Design Optimization of Functionalized Silica-Polymer Nanocomposite through Finite Element and Molecular Dynamics Modeling
Authors:   , Almahmoud Omar H. M. 
Published: February 2025

This dissertation focuses on studying membrane air dehumidification for a membrane moisture exchanger in a membrane heat pump system. The study has two parts: an optimization of membrane moisture exchanger for air dehumidification in the macroscale, and diffusion of water vapor in polymer nanocomposites membrane for humid air dehumidification in the nanoscale. In the first part of the research, the mass transport of water vapor molecules through hydrophilic silica nanochannel chains in hydrophobic polyurethane matrix was studied by simulations and experiments for different membrane moisture exchanger design configurations. The mass transport across the polymer nanocomposite membrane occurs with the diffusion of moist air water vapor molecules in the membrane moisture exchanger in a membrane heat pump air conditioning system for air dehumidification purposes. The hydrophobic polyurethane matrix containing the hydrophilic silica nanochannel chains membrane is responsible for transporting water vapor molecules from the feed side to the permeate side of the membrane without allowing air molecules to pass through.In the second part of the research, diffusion analysis of the polymer nanocomposite membrane were performed in the nanoscale for the polymer nanocomposite membrane. The diffusion phenomena through the polymer, the polymer nanocomposite without modifying the silica surfaces, and the polymer nanocomposite with two different silica modified surfaces were studied in order to obtain the highest water vapor removal through the membrane. Different membrane moisture exchanger configurations for optimal water vapor removal were compared to get the desired membrane moisture exchanger design using the finite element method (FEM) with the COMSOL Multiphysics software package. The prediction of mass transport through different membrane configurations can be done by obtaining the mass flux value for each configuration. An experimental setup of one membrane moisture exchanger design was introduced to verify the simulation results. Also, for different membrane structures, permeability was measured according to the ASTM E-96 method. The prediction of water vapor diffusion through the polymer nanocomposite was studied by molecular dynamics simulation with the MAPS 4.3 and LAMMPS software packages. As a new nanocomposite material used in air dehumidification application, water vapor diffusivity through Silica-Polyurethane nanocomposite membranes was measured by the random movement of water vapor molecules through the formed nanochannels in the nanocomposite. For the diffusivity value, the Einstein's relationship was employed for the movement of each single water vapor molecule during the simulation time for all suggested membranes. The results of the proposed research will contribute to enhancing the energy efficiency of air conditioning systems by choosing the membrane moisture exchanger configuration which maximizes water vapor removal while, at the same time, enhancing the silica surfaces with the desired surface modifier that will maximize diffusion through the membrane itself.