Effects of rib-configuration on the thermal performance of one-sided heated, rib-roughened cooling channels

Abstract

Detached-Eddy-Simulations (DES) were performed for investigating the thermal-hydraulics of a one-sided heated and rib-roughened cooling channel at Reynolds numbers ranging from 2.5·104 to 1.58·105. Heat transfer and flow characteristics for three different types of centrally positioned, transversally oriented rib-elements with a rib-height and rib-top-width of e and (a) 90 deg. edged, (b) 2 e radius round-edged or (c) 30 deg. inclined front- and rear-rib-surface haven been analyzed. The channel cross section was 15 e x 15 e with 2 e inside radiuses, the rib-pitch-to-rib-height-ratio was p/e = 10 and the rib-heightto- hydraulic-diameter-ratio was e/Dh = 0.0638. For all simulations, friction factors decrease and heat transfer coefficients increase for increasing Reynolds numbers. For varying rib-shapes, the averaged friction factor ratios differ up to 30 pct. and the Nusslet Numbers at the rib-roughened and the overall Nusselt Numbers differ up to 12 pct. and 8 pct., respectively. Maximum flow resistance and heat transfer occur for the 90 deg. edged rib-configuration. For all rib-shapes, the thermal performance factor (of increased heat conductance and equal pumping power) for cooling the rib-roughened wall decreases for increasing Reynolds numbers. Best thermal performance was obtained for the 90 deg. edged ribconfiguration. Correlations for Nusselt number and average friction factor prediction were derived for the entire Reynolds number range.