氧化鎢奈米線及二氧化鈦奈米管於沸騰熱傳之影響

Abstract

沸騰熱傳具備極佳的傳熱能力先前相關文獻指出加熱表面之表面處理有助於在沸騰熱傳表現上之提升。本研究建立了一套池沸騰實驗設備，使用板狀試片以便拍攝 SEM 照片觀察經表面處理後之加熱表面，親水性可由量測接觸角來觀察。本研究之表面處理方式包含 銅基材熱壓 銅網、氧化鎢奈米線於銅基材銅網、鈦薄片、燒結鈦粉於鈦薄片、二氧化鈦奈米管於鈦薄片及二氧化鈦奈米管於燒結鈦粉於鈦薄片之應用。沸騰實驗以不同加熱棒之輸入電壓為參數，由40、45、50至55 ACV，經由SolidWorks Flow Simulation 模擬後，計算而得之加熱表面之過熱度及熱通量，可將其繪製成沸騰曲線圖作後續沸騰熱傳表現之分析。結果顯示銅網之應用提升沸騰熱傳係數43.5%。而相較於銅基材熱壓銅網，氧化鎢奈米線之應用 有效降低初始過熱度約2.8 oC。相較於鈦薄片燒結鈦粉之應用提升沸騰熱傳係數95.5%二氧化鈦奈米管之應用降低初始過熱度約1.8 oC，提升沸騰熱傳係數125.5%同時應用二氧化鈦奈米管及燒結鈦粉則降低初始過熱度達5.4 oC，提升沸騰熱傳係數66.2%。然而，目前使用之奈米結構耐用度低，實驗結果不具重複性而隨實驗次數逐漸衰退。本實驗裝置具良好穩定性，因此提供了一實驗平臺供未來表面處理之研究所用。

Boiling heat transfer exhibits great ability to transport energy. Researches have shown the surface modifications is able to enhance the boiling heat transfer performance. In this study, a pool boiling apparatus was established. A Plate sample was used and therefore the surface modification can be observed by taking the SEM image, and the wettability can be observed by measuring the contact angle. Copper substrate with copper mesh, WO3 nanowires on copper substrate with copper mesh, Ti foil, Ti foil with sintered Ti, and TiO2 nanotubes on Ti foil with sintered Ti or without sintered Ti coating were the modifications to be investigated. Pool boiling experiments were performed by adjusting the input voltage which were 40, 45, 50, and 55 ACV to the cartridge heaters, the superheat and heat flux of heating surface can be calculated with help from SolidWorks Flow Simulation, then the boiling curves were plotted to analyze the boiling heat transfer performances. The results of boiling curves showed that the application of copper mesh increased the boiling heat transfer coefficient by 43.5%. The application of WO3 nanowires reduced the incipient superheat by 2.8 oC comparing to the copper substrate with copper mesh. Comparing to the Ti foil, the application of sintered Ti coating increased the boiling heat transfer coefficient by 95.5%, the application of TiO2 nanotubes reduced the incipient superheat by 1.8 oC and increased heat transfer coefficient by 125.5%. The combined application of TiO2 nanotubes and sintered Ti coating significantly reduced the incipient superheat by 5.4 oC and increased heat transfer coefficient by 66.2% comparing to the Ti foil. The current nanostructures were not durable enough to have consistent results. The pool boiling apparatus was solid, it provided a platform to discover future surface treatments.