Three-step method to determine the eutectic composition of binary and ternary mixtures Tested on two novel eutectic phase change materials based on salt hydrates

摘要

A three-step method to determine the eutectic composition of a binary or ternary mixture is introduced. The method consists in creating a temperature-composition diagram, validating the predicted eutectic composition via differential scanning calorimetry and subsequent T-History measurements. To test the three-step method, we use two novel eutectic phase change materials based onZn(NO_3)_2 ? 6H_2O andNH_4NO_3 respectively Mn(NO_3)_2 ? 6H_2OandNH_4NO_3 with equilibrium liquidus temperatures of 12.4 and 3.9 ℃ respectively with corresponding melting enthalpies of 135 J g~(-1) (237 J cm~(-3)) respectively 133 J g~(-1) (225 J cm~(-3)). We find eutectic compositions of 75/25 mass% for Zn(NO_3)_2 ? 6H_2O and NH_4NO_3 and 73/27 mass% for Mn(NO_3)_2 ? 6H_2O and NH_4NO_3. Considering a temperature range of 15 K around the phase change, a maximum storage capacity of about 172 J g~(-1) (302 J cm~(-3)) respectively 162 J g~(-1) (274 J cm~(-3)) was determined for Zn(NO_3)_2 ? 6H_2O and NH_4NO_3 respectively Mn(NO_3)_2 ? 6H_2O and NH_4NO_3.