Simultaneous energy storage and recovery in the triplex-tube heat exchanger with PCM, copper fins and Al2O3 nanoparticles

The intermittent nature of renewables such as solar and wind necessitates integration with energy-storage to enable realistic applications. The triplex-tube heat exchanger (TTHX) with phase change materials (PCMs) has been found to be a very efficient energy storage application for this purpose. However, the low thermal conductivity of PCMs used makes them unable to give the desired response for storage and recovery. Various techniques like application of fins, metal foams etc. have been explored to solve the problem but focus has been mainly on energy storage and recovery separately, but in real life, the systems operate mostly through simultaneous storage and recovery or charging and discharging (SCD). In this study, performance enhancement of the TTHX with a novel fin configuration under SCD conditions was investigated. Numerical studies were done to investigate performance of the system with different fin geometrical parameters. Optimization was applied using response surface methodology (RSM) to find the optimum fin configuration. The effects of adding aluminum oxide (Al2O3) nanoparticles to the PCM were also investigated. Results indicate that for SCD operations, the proposed optimum fin structure in the TTHX is better than incorporating nanoparticles for the same system's volume usage.