介電液FC-87與冷媒R-134a對水平圓管的池核沸騰增強熱傳分析

Abstract

本研究論文主要是探討介電液FC-87與冷媒R-134a的池核沸騰熱傳增強方法。在池沸騰的測試容器中，分別以平滑管、16fpi標準鰭片管、塊狀鰭片管、L型鰭片管、表面噴砂粗糙管、覆網鰭片管及針狀鰭片管共七種不同表面的圓管，以控制電壓及電流的方式對工作流體加熱，在不同飽和壓力下進行水平加熱的池核沸騰實驗，以了解不同結構的熱傳增強表面（enhancement surface）對池核沸騰熱傳性質的影響，進而找出較佳的熱傳增強表面結構及影響池核沸騰熱傳表現的參數。實驗結果顯示：對冷媒R-134a而言，平滑管的實驗熱傳係數由Cooper熱傳關係式可預測90﹪的值於誤差±20%內；由Stephan and Abdelsalam熱傳關係式可預測85﹪的值於誤差35%上限及45%下限內。熱傳效果最佳為針狀鰭片管，其次為L型鰭片管，覆網鰭片管與塊狀鰭片管居中，表面粗糙管與標準鰭片管表現較差。對介電液FC-87而言，可利用Rohsenow關係式，對平滑管沸騰熱傳係數的預測值其實驗值誤差在45%範圍內。針狀鰭片管有最佳的沸騰熱傳係數，其次為L型鰭片管，塊狀鰭片管與標準鰭片管居中，其後為覆網鰭片管與表面粗糙管。

The method of enhanced nucleate pool boiling of dielectric fluorocarbon liquid FC-87 and refrigerant R-134a on horizontal circular tubes were investigated in this study . In order to understand the pool boiling heat transfer characteristics for different enhancement surfaces and the related parameters of the pool boiling heat transfer , the experiments were conducted using a plain tube and six enhanced tubes with the applications of decreasing heat flux at different saturated pressures . The experimental results show that , for refrigerant R-134a , the Cooper correlation can predict 90% of the experimental data of the plain tube within 20% band of uncertainty ; the Stephan and Abdelsalam correlation can predict 85% of the experimental data of the plain tube within 35% upper and 45% lower band of uncertainty . Pin finned tube has the highest heat transfer coefficient and that the L-shaped finned tube have the next highest value , mesh finned tube and segmented finned tube perform worse , rough tube and 16fpi finned tube are worst . For FC-87 , Rohsenow correlation can well predict the heat transfer coefficient of plain tube in 45% agreement . Pin finned tube has the highest heat transfer coefficient and that the L-shaped finned tube have the next highest value , follow behind segmented finned and 16fpi finned tubes , mesh finned tube and rough tube perform worse .