Numerical Study of a Latent Heat Storage System’s Performance as a Function of the Phase Change Material’s Thermal Conductivity

The thermal conductivities of most commonly used phase change materials (PCMs) are typically fairly low (in the range of 0.2 to 0.4 W/m·K) and are an important consideration when designing latent heat energy storage systems (LHESSs). Because of that, material scientists have been asking the following question: “by how much does the thermal conductivity of a PCM needs to be increased to positively impact the design and performance of a LHESS?” The answer to this question is not straightforward as the performance of a LHESS depends on the PCM’s thermal conductivity, other PCM thermophysical properties, the type of heat exchange system geometry used, the mode of operation, and the targeted power/energy storage of the LHESS. This paper presents work related to this question through a numerical study based on a simplified 2D model of an experimental setup studied previously in the authors’ laboratory. A model created in COMSOL Multiphysics, based on conduction and accounting for the solid-liquid phase change process, was initially validated against experimental results and then used to study the impact of the PCM’s thermal conductivity (dodecanoic acid) on the discharging power of the LHESS. The results show that even increasing the thermal conductivity of the PCM by a factor of 50 only leads to a maximum instantaneous power increase by a factor of 2 or 3 depending on the LHESS configurations.