Nanofluids offer the exciting new possibilities to enhance heat transfer performance. In this paper, experimental and theoretical investigations have been conducted to determine the effect of CuO nanowires on the thermal conductivity and viscosity of dimethicone based nanofluids. The CuO nanowires were prepared through a thermal oxidation method, and the analysis indicated that the as-prepared CuO nanowires had high purity, monocrystalline with a monoclinic structure and large aspect ratio compared to CuO nanospheres. The experimental data show that the thermal conductivity of the nanofluids increases with the volume fraction of CuO nanowires or nanospheres, with a nearly linear relationship. For the nanofluid with the addition of 0.75 vol.% CuO nanowires, the thermal conductivity enhancement is up to 60.78%, which is much higher than that with spherical CuO nanoparticles. The nanofluids exhibit typical Newtonian behavior, and the measured viscosity of CuO nanowires contained nanofluids were found only 6.41% increment at the volume fraction of 0.75%. It is attractive in enhanced heat transfer for application. The thermal conductivity and viscosity of CuO nanofluids were further calculated and discussed by comparing our experimental results with the classic theoretical models. The mechanisms of thermal conductivity and viscosity about nanofluids were also discussed in detail.
The development of thermal conductive polymer composite is necessary for the application in thermal management. In this paper, the experimental and theoretical investigations have been conducted to determine the effect of copper nanowires (CuNWs) and copper nanoparticles (CuNPs) on the thermal conductivity of dimethicone nanocomposites. The CuNWs and CuNPs were prepared by using a liquid phase reduction method, and they were characterized through scanning electron microscopy (SEM) and X-ray diffraction (XRD). The experimental data show that the thermal conductivity of composites increases with the increase of filler. With the addition of 10 vol.% CuNWs, the thermal conductivity of the composite is 0.41 W/m/K. The normalized thermal conductivity enhancement factor is 2.73, much higher than that of the analogue containing CuNPs (1.67). These experimental data are in agreement with Nan’s model prediction. Due to the high aspect ratio of 1D CuNWs, they can construct thermal networks more effectively than CuNPs in the composite, resulting in higher thermal conductivity.
Perfluorooctanoic
acid (PFOA) poses a serious threat to the ecological
environment and biological health because of its ubiquitous distribution,
extreme persistence, and high toxicity. In this study, we designed
a novel gas–liquid dielectric barrier discharge (GLDBD) reactor
which could efficiently destruct PFOA. PFOA removal efficiencies can
be obtained in various water matrices, which were higher than 98.0%
within 50 min, with energy yields higher than 114.5 mg·kWh–1. It was confirmed that the reactive species including
e–, ONOOH, •NO2, and hydroxyl
radicals (•OH) were responsible for PFOA removal. Especially,
this study first revealed the crucial role of reactive nitrogen species
(RNS) for PFOA degradation in the plasma system. Due to the generation
of a large amount of RNS, the designed GLDBD reactor proved to be
less sensitive to various water matrices, which meant a broader promising
practical application. Moreover, influential factors including high
concentration of various ions and humic acid (HA), were investigated.
The possible PFOA degradation pathways were proposed based on liquid
chromatograph–mass spectrometer (LC-MS) results and density
functional theory (DFT) calculation, which further confirmed the feasibility
of PFOA removal with RNS. This research, therefore, provides an effective
and versatile alternative for PFOA removal from various water matrices.
Two kinds of silver nanowires (100 nm in diameter, 20 μm and 100 μm in length) are prepared. The thermo‐physical characteristics, viscosity, and photothermal conversion performance of the silver nanowires (AgNWs) contained ethylene glycol nanofluids are investigated in detail. It is found that thermal conductivity of 100 μm AgNWs contained nanofluids is higher than that of 20 μm AgNWs with the same diameters of 100 nm. Viscosity test shows that the nanofluid is a Newtonian fluid, and the longer silver nanowires, the greater viscosity. In addition, photothermal conversion efficiency of silver nanowires contained nanofluid is studied. We can observe that the 100 μm AgNWs contained nanofluid has a higher photothermal conversion efficiency than that containing 20 μm AgNWs. Moreover, we find that there is a certain correlation between heat transfer and photothermal conversion of nanofluid. It demonstrates that the high heat transfer property of nanofluid will benefit for its photothermal conversion efficiency and the mechanism is proposed. This work provides a new idea to improve photothermal conversion efficiency. We can choose materials with high thermal conductivity and strong light absorption ability to enhance the photothermal conversion performance of nanofluids.
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