Ultrahigh 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. The direct integration of 3-D flat-plate oscillating heat pipes (3-D FP-OHPs) for the thermal management of EML bore components is proposed. Unlike conventional heat pipes, the 3-D 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 3-D FP-OHP (130.18 mm × 38.10 mm × 2.86 mm) filled with HPLC-grade water at a filling ratio of 72%. The 3-D 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 3-D FP-OHP configured for axial EML thermal management. These results indicate that the high thermal conductivity of 3-D 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 3-D FP-OHP is appealing for future EML thermal management solutions; however, significant work is required for their optimal integration.