Pressure drop and heat transfer performance in a rotating two-pass channel with staggered 45-deg ribs

A rotating two-pass ribbed square channel is applied to perform the pressure drop and heat transfer study. The inlet Reynolds number and rotation number vary from 20,000 to 60,000, and 0 to 1.02, respectively. The regional heat transfer coefficients are obtained by heated cooper plate technique. The rotational pressure drops are measured by the rotation-to-stationary pressure measurement system. The ribs with attack angle of 45-deg are staggered roughened on leading and trailing walls. Due to only one wall-temperature ratio was performed in current study, the isolated buoyancy effect was not able to be disclosed. The results show that the 45-deg ribs bring 40-80% higher heat transfer for ribbed walls and 15-65% for smooth walls. The rib-to-smooth Nu ratio declines with Reynolds number and is more sensible in the second passage. Meanwhile, 150-210% higher pressure drop in ribbed channel is observed compared to smooth one, but this penalty decreases with Reynolds number. Rotation presents more dominant influences on pressure drop in heated channel than unheated one. But rotation-to-stationary friction factors decrease with rotation number for both heated and unheated channel as Ro < 0.55, after which an increase trend is observed. The presence of buoyancy effect in heated channel helps to promotes rotational pressure drop variation. Also, ribbed-to-smooth thermal performance is significantly elevated by rotation when rotation number reaches over 0.25. The surface averaged heat transfer coefficients are developed with respect to buoyancy parameters. (C) 2017 Elsevier Ltd. All rights reserved.