Development of a Simulator for Laboratory HVAC System

Space conditioning of a laboratory environment is more complicated than that of a typical commercial office building space. Safety considerations impose additional constraints over the usual comfort requirements. The control actions required to provide safety often counteracts those needed to meet comfort criteria. The dynamic interaction between the different control systems is complex and critical to laboratory safety. A description of a dynamic simulator for use in design and evaluation of laboratory HVAC systems is presented in this paper. The simulator includes the laboratory envelope, air flow system, heating and cooling coils, and a proportional-integral controller. The simulator is based on physical mechanisms and generates the transient response of the controlled variables (i. e. room temperature and pressure differential) to forcing functions (e.g. thermal loads, exhaust flows). The controller incorporates a model-based predictor that provides a rapid response to maintain comfort in the space while at the same time meeting safety criteria. The dynamic response of the pressure differential control and temperature control for both heating and cooling are important to energy use and safety in a laboratory environment. Significant changes in air flow rates and loads occur rapidly and tolerances are small. Results using the simulator are presented for the common control sequences found in a variable air volume (VAV) laboratory system. The simulator is found to be a promising approach to designing the control systems for a laboratory environment. The simulator provides insight into the dynamic interaction of the different control systems and the response of the laboratory environment. The simulator may serve as a model for developing the next generation of laboratory controllers.