Solid–liquid phase equilibria of (n-octadecane with myristic, and palmitic acid) binary mixtures used as phase change materials (PCMs)

• The phase diagram of binary systems of n-octadecane with myristic, or palmitic acid was determined.
• All systems show simple eutectic behaviour.
• SLE data were correlated with Buchowski (λh) equation, UNIQUAC, and UNIFAC models.

Values of solid–liquid equilibrium (SLE) for the organic binary mixtures of {n-octadecane (1) + myristic acid (2)} (eutectic temperature TE = 299.65 K, eutectic composition x1E = 0.897, latent heat of melting of eutectic mixture ΔfusHEΔfusHE = 236 J g−1), {n-octadecane (1) + palmitic acid (2)} (TE = 300.35 K, x1E = 0.950, ΔfusHEΔfusHE = 238 J g−1) were measured in this study using differential scanning calorimetry (DSC). Simple eutectic behaviour is observed for these systems. The experimental and predicted solid–liquid phase diagrams investigated in this work are characterised by positive deviations from ideality (γγ > 1). The experimental data are correlated as functions of the temperature using non-ideal solution models, namely, the Buchowski (λh) equation, UNIQUAC, and UNIFAC models, respectively, and satisfactory results are presented.