Effect of using nanoparticles on the performance of thermal energy storage of phase change material coupled with air-conditioning unit

Abstract

In this work, the effect of using nanoparticles (aluminum oxide (Al2O3), copper oxide (CuO), and copper (Cu)) with a phase change material (PCM) on the performance of a new technique used to improve the working of the air-conditioning (AC) unit is presented. The technique is based on coupling the condenser of the AC unit with a heat exchanger of the cold energy storage PCM. The cold energy storage of the PCM is transferred to the condenser of the AC unit by the cooled ambient air passing through the PCM heat exchanger. The cold energy storage is charged to the PCMs by using the cold ambient air at night during the charging process where the PCMs are solidified during this process. Then, at the next daytime, the charged cold energy storage is discharged by the hot ambient air which is cooled down and transferred to the condenser of the AC unit. The effect of adding the studied nanoparticles on the charging and discharging process of the PCMs, and the performance of the AC unit is studied. The study is carried out at inlet air temperatures to the PCMs of 40 and 45 °C and concentrations ratios of the nanoparticles with the PCMs of 1% and 5%. The mathematical model of the physical model is solved numerically by using finite volume method and the numerical model is validated with an experimental setup. The results indicate that, during the discharging process, increasing the inlet air temperature to the PCM decreases the melting time and increases the saving power of the AC unit. Using the nanoparticles with the PCM, and increasing nanoparticles concentration ratio decrease the outlet air temperature, and increase discharging liquid fraction, COP, charging time and saving power of the AC unit. At inlet air temperature 45 °C to the PCM, this technique achieves a saving power of the AC unit about 7.18% in case of using PCM without nanoparticles and a saving power 7.41% in case of using Cu nanoparticles with the PCM at concentration ratio 5% compared to conventional AC unit.