MITIGATION OF BOILING-INDUCED THERMAL DEGRADATION USING MICROPOROUS NICKEL INVERSE OPAL (NIIOS) STRUCTURES

초록

Engineered microporous structures have received much attention in high-heat-flux electronics cooling due to their high thermal conductivity and permeability, and large surface area for heat transfer, but are susceptible to boiling-induced thermal degradation. This study investigates the efficacy of nickel inverse opals (NiIOs) in mitigating structural degradation caused by corrosion-assisted erosion during pool boiling with water as working fluids. First, we compared the reliability of NiIOs to copper inverse opals (CuIOs), for a 3-day pool boiling test at constant heat flux. The NiIOs demonstrated superior resistance to thermal degradation due to their inherent corrosion resistance and mechanical strength. Only partial oxidation was observed on NiIOs surface while CuIOs structures were completely diminished after 3 days. Subsequently, we conducted a more controlled experiment to show the effect of heat flux and bubble dynamics on the degradation of the NiIOs. To exclude the effect of temperature variations, pool boiling reliability tests of 20-µm-thickness NiIOs covering ~10×10 mm2 with a 2.5×2.5 mm2 heater at the center were conducted at heat flux levels of 20%, 40%, and 60% of the critical heat flux (CHF) for 3 days. The NiIOs subjected to heat flux levels of 20% and 40% CHF showed minimal degradation while the top surface of the NiIOs subjected to 60% CHF underwent some erosion, possibly due to a higher bubble formation and departure rate. These results show the potential of NiIOs as a promising solution for long-term thermal management in high-power electronic devices, although design considerations for maximum allowable heat flux are necessary for reliable operation. The next step is to repeat the reliability tests for > 30 days while monitoring the changes in surface temperature, NiIOs structure, and bubble dynamics over a longer period. Copyright © 2024 by National Renewable Energy Lab (NREL)

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