Numerični model adsorpcijskega procesa pri toku v kanalu : doktorska disertacija

slovenian

doktorska dela

2013

Univerza v Mariboru, Fakulteta za strojništvo

In this doctoral dissertation a numerical model is presented for simulation ofan adsorption process in a honeycomb channel that has a thin layer of adsorbent on its walls. In the channel there is a flow of carrying fluid with very low concentration of adsorbate, which accumulates in the adsorbent layer on channel walls due to adsorption forces. Because the concentration of adsorbate in the carrying flow is very low it has no influence on the general flow conditions and it is only involved in adsorption process. Simulation of flow in the channel is made by solving Navier-Stokes system of conservation equations with the use of boundary element method. Adsorption mass flow from the bulk fluid to the layer of adsorbent is modelled with the correction of values of adsorbate concentration on the channel wall. Concentration of adsorbate near the phase surface in the fluid and above the adsorbent layer gets lowered due to adsorption process and this causes concentration gradient and adsorbate mass flux in the direction towards the channel wall. Value of wall concentration of adsorbate depends on the distribution coefficient that is governed by the ratio of accumulated mass of adsorbate in the layer and equilibrium mass of adsorbate in the adsorbent layer. Equilibrium mass of adsorbate per volume of adsorbent is calculated with an appropriate equilibrium model on the basis of known values of temperature, concentration of adsorbate and other material properties available from the literature. Fourdifferent equilibrium models were used and this were: Freundlich and Dubinin-Radushkevich equations, SLD equilibrium model based on Van der Waals equation of state and Peng-Robinson SLD equilibrium model. Presented numerical scheme was then used to perform a larger number of different simulations for a problem of channel flow of poor mixture of air and butane. Channel walls were covered with thin layer of active carbon. Based on the simulations results an analysis of suitable calculation mesh, suitable simulation time step and comparison with benchmark results from other authors were made. This comparison shows that presented numerical scheme offers good results and enables accurate simulations of adsorption processes in channels. At the end the parametrical analysis of flow rate and temperature influence onthe adsorption process in a channel is made and future research guidelines are given.

08.08.2023