Application of Copper-Water Nanofluids to Improve the Heat Transfer Performance of Cooling System via free Convection Mechanism

In the present study, the natural convection heat transfer in a L-shape enclosure, filled with copper-water nanofluid is investigated by considering the effect of different factors such as aspect ratio, volume fraction of copper nanoparticles and Rayleigh number on the heat transfer coefficient, temperature and velocity distributions. All governing equations are solved by finite volume method. The results indicated that at high Rayleigh number, the dominant heat transfer mechanism will change from conduction to free convention and the maximum heat transfer coefficient will decrease. While at low Rayleigh numbers, the fluid in the horizontal part of the enclosure is approximately static and the predominant mechanism of heat transfer is conduction. The transition of conduction mechanism to free convection occurs at Rayleigh number in the range of 105 to 106. Also, the presence of copper nanoparticles, leads to significant enhancement in the heat transfer coefficient, for all values of Rayleigh number. In addition, the simulation results indicate that inclusion of a number of pins inside the enclosure has a significant effect on increasing the heat transfer coefficient. The achieved results indicated that inserting three fins in the structure of enclosure at aspect ratio of 0.4, nano particle volume fraction of 0.1 and Rayleigh number of 106 enhances the heat transfer coefficient from 984.3 to 1093.8 W/m2.K.