Compact and Efficient Cooling Techniques for High Energy Solid State Lasers

In Phase I of this effort RTI performed ammonia evaporative spray cooling (ESC) experiments on both 2 cm^2 and 21 cm^2 surfaces to establish feasibility and scalability of ESC to cool 500 W/cm^2 while maintaining temperature uniformity within +/-2.5C over the entire surface area. RTI's two-phase ESC approach achieved this performance with 10x less coolant flow rate than traditional single-phase water micro-channel (MC) coolers. These experimental results were used to complete a design trade study for a 100 kWo solid-state laser (SSL) cooling system intended for deployment on compact tactical platforms. In Phase II of this effort RTI proposes to build a 25 kW breadboard cooling system that validates the cooling system architecture identified in Phase I, providing cooling for two 21 cm^2 large area diode array coolers, as well as cooling for a secondary heat source representative of gain material heat generation. As part of the Phase II effort, RTI will also design, build and test customized liquid pump and vapor compressor prototype units that are ammonia compatible, efficient, compact and lightweight. The overall goal of the Phase II effort is to validate the ESC design by combining all the critical ESC components into a breadboard system showing system-level viability and providing a pathway for the further advancement of ESC technology as a thermal management approach for HELs deployed on tactical platforms.