Growth of a vapour bubble in a viscous, superheated Nanofluid under Effect of Variations in Surface Tension

Abstract

This study analyzes the growth of a vapour bubble in a superheated nanofluid with variable surface tension at the bubble interface. The governing equations describing the problem are formulated, converted to a single integrodifferential equation, and solved analytically. The results are implemented in one of the favorable nanofluids, namely, Al2O3/water, since it is widely used in nanofluid applications, which include self-cooling devices and as a coolant in newly designed photovoltaic/thermal systems, because it has higher thermal and electrical physical properties than the base fluid and a lower economical preparation cost. The results showed that the growth process is proportional to the thermal diffusivity and the Jakob number, while it is inversely proportional to surface tension, dynamic viscosity, initial bubble radius, coefficient of the initial pressure difference, initial void fraction, and nanoparticle volume fraction. Moreover, we conducted a comparison to the experimental data obtained by Hamda and Hamed (2016), and our results achieved a better agreement with these data than some famous studies for both experiments for superheated Al2O3/water nanofluid and pure water (base fluid), because our model considered the effects of several parameters that were ignored in the previous theories, which have been derived as special cases of our result. Furthermore, the effects of nanoparticle characteristics and slip mechanisms; base fluid type and temperature; and the addition of surfactants on bubble growth rates are investigated. Implications drawn from this study may have consequences for the optimum design of thermal systems/devices based on nanofluid technology.

Keywords

• Bubble dynamics
• Superheated liquid
• Variable surface tension
• Nanofluid
• Aluminum oxide