Eutectic mixtures of some fatty acids for low temperature solar heating applications: Thermal properties and thermal reliability

The thermal properties and thermal reliability of the eutectic mixtures of lauric acid-myristic acid (LA-MA), lauric acid-palmitic acid (LA-PA), myristic acid-stearic acid (MA-SA) as phase change material (PCM) were determined after repeated melt/freeze cycles by the method of differential scanning calorimeter (DSC). The DSC thermal analysis results indicate that the binary systems of LA-MA in ratio of 66.0:34.0 wt.%, LA-PA in ratio of 69.0:31.0 wt.% and MA-SA in ratio of 64.0:36.0 wt.% form eutectic mixture with a melting temperature of 34.2 °C, 35.2 °C and 44.1 °C, and with a latent heat of fusion of 166.8 J g^-1, 166.3 J g^-1 and 182.4 J g^-1, respectively. The changes in the melting temperatures and the latent heats of fusion are in the range of -0.31 °C-0.14 °C and 0.9%-2.4% for LA-MA, -0.40 °C-0.23 °C and 1.5%-3.0% for LA-PA, and 1.11 °C-0.26 °C and -1.10%-2.2% for MA-SA during the 1460 thermal cycles. Based on the results, it can be concluded that the studied PCMs have good thermal properties and thermal reliability for a four-year energy storage period, which corresponds to 1460 thermal cycles, in terms of the change in their melting temperatures and latent heats of fusion.