SBIR-STTR Award

The use of the heat of vaporization of the coolant can significantly reduce the required flow rate, and this reduction flows down throughout the thermal management system. Two-phase systems, however, are subject to buoyancy effects which can make them vulnerable to high-g maneuvers of military aircraft. Two-phase microchannel coolers can be designed such that surface tension effects dominate buoyancy forces, even in high g environments, desensitizing the thermal and flow performance to aircraft maneuvers. In the proposed effort, a two-phase microchannel cooling system with large surface tension forces will be designed, fabricated and tested to demonstrate operation. The result will be a compact, survivable cooling system with a significant reduction in flow rate compared to a single-phase water-cooled microchannel systems. Approved for Public Release 14-MDA-8047 (14 Nov 14)

Two-phase cooling systems are an enabling technology for high energy lasers deployed on aircraft, but the flow morphology can be influenced by the accelerations of airborne platforms, affecting the thermal and flow performance of the cooler. Microchannel coolers using low Bond number coolants can reduce these effects, since surface tension forces dominate over buoyancy effects. The insensitivity to accelerations was demonstrated in the Phase I program: this Phase II effort will provide the understanding and computational tools required to design two-phase microchannel systems with confidence.The program will study the behavior of two-phase flows in high aspect ratio rectangular microchannels at high heat fluxes, using flow visualization and computational fluid dynamics to create reliable flow maps. The understanding gained from these studies will be used to improve computationally efficient numerical analysis tools, which can be used in future design efforts. Test assemblies will be delivered for high-acceleration centrifugal testing, and two-phase microchannel coolers will be designed, built and tested with laser diodes to demonstrate the performance.