Dynamics of boiling from a short capillary tube

Abstract

The phenomenon of boiling from a short capillary tube is studied experimentally, with the objective of better understanding the dynamics of phase change at nucleation shes. Boiling is achieved by electrical heating of a resistor in a short, water-filled capillary tube immersed in a pool of hot water. Bubble departure is detected by a phototransistor when a bubble passes through a laser beam. Two qualitatively different behaviors are observed. At low heat rates, bubbles depart with two possible periods. There are packages of a small number of bubbles departing with an almost constant period, separated by sets of two bubbles emitted at a shorter period. The behavior at large heat rates is singly periodic. In both cases, a small, apparently stochastic perturbation is superposed on the regular pattern. A statistical analysis of the experimental data is also carried out. For the low heating case, the output signal of the detector has been used as a time series to reconstruct the system attractor in phase space. The largest Lyapunov exponent obtained from the time-series information is positive, indicating that the phenomenon can be considered as chaotic. A physical model has been developed to interpret the various physical mechanisms that yield the observed qualitative behavior.