Date

2015

Document Type

Dissertation

Degree

Doctor of Philosophy

Department

Mechanical Engineering

First Adviser

Oztekin, Alparslan

Other advisers/committee members

Webb, Edmund; Moored, Keith; Pearson, Raymond

Abstract

Computational fluid dynamics simulations are conducted for multicomponent fluid flows in a channel containing spacers. The channel is bounded by membrane boundaries. A new and unique model has been presented for the treatment of the membrane boundaries in the separation of CO2 from CH4 in a binary mixture. The equation governing the flux through the membrane is derived from the first principle. The membrane is modeled as a functional surface, where the mass fluxes of each species will be determined based on the local partial pressures, the permeability, and the selectivity of the membrane. The approach introduced here is essential simulating gas-gas separation. Baseline Reynolds Stress, k-ω BSL, and Large Eddy Simulation, LES, turbulence models are employed to study spatial and temporal characteristics of the flow for a wide range of the Reynolds number. This study focuses on the improving the membrane performance by enhancing the momentum mixing in the feed channel by placing flow restricting bodies. The membrane properties such as membrane permeance and selectivity are fixed. Both spiral wound membrane and the hollow fiber membrane systems are considered here for gas separation applications. For the spiral wound membrane, it is shown here that the spacers have a strong effect on the membrane performance. The process of separating CO2 from CH4 is improved by the presence of spacers in the spiral wound membrane module. It is demonstrated that spacers should be an integral part of the membrane system design in the application of gas-gas separation. For the hollow fiber membrane it is illustrated here the porous support layer has strong influence on the membrane performance. Enhanced momentum mixing has been utilized to mitigate the adverse effects of the porous support layer. Flow restricting devices such as orifice, diffuser and helical grooves and fins are considered to achieve the promotion of momentum mixing. It has been shown here that the hollow fiber membrane performance can be improved by careful design of these devices in the feed channel. Further study of optimization is essential to achieve better performance in hollow fiber modules.

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