Heat Transfer in Two-Pass Rotating Rectangular Channels (AR=2:1) with Discrete Ribs

This paper reports the heat transfer coefficients and friction factors in a two-pass rotating rectangular channel with ribs, applicable to an internally cooled turbine blade. The channel aspect ratio is 2:1. Five different turbulators are studied: 45-deg angled ribs, V-shaped ribs, discrete 45-deg angled ribs, discrete V-shaped ribs, and crossed V-shaped ribs. The ribs are placed on the leading and trailing surfaces. The Reynolds number ranges from 5000 to 40,000. The corresponding rotation numbers vary from 0.206 to 0.026 for a fixed rotation speed of 550 rpm. The rib-height-to-hydraulic-diameter ratio (elD) is 0.094, the rib-pitch-to-height ratio (Pie) is 10, and the inlet-coolant-to-wall-density ratio (Ap/p) is maintained around 0.115. For each case, two channel orientations with respect to the plane of rotation are studied, 90 and 135 deg. The results show that the V-shaped ribs and discrete V-shaped ribs have higher heat transfer enhancement than the 45-deg angled ribs and discrete 45-deg angled ribs for both rotating and nonrotating cases. The pressure measurements show the 45-deg angled ribs incurred the highest frictional losses. Based on the present study, the discrete V-shaped ribs have the best overall thermal performance in both rotating and nonrotating channels.