Assessment of basic control strategies through dynamic simulations: A CO2-based chiller under extreme off-design conditions

Modelling and simulation tools offer peerless possibilities to dominate the increasing complexity of industrial applications, accelerating innovation cycles by quickly exploring and exploiting new efficient, reliable, and green possible solutions. In this paper, a dynamic model of a chiller system is developed through a mixed causal and acausal modelling approach. The chiller system uses carbon dioxide as a refrigerant and satisfies the cooling needs of high energy-demanding buildings. The model is validated against experimental data under various operating conditions and can be used to investigate the performances of different control logics under a wide partialization spectrum ranging from around 15% to 100% of the design cooling power of the system. Three simple control strategies, combining rule-based control and PID control, are presented and compared through both steady load simulations and daily characterizations. Simulation results point out opportunities that arise from the integration of the presented model in Computer-aided Control System Design (CACSD) software tools.