Ultra-high thermal conductivity of three-dimensional flat-plate oscillating heat pipes for electromagnetic launcher cooling

Bore components within electromagnetic launchers (EMLs) experience very high heating rates during and after the shot of a projectile. This is a challenge for the next-generation EML which will shoot projectiles repetitively within a specified time frame. Direct integration of three-dimensional flat-plate oscillating heat pipes (3D FP-OHPs) for thermal management of EML bore components is proposed. Unlike conventional heat pipes, the 3D FP-OHP contains no wick structure and can operate at higher heat fluxes with fewer limitations. Proof-of-concept experiments were performed on a copper 3D FP-OHP (130.18 mm × 38.10 mm × 2.86 mm) filled with HPLC-grade water at a filling ratio of 72%. The 3D FP-OHP was found to have an effective thermal conductivity that increased with heat input - approaching 15,000 W/m-K at heat inputs on-the-order of 0.3 kW. This experimentally-determined thermal conductivity was used for numerically analyzing the thermal performance of a longer 3D FP-OHP configured for axial EML thermal management. These results indicate that the high thermal conductivity of 3D FP-OHP coupled with an external, active cooling solution (h ~ 50,000 W/m²-K) can provide for peak heat transfer rates on-the-order of 10 kW. Based on these results, the 3D FP-OHP is appealing for future EML thermal management solutions, however significant work is required for their optimal integration.