探討具有非等向濕潤性質之微溝槽表面對於介電溶液池沸騰熱傳影響

Abstract

本研究使用飛秒雷射技術於銅表面上製造出微溝槽的結構，使表面呈現非向的濕潤性質。本研究的目標是探討與比較光滑銅表面以及微溝槽表面的池沸騰熱傳表現，池沸騰實驗皆是於一大氣壓且飽和狀態下進行，使用的工作流體為介電溶液Novec-7100。實驗中所得到的沸騰曲線以及所拍攝的氣泡動態顯示，具備非等向濕潤性質的微溝槽結構對沸騰熱傳係數以及臨界熱通量皆有影響。比較微溝槽結構表面以及未改質的光滑銅表面的熱傳表現可以得知，具有微溝槽的表面氣泡成核數量大幅上升，使得沸騰熱傳係數隨之提高。研究結果顯示，在所有微溝槽結構表面中，微溝槽間距為100 μm的表面具有最佳的熱傳增強效果，沸騰熱傳係數為未改質表面的1.37倍。本研究也利用接觸角量測結果、氣泡動態以及理論預測模型來分析臨界熱通量，並取得與理論模型良好的相容性。

A femtosecond laser–texturing method was employed to create microgrooves with anisotropic wettability on a copper surface. The objective was to examine the pool boiling heat transfer performance on plain copper surfaces and microgroove surfaces under saturation at atmospheric pressure. In the experiments, Novec-7100 dielectric liquid was used as the working fluid. An analysis of boiling curves and of high-speed-image data on the formation of bubbles revealed that the anisotropic wettability induced by microgroove surfaces with varying groove spacing affected both the heat transfer coefficient and critical heat flux values. Relative to the smooth copper surface, microgroove surfaces enhanced the heat transfer performance by increasing the number of bubble nucleation sites. The experimental boiling results indicated that a groove spacing of 100 μm achieved the largest heat transfer coefficient enhancement, namely 1.37 times (relative to the smooth surface). Furthermore, critical heat flux analysis was conducted on the basis of contact angle measurement results, high-speed images of evolution bubbles, and theoretical prediction models. Good agreement of CHF values was achieved between our study and the prediction model.