在許多的工業製程中，若需要利用除濕效果來輔助產能的提升或有效率地清除工業過程中排放的產物，矽膠是業界很常用的多孔性材料，因其價格低廉且吸附效率又好，並能利用脫附機制，使我們能在安全的情況下將產物回收。在過往的研究中，本實驗室持續針對矽膠填充床系統之數值模擬及實驗進行研究。隨著模型幾何複雜程度的提升，與對填充床內部流場更全面的設定，在模擬結果上一直有著更好的表現，但也伴隨著計算時間倍增與增加模型建置的困難度。
為了提升模擬計算上之工作效率，與方便改良填充床系統的各項可控參數與幾何構造，使我們能在多種情況下進行分析與比較，本研究使用模擬軟體建立一矽膠填充床吸/脫附反應之準氣體側控制(pseudo-gas-side controlled; PGC)計算模型，以探討吸/脫附過程中控制參數的變化對反應速率與反應結果之影響，讓我們能透過後處理比較出在何種情況下是有利於進行矽膠填充床吸/脫附反應。另外，本研究將過去為了減少迭代計算時間所對數學方程式中簡化的軸向擴散項重新加入至方程式，使我們能更精確地模擬出填充床內空氣的流動過程，但由於本研究是採用PGC模型進行計算，因此相較於考慮矽膠固體測阻抗(solid-side resistance; SSR)之模型，SSR模型更能準確預測反應過程，也是未來在研究上能對此計算模型進行改良之部分。經過模擬後，我們發現由於填充床系統內入、出口壓差僅有2.43 Pa的變化，故反應達穩態系統內部各點之矽膠含水量不會有太大的差異。除此之外，在矽膠吸/脫附反應過程與結果上均與實驗室學長姐的模擬成果有相同之趨勢，當入口濕度提高與溫度下降時，會提升整體吸附水汽之反應速率，若是脫附反應則恰好相反；另一方面我們發現入口速度越大將有助於提升系統吸/脫反應之效率，令系統達穩態所需耗費時間均有一定程度的降低。此外我們亦發現在給定的室溫23.3℃與出口壓力為1 atm之情況下，脫附反應需要花費約50000 s達到系統內部平衡，而吸附反應僅需35000 s就完成填充床系統的平衡。

Silica-gel packed bed is extensively used in various industrial processes such as the solar dehumidification air conditioning system and adsorption of volatile organic compounds. In order to help design these industrial applications, it is necessary to understand the heat and mass transfer mechanism of moisture adsorption/desorption in a silica-gel packed bed. In previous works of our group at NCKU, we have developed numerical models for the aforementioned objectives. As the geometric and flow complexities of such models increase, more accurate results generally can be obtained. But the computation time and difficulty of model construction will increase as well. In order to facilitate the implementation of numerical computations, so as to examine the effects of various process parameters on the reaction characteristics more efficiently, in this study software is used to establish a pseudo-gas-side controlled (PGC) calculation model for the moisture adsorption/ desorption reaction in a silica gel packed bed. The numerical results obtained in this work indicate that, when the inlet humidity increases and the system temperature decreases, the average reaction rate of adsorption of water vapor will increase. And for desorption reaction, the opposite trend is observed. It is also found that the higher the inlet speed is, the higher the average rate of the absorption/ desorption reaction will be.

[1] J. Clark, A. Mills, and H. Buchberg, “Design and testing of thin adiabatic desiccant beds for solar air conditioning applications,” Journal of Solar Energy Engineering, vol. 103, pp. 89-91, 1981.
[2] H. Sui, H. Liu, P. An, L. He, X. Li and S. Cong, “Application of silica gel in removing high concentrations toluene vapor by adsorption and desorption process,” Journal of the Taiwan Institute of Chemical Engineers, vol. 74, pp. 218-224, 2017.
[3] H. Deshmukh, M. P. Maiya and S. S. Murthy, “Study of sorption based energy storage system with silica gel for heating application,” Applied Thermal Engineering, vol. 111, pp. 1640-1646, 2017.
