Deposition of suspensions in laminar flow in the entrance region of channels with diffusive, electrostatic and gravitational effects
Department of Mechanical Engineering
Doctor of Engineering Science
Kirchner, Robert P.
Pawel, Hans E.
Andrushkiw, Roman I.
Hsieh, Jui Sheng
This investigation entailed the consideration of the deposition of suspensions in laminar flow in the entrance region of a parallel-plate channel, and both converging and diverging channels, under the combined influences of diffusive, electrostatic and gravitational effects. The fluid phase was assumed to be incompressible, steady and laminar; the particle phase was assumed to be steady, laminar, dilute, and with negligible lift force.
The complete solution of the problem involved solving the boundary layer equations for the completely viscous fluid phase, and the particulate momentum, continuity and potential equations for the particle phase. Since the resulting equations are non-linear partial differential equations, numerical techniques were utilized to obtain solutions.
The flow characteristics of the particulate phase along with the deposition rate of the solid particles were investigated under varied flow conditions. Deposition due to surface adhesion, gravity and electrostatic charge was considered.
Tt was found that an appreciable amount of particle deposition can result because of gravity on the solid particles especially on the bottom wall which showed a much higher deposition rate than the top wall. Moreover, when the combined influence of gravity and electrostatic charge was considered, it was found that a much higher deposition rate occurs on the bottom wall as compared to the case without the electrostatic charge effect.
Furthermore, it was observed that the deposition lessened with increased convergence angle; however, a much higher deposition rate was found on the bottom wall with increased divergence(diffuser) angle due to the separation phenomenon of the boundary layer.
njit-etd1978-002 (185 pages ~ 5,293 KB pdf)
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Created July 26, 2005