Novel hybrid nanofluid with tunable specific heat and thermal conductivity: Characterization and performance assessment for energy related applications

The utilization of heat transfer fluids with improved specific heat and thermal conductivity will be beneficial for enhanced energy collection in solar thermal systems. Accordingly, hybrid nanofluids comprising ZnO nanoparticles and encapsulated paraffin wax in propylene glycol-water mixture were prepared and characterized. The influence of encapsulated paraffin wax concentration (4-16 wt. %) and ZnO nanoparticle concentration (0-2 vol %) revealed that the thermal conductivity and specific heat could be improved to a maximum of 10.4% and 18.7% respectively, in comparison with those of propylene glycol-water mixture, at their appropriate concentrations. The presence of ZnO nanoparticles was found to influence the phase change characteristics of encapsulated paraffin wax, in such a way that the latent heat due to phase change was increased at an optimum concentration of ZnO nanoparticle concentration. While the maximum enhancement in overall heat transfer coefficient of 15.37% was obtained for the hybrid nanofluid sample that had both thermal conductivity and specific heat higher than the base fluid, the maximum enhancement in heat transfer rate (13.54%) was obtained for the hybrid nanofluid that had 18.65% enhancement in specific heat. The results of present investigation reveal the potential of hybrid nanofluids for energy management.