Numerical heat and mass transfer analysis for moisture adsorption / desorption in porous silica-gel packed beds

Abstract

Silica-gel packed bed systems are extensively used in various industrial processes for dehumidification or adsorption of volatile organic compounds In order to improve the design of the system understanding the heat and mass transfer mechanism during moisture adsorption/desorption process is important Recently a solid-side resistance model (SSR) which consider the resistance of solid part of silica gel has better computation performance In our group we did both experiment and numerical work for the system In previous work we built the one-dimensional (1-D) and two-dimensional (2-D) model and found that the 2-D model has better result of simulations because it considered temperature and humidity distribution in radial direction But the model neglects the nonhomogeneous velocity field of a porous medium so the total water adsorption will be overestimated To consider the non-homogeneous pressure and velocity field we add Darcy’s law into our models During our work we found that there was some problems of velocity field for just adding the Darcy’s law inside our previous model So we also use the first order correction of Darcy’s law to have a better velocity field and also build a model for the pressure inside the silica gel After the computation of the process we found that pressure is an important factor of water adsorption Higher pressure will cause higher water content of silica gel when reaction reaches steady state Moreover we analyzed the effect of geometry and other parameters we found that big caliber size comparing to the packed bed radius smaller length and bigger radius will cause higher speed of adsorbing water vapor at the beginning of reaction And high inlet velocity and bigger size of packed bed will lead to more water vapor adsorption

Date of Award	2019
Original language	English
Supervisor	Tian-Shiang Yang (Supervisor)