液體除濕過程之操作參數探討

液體除濕系統相較於固體除濕系統，有較低再生溫度、彈性的再生時間及可分離的除濕與再生部，加入製冷裝置即可成為空調的另一種選擇。液體除濕空調系統相較於一般傳統空調系統，有較低的運作成本及低階能源需求，空氣品質及濕度控制方面也有較佳的表現，由此可看出液體除濕劑除濕系統深具發展潛力。此研究將建構出一個大型液體除濕單元，對影響除濕劑質傳之參數進行探討，並針對液滴夾帶問題 (carry-over) 製作外加量測系統且建立指標。測量近幾年出現的混和溶液表面蒸汽壓，找到最佳混合比例以達到節省成本的效果，最後建構一個小型液體除濕單元，測量較昂貴除濕溶液的效果。本研究經內部風場模擬結果，採用高度為200 mm之外加裝置應用於大型除濕系統進行液滴夾帶問題量測，經平均風速及液滴殘留程度決定使用KDM421除霧網進行除濕實驗。大型及小型除濕系統測試各種操作參數，如空氣流量、入口空氣溫度等。大型除濕系統搭配氯化鋰溶液的實驗結果，換算為一般市售除濕機的除濕能力為19.48 L/d ，能源因數值為 2.50 L/kWh，落於能源效率分級的第2級。小型除濕系統氯化鈣、氯化鋰及醋酸鉀溶液的實驗結果，顯示各除濕溶液所對應的表面蒸汽壓與空氣水分移除率有所關聯。關於混和除濕液的表面蒸汽壓量測，CaCl2+LiCl及LiCl+MgCl2混和除濕液蒸汽壓，皆隨著氯化鋰比例的增加而下降。LiBr+CaCl2混和除濕液蒸汽壓會隨著溴化鋰比例增加而有上升的趨勢。混和除濕液成本部分，CaCl2+LiCl混和除濕液成本，隨著氯化鋰比例上升而增加，根據成本與蒸汽壓考量，推薦比例為70 %CaCl2+30 %LiCl。LiCl+MgCl2混和除濕液部分，因採用的氯化鎂單價較氯化鋰貴，成本隨著氯化鋰比例增加而下降。LiBr+CaCl2混和除濕液成本隨著溴化鋰比例上升而增加。

關鍵字

液體除濕；混和除濕劑；蒸汽壓；液滴夾帶

並列摘要

Compared with solid desiccant dehumidification systems, liquid desiccant dehumidification systems are characterized by the low regeneration temperature, flexible regeneration time, and separable dehumidification and regeneration unit. Liquid desiccant dehumidification systems with thereafter cooling devices, which come with lower operating cost, lower-grade energy demand, and better performance in air quality and humidity control, could be an alternate for air conditioning. Therefore, there is great development potential in liquid desiccant dehumidification systems. A large liquid desiccant dehumidifier has been constructed in this study. The parameters affecting the mass transfer of liquid desiccant have been discussed. The additional measurement system and the indicators for desiccant carry-over have been made and established. Vapor pressures of the mixed liquid desiccant aqueous solution reported in recent years have been measured in order to find the optimum mixing ratio for cost reduction. Finally, a small liquid desiccant dehumidifier has been constructed to test some more expensive liquid desiccant solutions. In this study, with the CFD results in the large liquid desiccant dehumidifier, the additional measurement device with a height of 200 mm was designed and used in the system for the carry-over problem. The KDM421 demister was used on dehumidifier experiments because of the high average wind speed and the low degree of droplet residue. For the large and small dehumidifiers, various operating parameters such as air flow rate, inlet air temperature, and so on were explored. The performance of the large dehumidifier with lithium chloride solution was equivalent to a commercial dehumidifier with the dehumidifying capacity of 19.48 L/d and the energy factor of 2.50 L/kWh, falling on the second level of dehumidifier energy efficiency grade. The experimental results of calcium chloride, lithium chloride and potassium acetate solutions in the small dehumidifier show that the surface vapor pressure of the liquid desiccant solution is strongly related to the moisture removal rate in air. Regarding the vapor pressure measurement of the mixed liquid desiccant solutions, the vapor pressure of the CaCl2+LiCl and LiCl+MgCl2 solutions both decreases with the increase of lithium chloride proportion. The vapor pressure of the LiBr+CaCl2 solutions increases with the increase of lithium bromide proportion. About the cost of mixed solutions, the cost of the CaCl2+LiCl solution increases with the increase of lithium chloride proportion. According to the cost and vapor pressure of the CaCl2+LiCl solution, the optimum ratio is 70% CaCl2+ 30% LiCl. Because the magnesium chloride used is more expensive than the lithium chloride, the cost of LiCl+MgCl2 solution decreases with the increase of lithium chloride proportion. The cost of the LiBr+CaCl2 solution increases with the increase of lithium bromide proportion.