Investigation of melting of nanoparticle-enhanced phase change materials (NePCMs) in a shell-and-tube heat exchanger with longitudinal fins

摘要

Latent heat storage units are considered as an effective solution for the mismatch problem between energy consumption and energy supply when utilizing solar energy. However, the low thermal conductivity of the current phase change materials (PCMs) is regarded as their main drawback. The present study used dispersing nanoparticles in PCM and installing longitudinal fins on the inner tube simultaneously to enhance the melting rate of PCM in a horizontal shell-and-tube heat exchanger. Different compositions of stearic acid (SA) and titanium dioxide TiO_2-NPs were employed as nano-encapsulated PCMs as well. The results demonstrated that installing fins have a significant effect on the melting rate of PCM and can improve the melting rate by 68%. Although adding 0.39 wt% TiO_2-NPs to PCM enhanced its thermal conductivity of SA by 7 and 15% in liquid and solid phases, respectively, its effect on improving the melting rate of PCM was less than 4%, which is related to the weakening of the natural convection flows because of the increased viscosity.