Experimental and numerical investigation in rotating double-wall channel with side outflow

This study examines flow and heat transfer characteristics in rotating double-wall cooling channels with side outflow, focusing on the pin-fin geometries (square, circular, rhombic) within the impingement cavity. Steady-state liquid crystal measurements and steady-state RANS simulations were conducted at a fixed inlet Reynolds number (Re = 25,000, Re_j = 10,150), with inlet rotation number (Ro) ranges from 0 to 0.57 (Ω = 0∼300 rpm) and jet rotation number (Ro_j) from 0 to 0.0075. Key findings reveal that under stationary conditions, heat transfer is governed by jet distribution and axial crossflow. Pin fins increase flow resistance but enhance heat transfer, with square pins yielding the highest overall thermal performance. Under counter-rotation conditions (leading impingement), low rotation speeds weaken jets via Coriolis force, reducing stagnation region heat transfer, while enhanced near-wall disturbance improves wall-jet region heat transfer. High rotation speeds induce dominant spanwise crossflow and elevated turbulence, boosting heat transfer in all regions. Conversely, positive rotation (trailing impingement) consistently strengthens jets and near-wall disturbance, monotonically increasing heat transfer and thermal performance. Crucially, positive rotation (trailing impingement) outperformed counter rotation (leading impingement) at equivalent rotation speeds, offering lower flow resistance, higher heat transfer coefficients, and superior thermal performance. Across all rotation conditions, the flow disruption generated by pin fins is consistently diminished reducing performance differences between pin fin types. The thermal advantage of square pin fins progressively diminishes and is eventually surpassed by circular pin fins. These results provide critical insights for optimizing rotating double-wall cooling channel.