated collector was observed as 29.62%, 30.96% and 50.60% respectively. Results show that baffle solar air collector was more efficient as compared to corrugated air collector in terms of their thermal efficiency.