A comparative study of helical and spiral flow paths in solar air heaters: Experimental testing and CFD modeling

This study conducted a comparative analysis of Solar Air Heaters (SAHs) with Spiral and Helical flow paths. It evaluates their thermal performance and pressure drop, providing new insights for SAH design and optimization. The prototypes were constructed and tested at the Mechanical Modelling, Energy & Materials (M2EM) Laboratory in Gabes, Tunisia. A numerical model was developed using ANSYS Fluent 2021 R1. The mesh independence was analyzed to ensure accuracy of the numerical results. The results demonstrated excellent agreement between numerical and experimental data, with an average deviation of 4.5 %. The experimental results indicated that the maximum air temperature attained 76.2 degrees C and 72 degrees C for the HSAH and the SSAH, respectively at a mass flow rate of 0.01 kg/s. The numerical results showed an increase in air temperature of 62 degrees C and 59.4 degrees C for the HSAH and SSAH, respectively, at a mass flow rate of 0.005 kg/s. At higher flow rates, both systems exhibited closer air temperature. Pressure loss analysis showed that the HSAH incurred higher losses (1797.7 Pa) compared to the SSAH (927 Pa) at a mass flow rate of 0.03 kg/s. Consequently, the pumping power was 22 W and 44 W for the SSAH and the HSAH, respectively. In addition, the thermal efficiencies of the two systems became identical at higher flow rates and reached 65 % at a mass flow rate of 0.03 kg/s. Therefore, this study highlights the superiority of the spiral flow path design in terms of thermal efficiency and lower pressure losses compared to the helical configuration.