Optimization of artificial roughness parameters in a solar air heater duct roughened with hybrid ribs

Abstract

The article presents experimental and computational investigation of solar air heater using hybrid configuration of broken arc and staggered rib for heat transfer enhancement. The performance of the solar air heater is investigated through a series of experimental trials by varying flow and geometrical parameters like non-dimensional staggered rib position (0.2–0.8), roughness pitch (4–12), gap width (0.5–2.5), gap position (0.2–0.8), roughness height (0.022–0.043), arc angle (15°-75°), staggered rib piece size (1–6), and Reynolds number(2000–16000). The impact of staggered rib on the fluid flow pattern has been observed using numerical approach based on Finite volume method. The proposed design increases the friction factor & Nusselt number by 2.57 and 3.16 times respectively in comparison with a smooth duct. Moreover, the Nusselt number augments by 1.22 times in comparison with broken arc rib. The optimum values of both the flow and geometric parameters are evaluated and empirical correlations for pressure loss & Nusselt number are also reported. It is concluded that the thermal–hydraulic performance of the proposed hybrid rib roughness (2.33) is found to be superior in comparison with similar rib roughness geometries.