Geometrical Effects of Duct on the Entropy Generation in the Laminar Forced Convection Separated Flow

Subject Areas : Mechanical Engineering

Nasrin  Aminzadeh ¹ (Department of Mechanical Engineering, Sirjan University of Technology, Sirjan, Iran)
Shima  Sotoodehnia ² (Sirjan Branch. Islamic Azad University, Sirjan, Iran.)
Meysam  Atashafrooz ³ (Department of Mechanical Engineering, Sirjan University of Technology, Sirjan, Iran)

Received: 2018-05-18 Accepted : 2018-09-10 Published : 2018-09-10

Keywords: Flow Irreversibility, Entropy Generation, Blocked-Off Method, Convection Heat Transfer, Variable Cross-Section,

Abstract :

In this research paper, irreversibility analysis of laminar forced convection flow in a duct with variable cross-section are numerically studied. Two-dimensional Cartesian coordinate system is used to solve the set of governing equations and also the blocked-off method is considered for simulation of the inclined surfaces. To obtain the velocity and temperature fields, the basic equations are numerically solved using the finite volume method and SIMPLE algorithm. To determine the flow irreversibility, the entropy generation number is calculated according to the thermodynamic second law. The geometrical effects of duct on the distributions of streamlines, friction coefficient, Nusselt number, entropy generation, and Bejan number are presented with details. The results show that the duct heights and inclination angle of surfaces have great effects on the flow irreversibility and the hydrodynamics and thermal behaviours. Also, comparison of the present numerical results with the available data published in the open literature shows an excellent consistency.

References:

[1]       Tylli, N., Kaiktsis L., and Ineichen, B., Side Wall Effects in Flow Over Backward-Facing Step: Experiments and Numerical Solutions, Physics Fluids, Vol. 14, No. 11, 2002, pp. 3835-3845.

[2]       Erturk, E., Numerical Solutions of 2-D Steady Incompressible Flow over a Backward-facing Step, Part I: High Reynolds Number Solutions, Computers & Fluids, Vol. 37, No. 6, 2008, pp. 633–655.

[3]       Abu-Mulaweh, H. I., A Review of Research on Laminar Mixed Convection Flow over Backward and Forward-facing Steps, International Journal of Thermal Sciences, Vol. 42, No. 9, 2003, pp. 897-909.

[4]       Armaly, B. F., Li, A., and Nie, J. H., Measurements in Three-Dimensional Laminar Separated Flow, International Journal of Heat and Mass Transfer, Vol. 46, No. 19, 2003, pp. 3573–3582.

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

[6]       Selimefendigil, F., Oztop, H. F., 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]       Atashafrooz, M., Gandjalikhan Nassab, S. A., and Lari, K., 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]       Brakely, D., Gabriela, M., Gomes M., and Henderson, R. D., Three-Dimensional Instability in Flow Over a Backward- Facing Step, Journal of Fluid Mechanics, Vol. 473, 2002, pp. 167-190.

[9]       Nie, J. H., Armaly, B. F., Three-Dimensional Convective Flow Adjacent to Backward-Facing Step - Effects of Step Height, International Journal of Heat and Mass Transfer, Vol. 45, No. 12, 2002, pp. 2431–2438.

[10]    Atashafrooz, M., Gandjalikhan Nassab, S. A., and Lari, K., Numerical study of Coupled Non-Gray Radiation and Separation Convection Flow in a Duct Using the FSK Method, International Journal of Advanced Design and Manufacturing Technology, Vol. 9, No. 4, 2016, pp. 23-38.

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

[12]    Tsay, Y. L., Chang, T. S., and Cheng, J. C., 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.

[13]    Oztop, H. F., Mushatet, K. S., and Yılmaz, I˙., 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.

[14]    Chen, Y. T., Nie, J. H., Hsieh, H. T., and Sun, L. J., Three-Dimensional Convection Flow Adjacent to Inclined Backward-Facing Step, International Journal Heat Mass Transfer, Vol. 49, 2006, pp. 4795–4803.

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

[16]    Lari, K., Gandjalikhan Nassab, S. A., Analysis of Combined Radiative and Conductive Heat Transfer in Three-Dimensional Complex Geometries Using Blocked-off Method, Transactions of Mechanical Engineering, Vol. 35, M2, 2011, pp. 107-119.

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

[18]    Atashafrooz, M., Gandjalikhan Nassab, S. A., 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.

[19]    Atashafrooz, M., Gandjalikhan Nassab, S. A., and Sadat Behineh, E., Effects of Baffle on Separated Convection Step Flow of Radiating Gas in a Duct, International Journal of Advanced Design and Manufacturing Technology, Vol. 8, No. 3, Sep. 2015, pp. 33-47.

[20]    Byun, D. Y., Beak, S. W., and Kim, M. Y., Investigation of Radiative Heat Transfer in Complex Geometries Using Blocked-off, Multiblock and Embedded Boundary Treatments. Numerical Heat Transfer, Part A: Applications, International Journal of Computation and Methodology, Vol. 43, No. 8, 2003, pp. 807-825.

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

[22]    Ko, T. H., Ting, K., Entropy Generation and Optical Analysis for Laminar Forced Convection in Curved Rectangular Ducts: A Numerical Study, International Journal of Thermal Sciences, Vol. 45, No. 2, 2006, pp. 138–150.

[23]    Mohaghegh, M. R., Esfahani, J. A., Entropy Generation Analysis of Free Convection from a Constant Temperature Vertical Plate using Similarity Solution, Thermal Science, Vol. 20, No. 6, 2016, pp. 1855-1866.

[24]    Kolsi, L., Abidi, A., Borjini, M., and Aissia H. B., The Effect of an External Magnetic Field on the Entropy Generation in Three-Dimensional Natural Convection, Thermal Science, Vol. 14, No. 2, 2010, pp. 341-352.

[25]    Mamourian, M., Shirvan, K. M., Ellahi, R., and Rahimi, A. B., 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.

[26]    Oztop, H. F., Kolsi, L., Alghamdi, A., Abu-Hamdeh, N., Borjini, M. N., and Aissia, H. B., 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.

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

[28]    Abu-Nada, E., Numerical Prediction of Entropy Generation in Separated Flows, Entropy, Vol. 7, No. 4, 2005, pp. 234-252.

[29]    Atashafrooz, M., Gandjalikhan Nassab, S. A., and Ansari, A. B., 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, Vol. 5, No. 5, 2011, pp. 898-907.

[30]    Atashafrooz, M., Gandjalikhan Nassab, S. A., and Ansari, A. B., 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.

[31]    Bahrami, A., Gandjalikhan Nassab, S. A., 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.

[32]    Patankar, S. V., Spalding, D. B., 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.