Dynamic Modeling of HVAC System with State-Space Method

The design of an efficient HVAC controller that maintains an anticipated indoor thermal environment at minimum energy consumption largely depends on the availability of a valid dynamic model of the system. This paper presents a state-space-based dynamic model for a HVAC system whose components are mainly air-to-water surface heat exchangers, air-supply ducts and water pipes. Firstly, the dynamic models for the components are developed according to the principle of energy and mass conservation. By introducing the vector-matrix notation, the ordinary differential equations describing the component dynamics are converted into the state-space form. Then, the state-space model for the whole HVAC system is developed based on the component models and model connection algorithms. Afterward, experiments have been performed to verify the HVAC system state-space model in predicting the transient responses of exit air temperature and humidity as well as outlet water temperature of the surface heat exchanger under inlet perturbations. The proposed modeling procedure can be especially useful for the development of the dynamic toolbox for the control design of HVAC system.