應用疊層組裝於微流道沸騰熱傳增強研究

Abstract

相變化熱傳應用於微流道具高均溫性、低工質量、高熱傳係數等優點，為未來高發熱問題最佳解決方案。近年來，表面改質應用於沸騰熱傳已獲得良好的應用。相關研究中指出，疏水表面相較於未改質表面可提供較多成核址，熱傳性能有所提升。因此本研究之目的為利用疊層組裝之技術，在一英吋之銅表面進行改質，探討疏水表面在流動沸騰中對微流道熱傳性能的影響，並與未改質表面進行比較。 本實驗以水為工作流體，在流量 172 kg/m^2-s，飽和壓力 101kpa 下進行熱傳實驗。結果可分為接觸角量測與熱傳實驗兩部分。在接觸角量測部分，固定製程條件下，靜態接觸角由 78°增加至 113°。在熱傳實驗部分，首先先將未改質微流道沸騰熱傳數據代入 Mudawar 在 2005 年提出的微流道熱傳與壓降經驗式，平均誤差約為 7.8%與 26%。未改質微流道在乾度小於 0.14 前，熱傳係數不隨乾度而改變，而疏水表面之熱傳係數在起始沸騰時達峰值，遞減後隨乾度增加而保持定值，相較於未改質的微流道，整體熱傳性能有 100%的提升，顯示疏水表面的微流道蒸發器在散熱應用上極具潛力。

Phase-change heat transfer in microchannels provides good temperature uniformity, less coolant flow rates requirement and high cooling efficiency. Previous studies indicates hydrpophobic surface proposed more nucleation sites after onset of nucleation boiling, which enhancing boiling heat transfer. In present study, we demonstrate a layer-by-layer processing scheme that can create hydrophobic surface from silicon dioxide nanoparticles on 1 square inch copper substrate. The purpose of this research is to investigate flow boiling heat transfer behavior of hydrophobic and uncoated surface on microchannels. Experiments are conducted with water, under mass fluxes of 172 kg/m2-s, saturated pressure of 101kpa. After layer-by-layer processing, the static contact angle from 78° to 113°. The experimental data of uncoated surface was substituted into Mudawar’s heat transfer and pressure drop microchannels correlation, the mean average was 7.8% and 26%. The heat transfer coeficient of uncoated surface keeps constant when quality before 0.14, but the heat transfer coefficient of hydrophobic surface reached peak value at onset nucleation boiling, then decrease to constant. The experimental results showed that microchannels with hydrophobic surface enhanced 100% heat transfer coefficient than uncoated surface overall. To conclude this study, the hydrophobic surface on microchannels is highly potential for cooling applications.