Thermo-hydraulic performance of rectangular channel roughened with combined semi-circular and triangular ribs

Ribs of different geometrical shapes are used on the surface for heat transfer enhancement. However, the combination of different shapes of ribs on the heat transfer surface is found less in literature. The objective of the present investigation is to design ribs roughness pattern of semi-circular, triangular, and hybrid ribs (combined semicircular and triangular ribs) on the bottom heated surface of the channel. Then, find optimum configuration and geometry of ribs pattern that has highest thermo-hydraulic performance. This combination of different shape of ribs pattern may be used for cooling of the heated channel such as in gas turbine blade, and high-temperature gas cooled reactors, etc. The rib pitch to rib height ratio (p/e) is considered in the range from 6.6 to 53.3 and Reynolds number in the range from 12,640 to 52,410. Turbulence model used for analysis is shear stress transport (SST) k-ω model. The effect of different geometry and configuration of ribs pattern on Nusselt number and friction factor are investigated and compared with that of the smooth channel. It is found that the Nusselt number (Nu) is maximum at p/e of 13.3 and friction factor (f) is maximum at p/e of 6.6 for all geometry of ribs pattern considered. Furthermore, Thermal enhancement factor (TEF) is determined for all geometry and configurations of ribs pattern. It is found that Thermal enhancement factor is maximum for hybrid ribs (1.34) at p/e of 13.3 and Reynolds number of 12,640 from the geometry and configuration of ribs pattern considered.