Experimental study on the performance of spiral solar air heater

A new type of solar air heaters was proposed by using the spiral shape of spoilers instead of the serpentine shape. The function of the spiral solar air heaters (SSAH), including heat collection efficiency, temperature differences between inlet and outlet, irradiance, and air volume were experimentally studied in this paper. According to the testing, the difference of temperature between inlet and outlet is related linearly to irradiation, and heat collection efficiency is related the quadratic function relationship to irradiation with a constant flux. Finally, the heat loss coefficient of the SSAH is determined by the normalized temperature to be 5.69 W m⁻² K⁻¹. Compared with the conventional and serpentine SAH, this kind of solar air heaters had a higher heat collection efficiency.