A review of the mathematical models for predicting rotary desiccant wheel

In the solid desiccant wheel air-conditioning system, the performance of the desiccant wheel is critical to the capability, size and cost of the whole system. Constructing mathematical model is an effective method for analyzing the performance of the rotary wheel as well as the system. The model can also be used to guide system operation, interpret experimental results and assist in system design and optimization. The overall objective of this paper is to provide a review of various efforts that researchers have made to mathematically model the coupled heat and mass transfer process occurring within the wheel. The paper first briefly describes desiccant wheel including fundamental principle, heat and mass transfer mechanism and the method of model establishment. Then various models consisting of ideal assumptions, governing equations, auxiliary conditions, solution methods and main results are presented. The models can be classified into two main categories: (1) gas-side resistance (GSR) model; (2) gas and solid-side resistance (GSSR) model which can be further subdivided into pseudo-gas-side (PGS) model, gas and solid-side (GSS) model and parabolic concentration profile (PCP) model. It shows that GSSR models are higher in precision and more complex compared with GSR models. In addition, the simplified empirical models based on measured data are briefly discussed. This review is useful for understanding the evolution process and status quo of the mathematical model and highlighting the key aspects of model improvement such as taking account of pressure loss or air leakage.