Pressure drop and heat transfer in rotating smooth square U-duct under high rotation numbers

The experimental results show that the rotating-to-stationary ratios of these three parameters correlate with Rotation number in a very good way. In general, Nusselt number ratio increases linearly with Rotation number, but the friction ratio is oscillating when Rotation number increases. More detailed analysis of rotation effects on heat transfer shows that rotation has most dominate effects on averaged Nusselt number at the sharp turn compared with two straight passages by reinforcing the impingements over there. Due to the influence of sharp turn, rotation effects in second passage become dominant at high Rotation numbers. The friction ratio data suggest that the rotation has more apparent effects on friction ratio in heated channel than unheated channel. The Buoyancy force plays a very important role in channel's friction factor. Generally, it reduces the friction resistance in a smooth U-duct especially at high Rotation numbers.