Medium dynamic diffusion characteristics in the pipeline network of variable flow HVAC system towards online decoupling control oriented

The coupling characteristics of the control loops in the optimization process of the heating, ventilation, and air conditioning (HVAC) systems are critical to control effect and system stability. This is particularly prominent during the diffusion process of quality and quantity parameters in the pipeline network, because the obvious delayed response characteristics of medium parameters (e.g., temperature and pressure) will intensify the coupling issues. Therefore, the real-time diffusion characteristics of the medium parameters in a pipeline network must be studied to provide a reference for decoupling optimization. In this study, the dynamic characteristics of parameter diffusion in the pipeline network were studied essentially from the perspective of online decoupling control. An online application mechanism to improve the online feasibility of the dynamic characteristics in a practical system has been proposed, which also provides a new orientation for the online optimization of HVAC systems. Based on a simulation analysis, the qualitative and quantitative relations between the delayed response time and constitutive parameters in the pipeline network were identified, which is significant for the selection of the control period and optimization timing during the decoupling control in practice. Finally, the simulation results and online feasibility were verified experimentally in a real HVAC system. The experimental results show that the R-2 for the hydraulic and thermal response models are 0.9596 and 0.9865, and the RMSE for predicting the flow rate and temperature are 0.0204 and 0.3791. This research is expected to provide considerable reference values for the time-oriented optimization of online decoupling control in practice and function as a theoretical foundation of our subsequent studies. (C) 2022 Elsevier B.V. All rights reserved.