Heat transfer in two-pass smooth square channel under large rotation numbers

The rotation number range was expanded significantly through increasing the absolute pressure of the channel to about 5 atm. Experiments were carried out to investigate heat transfers in a smooth square two-pass channel under large rotation numbers. In current study, Reynolds and rotation number range from 10 000 to 70 000 and zero to 2.08 respectively, which covered the real engine parameters. It is found that when the rotation number is large enough, the effect of rotation dominates the heat transfer at the inlet and the turn portion, instead of the entrance effect and the turn effect. As the channel rotated, the Nusselt number of the first pass was found to increase monotonically on the trailing wall, however to increase on the middle and downstream of leading wall exceeding certain critical rotation numbers. And a new phenomena is found in the downstream of the second pass, which is that the heat transfer on trailing surface exceeds the leading surface at high rotation numbers.