Preparation of nanocomposite phase change cold storage materials and analysis of cold storage characteristics

Here, one kind of cheap cold storage material was prepared to fully meet the requirements of temperature in the cold chain logistics field of fresh refrigerated transport. Firstly, the aqueous solutions of different concentrations were configured to dividually mix the solutions of the energy storage agents, including glycine, sorbitol, mannitol, and potassium chloride. Differential Scanning Calorimetry (DSC) was then used to determine the latent heat of phase transition and onset temperature at different concentrations. The combination of glycine and sorbitol, potassium chloride, and mannitol was finally selected to obtain two kinds of combination schemes. The first one was using 0.1 mol/L sorbitol aqueous solution as the compound of Onset temperature adjustment. According to the volume ratio of 1:1, 0.8, 0.6, 0.4, 0.2, and 0.1 mol/L glycine aqueous solution (named composite solution A1-A5) were added, respectively. In the other compound scheme, 0.6 mol/L mannitol aqueous solution was used as the compound agent to adjust the temperature of Onset. According to the volume ratio of 1:1, 0.8, 0.6, 0.2, 0.1, and 0.05 mol/L potassium chloride aqueous solution (named composite solution B1-B5) were added, respectively. The undercooling test was performed on the composite solution A1-A5, indicating the better performance of composite solution A2. The thermal properties of compound solutions A2 and B1-B5 were determined by DSC. The composite solution B1-B5 was prone to undercooling. As such, the composite liquid A2 was chosen as the main energy storage agent of the final composite phase change cold storage material. Finally, the mixed solution A2:0.6 mol/L glycine +0.1 mol/L sorbitol was determined as the main coolant, which was named TA2. Then, the nano-sized titanium dioxide and alumina were added to the system TA2 as the base liquid, and the Super Absorbent Polymer (SAP) was added to optimize the leakage prevention phenomenon, in order to explore the latent heat and thermal cycle stability of composite phase change cold storage materials after the addition of nanoparticles. It was found that the addition of 0.5% nano-TiO2 presented the best effect on the supercooling degree and thermal conductivity of cold storage materials. In view of the leakage of the cold storage bag, 0.25% SAP was added to effectively prevent leakage. The optimized nanophase change cold storage material was TA2+0.5%TiO2+0.25%SAP, where the latent heat was 294.57 J/g, and the initial temperature was -5.8℃. The temperature zone fully met the performance requirements of fresh refrigerated transport. The 200-cycle tests show that the new material can be expected to serve as excellent stability in practical cold chain logistics. The nano-composite phase change cold storage material has been applied to the domestic incubator. The cooling properties of the incubator were also tested with the crystal pear as the test object. In addition, the temperature changes of each point were compared in the cold storage incubator under loaded and empty conditions, considering the influence of side and top+side arrangement on the cooling performance of the cold storage incubator. The results show that the average temperature in most of the boxes under the arrangement of side and top cloth, which can be kept at 0-5 ℃ for 480 min. The temperature field was more uniform to maintain the freshness of fresh products.