Jiafeng Geng

Modeling of anisotropic flow and thermodynamic properties of magnetic nanofluids induced by external magnetic field with varied imposing directions

Magnetic field can enhance both thermal conductivity and Lorentz force resistance of the magnetic nanofluids (MNFs), in which the former is favored while the latter often leads to pressure drop of the flow. It is assumed that there would exist a balance between the magnetic field induced thermal conductivity and Lorentz force if one can appropriately adjust the angle of the imposing magnetic field with respect to the direction of the flow. In the present study, the effects of direction of magnetic field ( α) on anisotropic thermodynamic properties of magnetic nanofluids in channel were studied. The effects of direction of magnetic field on thermal conductivity, Nusselt number, global total entropy generation, and other parameters, such as velocity, temperature, and concentration, have been discussed in detail. A greater α can lead to a larger thermal conductivity normal to the walls of channel and a more uniform temperature field. However, the velocity of magnetic nanofluid tends to decrease. There is a t...

Characteristic oscillation phenomenon after head-on collision of two nanofluid droplets

One falling liquid droplet impacting a sessile droplet and then undergoing oscillation is a common phenomenon in both nature and industry. However, to the best of our knowledge, the head-on collision of two nanofluid drops has not been studied when both the nanoparticle and surfactant exist in the drop. In this work, the characteristics of oscillation after head-on collision of two TiO2-water nanofluid drops were investigated experimentally. The effects of impact velocity, drop size, and nanoparticle concentration have been considered to understand how they influence the drop spreading, recoiling, and rebounding. For the influence of the drop size, it shows that in 0% and 0.001% of nanoparticle concentrations, the relative spreading radius of small drop size is higher than that with large size, while it is reversed in 0.01% and 0.1% of nanoparticle mass fractions. Interestingly, it was found that there is an optimal nanoparticle mass fraction of 0.1% for nanofluid droplets where the oscillation of head-on...