Modelagem matemática e simulação numérica dos rotores dessecantes utilizados em sistemas de condicionamento de ar por adsorção

Abstract

The present work presents the modeling, numerical simulation and analysis of the heat and mass transfer phenomena in desiccant and energy wheels used in the air dehumidification and enthalpy recovery, respectively. The problem studied consists of a honeycombed rotary desiccant wheel divided into two sections: adsorption and regeneration sections, where the adsorption and regeneration occur in a counter-flow arrangement. One mathematical model was tested and validated, steady and one-dimensional, considers the heat and mass transfers in fluid flow as well as in the adsorptive porous matrix; besides it is composed of energy and mass conservation equations, one adsorption isotherm and psychometrics relationships. This system of equations was discretized by finite volume method using fully implicit scheme with a staggered arrangement. Gauss-Seidel iteration under relaxation conditions was the numerical technique used to obtain the solution, except in the energy equation in the desiccant one where the Tridiagonal Matrix Algorithm (TDMA) was used. The results reached are presented in terms of temperature and absolute humidity profiles for both supply and exhaust air flows. Concerning to enthalpy wheels, it was observed that the instantaneous equilibrium model presents good fit without significant computational cost. On the other hand, relating to desiccant wheels, it was noticed certain discrepancy that can be associated to internal moisture diffusion resistance in the desiccant matrix.