[4] 方煒, “設施生產自動化技術,” E-book, Bio-Industrial Mechatronics Engineering, National Taiwan University http://WWW.ECAA.NTU.EDU.TW/weifang/Hort/default.htm, 2012/8/29
[5] A. A. Pesaran and A. F. Mills, “Moisture transport in silica gel packed beds—I. Theoretical study,” International Journal of Heat and Mass Transfer, vol. 30, pp. 1037-1049, 1987.
[6] A. A. Pesaran and A. F. Mills, “Moisture transport in silica gel packed beds—II. Experimental study,” International Journal of Heat and Mass Transfer, vol. 30, pp. 1051-1060, 1987.
[7] K. Kafui, “Transient heat and moisture transfer in thin silica gel beds,” Journal of Heat Transfer, vol. 116, pp. 946-953, 1994.
[8] J.-Y. San and G.-D. Jiang, “Modeling and testing of a silica gel packed-bed system,” International Journal of Heat and Mass Transfer, vol. 37, pp. 1173-1179, 1994.
[9] T. Dobre, O. C. Parvulescu, G. Iavorschi, M. Stroescu and A. Stoica, “Volatile organic compounds removal from gas streams by adsorption onto activated carbon,” Industrial and Engineering Chemistry Research, vol. 53, pp. 3622-3628, 2014.
[10] J. A. Bernstein, N. Alexis, H. Bacchus, I. L. Bernstein, P. Fritz and E. Horner, “The health effects of nonindustrial indoor air pollution,” Journal of Allergy and Clinical Immunology, vol. 121, pp. 585-591, 2008.
[11] J. F. Saldarriaga, R. Aguado and G. E. Morales, “Assessment of VOC emissions from municipal solid waste composting,” Environmental Engineering Science, vol. 31, pp. 300-307, 2014.
[12] W. Wei, S. Wang, J. Hao and S. Cheng, “Trends of chemical speciation profiles of anthropogenic volatile organic compounds emissions in China, 2005–2020,” Frontiers of Environmental Science & Engineering, vol. 8, pp. 27-41, 2014.
[13] B. P. Kelleher, A. M. Doyle, B. K. Hodnett and T. F. O’Dwyer, “An Investigation into the Adsorption Characteristics of Grafted Mesoporous Silicates for the Removal of Tetramethyl Ammonium Hydroxide from Aqueous Solution,” Adsorption Science & Technology, vol. 20, pp. 787-796, 2002.
[14] D. Prahas, J. Liu, S. Ismadji and M. J. Wang, “Adsorption of tetramethylammonium hydroxide on activated carbon,” Journal of Environmental Engineering, vol. 138, pp. 232-238, 2012.
[15] D. S. Ju, “Effects of release-pressure control on the hydrogen supply characteristics of metal hydride reactors,” Master’s Thesis, National Cheng Kung University, 2008.
[16] W. L. Tsui, Theoretical Modeling and Numerical Simulation for The Hydrogen Storage Characteristics of Metal Hydride Particles, Master’s Thesis, National Cheng Kung University, 2010.
[17] M. L. Tsai, Thermofluid analysis of metal-hydride hydrogen storage systems: Effects of exit pressure control and metal-foam volume fraction on system performance, Doctor’s Thesis, National Cheng Kung University, 2011.
[18] C. E. Li, Effects of metal foam volume-fraction distribution on the performance of metal-hydride hydrogen storage systems, Master’s Thesis, National Cheng Kung University, 2011.
[19] C. M. Wu, An experimental study on the thermal management of porous adsorption reactors, Master’s Thesis, National Cheng Kung University, 2013.
[20] S. H. Lin, Experimental Performance Analysis of Thermal Management for Porous Adsorption/ Desorption Reactors, Master’s Thesis, National Cheng Kung University, 2014.
[21] T. P. Syawitri, Numerical Investigation into The Effect of Metal-foam Volume Fraction on The Performance of Metal Hydride Reactor Subjected to Periodic Charging and Discharging, Master’s Thesis, National Cheng Kung University, 2015.
[22] K. C. Chuang, Numerical Performance Simulation of a Metal Hydride Reactor with Spatially Distributed Metal-foam Volume Fraction, Master’s Thesis, National Cheng Kung University, Tainan, 2015.
