Experimental study on characteristics of a nano-enhanced phase change material slurry for low temperature solar energy collection

Abstract

Phase change material (PCM) slurry with nanoparticles added has been proved to improve the performance of solar thermal storage. While, it is found that previous studies have not systematically dealt with the thermo-physical properties of PCM slurry (PCS) based on the type and mass fraction of nanoparticles and its stability and viscosity. Therefore, the purpose of this research is to experimentally evaluate the effects of nanoparticles and dispersants on the thermal-physical properties of PCS and determine the role and the associated optimal mass fraction ratio of dispersants in promoting the stability of suspension. The 30% mass fraction alkyl hydrocarbon PCS was employed for our study. Three types of nanoparticles (i.e., Cu, Al2O3 and TiO2) were selected for the study on performance improvement of PCS. Static and dynamic stability were measured by the static precipitation method and thermal cycle method. Thermo-physical properties including viscosity, thermal conductivity and latent heat were measured by a digital display rotary viscometer, a thermal conductivity measuring instrument and a differential scanning calorimeter, respectively. The experimental results revealed that the nanoparticles can improve the thermal properties of PCS, while the dispersants can improve the stability of the nano-enhanced PCS. The PCS with 0.1% TiO2 added had the best latent heat property and minimum viscosity. The 30% mass fraction PCS with 0.1% TiO2 and 0.1% SDBS added was the ideal choice for the application on low temperature solar energy collection.