Jörg Worlitschek

Modeling and Experimental Analysis of PSD Measurements through FBRM

The Focused Beam Reflectance Measurement (FBRM) technique provides on-line and in-situ information about the chord length distribution of a population of particles in dispersion. This is rather promising for applications such as crystal size distribution control in crystallization processes. The objective of this study is to deepen the understanding of the characteristics of the FBRM measurement. On the one hand, a model is presented, which allows in principle to transform particle size distributions (PSD) into chord length distributions (CLD). On the other hand, measurements with particles in suspension show the critical dependence of the measurement on the optical properties of the system. A special technique has been developed to measure CLDs of single particles. These measurements clarify some of the above effects, detect possible over- and underestimations of particle size and give indications about how to interpret and exploit on-line CLD spectra.

Use of Microencapsulated Phase Change Materials in Bitumen to Mitigate the Thermal Distresses in Asphalt Pavements

In asphalt pavements, the temperature variations due to extreme weather conditions are mainly responsible for thermal distresses. Cracking and rutting are the main types of damages in asphalt mixtures from extreme low and high temperatures. Recently, in building construction, phase change materials (PCM) are efficiently used as a source of thermal energy preservation by storing thermal energy in a latent form. The use of microencapsulated phase change material (µPCM) enables thermal energy storage and release inside bitumen. The PCM’s crystallization/melting temperature define the temperature at which thermal energy can be stored/released. In this study, a low temperature µPCM was incorporated in bitumen and its rheological and thermal properties were evaluated using dynamic shear rheometer (DSR) and differential scanning calorimeter (DSC) respectively. It was observed that upon cooling, the addition of 25% µPCM by mass of bitumen crystallizes and releases the stored thermal energy. The surface temperature variations captured by means of thermal infra-red camera illustrate that compared to controlled specimen, in modified bitumen a delaying effect of cooling was found during the crystallization temperature of µPCM.

Storage of Heat, Cold and Electricity.

A promising energy storage system is presented based on the combination of a heat pump, a heat engine, a hot and a cold storage. It can be operated as a pure bulk electricity storage (alternative to Pumped Heat Electrical Storage (PHES)/Compressed Air Energy Storage (CAES)) or as combined storage of heat, cold and electricity. Both variations have been evaluated using a steady state, thermodynamic model and two promising concepts are proposed: A transcritical CO(2) cycle for the pure electricity storage and a subcritical NH(3) cycle for combined storage of electricity, heat and cold. Parametric studies are used to evaluate the influence of different parameters on the roundtrip efficiency of the storage system.