International Scientific Journal

Thermal Science - Online First

online first only

Heat transfer and flow structure through a backward-and forward-facing step micro-channels equipped with obstacles

This study presents two-dimensional simulations of a flow-through a sudden expansion/contraction micro-channel with the existence of obstacles. The bottom wall is maintained at constant flux, while the other walls are adiabatic. Rectangular adiabatic obstacles are mounted before the expansion region on the upper and lower wall of the channel used. The finite element method was used to discretize the equations that govern the physical model. Results indicate the apparition of a separate vortex, situated in the corner after the sudden expansion of the microchannel for low Reynolds numbers. For higher values and expansion ratios, the vortex separation length increases. The obtained results show that the obstacles have a considerable effect on the dynamics of the flow and enhancement of heat transfer.
PAPER REVISED: 2020-06-23
PAPER ACCEPTED: 2020-07-16
  1. Abu-Mulaweh H., A review of research on laminar mixed convection flow over backward-and forward-facing steps. International Journal of Thermal Sciences, 42(9) (2003), pp. 897-909
  2. Kiflemariam R,. et al., Numerical simulation, parametric study and optimization of thermoelectric generators for self-cooling of devices, Proceedings, 11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference; 2014, Vol.1, pp.1-16
  3. Ekiciler R and Arslan K., CuO/Water Nanofluid Flow over Microscale Backward-Facing Step and Analysis of Heat Transfer Performance. Heat Transfer Research. 49(15) (2018), pp. 1489-1505
  4. Javaherdeh K, et al., Experimental and numerical investigations on louvered fin-and-tube heat exchanger with variable geometrical parameters. Journal of Thermal Science and Engineering Applications, 9(2) (2017), pp. 1-8
  5. Saffari H and Moosavi R., Numerical study of the influence of geometrical characteristics of a vertical helical coil on a bubbly flow, Journal of Applied Mechanics and Technical Physics, 55(6) 2014, pp. 957-69
  6. Chen Y, et al., Three-dimensional convection flow adjacent to inclined backward-facing step. International Journal of Heat and Mass Transfer, 49 (2006), pp. 4795-803
  7. Kherbeet AS, et al., The effect of step height of microscale backward-facing step on mixed convection nanofluid flow and heat transfer characteristics, International Journal of Heat and Mass Transfer, 68 (2014), pp. 554-66
  8. Le H, et al., Direct numerical simulation of turbulent flow over a backward-facing step. Journal of fluid mechanics, 330 (1997) pp. 349-74
  9. Selimefendigil F and Öztop HF. Forced convection and thermal predictions of pulsating nanofluid flow over a backward facing step with a corrugated bottom wall. International Journal of Heat and Mass Transfer, 110 (2017), pp. 231-47
  10. Inagaki T., Heat transfer and fluid flow of turbulent natural convection along a vertical flat plate with a backward-facing step. Experimental Heat Transfer, 7(4) (1994) pp. 285-30.
  11. Togun H, et al., Thermal performance of nanofluid in ducts with double forward-facing steps. Journal of the Taiwan Institute of Chemical Engineers, 47 (2015), pp. 28-42.
  12. Öztop HF., Turbulence forced convection heat transfer over double forward facing step flow. International communications in heat and mass transfer, 33(4) (2006), pp. 508-517
  13. Xie W and Xi G. Geometry effect on flow fluctuation and heat transfer in unsteady forced convection over backward and forward facing steps. Energy, 132 (2017), pp. 49-56
  14. Nassab SG, et al., Turbulent forced convection flow adjacent to inclined forward step in a duct. International Journal of Thermal Sciences.;48(7) (2009), 1319-3126.
  15. Barman A and Dash SK. Effect of obstacle positions for turbulent forced convection heat transfer and fluid flow over a double forward facing step. International Journal of Thermal Sciences, 134 (2018), pp. 116-28.
  16. Selimefendigil F. and Öztop H.F., Effects of local curvature and magnetic field on forced convection in a layered partly porous channel with area expansion, International Journal of Mechanical Sciences, 179 (2020), pp. 105696
  17. Tsai, C. H., et al., Capabilities and limitations of 2-dimensional and 3-dimensional numerical methods in modelling the fluid flow in sudden expansion microchannels, Microfluidics and Nanofluidics, 3 (2007), pp. 13-18.
  18. Zhang Z., et al., Enhancement of combustion performance in a microchannel: Synergistic effects of bluff-body and cavity, Fuel: 265(2020), pp. 116940
  19. Purva P., et al., Fluid Rheological Effects on the Flow of Polymer Solutions in a Contraction-Expansion Microchannel, Micromachines, 11(3) (2020), pp. 278.
  20. Khudheyer S. et al., Numerical study of laminar flow in a sudden expansion obstacled channel, Thermal Science, 19 (2) (2015), pp. 657-668.
  21. Al-Aswadi A.A., et al., Laminar forced convection flow over a backward facing step using nanofluids, International Communications in Heat and Mass Transfer, 37 (2010), pp. 950-957
  22. Praveen T. and Eswaran V., Transition to asymmetric flow in a symmetric sudden expansion: Hydrodynamics and MHD cases; Computers and Fluids,148 (2017), pp. 103-120