Heat transfer characteristics in U-shaped rib-roughened channel at high rotation numbers

To match the rotor blade of real engine operating condition, the Reynolds and rotation number range of current experiment were expanded from 10 000 to 70 000 and 0 to 2.08 by increasing the pressure of the air in the U-shaped channel to 500 kPa. Experiments were conducted to investigate the heat transfer characteristics in a square U-shaped channel with inclined 45 deg ribs. Results indicated that, in the first passage of the U-shaped channel, heat transfer coefficient of leading wall firstly decreased with the increase of the rotation number, then increased with the rotation number after reaching a critical value; in the second passage of the U-shaped channel, the difference of heat transfer coefficient between leading and trailing walls was not obvious at low rotation number, but kept increasing with the rotation number to a higher level; the heat transfer of leading wall behaved better than trailing wall, which was totally different from that of a smooth channel.