The numerical analysis of the melting process in a modified shell-and-tube phase change material heat storage system

Thermal energy storage plays a major role in applying thermal energy sources such as waste heat and solar energy. As an efficient storage technique, the development of latent heat storage systems is a key factor for the successful application of thermal energy. This work presents thermal characteristics of a shell-and-tube phase change material (PCM) latent energy storage system with shell and tube forms of octagonal and three-lobe, respectively. The nano-enhanced paraffin wax was employed PCM, and the transient performance of the sys-tem was examined using the enthalpy-porosity method. The PCM temperature, melted fraction, and the Nusselt and Bejan numbers were adopted as system evaluation indexes, and sensitivity analysis was made to unveil the effect of copper nanoparticle (NP) concentration, the tube orientation angle and the eccentricity on system performance. The obtained results demonstrate that between the studied parameters, altering the eccentricity has the most effect on system characteristics; in the case of the above-located tube (denoted by case1), the melting time was reduced by 62 % compared to the base case. Changing the tube inclination angle and NP concentration does not show a significant effect on profiles of PCM temperature and melted fraction and mainly affect the Be number; using the case of 60 degrees tube inclination angle and NP concentration of 4 % shows a slight improvement of temperature and melted fraction and reduces the average Be number.