Effect of Particle Size on the Heat Transfer Performance of SiO2-Water Nanofluids

It is common to improve heat transfer performance to meet the needs of small volume, low energy consumption, and high heat transfer performance of heat exchangers and mixers in industrial production. In the process of heat transfer, the fluid type considerably influences the heat transfer performance. Consequently, nanofluids-which do not easily cause friction or blockages and which have the advantage of enhancing heat transfer-are used in place of traditional fluids to meet the abovementioned heat transfer requirements. In this work, an experimental system is established to measure the heat transfer performance of SiO2-water nanofluids. The convective heat transfer coefficients of SiO2-water nanofluids with different particle sizes are measured. The effects of particle sizes and the Reynolds number (Re) on the heat transfer coefficients are discussed. The results show that the particle size of SiO2 nanoparticles and Re have an important influence on the convective heat transfer coefficient. By adding SiO(2 )nanoparticles with particle sizes of 15, 30, and 80 nm in water, it is found that the convective heat transfer coefficient of nanofluids increases by 36.8, 30.2, and 23.6%, respectively, compared with that of pure water under the same Re. The change in the convective heat transfer coefficient in different regimes is compared. It is found that the convective heat transfer coefficient increases most near the transition point of laminar turbulence. The changes in physical properties of nanofluids with different particle sizes and the contribution ratio of micro-motion of nanoparticles to the increase in the convective heat transfer coefficient are investigated. The results show that with the change in the Reynolds number, the contribution of physical parameters to the convective heat transfer coefficient has not exceeded 50%. At the same time, it is found that the traditional single-phase convection heat transfer formula is not suitable for calculating the heat transfer coefficient of SiO2-water nanofluids. Therefore, the correlations for calculating the convective heat transfer of SiO2-water nanofluids in laminar and turbulent regimes are established.

Automated summary

This study investigates the heat transfer performance of SiO2-water nanofluids, revealing that the particle size of nanoparticles and Reynolds number significantly affect the convective heat transfer coefficient. The convective heat transfer coefficient of nanofluids increases most notably near the laminar-turbulent transition point. The study also establishes correlations for calculating convective heat transfer of SiO2-water nanofluids in laminar and turbulent regimes.