Heat transfer and pressure drop in two-pass rib-roughened square channels with bleed from sharp bend

This experimental study investigates the heat transfer, pressure drop and thermal performance factor for the two-pass rib-roughened channel with and without bleed from its sharp bend. Detailed distributions of Nusselt number (Nu) and dimensionless wall temperature (ηw) over the rib floor with coolant extractions from three different locations on the outer wall of the sharp bend at 0%, 10%, 20%, 30% of the total airflow rate are comparatively analyzed with 5000 < Re < 25,000. Area-averaged Nu and pressure drop coefficients (f) for the entire two-pass ribbed channel with and without bleed are generated with thermal performance factors (η) compared. The bleed from the outer wall of the sharp bend provides considerable heat transfer enhancements (HTE) over the turning section with substantial reductions in pressure drops; while undermines both Nu and ηw performances in the outlet-leg from the no-bleed conditions. Thermal performance factors for the bleed channel at each Re and bleed condition tested are improved from the no-bleed references. Empirical Nu and f correlations are derived for the present two-pass rib-roughened square channel with and without bleed.