Experimental and application study of Na2SO4·10H2O with additives for cold storage

Abstract

Based on the current market demand for effective cold storage for food, we propose an optimal phase change material composed of Na2SO4·10H2O and other agents. By means of different scanning calorimetry, transient plane source, temperature time curve, and step cooling curve analysis methods, the effects of various additives to a sodium sulfate hydrate system as a cold storage material were studied. The experimental results show that the optimal percentages of the components of the system are 75.5% Na2SO4·10H2O, 3% borax, 1.25% PAAS, 16%/4% NH4Cl/KCl, and 0.25% deionized water, which effectively prevented the supercooling phenomenon. The system’s phase change temperature, latent heat, and thermal conductivity were determined to be 6.4 °C, 141 J g−1, and 0.547 W m−1K−1, respectively. After 20, 50, and 100 cycles of thermal cycling, the thermal properties of the system were basically unchanged, and the system exhibited good thermal stability. Apples were used as the object of preservation to analyze the sodium sulfate hydrated salt system and cold storage material loaded into an insulation box. Compared to an unloaded insulation box, the material kept the apples fresh for about 9.63 h based on the cold holding temperature of the material. The results suggest that the proposed material with optimal percentages of nucleating, thickening, and cooling agents is feasible and has good preservation characteristics for potential application in cold storage methods for food and medicinal products.