Design of phase change materials based on salt hydrates for thermal energy storage in a range of 4–40 °C

Melting temperatures and eutectic mixture compositions of LiNO₃–LiClO₄–H₂O, NaNO₃–Ca(NO₃)₂–H₂O and NH₄NO₃–Mn(NO₃)₂–Mg(NO₃)₂–H₂O systems were predicted using the modified Brunauer, Emmett and Teller (BET) thermodynamic model. For the ternary system with calcium nitrate and for the quaternary system, it was necessary to estimate the Ω_ij mixing parameters with solid–liquid equilibrium data, which quantify the interaction between the compounds NaNO₃–Ca(NO₃)₂ and NH₄NO₃–Mn(NO₃)₂, respectively. The results calculated with the modified BET thermodynamic model show melting temperatures of 28.3 °C and 27.0 °C for the system with lithium perchlorate, 33.2 °C for the system with calcium nitrate and 4.0 °C for the quaternary system. Calculated values were tested experimentally with the T-history method for the LiNO₃–LiClO₄–H₂O and NH₄NO₃–Mn(NO₃)₂–Mg(NO₃)₂–H₂O systems and with the DSC method for the NaNO₃–Ca(NO₃)₂–H₂O system. The experimental results of eutectic mixtures predicted in this work present a good thermal behavior and can be useful as phase change materials (PCM) for their application in the design and simulation of refrigeration and air conditioning systems in residential and commercial buildings. Graphic abstract: