Effect of Coolant Ejection in Rectangular and Trapezoidal Trailing Edge Cooling Passages

Heat transfer coefficients are experimentally determined in various trailing edge cooling channels. A rectangular channel (AR = 3:1) with fully developed flow is used as a baseline for the study with the Reynolds number varying from 20,000 to 80,000. The heat transfer coefficients in this channel are compared to those in a similar rectangular channel with coolant extraction, which would likely be encountered in a trailing edge cooling passage. The heat transfer trends in the rectangular channel are compared to those obtained in a passage with a trapezoidal (or wedge-shaped) cross-section. The heat transfer coefficients are also obtained in the channel without coolant extraction and with extraction from the narrow side of the channel. The effect of V-shaped rib turbulators is also considered in the rectangular and trapezoidal cooling passages. In addition, the effect of entrance condition is considered with the wedge-shaped channel. Heat transfer coefficients obtained with hydrodynamically developed flow are compared to those with flow through a contraction into the heated section of the channel. In the rectangular channel without ejection, the heat transfer coefficients are uniform across the span of the channel; however, with coolant ejection, the heat transfer coefficients increase near the ejection slots. In addition, in the trapezoidal channels, the heat transfer coefficients are uniform across the cross-section of the smooth channel. When coolant is extracted for trailing edge ejection, the outer surface sees the most significant heat transfer enhancement. The outer surface of the smooth, trapezoidal channel is most profoundly affected by the entrance condition, and the effect of the entrance condition is marginal in trapezoidal channels with ribs and ejection.