CFD Modelling and Thermal Performance Evaluation of a Double-Pass Solar Air Collector

This paper conducts a numerical analysis based on computational fluid dynamics (CFD) of a double-pass solar air collector with the help of COMSOL Multiphysics. The collector will have a perforated corrugated absorbent plate and this allows increased turbulence and increased convective heat transfer. The five inlet holes are located below the absorber and air is admitted invrino with the vertical orientation followed by passing through the overheated absorber surface and finally out through the outlet. The simulation is provided with varying values of solar radiation that reflect the actual daytime spatial values which varies between 552-855 W/m2 of solar irradiance. The influence of the velocity of inlet air (0.5 m/s) and inlet temperature (298.15 K) on the thermal performance is considered. Important performance factors including temperature distribution, convective heat transfer coefficient, useful energy gain and the overall thermal efficiency are numerically calculated. A double-pass design improved the outlet air temperature by 10-14 0C, the convective heat transfer coefficient by 22-31 %, and thermal efficiency by 18.4 % over a conventional single-pass collector. The findings indicate that the double-pass system is highly effective in thermal performance than the conventional single-pass systems especially when exposed to changing solar conditions.