Heat transfer measurements in a rotating equilateral triangular channel with various rib arrangements

The present research investigates the heat transfer characteristics in an equilateral triangular channel to simulate the leading edge cooling passage of a gas turbine blade. The experiments are conducted for the stationary and rotating ribbed channel with three different attack angles (45 degrees, 90 degrees and 135 degrees). Square ribs are installed in a staggered manner on the pressure and suction side surfaces of the channel. The rib height to channel hydraulic diameter ratio (e/D-h) is 0.079 and the rib-to-rib pitch (p) is 8 times of the rib height. To measure regional-averaged heat transfer coefficients in the channel, two rows of copper blocks with heaters are installed on each surface. The rotation number ranges from 0.0 to 0.1 for the fixed Reynolds number of 10,000. Inlet coolant-to-surface density ratio is about 0.2. For the channel with 90 degrees ribs, the heat transfer rates of all regions have similar values for stationary case. However, for the rotating channel, heat transfer coefficients on the pressure side surface are significantly increased while the suction side surface has quite low heat transfer coefficients due to a single rotating secondary flow induced by Coriolis force. For the channel with angled rib arrangements, a pair of counter-rotating vortices is induced by the angled rib arrangements. High heat transfer coefficients are obtained on the regions near the inner wall for 45 degrees angled ribbed channel and near the leading edge for the 135 degrees angled ribbed channel. The heat transfer coefficients in rotating channel with angled ribs are almost the same as those of stationary case for the tested conditions because the secondary flow dominates the heat transfer. The channel with angled ribs consistently yields better thermal performance than the transverse ribbed channel for the test conditions of the present study.