شبیه‌سازی عددی جریان جابجایی اجباری آرام همراه با آنالیز تولید انتروپی در یک کانال دارای دو انبساط ناگهانی - روش انسداد کردن

نوع مقاله: مقاله مکانیک

نویسندگان

1 باشگاه پژوهشگران جوان و نخبگان، واحد سیرجان، دانشگاه آزاد اسلامی، سیرجان، ایران

2 استادیار، دانشکده مهندسی مکانیک، دانشگاه صنعتی سیرجان، سیرجان، ایران

چکیده

در تحقیق حاضر، شبیه ‌سازی عددی جریان جابجایی اجباری آرام همراه با آنالیز تولید انتروپی، در یک کانال دو بعدی و دارای دو انبساط ناگهانی مورد مطالعه قرار می‌گیرند. این دو انبساط، توسط چهار پله‌ شیب‌دار پسرو ایجاد شده و باعث به وجود آمدن جدایش جریان و نواحی گردابه‌ای می‌شوند. نواحی گردابه‌ای ایجاد شده در کانال نیز، بطور قابل توجه‌ای بر نرخ انتقال حرارت و میزان بازگشت ناپذیری جریان تأثیر می‌گذارند. اندازه زاویه شیب پله‌ها، یکی از مهم‌ترین پارامترهای مؤثر بر کنترل نواحی گردابه‌ای، نرخ انتقال حرارت و میزان بازگشت ناپذیری جریان است. در این مطالعه، بعد از محاسبه میدان‌های سرعت و دما، به بررسی اثرات شیب پله بر نواحی جدایش جریان، ضریب اصطکاک، عدد ناسلت، عدد تولید انتروپی و عدد بژان پرداخته می‌شود. برای محاسبه میدان‌های سرعت و دما، معادلات حاکم شامل معادلات بقای جرم، ممنتوم و انرژی برای جریان تراکم ناپذیر و پایا با استفاده از روش‌های حجم محدود و تکنیک‌های دینامیک سیالات محاسباتی حل می‌شوند. برای شبیه‌سازی سطوح شیب‌دار پله‌های پسرو در مختصات کارتزین، از روش انسداد کردن (روش ناحیه غیر فعال)، استفاده می‌شود. همچنین، با استفاده از روابط مربوط به آنالیز قانون دوم ترمودینامیک، به محاسبه‌ی تولید انتروپی و میزان بازگشت ‌ناپذیری جریان سیال پرداخته می‌شود. در نهایت، تأثیر عدد بریکمن بر عدد تولید انتروپی و عدد بژان به‌صورت نموداری بررسی می‌شود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Numerical simulation of laminar forced convection flow with entropy generation analysis in a duct with two expansions - Blocked-off method

نویسندگان [English]

  • Shima Sotoodehnia 1
  • Nasrin Aminizadeh 2
  • Meysam Atashafrooz 2
1 Young Researchers and Elite Club, Sirjan Branch, Islamic Azad University, Sirjan, Iran
2 Department of Mechanical Engineering, Sirjan University of Technology, Sirjan, Iran
چکیده [English]

In the present paper, numerical simulations of laminar forced convection flow and entropy generation analysis in a 2-D duct with two sudden expansions are investigated. These two expansions are created by four inclined backward facing steps and beget the separation flows and vortex regions. The vortex regions have the significant effects on the heat transfer rates and flow irreversibility. The inclination angle of steps is one of effective parameters on the control of the separation flows, heat transfer rates and flow irreversibility. In this paper, after calculation of velocity fields and temperature distributions, the effect of the step inclination angle on the separated flows, Nusselt number, friction coefficient, entropy generation number and Bejan number is studied. To obtain the temperature distributions and velocity fields, the set of governing equations including mass, momentum and energy equations are solved by the finite volume methods and computational fluid dynamic (CFD) techniques. For simulating the inclined surfaces of steps in Cartesian coordinates, the blocked-off method is used. Also, thermodynamic second law analysis is employed to calculate the entropy generation and flow irreversibility. Finally, the effect of the Brickman number on the entropy generation number and Bijan number is investigated graphically.

