Experimental investigation on influence of microcapsules with PCM on propylene glycol rheological properties

Abstract

This paper details an experimental study that was performed to investigate rheological properties of microencapsulated phase change slurry - mPCM (Micronal ® DS 5039 X and ERGOLID EKO ® - an aqueous solution of propylene glycol). Seven samples of mPCM slurry were prepared with different mass ratio of the Micronal ® to the ERGOLID EKO ® : 30:70, 40:60, 50:50, 60:40, 70:30, 80:20 and 90:10. The apparent viscosity-shear rate curves were obtained for spindle speed from 0.01 to 100 rpm (shear rate 0.0132 to 132.00 s -1 respectively). The steady state measurement of viscosity was carried out when the slurry reached constant temperatures, namely: 10.0; 15.0, 17.5, 20.0, 22.5, 25.0, 27.5, 30.0, 40.0 and 50.0°C. The apparent viscosity of slurries increases with the mPCM concentration in dispersion rises. Only the sample of 30% Micronal ® may be considered as a Newtonian fluid within the test range. Increasing the shear rate ultimately causes apparent viscosity to decrease down to the Newtonian plateau, where it seems to be constant. The variation of the viscosity as a function of temperature and microcapsules concentration was accurately represented by a modified Vogel-Tamman-Fulcher equation at a mean absolute error (MAE) of 10.76%.