A comparison of simplified modeling approaches and simulation quality of an industrial R717-HTHP

The industrial sector offers considerable potential for reducing energy consumption and greenhouse gas emissions through the use of high-temperature heat pumps (HTHPs). In this context, simulations can serve as a useful tool to pinpoint optimization opportunities for the process heat supply and its interaction with subsystems. However, as the complexity of the calculations and the effort required for model parameterization escalate with the level of detail, certain simplifications are necessary.
This study describes the development of simplified simulation models of an ammonia (R717) chiller (nominal cooling capacity: 900 kW, source outlet temperature of 1 °C) and an add-on HTHP (nominal heating capacity: 550 kW, sink outlet temperatures up to 90 °C). For this purpose, different model approaches, such as second law efficiencies and component-based modeling using UA-values, are explored and evaluated through a comparative analysis of simulation quality. Validation is conducted using measurement data at varying operating conditions, which shows mean errors in sink & source capacities and COPs below 5.2 %.