Thermal energy storage characteristics of Cu–H2O nanofluids

The thermal energy storage characteristics of Cu–H2O nanofluids as a new PCM (phase change material) for cooling systems was investigated. The influence of the nanoparticle agent on supercooling of water PCMs was experimentally studied. The temperature distribution and the ice shape of the cold storage process were observed on line by using an Infrared Heat Camera and a High Speed Color Digital Camera. A mechanism to improve thermal energy storage characteristic was detailed by measuring the contact angle and thermal conductivity of nanofluids. The experimental results show that the Cu–H2O nanofluids have a remarkably lower supercooling degree than water PCMs, and as the mass fraction increases, the freezing time of Cu–H2O nanofluids is lower than that of water PCMs. By adding 0.1 wt% Cu nanoparticles, the supercooling degree can be reduced by 20.5% and the total freezing time can be reduced by 19.2%. These promising results highlight their great and diverse thermal energy storage applications. •The thermal response test was performed on a low temperature test system.•It is that the Cu–H2O nanofluid has remarkably lower supercooling degree than water.•The cold storage process was observed with an Infrared Heat Camera.•It is found that nanoparticles can enhance the freezing rate of fluids.•The improvement of thermal energy storage of nanofluids was detailed.