Heat transfer enhancement of X-lattice-cored sandwich panels by introducing pin fins, dimples or protrusions

The special topology of the X-lattice induces a large-scale primary spiral flow and three kinds of secondary flow skewed towards and away from the endwall regions and behind each ligament. To make full use of secondary flows produced in different regions, dimples, protrusions and pin fins are separately introduced to the endwall of a sandwich panel to further improve the overall cooling performance. Forced air convection in the six sandwich panels is numerically investigated based on a validation of the numerical model against experimental data available in the literature. Results reveal that the case with pin fins installed in the region upstream of the crosses in the X-lattice (Region A) exhibits the best overall heat transfer performance, while the case with dimples installed downstream of the crosses in the X-lattice (Region B) shows the poorest heat transfer. In terms of the pressure drop, the introduction of protrusions or pin fins in Region A slightly decreases the pressure drop within a certain range of Reynolds number, but the other four cases show an increase in pressure drop. Taking the pressure drop and heat transfer into consideration, a proper combination of the X-lattice and the elements can enhance the overall thermal performance of the sandwich panel. The modifications of the fluid flow and local heat transfer characteristics by the added elements are well analyzed to understand the underlying mechanisms.