Naveen Daham Weerasekera, Aurelie Laguerre
Abstract: In this paper, convection-diffusion based mass transport model is proposed for parallel flow driven species transport in microporous membranes. An individual membrane is modeled with the help of macroscopic concentration measurements, considering mass transfer effect in a core of residential energy recovery ventilator sandwiched membrane arrangement, utilizing proton transfer reaction mass spectrometry. Isopropyl alcohol (C3H8) is used as the trace compound in experimental analysis. Computational model is developed focusing on a local effect occurring at the sandwiched core structure. Through the model, a porous membrane exposed to parallel air flows in both sides are studied. Trace compound injection is modeled by creating constant concentration boundary condition at the channel inlet. Fluid-membrane interface mass transfer is represented by source and sink terms proportional to the interface concentration and transfer coefficients (adsorption and desorption). Mass transport in the membrane is attributed to effective diffusion parameter considering both molecular and Knudsen diffusion processes. In addition, membrane pore size distribution is simplified to a lognormal distribution, with a known mean and standard deviation. The proposed model successfully demonstrated the conjugate transport phenomena in microporous membranes demonstrating the development of concentration boundary layers at the interfaces. Also, it is observed that decrease in adsorption coefficients with the increase of adjacent flow velocities near the membrane. In contrary, increase in desorption coefficient is observed at the interface with the increase of flow velocity. The change in adsorption and desorption parameters in the model confirmed previously reported experimental outcomes.
Keywords: Membrane Mass Transport, Advection and Diffusion in Mini-Channels, Mass Spectrometry, Numerical Modeling, Monte-Carlo Simulations, Lognormal Pore Size Distribution, Effective Diffusivity