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The solar air heater (SAH) is a flow device of various forms. The presence of rib turbulators is one of the basic characteristics of heat transfer changes. Two-dimensional numerical simulation of heat transfer provided by a SAH with inclined ribs at different angles (60°, 90°, 120°, 150°, 180°, and 210°) is investigated to determine the optimum angle of the inclined ribs leading to the maximum qualification of the SAH. The model is validated by comparing computed results with experimental data obtained under the same conditions. A good agreement using the standard k-epsilon model is assigned. Additionally, different Reynolds numbers (from 3800 to 18,000) are used to evaluate its effects on Nusselt number and friction factor, providing insights into the optimal operating conditions of the SAH. The design of inclined ribs significantly affects the thermal performance of SAHs. Results indicate that the thermal performance is improved when using an angle of the ribs greater than 90°. Specifically, an angle of 180° for the ribs was found to provide the optimum thermal performance. Results also demonstrate that the optimum angle is 180° for a Reynolds number of 18,000 where the Nusselt number and the friction factor are improved by 25% and 93% respectively, compared to its value obtained for an angle of 90°. The findings revealed the effect of increasing the angle of the inclined ribs on the thermal hydraulic performance parameter that the optimal angle of 180° enhances convection heat transfer and improves the efficiency of the system. The variation of the Reynolds numbers can impact the performance of the SAH, providing useful insights for the optimal operation. [ABSTRACT FROM AUTHOR]

The solar collector has received great interest in many industrial applications. This paper investigates numerically the influence of the absorber shape on the thermal performance of the solar air heat collector. Turbulent 3D air flow is simulated using the turbulence RNG k-epsilon model. The validation of the used model is achieved by comparing the simulated Nusselt numbers to the experimental ones obtained under the same conditions in the case of the simple shape. A good agreement between numerical results and experimental data is obtained. Three other geometric shapes including oval, rectangular, and hexagonal forms of the absorber are also tested. A maximum improvement in the Nusselt number of 36% is obtained using the hexagonal shape of the absorber and a Reynolds number of 12,000. Predicted distributions of temperature, velocity, and pressure are also improved by using the hexagonal shape of the absorber. [ABSTRACT FROM AUTHOR]