Thermal Performance of Phase Change Material Based Heat Exchangers

Abstract

Phase change materials (PCM) tend to have high energy storage densities and can be an excellent option for thermal energy storage systems. However, the low thermal conductivity of PCM creates a critical problem in effectively transmitting heat energy into these thermal storage systems. One of the solutions is to design these heat exchangers to diffuse heat into the thermal storage systems effectively. Numerical simulations have been performed to investigate the thermal performance of two heat exchanger designs, fin base heat exchanger (FHE) and Helical coil-based heat exchanger (HCHE). Ansys, Fluent has been employed to carry out transient three-dimensional numerical simulations. These simulations are also compared with two different inlet velocities of 0.02m/sec and 0.1m/sec, corresponding Reynolds numbers of 2,012 (laminar regime) and 10,061 (turbulent regime), respectively. FHE melting rates were observed to be much more stable. Total accumulated energy stored during the charging process for the laminar flow regime is higher in HCHE than in FHE. Energy stored is comparatively higher in FHE when the flow is turbulent. The energy discharge followed the same trend as the charging cycle. FHE tends to maintain consistent energy charging and discharging rates compared to HCHE.