Studies On The Nonlinear Prediction In Boiling System With A Vapor-Liquid-Solid Flow

Recently, deterministic chaos theory is applied to investigate the system of flow boiling. However, the work is limited in the revelation of nonlinear characteristics of the system. In this paper, the time series of heat transfer coefficients in evaporation system with vapor-liquid and vapor-liquid-solid flow was forecasted by the chaotic method, so as to provide some foundations for the operation and control of such installation systems. The apparatus and parameter automatic measuring system of vapor-liquid-solid flow boiling was established. The time series of heat transfer coefficient, which can reflect the evolution information of flow and heat transfer of system, will be calculated by measured wall temperature, fluid temperature and heat flux. The methods of deterministic chaotic analysis and traditional analysis are used to analyze the data and the method of chaotic prediction is applied to forecast these time series. The investigation results show that vapor-liquid and vapor-liquid-solid flow boiling systems exhibit chaotic behavior on certain operating conditions. The predicted values of the two-phase system are consistent with the experimental values both in view of the time trajectory and in view of macroscopic or general characters. The predicted values of three-phase system are consistent with the experimental values in view of macroscopic or general characters but not completely in view of the time trajectory. The forecasting accuracy of two-phase flow is higher than that of three-phase flow, which reflects that the character of flow and heat transfer of three-phase flow boiling system is more complex than that of three-phase system. In addition, the forecasting accuracies are different for different flow state, different solid holdup in the tube and different axial position. The agreements can be well reflected by the phase map. However, the parameter value gained from the forecasting time series is a little less than that obtained from measuring, and the prediction method should be improved in future.