Doping effect of magnesium oxide (MgO) on the enhancement of the thermal storage properties of sodium nitrate (NaNO3)

Abstract

In this work, sodium nitrate (NaNO3) is used as the basic continuous PCM, and magnesium oxide (MgO) is dispersed inside it to enhance its global thermal storage properties, especially its thermal conductivity. The composite (NaNO3/MgO) was prepared by mixing sodium nitrate with the addition of 1 wt.%, 2 wt.%, and 3 wt.% of MgO. Furthermore, differential scanning calorimetry (DSC) is used to evaluate the main thermal properties of the obtained composite materials, namely: their latent heat, specific heat and sub-cooling temperature. Their thermal conductivity is estimated based on a validated theoretical model from the literature. Finally, the chemical structures of the pure PCM and the three composites are investigated using Fourier transform infrared spectroscopy (FT-IR). Overall, the experimental and numerical results have indicated a clear enhancement of the thermal storage properties (especially the thermal conductivity and the sub-cooling temperature) of NaNO3 when it is doped with MgO: The thermal conductivity of the pure PCM was enhanced by 5 % and 19%, when it is doped by 3 wt.% and 10 wt.% respectively. While, the sub-cooling degree was decreased up to 46% when it is doped by 3wt.%, which is very good for the thermal cycling of this PCM inside the LTES system. As far as it concerns the other properties, they remained almost stable: the measured value of melting temperature has an average of 306,85 °C, with a heat of fusion of 172,40 J/g.In this work, sodium nitrate (NaNO3) is used as the basic continuous PCM, and magnesium oxide (MgO) is dispersed inside it to enhance its global thermal storage properties, especially its thermal conductivity. The composite (NaNO3/MgO) was prepared by mixing sodium nitrate with the addition of 1 wt.%, 2 wt.%, and 3 wt.% of MgO. Furthermore, differential scanning calorimetry (DSC) is used to evaluate the main thermal properties of the obtained composite materials, namely: their latent heat, specific heat and sub-cooling temperature. Their thermal conductivity is estimated based on a validated theoretical model from the literature. Finally, the chemical structures of the pure PCM and the three composites are investigated using Fourier transform infrared spectroscopy (FT-IR). Overall, the experimental and numerical results have indicated a clear enhancement of the thermal storage properties (especially the thermal conductivity and the sub-cooling temperature) of NaNO3 when it is doped with MgO: The thermal c...