Numerical study of encapsulated nanoparticles enhanced phase change material in thermal energy cool storage packed bed system

Abstract

A numerical study is performed to investigate the dynamic behavior of a packed bed containing spherical capsules filled with Al2O3 nanoparticles dispersed in pure water as an enhanced phase change material (NEPCM) that can be utilized in ice storage of air conditioning systems. The heat transfer fluid (coolant) employed in the current work is an aqueous solution of 30 vol% ethylene glycol. For energy conservation of the coolant and the NEPCM, coupled partial differential equations are used to create a two-dimensional axisymmetric time-dependent model. While the energy equation for the NEPCM is solved using a completely explicit scheme, the energy equation for the coolant is discretized using a finite difference method and solved using the Alternating Direction Implicit (ADI) technique. The Al2O3 nanoparticles are dispersed in PCM with a volume concentration range of 0–5 %. The coolant inlet temperature with a range of -5 °C to -15 °C and mass flow rate of range of 0.2 to 0.8 kg/s for a storage volume of 0.5 m3 are the parameters used in the current study. The effect of the nanoparticles volume concentration, coolant mass flow rate, and coolant inlet temperature are investigated. The timewise variation of the solidified volume fraction of the bed, the cool energy stored in the bed, the bed centerline temperature, and the coolant exit temperature are predicted for both charging and recovery modes under different operating conditions.