State-space model for transient behavior of membrane-based liquid desiccant dehumidifier

Abstract

In this paper, a state-space model for a membrane-based liquid desiccant dehumidifier with counter-flow configuration was developed and validated experimentally. Compared with experimental data, the maximum relative error of model results is less than 2%, and the mean relative error is about 1%, which indicates that the state-space model can well predict the transient characteristics of the membrane-based liquid desiccant dehumidifier. Further, the transient responses of the dehumidifier to the step changes of inlet parameters (air temperature and humidity, air flow rate, solution temperature and flow rate) were investigated in detail. This dynamic model can clearly reflect the transient relationships among input, state and output variables. It was found that the effect of perturbation of the inlet air temperature on the moisture transfer in the membrane-based dehumidifier was too small to be neglected, and the variation of the inlet air humidity had little effect on the heat transfer. The response time constant of the outlet solution temperature to the inlet perturbations was obviously larger than that of the outlet air temperature and humidity. The air and the solution flow rate can be taken as the controllable parameters for the outlet air humidity control of membrane-based liquid desiccant dehumidifier. With the advantages of short calculation time and simple solving process, the state-space model is helpful for the control design and the optimization of the membrane-based liquid desiccant dehumidifier.