CFD analysis of rib roughened solar evacuated tube collector for air heating

Abstract

Using Computational Fluid Dynamics analysis, thermo-hydraulic performance of a rib roughened solar evacuated tube collector has been evaluated for different relative roughness pitch and mass flow rate values. Half portion of absorber tube is roughened and heated uniformly with a heat input of 1000 W/m2. The investigated roughness geometry parameters include relative roughness pitch (P/e) of the order 6–12 whereas relative roughness height is having a fixed value of 0.071. Reynolds number was varied from 2500 to 8000. In contrast to a smooth solar evacuated tube collector, Nusselt number and frictional resistance of a roughened solar evacuated tube collector increased by 1.88 and 2.89 times respectively. Thermo-hydraulic performance parameter of roughened solar evacuated tube collector was found to be 1.36 corresponding to Reynolds number and P/e values of 8000 and 10 respectively which indicates considerable benefit of applying rib roughness in a solar evacuated tube collector.