Figure 13 Comparison of experimental values of viscosity for SiO2/60EGW nanofluids with theoretical correlations (6) and (12)
Similarly, the experimental viscosity values of SiO2/40EGW nanofluids are compared with base fluid correlation (10) and nanofluid correlation (14) and are plotted inFigure 14 . The viscosity measurements were taken in the same operating conditions of SiO2/60EGW nanofluids as mentioned. A deviation less than 18% was observed with correlation (18). Additionally, the study established that given different concentrations, an increase in temperature causes a significant decrease in the nanofluids’ viscosity. As such, SiO2 nano particle loading was observed to cause an increase in flowing resistance and friction of the fluids, translating into increased viscosity.
The viscosity enhancement was plotted against temperature for the two given nanofluids in Figure 15 . It is quite clear that SiO2/40EGW shows a good enhancement in viscosity with a maximum enhancement of 102% than the base fluid at 1.5% volume concentration and 25oC temperature. Based on the observations 40EGW based nanofluids shows a higher enhancement in viscosity. This study indicates that, with the increase in percentage of ethylene glycol, the viscosity of SiO2 nanofluids also increases. The measurements have similar finding as Lotfizadeh Dehkordi et al. [61] who have used Al2O3dispersed in 60EGW and 40EGW base fluids by mass % and also Syam [62] has observed enhancement of 300% and they attributed it to the shear resistance offered by the particles onto the fluid layer. With larger the particle concentration in the base fluid, larger the quantity is of particles are required.