科研之友
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摘要
Bubble growth in superheated liquid is a fundamental process in vapor-liquid phase change which occurs widely in thermal and chemical engineering. The strong coupling of heat, mass and momentum transfer at the interface brings difficulties to accurately predict the dynamics of bubble growth. At present, bubble growth under three extreme conditions, i.e. the very early growth stage, low superheats and low pressures, cannot be well described by traditional asymptotic solutions. In this work, a mathematical model was presented for better prediction of bubble growth in a superheated liquid. The model was derived from the equations of motion for a bubble and took account of the heat and mass balances at the interface. The model was validated with a series of experiments from the literature, covering a wide range of operating conditions. The newly proposed model can well predict the features of bubble growth at the very early stage (less than 10 (6) s), for superheats varying from 0.8 K to 36 K and for system pressures reduced from 1.0 atm to 0.0124 atm. Analyses on the thermodynamics and hydrodynamics manifested that the bubble growth was characterized by three typical stages, i.e. a thermal delay stage, a fast expansion stage and a steady growth stage. The time lengths of these stages were related to the levels of superheat or system pressure. Characteristics of these stages were further discussed and the roles of interfacial forces under the different operating conditions were demonstrated.
