離子溶液應用於外氣除濕系統熱質傳性能研究與分析

Theoretical Analysis on Heat and Mass Transfer Characteristics of an Air Dehumidifier Using Ionic Liquid Desiccant

黃致學(Chih-Hsueh Huang)

指導教授 ： 陳希立

國立臺灣大學/工學院/機械工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202202233

摘要

如今空調佔據整體建築物的五成耗能，而這五成耗能中的20%~40%是用來對外氣進行除濕，因此如果採用液態除濕預先對外氣進行除濕，將有效將低空調負載。
本研究選用了Evonik所提供的離子溶液，與傳統除濕溶液相比，不僅有著相近的平衡蒸氣壓，還沒有結晶問題，且化學性質穩定，對金屬與人體無腐蝕性。
根據本研究顯示當溶液流量越大時，熱傳與質傳係數皆會變大，在88ml/s時會有最大質傳係數0.23 kg/m2s和熱傳係數0.531 kW/m2K；當風速越小時，系統的除濕性能較好，在0.116m/s時質傳係數來到0.23 kg/m2s，但熱傳係數稍微下降來到0.53 kW/m2K，因此本篇研究在風速0.116m/s 流量88ml/s時有最佳操作條件，並以上述實驗結果，去建構無因次化的迴歸模型，可知當m*從1.1提升到3.9時，除濕量會從294.27g/h提升到974.778g/h，提升了3.3倍。
添加板式熱交換器對於系統除濕效能有著正面的影響，當添加板熱後系統流量維持88ml/s，質傳係數會來到0.344 kg/m2s，並以此去迴歸計算，推算其餘有效度的除濕量，可知當板熱有效度從0.4提升到0.8，除濕量會從408.29 g/h提升到643.15 g/h。
噴灑型系統壓降會比填料式來的小，在小風速的情況下，系統壓降會下降5倍來到1Pa，而在大風速時會從28.8Pa下降到4Pa，因此採用噴灑型可有效節省風機耗能；另外在相同除濕能力下，將填料式改用噴灑型式hmv會從0.161kg/m3s提升到0.274 kg/m3s，體積質傳係數提升超過0.7倍，而熱傳係數也一樣提升超過0.7倍，從0.33 kW/m2K提升到0.59 kW/m2K。

關鍵字

離子溶液 ； 液態除濕 ； 熱質傳係數 ； 蒸氣壓

並列摘要

Nowadays, air conditioners account for 50% of the energy consumption of the whole building. About 20%~40% of energy consumption by air conditioner is used to dehumidify the external air. Therefore, if liquid dehumidification can used to dehumidify the external air in advance, it will effectively reduce the air conditioning loading.
In this study, the ionic solution provided by Evonik was selected. Compared with traditional ionic solution, it has the same equilibrium vapor pressure and also has no crystallization problems. Last but not least, it is harmless to metals and human body.
According to this study, the larger of air flow rate is, the higher of the heat and mass transfer characteristics. At 88ml/s, there will be a maximum mass transfer coefficient of 0.23 kg/m2s and maximum heat transfer coefficient of 0.531 kW/m2K; On the other hand, the lower of air flow rate is, the better of dehumidification performance. The mass transfer coefficient will reach 0.23 kg/m2s at 0.116m/s, but the heat transfer coefficient slightly drops to 0.53 kW/m2K. This study shows that when air Volume is 0.116m/s and liquid flow rate is 88ml/s the system will have best operating condition. Last but not least, based on the above experimental results, a regression model was constructed to predict the dehumidification of other parameters. According to this dimensionless model, when m* increase from 1.1 to 3.9, moisture remove rate will arise from 408.29g/h to 643.15g/h. It is triple amount of original number.
Adding plate heat exchanger has a positive impact on the dehumidification performance of the system. When the plate heat exchanger is added and the system flow is maintained at 88ml/s, the mass transfer coefficient will reach 0.344 kg/m2s.Depend on the experiment result, could also regresses the module to predict the benefits of system when system has the improvement on effectiveness of plate heat exchanger. When effectiveness is increased from 0.4 to 0.8, moisture remove rate will increase from 408.29 g/h to 643.15 g/h.
The pressure drop of the spray type system will be smaller than packed bed. In the case of small air velocity, the system’s pressure drop will decrease by 5 times to 1Pa. At high air velocity, it will drop from 28.8Pa to 4Pa. Thus, spray type can effectively save the energy consumption of the fan; Moreover, when packed bed is changed to spray type, volume mass transfer coefficient will increase from 0.161kg/m3s to 0.274 kg/m3s, which increase by more than 0.7 times, and the heat transfer coefficient will also increase by more than 0.7 times, from 0.33 kW/m2K to 0.59 kW/m2K.

並列關鍵字

ionic liquid desiccant ； liquid dehumidification ； heat and mass transfer coefficient ； vapor pressure

參考文獻

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