Combining different levels of detail in modelling for an improved precision of HVAC plant simulation

In this article, we will present a new multi-level modelling approach to obtain higher precision in HVAC plant simulation models. For this purpose, two different levels of detail in modelling, the coarse component-based approach of Modelica and the detailed physical-based approach of Computational Fluid Dynamics (CFD) were combined. In a first use case, we analysed the thermal hydraulic network of a simple heating system, both with the CFD-approach (3D-model) and the Modelica approach  (1D-model). Both simulation models consist of an ideal pump, an ideal heating source, two hydraulic loops and an ideal thermal sink. We compared the differences between the results (pressures, temperatures, mass flows) of both modelling approaches. Finally, we tried to improve the accuracy of the fast Modelica model by introducing correction models in the thermal hydraulic network.