Clarification of Boiling Complexity and Modeling - Approach based on Nonlinear Dynamics -

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With aims of making clear the complexity and nonlinear characteristics of boiling, five parallel studies were performed for pool and forced convection boiling. Namely, in 2002, The experiments of (1) boiling on an heated surface with an artificial cavity, (2) Bubble formation from an orifice in air-water isothermal system, (3) Interaction between twin bubbles generated from two neighboring orifices, (4) Nonlinear characteristics and identification of two-phase flow patterns, (5) Phase separation and fluctuation characteristics of two-phase flow impacting at a T-junction. In every experiment, nonlinear chaos theory was employed to analyze the data and have obtained interesting and valuable results. In the experiment of (1), it is found that cylindrical cavity is most stable among conical, cylindrical and entrained cavities. In the study of (3), it is found that the critical gas flow rate exists in the system. These are the new findings not ever known. These results have been published in the academic journals as well as National and international conferences. In 2001, the studies of (3)-(6) were continued to study, and in addition, basing on the results of experiment (1), new experimental study in which a single cavity, twin cavities and multiple cavities was started. In the study using a single cavity, the effects of cavity size (diameter and the depth of the cavity) to the boiling features were investigated in detail. In the study using twin cavities, nucleation site interaction was discussed. In the experiment employing multiple cavities, heat transfer characteristics were studied. Together with above experimental studies, modeling was tried for the bubble dynamics and two-phase flow pattern to show that there exists low dimensional chaos in pool boiling and two phase flow.