| Popis: |
This study seeks to understand the origins of intermittency in quantities of interest in pool boiling, such as bubble departure diameter and departure time. The intermittency of nucleation site activity due to nonuniform and unsteady near-wall temperatures is well-established; however, few mechanistic models have been developed that predict such intermittency. Here we assume a fluctuating pressure field at a nucleation site due to adjacent bubble activity, which acts in combination with convective effects to alter bubble growth depending on the phase of the pressure oscillation with respect to the instant of bubble nucleation. The results suggest that even when a single departure frequency is assumed for nearby bubbles, its effect on the nucleation site being considered is to cause aperiodicity and intermittency in bubble departure quantities. The effects of pressure field phase angle, degree of superheat, and choice of force balance model on the bubble departure quantities are examined. The phase angle of the pressure fluctuation at the instant of bubble nucleation is shown to play a major role in determining bubble departure diameter and growth time. Departure diameter is observed to have a broad distribution over long times of observation, belying the assumption of a unique value. Period doubling of the ebullition cycle is observed for some conditions, a phenomenon documented by other investigators. The effects of dynamic contact angle. |
