Gray-box identification of thermal transfer coefficients of desiccant wheels

• A dynamic model is obtained from energy and mass balance.
• A state-space representation is obtained form the first-principles.
• Data for non-linear model identification are obtained experimentally.
• Model parameters are identified by Gauss–Newton methods.
• A gray-box approach is used to identify the thermal transfer coefficients and Nusselt number.

Dynamic models are needed for automatic control and online fault detection and diagnosis of desiccant wheels used in solar cooling systems. The parameters of these models need to be experimentally identified during operation. A model based on the heat and mass transfer equations, given in state-space representation, is developed. Using this model, a gray-box approach is developed to identify experimentally the thermal transfer coefficients. The Nusselt number and the heat and mass transfer coefficients have been obtained by defining the unknown parameters of the model as a function of a single parameter, which itself depends on the heat transfer coefficient, and by expressing the other parameters as a function of the geometrical and physical properties of the wheel.The difference between the values of the thermal transfer coefficients given in literature and those obtained by this method is less than 10%. Therefore, the gray-box identification method may be adopted as a tool for experimental estimation of the thermal coefficients under various design and operation conditions for the desiccant wheels.