Untersuchung der Fließeigenschaften von Paraffin/Wasser-Dispersionen und Erstellung eines rheologischen Modells

A paraffin/water-dispersion is a pumpable latent heat storage medium. Latent heat storage mediums store energy by using the heat of crystallization during the phase transition from liquid to solid. Because of that mechanism these materials are also called phase change materials (PCM). To make solid PCMs pumpable they are dispersed in water. The aim of this work is to define the flow characteristics of paraffin/water-dispersions and to figure out the relationship between the sort of paraffin, paraffin concentration and additive compositions. The measurements for that analysis are done with a rheometer. The measurement results reveal that paraffin/water-dispersions show shear thinning behavior with a strong viscosity drop in a span of low shear rates. With an increasing paraffin and additive concentration the viscosity raises. For describing the flow properties, the mathematical relationship of the Ostwald- de Waele power law is used. The coefficient analysis of the Power-law fluid identifies an aberration during the phase transition. During this aberration viscosity is increasing and the nonlinear properties of the dispersion are enhancing