Research On Interfacial Transport Of Gas-liquid Two Phase Flow

As an analytical model to describe two-phase flow issues, two-fluid model isformulated of conservation equations of each phase. Because of dependence of eachphase the transfer terms are introduced into two-fluid model, including mass, momentumand energy transfers. Transfer terms are proportional to interfacial area concentration anddriving forces. This paper was focused on interfacial area transport equation oftwo-phase flow. Interfacial forces were calculated and analyzed. This paper was aimed ataccumulation of theoretical work and experimental data to apply two-fluid model tosolve two phase flow issues.The forces on bubbles in the two phase flow mainly contains drag force and virtualmass force in axial direction and sheared lift force, turbulence dispersion force and wallforce in radial direction. Based on experimental results the radial distributioncharacteristics of each micro forces were shown in details. Especially sheared lift force isto be investigated which is regarded as the main factor to affect radial movement ofbubbles. Once bubble diameter is larger than the critical size the direction of sheared liftforce will point to the center of flow channel instead of pointing to wall. Balance offorces equation could be used to calculate local void fraction, which predict well withmeasured values by optical probes.The expression of interfacial area transport equation under experimental conditionswas proposed in which random collision and turbulence impact terms of bubbleinteractions were modified. Both of them were derived renewedly by using binarycollision theory. The above-mentioned radial form of interfacial area transport equationin applied to predict local interfacial area concentration. It was shown that in fullydeveloped bubbly flow turbulence induced bubble coalescence and break-up exist rarely.Near wall region the predictions deviate from measured values. The reasons are that nearwall region besides the acceleration due to wake entrainment bubbles were affected bywall to move to channel center. The complicated movement of bubbles near wall resultedin the inaccuracy of wake entrainment term in interfacial area transport equation. The results showed that compared with variation due to void fraction the bubble interactioninduced variation of interfacial area concentration occupied smaller share. With theincreasing of liquid flow rate bubble interaction induced variation increased because ofstrengthened turbulent flow, whereas total interfacial area concentration variationdecreased due to bubble number density reducing.Based on experimental data by optical probes a new correlation of interfacial areaconcentration was proposed, which could be applied to calculate for large pipes. Its meanabsolute error is15.89%...