Future district heating networks are characterized by low supply and return temperatures and decentralized feed-in. Major challenges arise from the volatile energy supply due to the increasing share of renewable energies and the not yet utilized system flexibility to compensate for this. This necessitates new strategies for grid design and operation to ensure security of supply at all times. In the collaborative research project “EnEff:Wärme MeFlexWärme”, funded by the German Federal Ministry for Economic Affairs and Energy, different departments from the Technical University of Darmstadt as well as the industrial companies Siemens AG and Entega AG collaborate to develop a framework to simulate and evaluate future district heating network systems. The district heating network system of Darmstadt serves as a case study that allows empirical validation of the models developed in the project. In this paper, we present an exemplary physical simulation of the district heating network proving the feasibility of the approach which allows the simulation of different constellations by adapting operation modes to given optimization values (e.g. minimizing heat production costs). The framework is the key element to tackle further questions in “EnEff:Wärme MeFlexWärme”, such as an estimation of the network’s state based on a few carefully selected sensors in the grid, integration of renewable heat sources and analyzing CO2-emissions.