A Comprehensive Analysis of Double-Pass Counter Flow V-Groove Solar Air Collector Performance for Drying Applications

The economic viability of solar drying mainly depends on the appropriate design of air collectors, which are the main parts of a solar dryer. Although the V-groove collector has been reported to have one of the highest efficiencies, no comprehensive parameter analysis on this collector has been reported in the literature. This detailed study investigates the influence of different operating and design variables on the outlet temperature and the efficiency of the air collector. The parameter analysis also contributed to the development of the most effective design guidelines. The parameters examined include solar radiation, airflow rate, incoming air temperature, collector length, height of the vee, the spacing between the top of the vee and the transparent cover, number of such covers, and the thickness of the back insulation. The airflow rate is identified to be the essential operating parameter that affects the efficiency, and a better heat transfer rate is noticed in the intermediate flow state. It is also found that to achieve the best performance, it is necessary to maintain a mass airflow rate between 0.015 and 0.055 kg/m2s, to have incoming air at a near-atmospheric temperature, and to have two transparent covers on top.