Figure 11 Comparison of thermal conductivity enhancement of SiO2/60EGW and SiO2/40EGW nanofluids
It is pretty clear that SiO2/40EGW shows an enhancement in thermal conductivity with a maximum enhancement of 34% than the base fluid at 1.5% volume concentration and 55oC temperature. On the other hand, the thermal conductivity of SiO2/60EGW shows an enhancement of 28% at 1.5% volume concentration and 55oC temperature. The reason of thermal conductivity enhancement is with the Brownian motion and micro-convection of particles in the base fluids. The thermal conductivity enhancement not only depends on the particle concentration and temperature, but it also depends on the effect of base fluid.
Based on the regression analysis, the theoretical predictions were made for thermal conductivity of SiO2 and Al2O3 nanoparticles in both the base fluids and are shown plotted in Figure 12 . At a concentration 1.5%, Al2O3/40EGW predicts a higher thermal conductivity when compared to other nanofluids. At the same concentration Al2O3nanoparticles and 40EGW based nanofluids predicts a higher thermal conductivity values when compared to SiO2 nanoparticles and 60EGW based nanofluids respectively.