Comparative assessment of the linear driving force and pseudo-gas-side-controlled models for the prediction of mass transfer in desiccant matrices

Abstract

Simplified and realistic simulation models are of great relevance for industrial development of components and systems. The simplified approaches based on the pseudo-gas-side-controlled model and on the linear driving force model are investigated in the simulation of the mass transfer phenomena between the airflow and the channel wall of a solid desiccant matrix. The differences between the two approaches lie in the mass transfer coefficient and potential that are considered in the conceptual equation.The investigation is centred on the behaviour of an elemental cell of desiccant matrices. The reference data are provided by the results of a detailed model.The response of the desiccant wall to a step change in the airflow state is simulated, for both adsorption and desorption processes. For each approach, a mass transfer coefficient is estimated after the time evolutions predicted by the detailed model. It is concluded that, when adopting a constant mass transfer coefficient: (i) the pseudo-gas-side-controlled model with an adsorption–desorption averaged value is more suitable for predicting the behaviour of matrices with lower thickness desiccant wall and (ii) the linear driving force model is more appropriate for higher thickness desiccant wall if using a mass transfer coefficient of the specific sorption process.