Rheological investigations of paraffin based phase change slurry using a pipe viscosimeter.

In this work paraffin/water dispersions used as phase change slurries (PCS) for thermal energy storage systems have been investigated regarding their rheological behaviour. The fluids viscosity is an important parameter for dimensioning of the main peripheral components of storage systems like pumps, valves and piping. The experiments have been conducted with a pipe viscosimeter at different fluid temperatures, shear rates and varying paraffin fraction (25, 30 and 35 wt. %). The measurements show viscosity values between 2.8 and 27.7 mPa∙s depending on the set conditions. The paraffin/water dispersions show a shear thinning behaviour with a strong temperature dependency and a discontinuity during the phase change of the paraffin fraction. Consequently, reliable measurement results are now available to design technical systems based on such paraffin/water dispersions.