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Toward improved heat dissipation of the turbulent regime over backward-facing step for the AL2O3-water nanofluids: An experimental approach

Ahmed Syed Muzamil (University of Malaya, Faculty of Engineering, Department of Mechanical Engineering, Kuala Lumpur, Malaysia)
Kazi Salim Newaz (University of Malaya, Faculty of Engineering, Department of Mechanical Engineering, Kuala Lumpur, Malaysia)
Khan Ghulamullah (Balochistan University of Information Technology, Engineering and Management Sciences, Department of Chemical Engineering, Quetta, Pakistan)
Zubir Mohd Nashrul Mohd (University of Malaya, Faculty of Engineering, Department of Mechanical Engineering, Kuala Lumpur, Malaysia)
Dahari Mahidzal (University of Malaya, Faculty of Engineering, Department of Electrical Engineering, Kuala Lumpur, Malaysia)
Ibrahim Suriani (University of Malaya, Faculty of Engineering, Department of Mechanical Engineering, Kuala Lumpur, Malaysia)
Talip Mohammad Sofian Abu (University of Malaya, Faculty of Engineering, Department of Mechanical Engineering, Kuala Lumpur, Malaysia)
Ahmad Pervaiz (University of Azad Jammu and Kashmir, Department of Physics, Muzaffarabad, Pakistan)
Chowdhury Zaira Zaman (University of Malaya, Nanotechnology and Catalysis Research Centre (NANOCAT), Kuala Lumpur Malaysia)

Experimental study of nanofluid flow and heat transfer to fully developed turbulent forced convection flow in a uniformly heated tubular horizontal backward-facing step has reported in the present study. To study the forced convective heat transfer coefficient in the turbulent regime, an experimental study is performed at a different weight concentration of Al2O3 nanoparticles. The experiment had conducted for water and Al2O3 -water nanofluid for the concentration range of 0 to 0.1 wt.% and Reynolds number of 4000 to 16000. The average heat transfer coefficient ratio increases significantly as Reynolds number increasing, increased from 9.6% at Reynolds number of 4000 to 26.3% at Reynolds number of 16000 at the constant weight concentration of 0.1%. The Al2O3 water nanofluid exhibited excellent thermal performance in the tube with a backwardfacing step in comparison to distilled water. However, the pressure losses increased with the increase of the Reynolds number and/or the weight concentrations, but the enhancement rates were insignificant.

Keywords: backward-facing step, heat transfer, nanofluids, re-circulation flow