[23] L. Y. Huang, A numerical study on moisture adsorption/desorption in silica gel packed beds, Master’s Thesis, National Cheng Kung University, 2016.
[24] T. I. Wu, Numerical Heat and Mass Transfer Analysis for Moisture Adsorption/ Desorption in Axisymmetric Silica-gel Packed Beds, Master’s Thesis, National Cheng Kung University, 2017.
[25] O. Hougen and W. Marshall, “Adsorption from a fluid stream flowing through a stationary granular bed,” Chemical Engineering Progress, vol. 43, pp. 197-208, 1947.
[26] M. Firdaouss, J.-L. Guermond and P. Le Quéré, “Nonlinear corrections to Darcy’s law at low Reynolds numbers” J. Fluid Mech. vol. 343, pp. 331–350, 1997.
[27] J. Q. Ni, Development of a theoretical adsorption model under constant pressure condition and measurement of apparent solid-side mass diffusivity for a silica gel-water vapor adsorption system, Doctor’s Thesis, Mechanical Engineering, National Chung Hsing University, 2001.
[28] N. Wakao, S. Kaguei and T. Funazkri, “Effect of fluid dispersion coefficients on particle-to-fluid heat transfer coefficients in packed beds: correlation of Nusselt numbers,” Chemical engineering science, vol. 34, pp. 325-336, 1979.
[29] N. Wakao and T. Funazkri, “Effect of fluid dispersion coefficients on particle-to-fluid mass transfer coefficients in packed beds: correlation of Sherwood numbers,” Chemical Engineering Science, vol. 33, pp. 1375-1384, 1978.
[30] Ting-Hsuan Hsu, Numerical Heat and Mass Transfer Analysis for Moisture Adsorption/
Desorption in porous Silica-gel Packed Beds, Master’s Thesis, National Cheng Kung
University, 2019.
[31] Huang, Jianhua. "A simple accurate formula for calculating saturation vapor pressure of water and ice." Journal of Applied Meteorology and Climatology , vol.57.6,pp. 1265-1272, 2018.
[32] Chang, Kuei-Sen, Hui-Chun Wang, and Tsair-Wang Chung. "Effect of regeneration conditions on the adsorption dehumidification process in packed silica gel beds." Applied Thermal Engineering , vol.24.5-6,pp. 735-742, 2004
[33] Ruivo, C. R., J. J. Costa, and A. R. Figueiredo. "Analysis of simplifying assumptions for the numerical modeling of the heat and mass transfer in a porous desiccant medium." Numerical Heat Transfer, Part A: Applications ,vol. 49.9,pp. 851-872, 2006

[34] Ruivo, C. R., J. J. Costa, and A. R. Figueiredo. "Validity of pseudo-gas-side-controlled models to predict the behaviour of desiccant matrices." International journal of thermal sciences vol. 48.11,pp. 2171-2178, 2009
[35] Nam, Jinmoo, Johan Ko, and Hyunchul Ju. "Three-dimensional modeling and simulation of hydrogen absorption in metal hydride hydrogen storage vessels." Applied energy vol.89.1, pp. 164-175, 2012
[36] Kyoung, Sunghyun, et al. "Three-dimensional modeling and simulation of hydrogen desorption in metal hydride hydrogen storage vessels." international journal of hydrogen energy vol.40.41, pp. 14322-14330, 2015
[37] Zhuo, Yuting, Siwoo Jung, and Yansong Shen. "Numerical Study of Hydrogen Desorption in an Innovative Metal Hydride Hydrogen Storage Tank." Energy & Fuels 2021
[38] Sui, H., Liu, H., An, P., He, L., Li, X., & Cong, S. "Application of silica gel in removing high concentrations toluene vapor by adsorption and desorption process." Journal of the Taiwan Institute of Chemical Engineers vol. 74, pp 218-224, 2017
[39] Mohammed, R. H., Mesalhy, O., Elsayed, M. L., Su, M., & Chow, L. C. "Revisiting the adsorption equilibrium equations of silica-gel/water for adsorption cooling applications." International Journal of Refrigeration vol. 86, pp. 40-47, 2018