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

Hajji Hassnia (Laboratory of Metrology and Energy systems, National Engineering School of Monastir, University of Monastir, Tunisia)
Kolsi Lioua (Department of Mechanical Engineering, College of Engineering, Ha’il University, Ha’il City, Saudi Arabia), lioua_enim@yahoo.fr
Askri Faouzi (College of Engineering, Mechanical Engineering Department, King Khalid University, Abha, Saudi Arabia)
Maatki Chemseddine (Department of Mechanical Engineering, College of Engineering, Al Imam Mohammad Ibn Saud Islamic University, Riyadh, Kingdom of Saudi Arabia)
Hassen Walid (Laboratory of Metrology and Energy systems, National Engineering School of Monastir, University of Monastir, Tunisia)
Borjini Mohamed Naceur (Laboratory of Metrology and Energy systems, National Engineering School of Monastir, University of Monastir, Tunisia)

This study presents 2-D 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 micro-channel 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.

Keywords: sudden expansion/contraction, micro-channel, Reynolds number, Nusselt number