Exergy and economic analyses of nanoparticle-enriched phase change material in an air heat exchanger for cooling of residential buildings

Abstract

This paper studies the energy, exergy, and economic analyses of phase change material (PCM)-air heat exchangers filled with SiO2 based Nano-PCM of RT25 on enabling storage of night-time free-cooling from outdoor air or indoor air during off-peak hours, numerically. The stored cooling is subsequently utilized during a day-time or peak hours as auxiliary cooling, resulting in a reduction of the day-time refrigeration requirements. A computer model for seven days from June 22 to June 28 has been created using ANSYS FLUENT 18.2, to simulate the operation of PCM-air heat exchanger for domestic application. The setpoint temperature is considered at 23–25 °C, 23–26 °C, 24–25 °C, and 25–25 °C. The inlet airflow rate is varied between 2.5 m/s and 7.5 m/s. The PCM-air heat exchanger system is studied by varying the PCM thickness (10, 20, and 30 mm) and slab length (250, 500, and 750 mm). The nanoparticles volume fraction is from 0 to 5%. The maximum cooling power, exergy efficiency, and exergy destruction increase for the nanoparticles volume fraction of 5% is 9.4%, 4.1%, and 6.3%, respectively. To obtain the best balance between the exergy destruction cost rate and the capital cost rate, the exergoeconomic factor is defined for different cases.