Numerical Simulation of Effect of Size and Shape of Al2O3 Nanoparticles in a Double Tube Heat Exchanger

In this study, the effects of shape and size of Al2O3suspended nanoparticles in water-based fluid with 2%volume fraction at 25 °C are numerically investigated on the performance of double tube heat exchanger in the laminar and turbulent flow regimes. The nanoparticle’s diameter was considered between 10 and 100 nm. The nanoparticles with shapes of spherical, cylindrical, and combination of spherical-cylindrical with percentages of 30, 50, 60, 70, 80, 90 of cylindrical nanoparticles were studied. The effect of shape of nanoparticles showed that heat transfer rate increases in the heat exchanger by increasing the percentage of cylindrical nanoparticles and cylindrical nanoparticles offer better heat transfer characteristics and heat transfer rate in the turbulent flow regime as its Nusselt number is15.4% more than the spherical nanoparticles. It was also seen that this suspension has the maximum pressure drop in the heat exchanger. The results of size of alumina nanoparticles with diameters of 10, 50 and 100 nm showed that the nanoparticles with smaller diameter have the largest increase in Nusselt number as well as pressure drop.