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

为了明确沸腾过程的复杂性和非线性特征，对池沸腾和强制对流沸腾进行了五项并行研究。即，2002年，(1)人工空腔加热表面沸腾实验，(2)空气-水等温系统孔口气泡形成实验，(3)相邻两个孔口产生的双气泡相互作用实验，(4)两相流的非线性特性及流型识别实验，(5)两相流在t型交界处碰撞的相分离及波动特性实验。在每次实验中，我们都采用非线性混沌理论对数据进行分析，得到了有趣而有价值的结果。在(1)的实验中，发现在锥形腔、圆柱形腔和夹带腔中，圆柱形腔最稳定。在(3)的研究中，发现系统中存在临界气体流量。这些都是未知的新发现。这些研究结果已发表在学术期刊以及国内和国际会议上。2001年继续进行了(3)-(6)的研究，并在实验(1)的基础上开展了单腔、双腔和多腔的新实验研究。在单腔的研究中，详细研究了空腔尺寸（直径和深度）对沸腾特性的影响。在双腔研究中，讨论了成核部位的相互作用。在多腔实验中，研究了换热特性。结合上述实验研究，尝试对气泡动力学和两相流型进行建模，表明池沸腾和两相流存在低维混沌。

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.