مهندسی شیمی ایران

مهندسی شیمی ایران

شبیه‌سازی CFD برای بررسی کیفیت اختلاط به‌وسیلۀ همزن‌هایی با تیغه‌هایی به‌اشکال هندسی مختلف

نوع مقاله : مقاله پژوهشی

نویسندگان
1 کارشناس ارشد مهندسی شیمی، دانشگاه کردستان
2 دانشیار مهندسی شیمی، دانشگاه کردستان
چکیده
طراحی بهینۀ مخازن همزن‌دار به‌منظور افزایش میزان اختلاط در صنایع، بسیار مهم است. این تحقیق، به بررسی تأثیر مشخصه‌های عملیاتی مختلف، مانند نوع و زاویۀ پره‌های همزن و هم‌چنین، دور همزن بر میزان اختلاط اختصاص‌داده‌شد. چهار نوع مختلف پره، شامل: راشتون، اسمیت توربین، راشتون برگشتی و پروانۀ برگشتی طراحی و در دورهای 20، 40 و 60 دوربردقیقه و هم‌چنین، در سرعتهای مختلف جریان ورودی به مخزن؛ شامل 0/028، 0/03، 0/04 و 0/05 متربرثانیه بهمنظور بررسی عملکرد اختلاط با روش دینامیک سیالات محاسباتی مدلسازیشد. نتایج نشانداد که در بین مدلهای طراحیشده، پرۀ راشتون برگشتی بهترین میزان اختلاط و نزدیک‌ترین رفتار را نسبتبه حالت آرمانی دارد که درنسبت زمان اختلاط به زمان ماند (θ) برابربا 3، نسبت اختلاط آن برابربا 0/083879 تعیینشد. هم‌چنین، مشاهدهشد که با افزایش سرعت ورودی، شیب تغییرات اختلاط نیز تندتر شدهاست. مشاهدهشد که پرۀ راشتون برگشتی، کمترین حساسیت را نسبتبه تغییر دور درمقایسهبا سه پرۀ دیگر ازخود نشان‌می‌دهد. ازمیان کلیۀ موارد مطالعهشده، بهترین میزان اختلاط برای پرۀ راشتون برگشتی در دور برابربا rpm 20 و سرعت 0/03 متربرثانیه به‌دستآمد.
کلیدواژه‌ها

موضوعات


عنوان مقاله English

CFD Simulation to Evaluate the Mixing quality by Mixers with Different Blade Shapes

نویسندگان English

Y. Basereh 1
R. Beigzadeh 2
1 M. Sc. in Chemical Engineering, University of Kurdistan
2 Associate Professor of Chemical Engineering, University of Kurdistan
چکیده English

The optimum design of mixing tank reactors is very important to increase the mixing in industries. This study examined how varying operational factors, such as the type and angle of stirring blades, as well as the rotational speed, affect mixing rates. Four types of mixers (Rushton, Smith Turbine, Reversible Rushton, and Reversible Propeller) were modeled using computational fluid dynamics techniques to assess their mixing performance. The study analyzed the effects of varying rotational speeds (20, 40, and 60 rpm) and inlet flow velocities (0.028, 0.03, 0.04, and 0.05 m/s) on the mixing efficiency. The results showed that, among the designed models, the Reversible Rushton has the best mixing rate and the closest behavior to the ideal state. Where θ is equal to 3, its mixing factor is equal to 0.083879. Additionally, it was noted that as the inlet velocity increased, the rate of change in mixing also became more pronounced. It was observed that the Reversible Rushton shows the least sensitivity to the change of rotational speed compared to the other three blades. The Reversible Rushton model at 20 rpm rotational speed and 0.03 m/s inlet velocity demonstrated the highest mixing rate among all investigated cases.

