一般皆知在溶膠的乾燥過程中容易產生粒子的凝聚，此凝聚現象會因溶膠裡固體粒子的奈米化而更形嚴重。基於液態會在真空腔內瞬間汽化(當真空腔內壓力小於其飽和壓力時)，而且汽化的膨脹力可以抵消粒子間之吸收力，所以利用真空乾燥來避免或減輕粒子之再凝聚。
然而真空腔內水分子汽化現象很容易因為水分子汽化後體積急驟地增加(壓力也增加)而終止。所以在本文中吾人建立了一連續性的吸濕/排氣系統可持續的在真空腔內吸收汽化的水汽，並將所吸收之水排出真空腔體，來維持低壓真空環境。
為了提升吸濕能力，在實驗測試中採用了兩種方法，第一種是將真空腔內冷卻水管管型由平滑管改成微針鰭管來提升溴化鋰水溶液與冷卻水之間的熱傳率，第二種則是在溴化鋰水溶液中添加少量之2-乙基己醇(200ppm)而改變溶液之表面張力進而增強溶液與水汽之熱質傳遞，兩者皆可明顯地改善吸水率與總熱傳率。
由結果顯示，當以無介面活性劑的平滑管為比較基準，光改變成微針鰭管的效果可提升吸濕率約13~38%，提升總熱傳率約17~28%，而添加劑的效果可提升約11~65%之吸濕率及24~29%之總熱傳率。當同時改變針鰭管及加入添加劑後吸水率會上升至39~79%，而總熱傳量則上升到26~55%。

It is well known that drying of liquid-borne powders will create agglomerates, and the problem of agglomeration is particularly acute in the nanometer-size range. Since the liquid water will instantaneously flash into water vapor under the condition where the pressure is below its saturated state, and the outward expansion force during flashing is able to counteract the attracting force among fine particles, it is thus reasonable to use vacuum dry technique to prevent/mitigate agglomeration.

However, the flashing process will be terminated once the environment pressure risen above saturation state due to the tremendous volume expansion when liquid water converts to vapor. In order to maintain a low pressure environment for vacuum drying process, in this study, an absorption/ desorption system is successfully constructed to continuously absorb the flashed vapor in the vacuum chamber and desorb the absorbed water outside the vacuum chamber.

In the absorption/desorption tests, two techniques were applied to improve the absorption capability. The first kind is the replacement of cooling-water tube from bare tube to micro-pin-fin tube to enhance the heat transfer between aqueous lithium bromide solution and cooling water, while the second kind is the addition of 2-ethyl-1-hexanol(200ppm) to aqueous lithium bromide solution to increase the heat and mass transfers between solutions and vapors.

From the test results indicated that both the vapor absorption rate and the overall heat transfer rate were greatly promoted by each technique. Compared to the basic case(bare tube without surfactant), the effect of micro-pin fin tube can increase 13~38% on vapor absorption rate and 17~28% on overall heat transfer rate, the effect of additive can increase 11~65% on vapor absorption rate and 24~29% on overall heat transfer rate. With both micro-pin-fin tube and additive, the enhancement on vapor absorption is about 39~79% and on overall heat transfer rate is about26~55%.

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