Phase change heat transfer and energy storage in a wavy-tube thermal storage unit filled with a nano-enhanced phase change material and metal foams

Latent heat thermal energy storage plays a key role in the thermal management of heat transfer systems, shifting thermal loads, and developing renewable systems. A latent heat thermal energy storage (LHTES) unit can store/release a significant amount of heat in a compact space. However, the main issue of LHTES units is their poor heat transfer characteristics. Thus, the thermal response time of most LHTES is low, and they cannot absorb/release the required energy in a timely manner. Hence, the heat transfer enhancement approaches such as using nano additives, metal foams, and extended, wavy surfaces are promising approaches to improve the heat transfer capability of LHTES. The present study aims to address the impact of using wavy tubes in a composite phase change material and metal foam LHTES unit. A phase change heat transfer model based on enthalpy-porosity was introduced and solved via the finite element approach. The influence of nanoparticle volumetric fraction (VF_na), tube wave amplitude (A), tube wave number (N), and the porosity coefficient (ε) was investigated on the charging time, stored energy, and heat transfer behavior of the LHTES unit. According to the findings, employing metal foams and nanoparticles enhances heat transmission and decreases charging time. A simple tube with no wavy surface produces lower pressure drop and better charging power compared to a wavy tube.