The effects of surfactant concentration on the initial short-time-scale Marangoni convection around boiling nuclei in aqueous solutions have been computationally investigated. The model consists of a hemispherical bubble (1–100 μm radius) on a downward-facing constant-temperature heated wall in a fluid pool with an initial uniform temperature gradient. Time-dependent transport of liquid mass, momentum, energy, and surfactant bulk and surface convection along with the adsorption kinetics are considered. Conditions for bubble sizes, surfactant bulk concentrations, and wall heat flux levels are represented by a range of thermocapillary and diffusocapillary Marangoni numbers over a micro-scale time period (1 μs–1 ms). With a surfactant in solution, a surface concentration gradient develops at the bubble interface that tends to oppose the temperature gradient and reduce the overall Marangoni convection. The maximum circulation strength, which is dependent on the bubble size, corresponds to a characteristic surfactant adsorption time. This, when scaled by a ratio of bubble radius, is found to depend solely on the surfactant bulk concentration. Moreover, the interfacial surfactant adsorption does not display a stagnant cap behavior for the range of parameters and time scales covered in this study.
Short-Time-Transient Surfactant Dynamics and Marangoni Convection Around Boiling Nuclei
Contributed by the Heat Transfer Division for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received by the Heat Transfer Division September 18, 2002; revision received May 16, 2003. Associate Editor: V. P. Carey.
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Wasekar , V. M., and Manglik, R. M. (September 23, 2003). "Short-Time-Transient Surfactant Dynamics and Marangoni Convection Around Boiling Nuclei ." ASME. J. Heat Transfer. October 2003; 125(5): 858–866. https://doi.org/10.1115/1.1599367
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