Design and modeling of dual flow solar air heater in variable absorber plate geometries

This paper presents an experimental and numerical analysis of a dual-flow solar air heater (SAH) with 4 different types of absorber plates: flat, trapezoidal, and ucorrugated parallel and counter flow. The experimental study was conducted in Baghdad, Iraq (33.31ºN, 44.36ºE) and was carried out on different days between April and May 2022. It includes tests conducted under different outdoor weather conditions. The surface azimuth angle was zeroed by positioning the solar collector in a southerly orientation with a tilt angle from the horizontal. For the inlet conditions of the dual-flow SAH, the evaluation was performed using air flow rates ranging from 0.0011, 0.0023, 0.0036, and 0.0046 kg/s. Furthermore, numerical calculations were performed using ANSYS Fluent commercial software to compare the optimum thermal efficiencies of these three types of absorber plates, determine their performance, and validate them by computational fluid dynamics (CFD). The experimental results showed that the thermal efficiencies of solar air heaters with flat, U-groove, and trapezoidal plates were 43%, 51%, and 54%, respectively, at an inlet flow condition of 0.0046 kg/s. However, it was determined that the thermal efficiency of the SAH increased from 51% to 56% when applied for an airflow that is not parallel to the direction of the plate (counter flow). At this flow rate, the average efficiency of the dual-flow SAH with a flat plate was calculated to be 42.80%, 51.33% for a u-corrugated with parallel airflow, 54.38% for a trapezoidal corrugated plate with the reverse flow and 55.53% for a u -corrugated plate with the counter flow. It is concluded that the counter-flow u-corrugated plate heater is the optimum configuration and gives the best results compared to the other plates. A comparison of the simulated numerical calculations and experimental results showed good agreement with an average variation in thermal efficiency of 5.7%. Keywords: Solar Air Heater (SAH), Solar collector, CFD, U -corrugated plate