Experimental investigation on thermal properties of Al 2 O 3 nanoparticles dispersed paraffin for thermal energy storage applications

Addition of Al2O3 nanoparticles into paraffin wax is beneficial to improve the thermal conductivity of paraffin wax. Moreover, it has effect on the other thermophysical properties of paraffin wax such as the thermal diffusivity and volumetric heat capacity. In the present paper, the two-step method was used to prepare the nanofluids of Al2O3 nanoparticles and paraffin wax and then the influence of temperature and volume fraction of Al2O3 nanoparticles on the thermal conductivity, thermal diffusivity, and volumetric heat capacity of the nanofluids was investigated. The experimental results show that the changing trend of the above-mentioned properties of Al2O3/paraffin shows a slight regularity with increasing temperature. The thermal conductivity of nanofluids is enhanced at 20°C, and the largest thermal conductivity attained is 0.38 W/m·K at the volume fraction of 0.01%, which led to 40% augmentation, compared with paraffin. The thermal diffusivity of nanofluids with the volume fraction 0.01%, 0.1%, and 1% varies by −31%, 13.5%, and −21% in solid state, respectively. Moreover, the volumetric heat capacity fluctuates with the increase in temperature, and the volumetric heat capacity of nanofluids with the volume fraction 0.01% and 0.1% is higher than that of 1% in liquid state.