Thermal performance of undulant narrow channel with skewed sinusoidal wall-waves and 45° ribs

This experimental study examines the properties of heat transfer, pressure drop and thermal performance factor (TPF) of a narrow undulant channel enhanced by skew sinusoidal wall-waves and 45° ribs. Detailed Nusselt number (Nu) distributions over the wavy ribbed channel wall are generated by the steady-state infrared thermography method and examined along with the accompanying pressure drop coefficient (f) in the test Reynolds number (Re) range of 800–9000. With references to the Nusselt numbers (Nu∞) and pressure drop coefficients (f∞) of smooth plain tube, the area-averaged heat transfer enhancement (HTE) ratios, pressure drop augmentations (f/f∞) and TPF for the tested undulant channel are compared with those obtained from other passive HTE devices. Empirical correlations evaluating the area-averaged Nusselt number (Nu¯) over the undulant ribbed channel wall and the pressure drop coefficients are generated to assist design activities using this newly devised HTE measure.

► A new HTE measure taking hybrid form of skewed wall-waves and 45° ribs is devised. ► Detailed Nu distributions over undulant ribbed wall at 800⩽Re⩽9000 are measured. ► Thermal performances between wavy-ribbed, wavy and ribbed channels are cross examined. ► Synergetic wall-wave and rib induced flows further elevate HTE form wavy or ribbed channels. ► High HTE impacts at TPF above unity justify this HTE measure as effective and efficient.