Thermal-hydraulic performance of longitudinal wavy rib along wavy two-pass channel

An experimental study investigates the thermal-hydraulic characteristics of the novel longitudinal wavy ribs along a wavy two-pass square channel. The detailed Nusselt number (Nu) distributions over the ribbed wavy endwall are measured using the steady-state infrared thermography method together with the Fanning friction factors (f) evaluated from the pressure drop measurements. Relative heat transfer enhancements (HTE) and pressure drop augmentations for present HTE element are disclosed by comparing the Nu and f data measured from the wavy channels with and without wavy ribs, as well as the straight two-pass channels with V- or W-ribs. Acting by the additional HTE mechanisms induced by the wavy ribs, the regionally averaged Nu over inlet leg, sharp bend and outlet leg of present ribbed two-pass wavy channel are respectively raised to 5.8–5.5, 6.04–5.52, 5.81–4.94 and 5.7–5.12 times of Dittus-Boelter levels at 5000 < Re < 30,000. Accompanying with the channel averaged f factors in the range of 43.67–21.43 times of Balssius correlation values, the thermal performance factors (TPF) of 1.51–1.62 are achieved for present ribbed two-pass wavy channel. To assist relevant engineering applications, two set of empirical correlations permitting the evaluations of regionally averaged Nu and the channel averaged f are devised.