Abstract
The surface tension of ethanol and n-decane based nanofluid fuels containing suspended aluminum (Al), aluminum oxide (Al2O3), and boron (B) nanoparticles as well as dispersible multi-wall carbon nanotubes (MWCNTs) were measured using the pendant drop method by solving the Young-Laplace equation. The effects of nanoparticle concentration, size and the presence of a dispersing agent (surfactant) on surface tension were determined. The results show that surface tension increases both with particle concentration (above a critical concentration) and particle size for all cases. This is because the Van der Waals force between particles at the liquid/gas interface increases surface free energy and thus increases surface tension. At low particle concentrations, however, addition of particles has little influence on surface tension because of the large distance between particles. An exception is when a surfactant was used or when (MWCNTs) was involved. For such cases, the surface tension decreases compared to the pure base fluid. The hypothesis is the polymer groups attached to (MWCNTs) and the surfactant layer between a particle and the surround fluid increases the electrostatic force between particles and thus reduce surface energy and surface tension.
Highlights
Nanofluids are liquids with stable suspension of nanometer sized particles (1–100 nm)
For the case of multi-walled carbon nanotubes (MWCNT), it was found the surface tension initially decreases with particle concentration and increases
The results show that at high particle concentrations, surface tension of the nanofluids increases with increasing particle concentration, as compared to that of the base fluids
Summary
Nanofluids are liquids with stable suspension of nanometer sized particles (1–100 nm). The nanoparticles used in nanofluids are typically made of metals, oxides, carbides, or carbon nanotubes. The idea is to suspend nanomaterials (such as nanoenergetic particles and nanocatalysts) in traditional liquid fuels to enhance performance. Previous studies have shown nanofluid fuels with the addition of energetic nanomaetierals such as aluminum and boron and nanocatalyst such cerium oxide have shown promising performance [4,5,6,7,8,9,10,11], e.g., higher energy release, shortened ignition delay, increased burning rate, increased ignition probability, and enhanced catalytic effect
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