Thermische Speicher mit Phasenwechselmaterialien im Heizsystem

Aachen (2016, 2017) [Dissertation / PhD Thesis]

Page(s): 1 Online-Ressource (xx, 140 Seiten) : Illustrationen, Diagramme

Abstract

Many hydraulic systems implement thermal storages to profit from the combination of renewable energy and the heating system of a building. They serve as central component of the heating system. To analyze the thermal storage in combination with heating systems for one family houses, a study of the energetic and exergetic behaviour has been made.This PhD study outlines the influence of phase change material (PCM) which is integrated in a thermal storage (buffer storage). Therefore thermal storages are analyzed in dynamic simulations with a one dimensional modelling approach. In the first chapter the basics of thermal storages and the different modelling approaches are described.The models of the thermal storages are developed and validated and measurements of the behaviour of a water- and PCM-storage are made. The existing warm water storage model of the Institute for Energy Efficient Buildings and Indoor Climate was adapted with the help of parameter identification. For example the value of the number of nodes and the effective heat conduction are investigated.The centerpiece of the PCM-model is the implementation of the heat capacity in dependence on the temperature. More elements are the convection between fluid/PCM and the heat conduction inside of the PCM. The three developed PCM-storage-models -- a single plate, a stack and a pebble bed -- are build up with the mentioned elements. The influence on the heat transfer between water/PCM and different discretization numbers are analyzed. The last step is the validation of the PCM-model.In the fifth chapter the different thermal storages (stratified storage, buffer storage and a paraffin and salt hydrate storage) are evaluated in theoretical and dynamical studies. The theoretical potential of the PCM-storage is outlined by energetic and exergetic evaluations. Six hydraulic concepts consisting of boiler/heat pump with radiators or floor heating with/without solar thermal systems and two types of insulation standards from the years 1984 and 2009 are simulated and their energetic and exergetic behaviour is analyzed. The results show that the systems with salt hydrate have the lowest primary energy demand. The integration of a paraffin storage leads to the second lowest demand. The third one is the concept with a stratified storage and the last ones are the concepts with a buffer storage.It is not always possible to distinguish between the systems by their thermal efficiency or exergetic behaviour. Indeed the exergetic behaviour of the systems is sometimes equal. If the boundary is set up directly around the storage, it can be seen that the exergetic losses of the storage are different for each storage concept.

Authors

Authors

Leonhardt, Corinna

Advisors

Müller, Dirk
Zeller, Manfred

Identifier

  • URN: urn:nbn:de:hbz:82-rwth-2016-082932
  • REPORT NUMBER: RWTH-2016-08293