Aerothermal performances of two-pass wavy ribbed channels without and with internal effusion at three bypass angles

The detailed Nusselt number distributions, Fanning friction factors, and thermal performance indexes of four two-pass wavy ribbed channels are measured for highlighting the effect of the internal effusion on the aerothermal performance. The modified flow structures by the internal effusion at the bypass angles of 0° or +22.5° considerably alter the Nusselt number distribution from that without effusion. The local and spanwise-average heat transfer performances are respectively dominated by the effusion-rib induced flow phenomena and the local Reynolds number. The area-averaged Nusselt number (Fanning friction factor) ratio between the present two-pass channels with and without effusion is in the respective ranges of 91.39–187.68 (0.21–0.22), 100.43–196.08 (0.17–0.19), and 90.67–143.01 (0.22–0.22) for the bypass angles of 0°, +22.5°, and − 22.5° at the Reynolds numbers between 5000 and 15,000. The corresponding thermal performance indexes for present two-pass channels with the effusion at the bypass angles of 0°, +22.5°, and − 22.5° are 1.74–1.33, 2.07–1.47, and 1.71–1.01. The empirical correlations that evaluate the regional average Nusselt number and Fanning friction factor of the two-pass wavy ribbed channel with and without effusion are generated to assist the relevant applications.