טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMargarita Gimmelshtein
SubjectInvestigation of the Flow Next to Membrane Wall
DepartmentDepartment of Chemical Engineering
Supervisor Professor Emeritus Semiat Raphael


Abstract

Flow investigation trough a spacer between two membranes was performed by a Particle Image Velocimetry technique and theoretical simulation. The spacers allow mechanical strength and cause turbulence in the flow layers near the membrane in order to improve the mass transfer. The experiments reported here are based on a flat membrane demo-model. Average velocity, velocity profiles, turbulence levels, membrane fouling, and the spacer geometry difference were investigated.

  The flow between two membranes fluctuates next to the cell frame. The maximum velocities values were found to be located at the middle of the cell. The dominant direction of the flow is x, but close to the filament dominates z direction. The velocity profile across a single spacer cell has a parabolic shape. As larger the Re number, the more parabolic is the shape of the flow profile. Turbulence intensities was found to be minimal at the center of the cell, maximal at the edges, increased with flow rates, but are small for small Reynolds numbers. Neighboring filament of a unit cell is placed in different levels. As longer and thicker the filament, the grater turbulence intensity it exerts within the cell.

The simulation model was based on two parallel plates and two concentric cylinders. Most of the area calculated to have no fluctuations, with vorticity field equal to zero. Only a small area around the filaments could be characterized as area with higher vorticity. Two possible eddies regions were created above and under each filament. 

A good agreement was found between the experimental results and the simulation velocity profile.