Study Of The Distribution Of Liquid Flowing Along An Inclined Wall And The Surface Waves And The Mass Transfer Process

Liquid flow along an inclined wall is very common in industrial process.According to the properties of fluids and the surface properties of the inclined wall,different types of liquid distribution forms on the wall e.g. film flow, mono-rivuletflow and multi-rivulet flow. Among which film flow is the desired liquid distributionform in many industrial heat and mass transfer equipments. The liquid distributionforms are critical to the heat and mass transfer efficiency of the related equipments;hence the investigations of the factors that influence the distribution forms of theliquid flowing along the inclined wall, and the characters of the formed film flow arevery important.3D models for liquid flow along an inclined wall were created and are solvedby CFD software FLUNET. The common flow process for different flowdistribution forms were studied, and the ratio of the volume flow rate of fluid carriedby the rivulets when they just arrived at the outlet to that at the entrance was selectedas a criterion to evaluate the impacts of surface tension, contact angle, inclination ofthe plane and the velocity of liquid and gas phase on the ultimate distribution form.Favorable factors for the distribution of film flow were pointed out. For the filmdistribution form, the factors influencing film width and thickness were studied.Effect of heat transfer from the plane on the film was also studied.Instead of flat surface, there are always waves on the surface for film flowingalong a vertical plate. Corrugated plates are very common in heat and mass transferequipments, thus in this work, CFD model for the film flow along a vertical periodicrectangular corrugated wall was created. Disturbance with mono-chromaticfrequency was introduced at the liquid inlet to study the relation of the resultingwaves on the film surface to the perturbations at the inlet. First, the developmentprocess for the finite amplitude disturbance along the film surface was studied, andthen the circulations inside the solitary waves, the pressure distribution along asolitary wave, and the interactions of solitary wave with the surface waves resultingfrom the waviness on the wall were studied. The influence of frequency of thedisturbance, the geometry of the corrugated wall and the velocity of the liquid andthe drag force introduced by the counter-current gas phase on the surface waves andthe thickness of film flow were also studied. The finite perturbations at the inlet will develop into large waves on the filmsurface, and cause circulations inside the film, thus would have important effect onthe transfer behavior of the film flow. In this work, two-films theory was used tocalculate interphase mass transfer, and the effects of corrugations on the wall and thefrequencies of the disturbance on the mass transfer process were investigated. It wasfound that, corrugated walls can obviously enhance the mass transfer rate comparingto the flat wall; Perturbations introduced at the inlet can enhance the process furthermore, the average concentration of the film can be enlarged as far as30%. The masstransfer enhancement factor is strongly dependent on the frequency, limiting to therange of frequency investigated in this work, it is found that, the factor first increasethen decrease with the increasing frequency. Also the factor decreases with theincreasing liquid phase velocity and increase with the counter-current gas phasevelocity when the frequency is fixed at27Hz.