Nonlinear Modeling In Boiling System With A Vapor-Liquid-Solid Flow

The problem of fouling and heat transfer enhancement can be solved by vapor-liquid-solid flow technique. The analysis for this phenomenon indicated that the system of vapor-liquid-solid boiling flow is and should be investigated by the systematic theory and nonlinear methods. But up to now, the nonlinear studies on this system have been focused on the nonlinear heat transfer characters. However, little work has been done on the nonlinear modeling, which will be discussed in this paper. Based on the time series of key parameters, which display the features of vapor-liquid and vapor-liquid-solid systems, the genetic algorithm was used to construct a global model by which the hydrodynamic behavior of the system can be described. Comparison and analysis on the data obtained from model and experiment have been carried out. The results show that calculating value got from the model is in good agreement with that measured in experiment, and the hydrodynamic behavior of two-phase and three-phase systems can be well described by the models. Meanwhile the precision result from the model for two-phase system is higher than that for three-phase system. Moreover, the preliminary models for such systems have been built by making an attempt to use the inversion theory. The nonlinear quantitative analysis showed that the correlation dimension of the system is between 1 and 2, which indicated that two independent variables were needed to describe the dynamic behavior of the system. A group of two-order ordinary differential eaquations is constructed on the data of temperature and pressure time series. However, the comparison results between the values computed from the model and that measured show that more work remains to be done in the future.