Applications of Paraffin-Water Dispersions in Energy Distribution Systems
Aachen / E.ON Energy Research Center, RWTH Aachen University (2017, 2018) [Book, Dissertation / PhD Thesis]
Page(s): 1 Online-Ressource (xxviii, 177 Seiten) : Illustrationen
The subject of this work is to assess the use of paraffin-water dispersion in different energy distribution systems. Conventional thermal systems use mostly water as a heat and cold carrier or a storage medium, from small-scale systems such as floor heating in residential buildings up to large-scale systems like district heating networks. The use of phase change materials as a substitute for water to increase the storage capacity has been the subject of many studies in last decades. However, only few studies have covered the behavior of phase change materials in the form of slurries in energy distribution systems while none of them has explored the applications and benefits of such systems in detail.This research examines the advantages and disadvantages of using paraffin-water dispersion in both heating and cooling systems using the modeling and simulation language Modelica. For this purpose, the paraffin-water dispersion is modeled mathematically. The model includes all the properties of the fluid such as the thermodynamic properties, the flow, and the phase change behavior as well as the heat transfer characteristics. The modeled fluid is then validated based on available measurement data, and certain parameters are adjusted to match the measurements better. Because of the high uncertainty in measurements, sensitivity analyses are performed on all the key parameters of the fluid to ensure that reliable final results are obtained.Different thermal systems including floor heating and radiative cooling, heat pump, and solar thermal systems as well as district heating and cooling networks are modeled separately. The heat or cold carrier in these systems is then substituted by the new paraffin-water dispersion model. Each system is subsequently investigated under different conditions. The simulation results show that although the use of paraffin-water dispersion leads to a reduction of the peak temperatures and therefore of the heat losses, the increase in the pump energy consumption because of the higher viscosity of slurries as well as the lower heat transfer are significant, canceling the benefits of lower heat losses in smaller systems. On the other hand, using paraffin-water dispersion in heating networks allows more than 50 % reduction of the flow temperature without affecting the usability of the system. This ensures not only a higher efficiency of the system but also its high flexibility, making it a suitable component in a smart city as a low-temperature district heating network.The low temperature heating network concept is analyzed in combination with a data center as a heat source and several residential buildings equipped with heat pumps as heat sinks. The results show that to achieve the highest efficiency, substituting water with paraffin-water dispersion requires modifications in the distribution and control systems in order to maintain the optimal mass flow rate to use the whole stored energy in the fluid.
Hensen, Jan L. M.