Experimental and numerical investigation of solar air heater with novel V-rib geometry

摘要

Providing artificial roughness on the absorber surface is one of the most efficient heat transfer enhancement technique employed in the design of solar air heater (SAH) duct. This paper presents experimental analysis of SAH duct with novel V-rib roughness geometry. The investigated parameters are ratio of rib pitch to height (p/e) of 6, 8, 10, 12 and 14, ratio of rib height to hydraulic diameter (e/D-h) of 0.043, flow angle of attack (alpha) of 60 degrees, ratio of staggered rib pitch to pitch (p'/p) of 0.4, ratio of staggered rib size to rib height (r/e) of 4, ratio of gap width to rib height (g/e) of 4, relative gap position of gap in each symmetrical element (d/w) of 0.65, relative gap width of additional gap in each symmetrical element (g'/e) of 1, number of main gaps (N-g) of 3, number of additional gap (n(g)) of 4 and Reynolds number (Re) in the range of 4000-14500. The maximum augmentation in Nu take place at p/e of 10 while maximum increment in f take place at p/e of 8 as compared to smooth surface. The thermo-hydraulic performance parameter (THPP) is obtained maximum at p/e of 10 and Re of 12,364. Correlations have been developed for heat transfer and friction factor. Experimental data has been used to validate the mathematical model, which uses for SAH duct design and prediction of performance under different operating condition.