System simulation

Emerson develops components and systems for supermarket refrigeration. Due to its environmental benefits CO2 as refrigerant is becoming more and more important in this sector. But compared to traditional refrigerants the thermodynamic properties of CO2 are totally different (high pressures and low critical temperature). Designing efficient CO2 cycles is challenging and there are many different cycle concepts proposed. Together with Emerson experts we have developed simulation models for a number of different concepts and run a simulation study to compare the seasonal efficiency of these cycles.

In their development process of heat pump controllers Vaillant has established a comprehensive testing strategy. Before they connect developed controllers to real heat pumps in their lab, they are connected to virtual heat pumps running on special real time simulation hardware and software from dSPACE. Crucial ingredients for this so-called Hardware-in-the-Loop (HiL) tests are simulation models of the heat pumps, that are accurate, fast and robust. We developed these models for Vaillant using our Modelica library TIL Suite and set up a reliable tool chain to export these models to dSPACE platform. The models include a full dynamic physical model of the refrigeration cycle. It can handle switching of refrigerant flow direction caused by different modes for defrost, heating and cooling. Vaillant is now able to detect issues in control code much earlier and saves with this virtual testing a considerable amount of expensive lab experiments.

Together with Volkswagen we have developed simulation models for battery thermal management systems. Geometry of cooling plates and its flow patterns are taken into account by discretization with finite volumes. Compared to detailed CFD simulations the spatial resolution is much lower but still high enough to achieve confident results. This approach reduces the computation time dramatically enabling usage of numerical optimization algorithms or large-scale simulation studies. Cooling systems can be designed with less pressure loss and increased energy efficiency.