Heat transfer and pressure drop in pin-fin trapezoidal ducts

Experiments are conducted to determine the log-mean averaged Nusselt number and overall pressure-drop coefficient in a pin-fin trapezoidal duct that m odels that cooling passages in modern gas turbine blades. The effects of pi n arrangement (in-line and staggered), flow Reynolds number (6,000 less tha n or equal to Re less than or equal to 40,000) and ratio of lateral-to-tota l flow rate (0 less than or equal to epsilon less than or equal to 1.0) are examined. The results of smooth trapezoidal ducts without pin arrays are a lso obtained for comparison. It is found that, for the single-outlet-flow d uct the log-mean averaged Nusselt number in the pin-fin trapezoidal duct wi th lateral outlet is insensitive to the pin arrangement, which is higher th an that in straight-outlet-flow duct with the corresponding pin array. As f or the trapezoidal ducts having both outlets, the log-mean averaged Nusselt number has a local minimum value at about epsilon = 0.3. After about epsil on less than or equal to 0.8, the log-mean averaged Nusselt number is nearl y independent of the pin configuration. Moreover, the staggered pin array p ays more pressure-drop penalty as compared with the in-line pin array in th e straight-outlet-flow duct; however, in the lateral-outlet-flow duct, the in-line and staggered pin arrays yield almost the same overall pressure dro p.