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13,079 results on '"Rao, D."'

7. Evaporation of water-in-oil microemulsion droplet

Author

Krishan, Bal, Rastogi, Preetika, Rao, D. Chaitanya Kumar, Kaisare, Niket S., Basavaraj, Madivala G., and Basu, Saptarshi

Subjects
Physics - Fluid Dynamics
Abstract

Emulsion fuels have the potential to reduce both particulate matter and NOx emissions and can potentially improve the efficiency of combustion engines. However, their limited stability remains a critical barrier to practical use as an alternative fuel. In this study, we explore the evaporation behavior of thermodynamically stable water-in-oil microemulsions. The water-in-oil microemulsion droplets prepared from different types of oil were acoustically levitated and heated using a continuous laser at different irradiation intensities. We show that the evaporation characteristics of these microemulsions can be controlled by varying water-to-surfactant molar ratio ({\omega}) and volume fraction of the dispersed phase ({\phi}). The emulsion droplets undergo three distinct stages of evaporation, namely pre-heating, steady evaporation, and unsteady evaporation. During the steady evaporation phase, increasing {\phi} reduces the evaporation rate for a fixed {\omega}. It is observed that the evaporation of microemulsion is governed by the complex interplay between its constituents and their properties. We propose a parameter ({\eta}) denoting the volume fraction ratio between volatile and non-volatile components, which indicates the cumulative influence of various factors affecting the evaporation process. The evaporation of microemulsions eventually leads to the formation of solid spherical shells, which may undergo buckling. The distinction in the morphology of these shells is explored in detail using SEM imaging., Comment: 42 pages, 11 figures

Published
2024

47. Insights into bubble droplet interactions in evaporating polymeric droplets

Author

Raghuram, Gannena K S, Roy, Durbar, Rao, D Chaitanya Kumar, Kumar, Aloke, and Basu, Saptarshi

Subjects
Condensed Matter - Soft Condensed Matter, Physics - Fluid Dynamics
Abstract

Polymer droplets subjected to a heated environment have significance in several fields ranging from spray drying and powder formation to surface coating. In the present work, we investigate the evaporation of a high viscoelastic modulus aqueous polymeric droplet in an acoustically levitated environment. Depending on the laser irradiation intensity, we observe nucleation of a bubble in the dilute regime of polymer concentration, contrary to the previously observed bubble nucleation in a semi-dilute entangled regime for low viscoelastic modulus polymer droplets. After the bubble nucleation, a quasi steady bubble growth occurs depending on the laser irradiation intensity and concentrations. Our scaling analysis reveals that bubble growth follows Plesset-Zwick criteria independent of the viscoelastic properties of the polymer solution. Further, we establish that the onset of bubble growth has an inverse nonlinear dependence on the laser irradiation intensity. At high concentrations and laser irradiation intensities, we report the expansion and collapse of polymer membrane without rupture, indicating the formation of an interfacial skin with significant strength. The droplet oscillations are primarily driven by the presence of multiple bubbles and, to some extent, by the rotational motion of the droplet. Finally, depending on the nature of bubble growth, different types of precipitate form contrary to the different modes of atomization observed in low viscoelastic modulus polymer droplets.

Published
2023

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