1 Mechanical Engineering Department, University of Technology. Baghdad, Iraq

2 Mechanical Engineering Department, University of Technology, Baghdad, Iraq.


The stability of nanofluid plays a rule in heat transfer growth for different engineering systems. The stability and particle size of Al2O3-H2O nanofluid effects on heat transfer are studied experimentally. Two particle sizes (20 and 50 nm) with (0.1, 0.5 and 1%) concentrations were prepared and tested under constant heat flux (1404 W) with fully developed turbulent flow through a horizontal pipe. The results show an increase in Nusselt number by 20.7% and 17.6% with 1 vol.% concentration for 20 and 50 nm, respectively compared to distilled water. Examined nanofluid showed improvement in Nu number by (30.3 and 23.5) % at 1 vol.% concentration compared to water. Obtained results show minor decrease in the pressure drop and friction factor with nanofluid after stability treatment. Different correlations between Nu number and friction factor relating to studied parameters were observed


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