Numerical Research Of Influence Of Flow Field Environment On Gas Liquid Two Phase Flow And Heat Transfer Characteristics In Horizontal Channel

As an important branch of multiphase flow thermophysics,gas-liquid two-phase flow is closely related to people's life and industrial production safety.In the process of fluid flow,fluid is not only affected by its inherent properties,such as physical and chemical properties,but also closely related to the flow environment.The physical properties of fluid are controllable factors,most of which have controllable effect.In contrast,the influence of the change of flow field environment on the fluid flow is often obviously different from the theoretical calculation value and difficult to control.Therefore,in order to realize the efficient use of energy and accurately grasp the characteristic parameters of complex flow,it is particularly important to study the flow and heat transfer characteristics of fluid in different flow fields.Based on the method of numerical simulation,according to the classification of flow field and environment,the characteristics of gas-liquid two-phase flow and heat transfer in the channel of geometry flow field,environment flow field and heat load flow field were systematically and comprehensively analyzed.1.Flow field of geometric structure.A mathematical model of gas-liquid two-phase flow in a serpentine microchannel was established,and the effects of Y-shaped confluence structure on flow and heat transfer characteristics were analyzed.Unlike the conventional scale channels,fluid flow in microchannels was greatly influenced by inertia force,viscous force and surface tension,which means that wall properties and geometric structure were main factors affecting the distribution of gas-liquid interface.When the angle of Y type was 60 degrees,the gas-liquid two-phase pressure drop and Po number were the lowest.In addition,the mathematical model of micro-channel fluid flow under slip boundary condition was established by adding source term.The results showed that the hydrophobic wall can induce slip phenomena,while reducing pressure drop,surface friction coefficient and flow resistance coefficient,which is conducive to heat transfer.And the drag reduction effect in the channel with smaller height was better.Meanwhile,in view of the special geometric structure of serpentine microchannel,fluid flow and heat transfer in the curved channel were studied.And the effect of curvature on fluid flow and heat transfer was analyzed.The results showed that the increase of curvature enhances the symmetry of velocity distribution along the horizontal coordinates.The velocity distribution trend of cross-section was not affected,but the velocity and temperature of the fluid near the inner wall were higher than those near the outer wall.2.Environmental flow field.According to the effect of environmental flow field,the conventional horizontal channel was selected.A mathematical model of gas-liquid two-phase flow and heat transfer in a channel under heaving motion was established by adding a self-defined function and combining with a dynamic mesh model.Unlike the steady-state condition,gas-liquid interface distribution is influenced by the additional inertia force caused by vibration and the gravity of the gas-liquid interface itself,and the vibration parameters had a greater impact on low-velocity fluid.Compared with the amplitude of vibration,the change of vibration frequency had a more significant effect on fluid flow and heat transfer characteristics.By discussing and analyzing the law of fluid frictional pressure drop,void fraction and fluid temperature change under steady state and different vibration parameters,it was found that compared with the fluid flow in steady state,the effect of periodic vibration on flow rate and instantaneous frictional pressure drop was more obvious.Vibration amplitude mainly affected the height of liquid level fluctuation,i.e.the void fraction of cross section.Although the vibration parameters have no obvious influence on the definition of convection pattern,the vibration frequency will affect the intensity of liquid level fluctuation.In a certain range,vibration can enhance heat transfer,and the peak temperature occurs when the channel moves from the highest point of heaving motion to the equilibrium position.3.Hot-load flow field.Based on the classical model and related empirical formulas for predicting frictional pressure drop and void fraction of gas-liquid two-phase flow,the numerical results of fluid flow in horizontal channel under different vibration parameters in this paper were compared and analyzed.By comparing several typical frictional pressure drop correlations,it was found that the predicted values of Muller model were in good agreement with the numerical results of dynamic working conditions.By comparing the void fraction correlations of four typical models,it was concluded that the drift flux model had a better prediction effect when the vibration parameters were small.And when the vibration parameters were high,the flow-based model was more suitable to predict the drift flux.At the same time,according to the theory of field synergy analysis,the effect of hot-load flow field on heat transfer of gas-liquid two-phase flow in serpentine microchannels and horizontal channels under different vibration parameters was analyzed.The results showed that reasonable design of wall properties and curvature of curved microchannels can improve the heat transfer performance of microchannels.For the fluctuating vibration condition adopted in this paper,it was found that the fluctuating vibration in a certain frequency range was an effective method to enhance the heat transfer.Under the condition of low Re number and strong vibration parameters,the effect of vibration on the flow and heat transfer of fluid was significant.