Simulation towards demonstration: A Digital-Twin for developing control concepts of an industrial-scale Rotation Heat Pump

A Rotation Heat Pump (RHP) uses a Joule cycle in contrast to compression heat pumps using a vapor compression cycle. Due to the rotation of a rotor filled with a working fluid, the temperature of the fluid rises outwards as the working fluid is compressed. Basic elements are heat exchangers, compression and expansion pipes, and a fan to circulate the working fluid. Due to the rotation, these components differ in their operating behavior according to available literature data. A fixed/rigid pre-setting of the parameters to achieve a certain operating state is the current state of the art for controlling such heat pumps. This results in a simple but non-optimal control, e.g. regarding energy efficiency. To test different, more efficient control strategies even before a prototype is manufactured, a Digital Twin of the RHP is modeled. This requires correlations of the thermodynamic behavior of the components. These individual components were modelled using computational fluid dynamics (CFD) models and the behavior was analyzed using parameter studies and finally exported as individual functional mock-up units (FMU). The Digital-Twin of the RHP was created in the Dymola/Modelica simulation environment using the TIL-library supplemented by the FMUs. This modular structure allows efficient adaptions of various components. Different control concepts (e.g. extremum seeking control and model predictive control) are developed and compared based on the Digital Twin. The proof-of-concept of the developed control concept is first performed on the programmable logic controller (PLC) by means of controller-in-the-loop (CIL). Subsequently, the control concept is implemented and verified on a real industrial scale RHP.