Augmented heat transfer in a triangular duct by using multiple swirling jets

Measurements of derailed heat transfer coefficients on two principal walls of a triangular duct with a swirling flow are undertaken by using a transie nt liquid crystal technique. The vertex corners of the triangular duct are 45, 45, and 90 deg. The swirl-motioned airflow is induced by an array of ta ngential jets on the side entries. The effects of flow Reynolds number (860 0 less than or equal to Re less than or equal to 21000) and the jet inlet a ngle (alpha = 75, 45, and 30 deg) ave examined. Flow visualization by using smoke injection is conducted for better understanding the complicated flow phenomena in the swirling-flow channel. Results show that the heat transfe r for alpha = 75 deg is enhanced mainly by the wall jets as well as the imp inging jets; while the mechanisms of heat heat transfer enhancement for alp ha = 45 and 30 deg could be characterized as the swirling-flow cooling. On the bottom wall, jets at a = 75 deg produce the best wall-averaged heat tra nsfer due to the strongest wall-jet effect among the three angles (alpha) i nvestigated On the target wall, however, the heat transfer enhancements by swirling flow (alpha = 45 and 30 deg) are slightly higher than those by imp inging jets (alpha = 75 deg). Correlations for wall-averaged Nusselt number Sor the bottom and target walls of the triangular duct are developed in te rms of the flow Reynolds number for different jet inlet angles.