CFD analysis of MWCNT nanocomposite PCM melting in the latent heat storage tank

In this paper, the low thermal conductivity of the phase change material (PCM) used in the latent heat storage tank was improved by adding multi-walled carbon nanotubes (MWCNTs) to enhance the heat storage capacity and release rate. MWCNT was mixed in amounts up to 2.0 wt%, and the thermal conductivity of the mixture was numerically calculated using the modified Maxwell model. The calculation results indicated that the specific heat slightly decreased as the mass fraction of MWCNTs increased, while the thermal conductivity improved by an average of 41.26%. Additionally, the heat storage process by the copper tube and copper fin in the latent heat storage tank was analytically examined. The PCM/MWCNT mixture, which has relatively high thermal conductivity, effectively absorbed heat and transitioned into a liquid phase faster than pure n-eicosane. The thermal conductivity decreased due to the phase change to a liquid state, and the outlet temperature tended to rise rapidly because the heat was not effectively absorbed after the phase change, confirming the low heat storage capacity. In conclusion, the addition of MWCNTs enhanced the thermal conductivity, and the total stored energy increased compared to pure n-eicosane due to the improved heat storage rate.