Study of the performance of double pass solar air heater of a new designed absorber: An experimental work

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An experimental study on the performance of double pass Solar Air Heater (SAH) having a new designed absorber is performed. The new SAH absorber is constructed from conductive aluminum tubes adjacent to each other and installed in the same direction of the air flowing inside the SAH. The new SAH performance (called Tubular Solar Air Heater (TSAH)) is studied at various mass flow rates of air inside the SAH. Moreover, it is compared with the performance of Flat plate Solar Air Heater (FSAH) having the same dimensions and materials of the TSAH except the absorber design. Findings indicate that the TSAH has higher outlet air temperature, efficiency and net energy gain and lower top heat loss compared to FSAH. TSAH achieves maximum air temperature rise more than 6 °C compared to FSAH at 0.025 kg/s. TSAH efficiency is greater than FSAH efficiency by about 19.4%, 21%, and 40.3%, at inlet air flow rate of 0.075 kg/s, 0.05 kg/s and 0.025 kg/s, respectively. The outlet air temperature and top thermal energy loss of the TSAH decrease with increasing the air mass flow rate, while its efficiency, energy output, and pressure drop increase. Moreover, TSAH efficiency in case of double air pass is greater than single air pass. Despite the TSAH pressure drop is greater than FSAH pressure drop, but its value is very small to impact the TSAH net thermal energy gain. The designed TSAH performance is found greater than the performance of FSAH and previous designs of published SAHs.