Experimental investigations of thermal performance for flat and dimpled plate solar air heater under turbulent flow conditions

Conversion of solar energy into useful thermal energy through solar air heaters (SAH) enhances the practical application of the available solar energy. A comparative thermal analysis of two SAH's having different absorber plates is elucidated here. Experiments were conducted on a flat plate solar air heater (FPSAH) as well as on dimpled plate solar air heater (DPSAH) during bright and sunny days from 0930 am to 1430 pm at IIT (ISM) Dhanbad on six different days for six different flow rates between 0.028 kg /sec to 0.051 kg /sec (i.e. Re value = 5500 to 10300). For these two SAH's, different parameters and thermal properties were evaluated and compared. Quantitively, it is shown that the temperature difference, average extracted power, heat transfer coefficient, instantaneous efficiency and the effective efficiency of the DPSAH is higher than the FPSAH. Subsequently, it has been also observed that, the rise in effective efficiency of DPSAH at higher mass flow rates (MFR) is not significant; hence it is less suitable for high flow rate operations.