本論文主要是探討垂直加熱面，在FC-72 中加入可溶解氣體，對於不
同間隙大小的池沸騰性能之影響。加入的可溶解氣體含量分別為 0、
0.0016、0.0029 及 0.0038，間隙大小分別為 3、2、1 及 0.5 mm。根據實驗 的結果可以歸納出下列幾個結論：
一、在相同的間隙下，低熱通量(30%CHF 以下)時，增加可溶解氣體 含量會使沸騰有提早發生的情形，主要原因為液體中含有氣體會使氣泡容 易生成，所以在低過熱度下就會有沸騰產生，提早進入核沸騰區，熱傳係 數會有明顯的提升，尤其當可溶解氣體含量增加至0.0038 時最為明顯。但 是進入中高熱通量(30%CHF~90%CHF)時，加熱表面溫度逐漸升高，靠近 加熱面的流體溫度也隨之升高，當含有可溶解氣體的流體接近加熱面時就 已經被除氣(degassed)，到達加熱面已經為純流體，所以在中高熱通量下皆 為純次冷態沸騰，增加少量的可溶解氣體含量熱傳係數已無明顯的提升。
臨界熱通量不論在任何間隙皆會隨著氣體次冷度的增加而增加。
二、在相同次冷度下，起始沸騰也會隨著間隙的減小而提早發生，其 原因為在較小的間隙下會使液體比較容易過熱，到達沸騰所需的過熱度，
因此沸騰會提早發生。所以在低熱通量(30%CHF 以下)時，減小間隙使沸 騰提早發生，熱傳係數也隨之提升。至中高熱通量(30%CHF~90%CHF)時，
隨著間隙的減小，熱傳係數會逐漸降低，其原因為間隙的減小，使得核沸 騰區的氣泡合併提早發生，尤其間隙 0.5 mm 時最為明顯，蒸氣薄膜覆蓋 在加熱表面使流體無法有效的補充至加熱面，為熱傳遞降低的主要原因。
隨著間隙的減小，氣泡合併提早發生，臨界熱通量(CHF)也提早發生。上 述情況在不同氣體次冷度下皆相同，無明顯差異。
三、加入可溶解氣體在各間隙下都有提升熱傳係數的趨勢，尤其在低 熱通量時最明顯，熱傳遞係數會隨著氣體含量的增加而明顯增加，但是在 較高可溶解氣體含量(0.0038)下，熱傳係數隨著間隙減小已無明顯差異，顯 示在高氣體含量時，各間隙的熱傳係數都已經有很明顯的提升，逐漸不受 間隙的影響。如果繼續增加氣體含量，熱傳係數會趨於一致，但中高熱通
量還是會受到間隙逐漸減小的影響，而使熱傳係數逐漸降低。
四、雖然減小間隙可以增加自然對流，但是其影響在低熱通量下較明 顯。因為低熱通量下，熱傳遞從單相熱傳至初始雙相熱傳遞，能夠明顯的 增加自然對流，進而增加熱傳係數；但是進入核沸騰區，小間隙反而使氣 泡容易合併成大塊的氣膜覆蓋在加熱面，反而降低了熱交換，使壁面溫度 升高，所以小間隙不利於高熱通量下的沸騰熱傳。本實驗發現較佳的間隙 大小為 3 mm，其熱傳係數與開放加熱面相近，而且當可溶解氣體含量增 加後，其低熱通量的熱傳係數也逐漸接近1 及 0.5mm，在高氣體次冷度(30 K, Cg = 0.0038)時，間隙 3 mm 的熱傳係數甚至比 1 及 0.5 mm 還更好。所 以本實驗的最佳間隙大小為3 mm。
五、由於受到實驗設備的限制，氣體次冷度無法再繼續增加至 40 K 以上，也就是可溶解氣體含量增加至0.005 moles/mole 以上，才能夠觀察 到 You 等人[31]所得到的結果，即在低熱通量因為可溶解氣體的影響大幅 降低壁面過熱度，中高熱通量也因為受到氣體次冷度的影響使熱傳係數有 明顯的提升，所以繼續增加氣體次冷度為未來可以繼續努力的目標。
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附錄
2
qloss side bottom t side t bottom −
− +
(E) 熱傳遞係數( )不準度 h 本實驗的熱傳遞係數為
T h q
Δ
= ′′
由(a)式可得熱傳遞係數的不準度為
( )
22
⎟⎠
⎜ ⎞
⎝
⎛ Δ + Δ
⎟⎟⎠
⎜⎜ ⎞
⎝
⎛
′′
= ′′
T T q
q h
h δ δ
δ