Preparation and Melting/Freezing Characteristics of Cu/Paraffin Nanofluid as Phase-Change Material (PCM)

A new sort of nanofluid phase-change material (PCM) is developed by suspending a small amount of nanoparticles in melting paraffin. Cu, Al, and C/Cu nanoparticles were selected to add to the melting paraffin to enhance the heat-transfer rate of paraffin. Cu nanoparticles have the best performance for heat transfer. Five dispersants were chosen to make Cu nanoparticles stably suspended in melting paraffin. The nanofluids with Cu nanoparticles show good stability in melting paraffin under the action of Hitenol BC-10, even suspending for 12 h in a constant temperature trough. The Fourier transform infrared (FTIR) spentrum shows that it is a physical interaction among Cu, paraffin, and Hitenol BC-10. The differential scanning calorimetric (DSC) results reveal that the latent heats of Cu/paraffin shift to lower values compared to those of pure paraffin; however, the melting and freezing temperatures are kept almost the same as pure paraffin. The latent heats and phase-change temperatures change very little after 100 thermal cycles. Furthermore, the heating and cooling rates of PCMs were significantly improved upon the addition of Cu nanoparticles. For composites with 1 wt % Cu nanoparticle, the heating and cooling times can be reduced by 30.3 and 28.2%, respectively.