کلیدواژه‌ها [English]

  • Entropy Generation
  • Laminar Forced Convection
  • Inclined Step
  • Blocked off Method
  • Computational Fluid Dynamic (CFD)
[1] Y. L. Tsay, T. S. Chang, and J. C. Cheng, “Heat Transfer Enhancement of Backward-Facing Step Flow in a Channel by Using Baffle Installation on Channel Wall”, ACTA Mechanica, Vol. 174, 2005, pp. 63–76.

[2] E. Erturk, “Numerical Solutions of 2-D Steady Incompressible Flow over a Backward Facing Step, Part I: High Reynolds Number Solutions”, Computers & Fluids, Vol. 37, 2008, pp. 633–655.

[3] J. H. Nie, Y .T. Chen, and H. T. Hsieh, “Effects of a Baffle on Separated Convection Flow adjacent to Backward-Facing Step”, International Journal of Thermal Sciences, Vol. 48, 2009, pp. 618–625.

[4] H. F. Oztop, K .S. Mushatet, and İ. Yılmaz, “Analysis of Turbulent Flow and Heat Transfer over a Double Forward Facing Step with Obstacles”, International Communications in Heat and Mass Transfer, Vol. 39, NO. 9, 2012, pp. 1395–1403.

[5] M. Atashafrooz, and S. A. Gandjalikhan Nassab, “Simulation of Three-Dimensional Laminar Forced Convection Flow of a Radiating Gas over an Inclined Backward-Facing Step in a Duct under Bleeding Condition”, Institution of Mechanical Engineers, Part C, Journal of Mechanical Engineering Science, Vol. 227, NO. 2, 2012, pp. 332-345.

[6] F. Selimefendigil, and H. F. Oztop, “Numerical Analysis of Laminar Pulsating Flow at a Backward Facing Step with an Upper Wall Mounted Adiabatic Thin Fin”, Computers & Fluids, Vol. 88, 2013, pp. 93-107.

[7] M. Atashafrooz, S. A. Gandjalikhan Nassab, and K. Lari, “Numerical Analysis of Interaction Between Non-Gray Radiation and Forced Convection Flow over a Recess Using the Full-Spectrum K-Distribution Method”, Heat and Mass Transfer, Vol. 52, NO. 2, 2016, pp. 361-377.

[8] A. S. Kherbeet, M. R. Safaei, H. A. Mohammed, B. H. Salman, H. E. Ahmed, O. A. Alawi, and M. T. Al-Asadi, “Heat Transfer and Fluid Flow over Microscale Backward and Forward Facing Step: A Review”, International Communications in Heat and Mass Transfer, Vol. 76, 2016, pp. 237-244.

[9] M. Atashafrooz, S. A. Gandjalikhan Nassab, and K. Lari, “Coupled Thermal Radiation and Mixed Convection Step Flow of Non-gray Gas”, Journal of Heat Transfer (ASME), Vol. 138, NO. 7, 2016, 072701–9.

[10] A. Nouri-Borujerdi, and A. Moazezi, “Investigation of Obstacle Effect to Improve Conjugate Heat Transfer in Backward Facing Step Channel Using Fast Simulation of Incompressible Flow”, Heat and Mass Transfer, Vol. 54, NO. 1, 2018, pp. 135-150.

[11] A. Bejan, Entropy Generation Through Heat and Fluid Flow, John Wiley & Sons Inc., Canada, 1994.

[12] A. Bejan, Entropy Generation Minimization, CRC Press, Boca Raton, New York, USA, 1996.

[13] I. Dagtekin, H. F. Oztop, and A. Bahloul, “Entropy Generation for Natural Convection in Γ-shaped Enclosures”, International Communications in Heat and Mass Transfer, Vol. 34, NO. 4, 2007, pp. 502-510.

[14] H. M. S. Bahaidarah, and A. Z. Sahin, “Thermodynamic Analysis of Fluid Flow in Channels with Wavy Sinusoidal Walls”, Thermal Science, Vol. 17, NO. 3, 2013, pp. 813-822.

[15] R. K. Nayak, S. Bhattacharyya, I. Pop, “Heat Transfer and Entropy Generation in Mixed Convection of a Nanofluid within an Inclined Skewed Cavity”, International Journal of Heat and Mass Transfer, Vol. 102, 2016, pp. 596–609.

