兩相流封閉熱虹吸式熱管操作極限之研究

Abstract

熱虹吸式熱管又稱重力式熱管，由於構造簡單，所以常被設計成各種型式加以應用，例如：廢熱回收、儲熱系統、太陽能集熱器等。其運作原理為利用工作流體相變化時產生的潛熱來傳遞熱量。本研究探討兩相流封閉熱虹吸式熱管在高溫運作時，會因液氣交界面之剪應力過大，拖拉住液體回流而有飛濺極限的限制；或因其蒸發段之毛細結構因徑向熱通量過大而產生沸騰極限，影響其熱管的性能。 本實驗利用管長130mm、200mm、300mm之熱管進行實驗，求得當發生沸騰極限與飛濺極限時的操作溫度以及操作極限熱傳量，並與預測程式相互驗證。經由誤差分析，本實驗結果之沸騰極限與程式預測平均誤差為8.7%。飛濺極限平均誤差則為6.7%。因此日後在其他尺寸熱虹吸式熱管的操作極限實驗上，皆可以此做為一測試標準，並利用程式軟體進行極限預測。

The rmosyphons are also called gravity-supported heat pipes. They are highly efficient heat transfer elements which become increasingly applied in terrestrial heat transport and heat recovery system. Their performance is limit by various heat transport limitations. When thermosyphons work at high temperature , the maximum operating heat transfer rates for two-phase closed thermosyphons due to entrainment limitation or boiling limitation. And these limitations will affect the heat transfer performance. Experiments with three copper water thermosyphons, which are 130mm、200mm、300mm long respectively and 7mm outer diameter have been carried out. According to the error analysis, the error between the boiling limitation measured by experiment and the prediction by theory is 8.7 percentage, and the average error of entrainment limitation between experiment and theory is 6.7 percentage. We can take the result of this experiment as standard when we use the other size of thermosyphons to measure the operating limit limits in the future, and predict by the programs.