Transient heat transfer characteristics and process intensification with Al2O3-water and TiO2-water nanofluids: An experimental investigation

This paper aims to provide an experimental investigation on the thermal conductivity enhancement and heat transfer performance of water based Al2O3 and TiO2 nanofluids. Nanofluids at different concentrations of 0.125 %, 0.25 %, 0.5 % and 1.5 % of m/V were prepared by two-step method adding Polyvinyl alcohol and Polyvinylpyrrolidone as surfactants. Then, the stability of nanofluids was examined using visual inspection and zeta potential analysis. The thermal conductivity value of test samples was measured using sound velocities in test samples over 25 degrees C-55 degrees C for each10 degrees C rise. Heat transfer performance of nanofluids was examined under transient condition through an experimental setup over 25 degrees C-60 degrees C. Stable nanofluids with little sedimentation were obtained. Enhancements in Thermal conductivity and heat transfer performance of nanofluids were achieved. Al2O3 nanofluids have shown the best results with a maximum of 44 % increment in thermal conductivity and a maximum of 21 % increment in transient heat transfer performance. Polyvinylpyrrolidone showed better effect than Polyvinyl alcohol on improving the stability of nanofluids. However, superiority of any surfactant in context of the thermal conductivity and heat transfer performance of nanofluids was ambiguous. Finally, enhanced thermal conductivity and heat transfer performance compared to their basefluids enables them as a potential cooling medium.