Hybrid dynamic modeling of the evaporator for the development of the advanced optimal control strategies
A hybrid model of evaporator used in air conditioning and refrigeration systems is proposed to present the dynamic behavior of the two phase flow evaporators. The model is formulated as process fundamental governing equations based on the energy and mass balance, and thermodynamic principles, while some constants and some variables which vary very little as time goes on, such as cross-sectional areas, mean void fraction, the derivative of the saturation enthalpy with respect to pressure, etc., are lumped into several unknown parameters, which are obtained by identifying the experimental data using nonlinear least squares method. The method takes advantages of both physical and empirical modeling approaches and can accurately predict the transient behaviors in real-time, which can significantly reduce the computational burden. The greatest merits of this model are the order of the model is very low and all the state variables can easily be measured, which are very suitable for model based controller design. The model validation studies on an experimental system show that the complete dynamic model developed in Matlab/Simulink can well predict the system dynamics. The developed models will have wide applications not only in controller design, but also in transient behavior analysis.