[16] M. Mamourian, K. M. Shirvan, R. Ellahi, and A. B. Rahimi, “Optimization of Mixed Convection Heat Transfer with Entropy Generation in a Wavy Surface Square Lid-driven Cavity by Means of Taguchi Approach”, International Journal of Heat and Mass Transfer, Vol. 102, 2016, pp. 544-554.

[17] H. F. Oztop, L. Kolsi, A. Alghamdi, N. Abu-Hamdeh, M. N. Borjini, and H. B. Aissia, “Numerical Analysis of Entropy Generation due to Natural Convection in Three-dimensional Partially Open Enclosures”, Journal of the Taiwan Institute of Chemical Engineers, Vol. 75, 2017, pp. 131-140.

[18] A. Bahrami, and S. A. Gandjalikhan Nassab, “Study of Entropy Generation in Laminar Forced Convection Flow over a Forward-Facing Step in a Duct”, International Review of Mechanical Engineering,Vol. 4, NO. 4, 2010, pp. 399-404.

[19] E. Abu-Nada, “Numerical Prediction of Entropy Generation in Separated Flows”, Vol.7, NO. 4, 2005, pp. 234-252.

[20] E. Abu-Nada, “Investigation of Entropy Generation over a Backward Facing Step under Bleeding Conditions”, Energy Conversion and Management, Vol. 49, NO. 11, 2008, pp. 3237-3242.

[21] M. Atashafrooz, S. A. Gandjalikhan Nassab, and A. B. Ansari, “Numerical Investigation of Entropy Generation in Laminar Forced Convection Flow over Inclined Backward and Forward Facing Steps in a Duct under Bleeding Condition”, Thermal Science, Vol. 18, NO. 2, 2014, pp. 479-492.

[22] M. Atashafrooz, S. A. Gandjalikhan Nassab, and A. B. Ansari, “Numerical Study of Entropy Generation in Laminar Forced Convection Flow over Inclined Backward and Forward Facing Steps in a Duct”, International Review of Mechanical Engineering(I.RE.M.E.), Vol. 5, NO. 5, 2011, pp. 898-907.

[23] S. V. Patankar, and D. B. Spalding, “A Calculation Procedure for Heat, Mass and Momentum Transfer in Three-dimensional Parabolic Flows”, International Journal of Heat and Mass Transfer, Vol. 15, NO. 10, 1972, pp. 1787–1806.

[24] S. V. Patankar, Numerical Heat Transfer and Fluid Flow, Taylor & Francis, Philadelphia, Penn., USA, Chapter 7, 1981.

[25] D. Y. Byun, S. W. Baek, and M. Y. Kim, “Investigation of Radiative Heat Transfer in Complex Geometries using Blocked-off, Multiblock, and Embedded Boundary Treatments”, Numerical Heat Transfer—Part A, Vol. 43, 2003, pp. 807-825.

[26] M. Atashafrooz, and S.A. Gandjalikhan Nassab, “Numerical Analysis of Laminar Forced Convection Recess Flow with Two Inclined Steps Considering Gas Radiation Effect”, Computers and Fluids, Vol. 66, 2012, pp. 167-176.

[27] M. Atashafrooz, and S. A. Gandjalikhan Nassab, “Combined Heat Transfer of Radiation and Forced Convection Flow of Participating Gases in a Three-dimensional Recess”, Journal of Mechanical Science and Technology, Vol. 26, NO. 10, 2012, pp. 3357-3368.

[28] A. B. Ansari, and S. A. Gandjalikhan Nassab, “Numerical Analysis of Laminar Forced Convection Flow of a Radiating Gas over an Inclined Forward Facing Step”, International Review of Mechanical Engineering, Vol. 5, NO. 1, 2011, pp. 120-127.

[29] A. B. Ansari, and S. A. Gandjalikhan Nassab, “Forced Convection of Radiating Gas over an Inclined Backward Facing Step Using the Blocked-off Method”, Thermal Science, Vol. 17, NO. 3, 2013, pp. 773-786.