介電液FC-72在狹窄矩形空間的池沸騰研究

Abstract

摘要

本論文是以介電液FC-72為工作流體在一大氣壓下，狹窄矩形空間的池沸騰實驗。在狹窄矩形空間下方為面積10mm×10mm的銅片加熱面，上方為壓克力板，兩端以壓克力板檔住，可分別調整上下板的間隙S及加熱面與水平的夾角Θ，即S=0.5mm、1mm、2mm及3mm，以及Θ=0∘、45∘、90∘。實驗目的在比較間隙大小、加熱面角度在起始過熱度、核沸騰熱傳與臨界熱通量，並與開放式的池沸騰結果比較。實驗結果顯示Θ=0∘時，熱通量低於30kW/m2，S=1mm熱傳係數較開放式佳。水平加熱時，四種間隙的臨界熱通量都比開放式低很多。Θ=45∘與90∘時，小間隙(0.5mm)可以增強低熱通量時的熱傳係數，且S=2mm及S=3mm其臨界熱通量皆超越開放式。

ABSTRACT The goal of this experiment is to study characteristic of pool boiling of dielectric fluid FC-72 in a narrow rectangular space under one atmosphere. The narrow rectangular space consists of a heated surface made of a smooth copper plate with 10 mm × 10 mm area and a parallel acrylic plate with two confined side edges .The gap size S and the inclination angle Ө between the heated surface and the horizon are S=0.5 mm, 1 mm, 2 mm and S=3 mm, and Ө=0°, 45°, 90° separately. The onset of boiling, nucleate heat transfer and critical heat transfer were studied . The results showed that for Ө=0°, under low heat flux 30 kw/m2 and S=1 mm the heat transfer coefficients of this experiment were found better than those of unconfined one. For Ө=0°, the critical heat fluxes for all gaps were depressed compared those of the unconfined one. For Ө=45° and Ө=90°, the smallest gap of 0.5 mm could enhance the heat transfer coefficients and if under low heat flux, especially for S=2 mm and 3 mm and the comes critical heat fluxes were found higher than these of the unconfined one.