Energy and exergy analysis of a solar air heater which located in different types of obstacles on the absorbing plate

Solar air heaters are simple device to heat air by utilizing solar energy and employed in many applications requiring low to moderate temperature below 60ºC, such as crop drying and space heating. In a solar air heater, the fins or obstacles located in flow area increases the heat transfer coefficient and output temperature of air. Accordingly, collector efficiency increases too.This paper presents an experimental energy and exergy analysis for a new flat plate solar air heater (SAH) with several obstacles (Type I, Type II and Type III) and without obstacles (Type VI). The measured parameters were the inlet and outlet temperatures, the absorbing plate temperatures, the ambient temperature, and the solar radiation. Further, the measurements were performed at different values of mass flow rate of air (0.0074, 0.0052, 0.0016 kg/s). Solar air heater having free (Tip IV) and fixed obstacles (Tip I, Tip II, Tip III) is compared to flat-plate solar air heater as well as each other in terms of energy and exergy efficiencies and dimensionless exergy loss ratio.After the analysis of the results, the optimal values of efficiencies (energy and exergy) is Type II of absorbing plate in flow channel duct for all operating conditions and solar air heater (SAH) supplied with obstacles appears significantly better than that without obstacles (Type IV). The results show that the largest irreversibility is occurring at the flat plate (without obstacles, Type IV) collector in which collector efficiency is smallest. At the end of this study, the energy and exergy relations are delivered for different SAHs.