To match the rotor blade of real engine operating condition

the Reynolds and rotation number range of current experiment were expanded from 10000 to 70000 and 0 to 2.08 by increasing the pressure of the air in the U-shaped channel to 500kPa. 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.