Detail publikace

Effect of Nanoparticles Concentration on Nanofluid Sprays for Cooling Applications

Originální název

Effect of Nanoparticles Concentration on Nanofluid Sprays for Cooling Applications

Anglický název

Effect of Nanoparticles Concentration on Nanofluid Sprays for Cooling Applications

Jazyk

en

Originální abstrakt

This study addresses the effect of nanoparticles nature and concentration on the fluid dynamics and particularly on the atomization characteristics of the resulting nanofluids. Nanoparticles of alumina (Al2O3) and Zinc Oxide (ZnO) are mixed in water-based solutions, for concentrations varying between 0.5% and 2% wt for alumina and between 0.01% and 0.1% wt for the zinc oxide particles. FeCl2·4H2O (0.1% wt) was also used to infer on the effect of the nature (material) of the particles in the physico-chemical properties of the resulting solutions. Citric acid (0.15%) was found to work well as a surfactant, being able to assure the stability of the prepared nanofluids during the experimental campaign. Spray morphology was characterized using high-speed visualization. Droplet size and velocity distributions were then probed using a 2 component Phase Doppler Anemometer. For the range of nanoparticles concentrations covered here, the results show a mild increase in the viscosity of the nanofluids for higher nanoparticle concentrations. This slightly larger viscosity mainly affects the primary breakup region of the spray (Z<10mm), narrowing the cone angle and increasing the Integral Sauter Mean Diameter of the droplets. However, in the region where the spray is already fully developed (Z>20mm), surface tension forces become dominant and the effect of adding the nanoparticles becomes negligible. Under these conditions the spray presents size and velocity distribution characteristics, which are suitable for cooling applications. However, tests are required to actually characterize the cooling performance of the spray impinging on a surface. In this context, preliminary results suggest the occurrence of a local modification on the wettability, probably caused by the deposition of the nanoparticles, which is leading to the decrease of the equilibrium contact angle. Such effect should be investigated in future studies.

Anglický abstrakt

This study addresses the effect of nanoparticles nature and concentration on the fluid dynamics and particularly on the atomization characteristics of the resulting nanofluids. Nanoparticles of alumina (Al2O3) and Zinc Oxide (ZnO) are mixed in water-based solutions, for concentrations varying between 0.5% and 2% wt for alumina and between 0.01% and 0.1% wt for the zinc oxide particles. FeCl2·4H2O (0.1% wt) was also used to infer on the effect of the nature (material) of the particles in the physico-chemical properties of the resulting solutions. Citric acid (0.15%) was found to work well as a surfactant, being able to assure the stability of the prepared nanofluids during the experimental campaign. Spray morphology was characterized using high-speed visualization. Droplet size and velocity distributions were then probed using a 2 component Phase Doppler Anemometer. For the range of nanoparticles concentrations covered here, the results show a mild increase in the viscosity of the nanofluids for higher nanoparticle concentrations. This slightly larger viscosity mainly affects the primary breakup region of the spray (Z<10mm), narrowing the cone angle and increasing the Integral Sauter Mean Diameter of the droplets. However, in the region where the spray is already fully developed (Z>20mm), surface tension forces become dominant and the effect of adding the nanoparticles becomes negligible. Under these conditions the spray presents size and velocity distribution characteristics, which are suitable for cooling applications. However, tests are required to actually characterize the cooling performance of the spray impinging on a surface. In this context, preliminary results suggest the occurrence of a local modification on the wettability, probably caused by the deposition of the nanoparticles, which is leading to the decrease of the equilibrium contact angle. Such effect should be investigated in future studies.

BibTex


@inproceedings{BUT152070,
  author="Milan {Malý} and Ana {Moita} and Jan {Jedelský} and Ana {Ribeiro} and António {Moreira}",
  title="Effect of Nanoparticles Concentration on Nanofluid Sprays for Cooling Applications",
  annote="This study addresses the effect of nanoparticles nature and concentration on the fluid dynamics and particularly on the atomization characteristics of the resulting nanofluids. Nanoparticles of alumina (Al2O3) and Zinc Oxide (ZnO) are mixed in water-based solutions, for concentrations varying between 0.5% and 2% wt for alumina and between 0.01% and 0.1% wt for the zinc oxide particles. FeCl2·4H2O (0.1% wt) was also used to infer on the effect of the nature (material) of the particles in the physico-chemical properties of the resulting solutions. Citric acid (0.15%) was found to work well as a surfactant, being able to assure the stability of the prepared nanofluids during the experimental campaign. Spray morphology was characterized using high-speed visualization. Droplet size and velocity distributions were then probed using a 2 component Phase Doppler Anemometer. 
For the range of nanoparticles concentrations covered here, the results show a mild increase in the viscosity of the nanofluids for higher nanoparticle concentrations. This slightly larger viscosity mainly affects the primary breakup region of the spray (Z<10mm), narrowing the cone angle and increasing the Integral Sauter Mean Diameter of the droplets. However, in the region where the spray is already fully developed (Z>20mm), surface tension forces become dominant and the effect of adding the nanoparticles becomes negligible. Under these conditions the spray presents size and velocity distribution characteristics, which are suitable for cooling applications. However, tests are required to actually characterize the cooling performance of the spray impinging on a surface. In this context, preliminary results suggest the occurrence of a local modification on the wettability, probably caused by the deposition of the nanoparticles, which is leading to the decrease of the equilibrium contact angle. Such effect should be investigated in future studies.",
  address="Technical University Lisboa",
  booktitle="PROCEEDINGS OF THE 19th INTERNATIONAL SYMPOSIUM ON APPLICATION OF LASER AND IMAGING
TECHNIQUES TO FLUID MECHANICS",
  chapter="152070",
  howpublished="online",
  institution="Technical University Lisboa",
  number="02059",
  year="2018",
  month="july",
  pages="1--14",
  publisher="Technical University Lisboa",
  type="conference paper"
}