کلیدواژه‌ها English

Simulation
Computational Fluid Dynamics
Stirred Tank
Blade Shape
Mixing
[1]        Karpinska, A. M., & Bridgeman, J. (2016). CFD-aided modelling of activated sludge systems – A critical review. Water Research, 88, 861–879.
[2]        Sharan, V., Rohit, K., Ravishankar, M., Bhuvaneshwar, D., & Harish, R. (2020, December). CFD simulation of turbulent flow behaviour in a mixing reactor with Rushton impeller. In Journal of Physics: Conference Series, 1716, 012025.
[3]        Hoseini, S. S., Najafi, G., Ghobadian, B., & Akbarzadeh, A. H. (2021). Impeller shape-optimization of stirred-tank reactor: CFD and fluid structure interaction analyses. Chemical Engineering Journal, 413, 127497.‏
[4]        Ranade, V. V., Joshi, J. B. (1989). Flow generated by pitched blade turbines I. Measurements using laser Doppler anemometer. Chemical Engineering Communications, 81, 197–224.
[5]        We-Ming, L., Hong-Zhang, W., Nai-Yu, C., & Yu-Li, L. (2000). Effect of the blade size on the vortex structure and gas dispersion in gas–liquid stirred vessels with a single Rushton turbine impeller. Proceedings of the National Science Council, Republic of China, 24, 166–175.
[6]        Firoz, R. K., Chris, D. R., & Grahan, K. H. (2004). A multi-block approach to obtain angle resolved PIV measurements of the mean flow and turbulence fields in a stirred vessel. Chemical Engineering & Technology, 27, 264–269.
[7]        Fasano, J. B., Bakker, A., Penney, W. R. (1994). Advanced impeller geometry boosts liquid agitation. Chemical Engineering, 101: 110–116.
[8]        Rajavathsavai, D., Khapre, A., & Munshi, B. (2014). Study of mixing behavior of cstr using CFD. Brazilian Journal of Chemical Engineering, 31,119-129.‏
[9]        Karcz, J., & Cudak, M. (2003, October). Local momentum and heat transfer in a liquid and gas–solid–liquid systems mechanically stirred in a jacketed vessel. In 11th European Conference on Mixing, 14-17.‏
[10]      Yang, F. L., Zhou, S. J., Zhang, C. X., & Wang, G. C. (2013). Mixing of initially stratified miscible fluids in an eccentric stirred tank: Detached eddy simulation and volume of fluid study. Korean Journal of Chemical Engineering, 30, 1843.
[11]      Godleski, E. S., & Smith, J. C. (1962). Power requirements and blend times in the agitation of pseudoplastic fluids. AIChE Journal, 8, 617-620.‏
[12]      Zhang, Q., Yang, C., Mao, Z. S., & Mu, J. (2012). Large eddy simulation of turbulent flow and mixing time in a gas–liquid stirred tank. Industrial & engineering chemistry research, 51, 10124-10131.‏
[13]      Akiti, O., Yeboah, A., Bai, G., & Armenante, P. M. (2005). Hydrodynamic effects on mixing and competitive reactions in laboratory reactors. Chemical engineering science, 60, 2341-2354.‏
[14]      Kumaresan, T., Joshi, J. B, (2006). Effect of impeller design on the flow pattern and mixing in stirred tanks. Chemical Engineering Journal, 115: 173–193.
[15]      Torotwa, I., Ji, C., (2018). A Study of the Mixing Performance of Different Impeller Designs in Stirred Vessels Using Computational Fluid Dynamics. Designs, 2, 10.
[16]      Satjaritanun, P., Bringley, E., Regalbuto, J. R., Regalbuto, J. A., Register, J., Weidner, J. W., & Shimpalee, S. (2018). Experimental and computational investigation of mixing with
contra-rotating, baffle-free impellers. Chemical Engineering Research and Design, 130, 63–77.
[17]      Murthy, B. N., Ghadge, R. S., & Joshi, J. B. (2007). CFD simulations of gas–liquid–solid stirred reactor: Prediction of critical impeller speed for solid suspension. Chemical Engineering Science, 62, 7184–7195.
[18]      Amani, R., & Beigzadeh, R. (2021). Comparison of Hydrodynamic Performance of Three Types of Static Mixers Using Computational Fluid Dynamics and Artificial Neural Network. Iranian Chemical Engineering Journal, 20, 94-109, [In Persian].
[19]      , L. A., Shagarova, A. A.,  & Goncharov, I. O. (2020). Comparative Analysis of the Performance of Oscillating and Propeller Stirrers, International Conference on Industrial Engineering, 1340-1347.
[20]      Reviol, T., Kluck, S., & Böhle, M. (2018). A new design method for propeller mixers agitating non-Newtonian fluid flow. Chemical Engineering Science, 190, 320–332.
[21]      Moayeri Kashani, M., Lai, S. H., Ibrahim, S., & Moradi Bargani, P. (2016). Design factors affecting the dynamic performance of soil suspension in an agitated, baffled tank. Chinese Journal of Chemical Engineering, 24, 1664–1673.
[22]      Choupani, M., Ghaibi, S., Taghavi, M., & Moghadas, J., (2009). The effect of impeller type on mixing time in stirred tanks. Journal of Iranian Chemical Engineering, 8, 60-65, [In Persian].
[23]      Burghardt, A., & Lipowska, L. (1972). Mixing phenomena in a continuous flow stirred tank reactor. Chemical Engineering Science, 27, 1783-1795.‏