High Heat Flux Evaporator for Two Phase Transport Loops

This project addresses the development of high performance evaporators for loop heat pipes (LHP) or capillary pumped loops. Thermal management of future high-power laser instrumentation will require power dissipation of 2-5 kW at heat fluxes beyond 100 W/cm2. Although localized heat fluxes as high as 100 W/cm2 have been demonstrated using bi-disperse wicks, the maximum average heat flux capability of present LHP evaporators is an order of magnitude lower. Cooling high heat flux loads with present technology would necessitate the use heat spreaders, which would substantially increase the thermal resistance and weight of the system. We propose an evaporator configuration that can operate at average heat fluxes an order of magnitude larger, and thermal resistances an order of magnitude lower than present LHP evaporators. A novel fabrication approach enables vapor/liquid distribution networks to maximize capillary pumping and substantially reduce liquid and vapor flow pressure drops. Phase I proof-of-concept tests and scoping analyses demonstrated the feasibility and performance potential of the proposed evaporator. In Phase II we will develop the evaporator technology through a combination of modeling, fabrication trials, and separate effects tests. We will then demonstrate the technology by designing, fabricating, and testing a prototype LHP incorporating the proposed evaporator.