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Nanofluids have become more and more attractive to the modern industry due to their high performance in heat transfer and combustion. As one of the key influencing factors, the atomization mechanism of nanofluids induced by airflow is more complex than that of pure liquids, which has attracted great attention recently. In this study, the spray characteristics of TiO2–propylene glycol nanofluids were investigated by focusing on the effects of nano-TiO2 additives on atomization. On the basis of high-speed shadow imaging, the spray morphology of the base fluid injected from an air atomizing nozzle under different pressures was analyzed first. Then a laser particle size analyzer was used to obtain the droplet size distribution of the nanofluids. The air pressure at the inlet of the atomizer was found to have more contribution to the atomization of nanofluids. And when the air pressure exceeded 0.35 MPa, the Sauter mean diameter (D32) of the base fluid droplets was insensitive to the change of air pressure. Subsequently, the contribution of nanoparticles to atomization was discussed. An empirical correlation was proposed between the Sauter mean diameter (D32) and the dimensionless parameters such as the gas Weber number (Weg), liquid–gas momentum ratio (q), and the volume fraction of nano-TiO2, etc. Results indicated that adding nanoparticles enhanced the jet stability by increasing the viscosity at a low jet velocity, while the jet instability was increased due to the nanoparticles promoting the cavitation at a high jet velocity. [ABSTRACT FROM AUTHOR]

Adding nanoparticles with high thermal conductivity into the work fluid is one of the most significant ways to enhance heat transfer. In this article, the influences of nanoparticle mass concentration (0.5–10.0 wt.%) and temperature (5–25 °C) were investigated on the viscosity of TiO2-propylene glycol nanofluid. At the same time, eight kinds of mass concentrations (0.5–10.0 wt.%) were used to investigate the changing regularity on the surface tension of nanofluid; Accordingly, the modified correlations including nanoparticle concentration were proposed respectively. The experimental results show that the viscosity of the nanofluid increases with the increase in particle concentration. Within the concentration of 10.0 wt.%, the viscosity increases by about 7.0% for every 1.0 wt.%. While the viscosity decreases with the increase in the temperature. The surface tension of the mixture increases slowly with the increase in particle concentration. Within 2.0 wt.%, the surface tension of nanofluid increases by less than 1.0% for every 0.5 wt.%, when the concentration of nanofluid exceeds 2.0 wt.%, surface tension raises less than 1.0% per 2.0 wt.%. [ABSTRACT FROM AUTHOR]

Polypyrrole coated Fe3O4 nanoparticles decorated carbon nanotubes nanocomposites were prepared by in situ polymerization. The weight percentage of the Fe3O4 nanoparticles was only 18.4% according to the analysis of TGA. The microwave absorption performance of the polypyrrole coated Fe3O4 nanoparticles decorated carbon nanotubes nanocomposites was researched and the corresponding filler loading of paraffin in the tested samples was 80 wt%. The polypyrrole coated Fe3O4 nanoparticles decorated carbon nanotubes nanocomposites showed a maximum reflection loss value of − 51.67 dB at 10.2 GHz, and the corresponding thickness and frequency bandwidth (≤ −10 dB) were 3.0 mm and 4.88 GHz, respectively. The composite materials have both magnetic loss and dielectric loss. The coupling between different materials and the improved impedance matching can enhance the absorbing performance. [ABSTRACT FROM AUTHOR]