Validation of two distinct simulation models of district heating networks: application to efficient looping analysis

District Heating Networks (DHNs) offer a sustainable approach to thermal energy distribution by integrating low-carbon heat sources. However, their inherent complexity calls for optimized strategies that balance operational costs, user comfort, and capital investment. Rapid scenario assessment - enabled by reliable digital twins and efficient simulation tools - is essential to support such optimization. A key limitation in many existing simulation models is the lack of validation against real-world measurements. This paper presents a comparative validation of two fundamentally different quasi-dynamic simulation models, HeatGrid and PyDHN, using on-site measurements from a real-world meshed DHN. Despite their distinct methodologies, both models produced closely aligned results, with mean absolute differences of only 0.0268 kg/s in mass flow rate and 0.75°C in return temperature at the heating station. In addition to validation, the models were then used to evaluate the economic potential of adding new looping pipes scenarios to the network. Simulations revealed that although the additional pipes reduced pumping energy, they also led to significantly higher heat transport losses. As a result, the cost savings from reduced pumping energy were outweighed by the increased thermal losses - rendering all pipe addition scenarios economically unviable. Overall, the use of the prevalidated simulation models enabled rapid and informed evaluation of extension scenarios. The findings highlight that, contrary to intuition, adding pipes does not necessarily lead to lower operating costs in meshed DHNs.