Thermal Conductivity and Viscosity of Nanofluids Having Nanoencapsulated Phase Change Material

In this study, the thermal conductivity and viscosity of nanofluids, composed of a base fluid and nanoencapsulated phase change material (NEPCM), were investigated experimentally. The NEPCM was prepared by the encapsulation of n-nonadecane as phase change material with diethylenetriamine and toluene-2,4-diisocyanate using interfacial polymerization method. The NEPCM was characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) analyses. In the preparation of the nanofluids containing NEPCM, two different base fluids, water and ethylene glycol (EG), were used. The concentration of NEPCM and the working temperature were selected as the main parameters. It was found that the viscosity of the nanofluids decreases with increasing temperature and increases with increasing solid concentration. The viscosity was also expressed as a function of the solid concentration and temperature. The thermal conductivity of the nanofluids was found to increase with increasing temperature. Thermal conductivity exhibited an increasing tendency with increasing solid concentration, but the changes in thermal conductivity according to base fluid are in the range of uncertainty of the measurement for both nanofluids with a solid volumetric fraction lower than 1.68%.