Interfacial Transport Mechanism And Model Of Annular Flow Under The Motion Condition

Annular flow is an important flow regime of two phase flow for the equipment design and operation involved,and the motion condition,induced by a series of typical ship motions including inclining,heaving and rolling motion,has notable effect on the thermal-hydraulic characteristics of marine reactor,not least on the two-phase flow and heat transfer of reactor coolant.Therefore,accurate prediction of the flow and heat transfer characteristics of the annular flow under the motion condition is indispensable for the safety operations of the reactor device under the ocean condition.In view of the practical importance of the drift-flux model and the computational accuracy of the two-fluid model,they are used for two-phase flow analysis in general and the analysis of nuclear-reactor transients and accidents in particular.To extrapolate the drift-flux model and two-fluid model to the analysis of nuclear-reactor accidents under the motion condition,the interfacial transport models(or constitutive equations including drift velocity and interfacial area concentration)of drift-flux model and two-fluid model for annular flow should be developed.Based on the gas-liquid two phase flow test facility,the characteristics of liquid film for annular flow are attained according to the visualization system and images processing,and the dependent factors of liquid film thickness and gas-liquid interfacial properties are analyzed.On the base a correlation related to liquid film thickness is developed,which takes the liquid droplets entrained mechanism and physical property into account and can accurately predict the experimental data with the maximum relative error of ±20%.The mechanism models tailored to disturbance wave height and velocity respectively are proposed from the perspective of the formation mechanism of disturbance wave by considering gas-liquid interfacial instability and force balance respectively,which are in possession of prediction accuracy of ±25%.Additionally,a prediction model of gas–liquid interfacial shear stress for annular flow is also proposed.The effect of interfacial characteristics and the entrainment–deposition process are incorporated into the model which can satisfactorily predict the experimental data with maximum relative error of ±25%.To develop the one dimensional drift velocity model for annular flow,detailed theory derivations of one dimensional momentum equation are given in this paper according to the definition of the drift velocity,in which,the additional pressure drop and the variation of gravity pressure drop and friction pressure drop are highlighted for the case of motion condition.Moreover,the validations are also carried out in this paper by comparing the model predictions to the experimental data and the numerical results.Theory derivations of the group one bubble interfacial area transport sources which are the paramount ingredient to develop one group interfacial area transport equation are demonstrated in this paper by considering the bubble interactions(including random collision,wake entrainment and turbulent impact)on the basis of the visualization system,and the one group interfacial area transport equation for narrow rectangular channel is also developed,which stems from the discussion of channel cross-sectional shape effects on the group one bubble interfacial area transport sources.In addition,the one group interfacial area transport equations are validated by using the experimental data on basis of in-house Matlab code.Furthermore,the bubble interactions of random collision and turbulent impact are considered to develop the one group interfacial area transport equation under the motion condition,and distribution parameters of interfacial area transport sources are proposed to develop the one dimensional one group interfacial area transport equation under the motion condition.Additionally,to verify the validity of one group interfacial area transport equation under motion condition,the one group interfacial area transport equation is incorporated in the system code,which is developed based on the RELAP5 code by considering the motion condition.