Bachelor's thesis David Cornelius Arnolds


Evaluation of Energy Flows in District Cooling Networks

Energy efficient technologies for buliding climatisation are becoming increasingly important
in times of growing scarcity of ressources and increasing average temperatures. In contrast to
previous static studies, at the Institute of Energy Efficient Buildings and Indoor Climate at the
RWTH Aachen University dynamic simulations of district cooling networks are performed,
which are an alternative to individual air conditioners. In context of this project the aim of this
bachelor thesis is, to dynamically study and describe the characteristic flow behaviour of the
cooling networks at Campus Melaten and Research Center Juelich. Therefor a Matlab-Script
was developed, that is able to calculate the flow velocity, the running time and the pressure
drop in these district cooling networks on the basis of models. Different equations were used
and compared to calculate the pipe friction coefficient. To gather the results dynamically a
variation of the feed mass flow was made. To value the results for the district cooling network
at Research Center Juelich, they were compared with results of a measured data analysis.
The results for the cooling network at Campus Melaten showed, that the running times from
feed to purchaser behave almost proportional to the distances between feed and purchaser.
The pressure drop tendentially increases with growing distances between feed and purchaser,
too, but not proportionally and with exceptions. It was possible to show the high dependency
of the pressure drop on the diameters of the pipes, that lead to the purchasers. The
calculations of the cooling network at Research Center Juelich, where three feed stations are
installed, showed that the development with increasing distance between feed and purchaser
of the running times and pressure drops are dependend on the feed station. It could be
detected that the running times and pressure drops tendentially grow with increasing
distances, but irregular and with exceptions. Also, it could be pointed out, that the flow
velocity does not always behave analogously to the mass flow. In both cooling networks the
characteristic flow behaviour does not change with changing feed mass flows.
The comparison of the running times with the results of the measured data analysis showed,
that it is possible to study the approximate characteristic flow behaviour in district cooling
networks with the developed Matlab-Script. Exact values cannot be achieved, due to the
amount of simplifications and restrictions that were made to create the models of the
networks. To receive more precise values arcs and components could be observed in a further
development of the script. The script can be used to set starting values for the pressure in the
pipes to run further simulations.