Heat Transfer and Friction in a Square Channel with Ribs and Grooves

Turbulence promoters have been widely applied to enhance heat transfer in internal flow channels, although they cause pressure loss. This study employed the transient liquid-crystal technique to measure the heat transfer distribution in a square channel with compound turbulence promoters with orthogonal (90deg), continuous angled (45deg), discrete angled (45deg), V-shaped, and inverted-V-shaped rib configurations. The rib height-to-hydraulic diameter ratio (e/Dh) and the rib pitch-to-height ratio (P/e) were 0.1 and 8, respectively. Variations in the Nusselt number were observed after adding grooves between the ribs. The Reynolds number tested in this study ranged from 15,000 to 35,000. Adding grooves between the ribs enhanced the heat transfer. The convective heat transfer coefficient increased by up to 40%, whereas the friction factor ratio increased by less than 30%. The discrete angled configuration of grooved ribs exhibited the maximal heat transfer enhancement and thermal performance, whereas the orthogonal configuration attained the minimal heat transfer enhancement and thermal performance. The frictional loss of the V-shaped and inverted-V-shaped configurations was higher than that of the continuous or discrete arrangements for both ribs-only and ribbed-grooved configurations.