Hydrodynamics Research Of Vapor (GAS) Liquid Solid Multi-Phase Boiling Flow In Vertical Tube

Solid particles fluidized by the two-phase boiling mixture may accomplish sufficient deposit removal to keep boiling surfaces clean. This results in a self-cleaning fluidized flow boiling heat exchanger. The particles additionally enhance the heat transfer. This hydrodynamics of a vapor liquid solid boiling flow is very complex. This complexity which results mainly from the strong nonlinearity and structural heterogeneity of particle-fluid flow system, makes simple methods not sufficient for elucidating their intrinsic characteristics. In this paper, deterministic chaos theory is applied to study the nonlinear characteristics of this flow boiling system. And a set of software which were verified and can used to describe actual system dynamic behavior qualitatively and quantitatively were developed and modified. Hydrodynamics of boiling multi-phase flow were studied, so as to supply more theory foundation for the vapor (gas) liquid solid flow technique.Experiments are carried out in the paper to study the feature of pressure fluctuation in vertical tube for boiling multi-phase flow. The gas-liquid-solid, natural circulation of vapor-liquid two phase and vapor-liquid-solid three phase, forced circulation of vapor-liquid two phase and vapor-liquid-solid three phase were studied. On the basis of detailed study on chaos theory of pressure fluctuation in boiling multi-phase flow, such as statistical analysis, quantitative analysis and qualitative analysis, it is evidence that boiling multi-phase flow system is a deterministic system. In addition to, the prime analysis of temperature signal on vapor-liquid two phase natural circulation flow was carried.The investigation results show that the pressure fluctuation signal in coarse circulation fluidized bed with big particles had chaos characterization. And the effects of heat flux on power spectrum density function of the pressure fluctuations are stressed study, and the flow regime transitions is correlation to number and frequency of the main peak value of power spectrum density function. The temperature of circulation liquid decreases with liquid viscosity increasing, and the circulation process becomes more steady in the vapor-liquid two-phase natural circulation. The effects of solid holdup on correlation dimension, K entropy and Lyapunov exponent of pressure fluctuation signal are studied in vapor-liquid-solid three phase natural circulation and forced circulation. And flow pattern can be identified by chaos characteristic parameter. By comparing vapor-liquid two-phase with vapor-liquid-solid three phase, the advantage of mixed solid particle in vapor-liquid two phase boiling is that flow process become more steady and flow regime can maintain bubble flow. In different velocity of flow, the fractal dimension of the pressure fluctuation time series in vapor-liquid two-phase forced circulation increased with increase of heat flux. The Kolmogorov entropy and correlation dimension have change with difference of heat flux. A positive, nonfinite estimate of correlation dimension and Kolmogorov entropy provides further evidence that pressure fluctuation signals behave chaotically. It can be concluded that the flow pattern transition on basis of characteristic parameters can be predicted.