Performance enhancement of solar air heater with two-sided curvilinear transverse rib: Experimental and numerical investigation

Abstract

Solar energy as prime energy source draws attention of world due to its availability and eco-friendliness. Low performance of solar air heater create curiosity for researchers to increase its performance. To enhance performance of solar air heater active and passive techniques used by researcher. Surface modification is one of the most prominent passive techniques to improve the performance. Present experimental and numerical investigation explore thermal characteristics of two-sided curvilinear rib roughened solar air heater. An indoor experiment was performed on two side curvilinear rib roughened absorber plate having constant heat flux of 1000 W/m2. Parallelly 2-dimensional numerical simulation was also performed to explore flow behavior and to complete investigation within optimum cost. ANSYS Fluent 2021.R was used for performing this simulation with K-ε RNG model with enhanced wall treatment. Velocity inlet and pressure outlet was selected as boundary condition. Main roughness and flow parameters were relative roughness height ( e/ D h = 0.21–0.042), relative roughness pitch ( p/ e = 7.14–35.71), and Reynolds number ( Re = 3800–18,000). Maximum value of Nusselt number improvement ratio and friction factor improvement ratio was 3.17 and 3.26 at roughness and flow parameter of ( e/ D h = 0.042, p/ e = 15, Re = 15,000) and ( e/ D h = 0.042, p/ e = 7.14, Re = 3800) respectively. Thermohydraulic performance parameter achieved its maximum value of 2.77 at e/ D h = 0.042, p/ e = 17.85, and Re = 18,000.