Chaos in nucleate boiling - nonlinear analysis and modelling

The artificial surfaces are applied to study the pool boiling features, including the surface temperature fluctuation and nucleation sites interaction. The nonlinear analysis of temperature fluctuation has been carried out. Under the single nucleation site the low dimensional deterministic chaos has been observed. It has been found that the thermal interaction between two nucleation sites decreases and the hydrodynamic interaction increases the frequency of bubble departure. It has been also found out that hydrodynamic interaction makes that the process of bubbles departure becomes more predictable. To explain the mechanism of deterministic chaos appearance the simple model of heat transfer under the nucleation sites has been presented. The obtained results of simulations show that the nonlinearity introduced to heat transfer as a result of changing in time the heat flux absorbed by bubbles leads to chaotic changes of heating surface temperature at nucleation site. The model has been used to analyse the behavior of thermal interaction between nucleation sites with chaotically departing bubbles. The results obtained from simulation explain experimental results. (C) 2003 Elsevier Ltd. All rights reserved.