Local Cooling Enhancement in Incremental Impingement Pin-Fin Configurations: Role of Jet Diameter and Impingement Configurations

Abstract

This study numerically investigates low aspect ratio incremental impingement configurations to evaluate the effect of jet hole size on both local and global heat transfer. The large eddy simulation (LES) model is developed based on the geometry and boundary conditions detailed by Busche et al. (2013, “Heat Transfer and Pressure Drop Measurements in High Solidity Pin Fin Cooling Arrays With Incremental Replenishment,” ASME J. Turbomach., 135(4), p. 041011). The model’s accuracy is validated by comparing its predictions with experimental results from the same study. The configuration consists of eight staggered rows of pin-fins with streamwise (X/D) and spanwise (S/D) spacings of 1.074 and 1.625, respectively, and a channel aspect ratio of 0.5D, where the pin-fin diameter (D) is 2.54 cm. Jets are directed into cut-out sections of the pin-fins to shield the jet stagnation region from crossflow. Coolant enters the pin-fin channels via five rows of jets, with four jet hole diameters: petite (P, 0.25D), small (S, 0.29D), medium (M, 0.36D), and large (L, 0.41D). The global Reynolds number, based on pin-fin diameter and maximum bulk velocity, is 7500. Twenty configurations are designed by varying the diameter of each jet row while keeping the others constant. The near-jet vortical structures are highlighted using isosurfaces of the Q-criterion. Jet mass velocities and mass flow rate distributions are compared across configurations. Row-by-row cooling parameters, as well as global Nusselt numbers and friction factors, are calculated to assess the relative advantages of each configuration.