厚度不均对纳米多孔镀层发热极限及熔毁失效的影响

采用纳米多孔膜可以实现新型的具有极高热流密度的薄液膜沸腾相变传热。在薄液膜沸腾的基础研究中,通过在纳米多孔膜表面加工纳米级别厚度的铂镀层实现加热和测温。通过扫描电镜观察,发现实验样品残骸表面有“河流”状形貌形成,结合元素分析推断铂镀层局部发生热熔。本文对铂镀层进行简化并建立电网络模型,计算并分析了铂镀层局部厚度不均对整体发热极限及熔毁失效的影响。分析结果表明,镀层厚度的不均,将会使镀层在达到极限热流密度后,极易出现“河流”状熔毁,使镀层永久失效;而厚度更加均匀的铂镀层,有助于获得更高的极限热流密度。

Influence of Uneven Thickness of Nanoporous Coating on the Critical Heat Flux and the Meltdown of the Coating

Utilizing nanoporous membranes can realize a new thin film boiling regime with ultrahigh heat flux.In thin film boiling studies,a nanoscaled platinum(Pt)layer coated on the nanoporous membrane serves as both heater and temperature sensor.However,river-shaped micro cracks were discovered by scanning electron microscope(SEM)in the Pt layer after boiling experiments.Together with the results of element analysis,it was inferred that the Pt layer was locally melted.A resistor network model was set up for the Pt layer to analyze the influence of the uneven thickness on the heating performance and the failure.The results indicated that the uneven thickness of Pt layer would inevitably lead to river-shaped cracks once the heat flux surpassed critical heat flux(CHF).Moreover,by using ideal Pt layer with even thickness,higher CHF could be achieved.