利用液滴來吸收氣體為溫室氣體減量的途徑之一，尤其是針對 CO2而言，為了瞭解單一液滴吸收溫室氣體的過程，本研究利用理論分析的方式探討一大氣壓力和壓力增加下靜止液滴吸收溫室氣體的質傳現象，所考慮的溫室氣體分別為CO2，N2O，CH4和O3。然而因為在交界面有分段連續函數的關係，故不能用完全解析的方式來分析此現象，取而代之，本研究所使用的方法為半解析方式，且因為這些溫室氣體的質量擴散數較小的緣故，所以質傳均由液相控制，根據其結果可以建立無因次吸收量的函數。本研究探討的溫度範圍為280-350K，壓力分布為1-20atm，隨著溫度和壓力的升高會使吸收量有所提升，若要使其有明顯的增加的話，只要提升溫度即可。更進一步，在溫度為298K，壓力為1atm下，利用液滴吸收CO2，並在液滴表面給予一個聲波擾動來控制液滴吸收溶質之情形，且引進兩個重要性參數，無因次振幅與無因次頻率，且其範圍分別為0.1-0.99與0.1-1000，若要使液滴吸收量增加，可選擇較大的無因次振幅，與較小的無因次頻率來進行吸收。針對無因次頻率等於1時，液滴則須控制在無因次時間為0.31-0.36，方能達到較大的吸收量。

Gas absorption by droplets is an important route to reduce greenhouse gas emissions, especially for carbon dioxide. To recognize the fundamental absorption processes of greenhouse gases by single droplets, the mass transport phenomena of greenhouse gas uptake by a quiescent water droplet at atmospheric and elevated pressures are analyzed theoretically and four common greenhouse gases of CO2, N2O, CH4 and O3 are taken into consideration. On account of piecewise function encountered at the droplet surface, it is impossible to obtain a fully analytical solution for describing the mass transfer process. Instead, a semi-analytical method is developed to predict the mass diffusion between the gas phase and the liquid phase. The obtained results indicate that, by virtue of the four greenhouse gases characterized by low mass diffusion number, the entire mass transfer is controlled by the liquid phase and a unified formula has been successfully established to aid in estimating the dimensionless solute uptake process. For the ambient temperature and pressure in the ranges of 280-350K and 1-20 atm, respectively, it is found that increasing the two parameters will intensify the solute absorption amount significantly, whereas the absorption process can be accelerated by increasing temperature alone. To recognize the CO2 capture dynamic by a quiescent water droplet, a theoretical analysis under the conditions of 25°C and 1atm is performed in this work, with emphasis on the effect of acoustic excitation upon the absorption process. The dimensionless fluctuated amplitude and frequency of the acoustic wave are in the ranges of 0.1-0.99 and 0.1-1000, respectively. The analyses suggest that an acoustic wave with smaller amplitude and higher frequency leads to a more drastic energy decay in the droplet due to the role of damping played by the droplet. In contrast, a pressure excitation with larger amplitude and lower frequency has a pronounced effect on the mass transfer process, as a result of higher efficiency of energy penetrating into the liquid phase. From the perspective of achieving carbon capture and storage (CCS), the acoustic excitation with the dimensionless frequency of unity is recommended to capture CO2 by a droplet and the exposure time of the droplet should be controlled at the dimensionless aqueous diffusion time (τι) of 0.31-0.36.

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