Research on optimization and performance of Na2HPO4·12H2O mixture system combining fuzzy optimization model based on analytic hierarchy process

In order to determine optimal salt hydrates matching and adding fraction of Na₂HPO₄ · 12H₂O, crystal characteristics, latent heat of phase change, supercooling degree, and phase change temperature were studied. According to experimental data, optimal salt hydrates matching and adding fraction of Na₂HPO₄ · 12H₂O are determined by adopting multi-objective fuzzy optimization model based on analytic hierarchy process. Aimed at 3% Na₂SiO₃ · 9H₂O-Na₂HPO₄ · 12H₂O optimized by the method, thermal cycling performance test is implemented. Test results show the following: the Na₂SiO₃ · 9H₂O-Na₂HPO₄ · 12H₂O system has lower supercooling degree than Na₂HPO₄ · 12H₂O. It forms stable crystal after multiple thermal cycles, the phase separation is eliminated completely, and supercooling degree is 3.6°C. Latent heat of phase change maintains at 164 J/g after 100 thermal cycles. It is a modified intermediate product of salt hydrates with development potential.