Bachelor's thesis Jürgen Hanke

 

Evaluation of energy flows in heating networks using simplyfied pipe models

With Modelica physical models can be created object-oriented using a graphical user interface.
With the Fluid-package of the Modelica Standard Library (MSL) it is possible to create Models of
pipe systems. The Models of the MSL are very complex and therefore have a high computational
cost. To reduce computational cost the EBC has created the SimpleHydraulic-Package which
contains simplifiedModels to simulate pipe systems. The topic of this Bachelor Thesis was the development
of a simplified dynamic pipe model for the SimpleHydraulic-Package. Afterwards the
createdmodel has been verified using measurement data provided by the heat grid at campusMelaten
of RWTH Aachen University. The pipe model of the Fluid-package of theMSL was used as an
additional reference.
The threemain aspects of the created pipe model were the computation of pressure loss, the computation
of the heat transfer through the pipe wall and the discretization of the pipe volume. The
plausibility of the pipemodel has been verified with the aid of parameter variation.
A comparison of the simulation results and the measured data of the heat grid suggested a discretization
of n = 500 for the simulation to tesult in a reasonable approximation to the measured
temperature profile. The root mean square deviation of the used measurement intervals were in
the range of 1,45 °C to 3,57 °C. A time displacement between the simulation results and themeasured
data could be reduced by taking a branched off mass flow between the two measuring points
into account.
Comparing the simulation results of the simplified pipe model and the pipe model of the MSL, a
constant time displacement between the two models could be observed. The variation of the pipe
diameter, the pipe length and the mass flow suggests a connection between the time the fluid
needs to pass through the pipe and the time displacement. However, the exact cause of the time
displacement between the two pipe models could not be determined.