Suppression of boiling and evaluation of surfactant adsorption capacity through dimensionless number of microwave local heating

Abstract

Dimensionless numbers, which are frequently used in fluid dynamics and thermal engineering, are important to generalize transport phenomena. Although dielectric heating of microwave has been attractive to enhance effectiveness of various processes in last decades, dimensionless number has not been introduced. Therefore, the difference between thermal effects and non-thermal effects has not been clear. In this study, by using our dimensionless number (As number), which was proposed as an index of non-equilibrium local heating of microwave in previous study, and the usefulness of our dimensionless number was verified through boiling and quick responses of interfacial tension. Experiments of interfacial tension and boiling were carried out when water phase includes surfactant and different NaCl concentration, and it was found that higher As number is required for surfactant desorption from the interface in the case of the higher NaCl concentration. Finally, boiling behavior by microwave local heating can be predicted from the double-logarithmic plot of the As number and the accumulation energy.

Keywords

• microwave heating
• interfacial tension
• dimensionless number
• boiling
• non-thermal effect