Food Phase Transition To The Development Of The Coolant

With the rapid development of economy and fast improvement of living condition, comsumer demand for fastfreezing and cold storage food is increasing day by day, so is the request for food quality. However, during their transportation especially in the last kilometer of cold chain, cold preserved food will be heavily damaged by fluctuant temperature, resulting in inferior quality and shortened storage life.Phase Change Materials (PCMs) is the hot topic of international material research in the latest years, and they have been widely applied in a lot of areas such as architecture materials, air conditioning and solar energy application. The emphasis of this article is the research and selection of main energy storage material, nucleation and carrier. Its aim is to develop a Cold Thermal Energy Storage Material(CTESM) with the characteristics of high phase enthalpy, low cost, safe, and with the potential of wide appications in the last kilometer of cold chain.The melting point and the phase enthalpy of the solutions of six energy storage materials (NaCl, NaF, KCl, C₃H₅(OH)₃, C₂H₅OH and sugar) were determined with the Differential Scanning Calorimetry (DSC). The results revealed that phase enthalpy of most materials will decrease with the increase of concentration, and the phase enthalpy of NaCl , KCL and NaF were found to be quite close to set selection standard . The Onset temperature of organic material solutions fall with the increase of concentration. The relationship between the onset temperature and concentration in inorganic materials is quite complicated: the onset temperature of NaCl solution fall down with the increase of concentration and the onset temperature of KCL and NaF is rather fixed, In the range of -2—8℃ ,the phase enthalpy of NaCl solution is less changed. The phase enthalpy of NaCl solution is higher than the other solutions except at -6℃,meanwhile at -10℃ the KCl is most ideal. Considering the similar phase enthalpy of the KCl and NaF solutions at -6℃ and the potential toxicity of NaF, we choose the NaCl solution as main energy storage material at -2 -8℃ and 9.91% KCl solution as the main energy storage material at -10℃.The super cooling phenomenon was studied through determining the T-t curves, and proper carrier was selected. The result shows that 1% SiO₂ and 0.1% CuS can minimize the super cooling phenomenon in KCL solution, 3% Na₂B₄O₇ can better alleviate the super cooling phenomenon. Both of them can be used as artificial nucleation agents. The water absorbing ability of Super-absorbent Polymers(SAP) decreases rapidly with the increase of ion concentration. The absorbing rate for 1.99% NaCl solution was 621.47g/g and that for 9.91% KCl solution was 63.83g/g. The SAP and artificial nucleation agents had little impact on the thermodynamic characteristics of selected main energy storage materials . Comparing the CTESM we developed with that mentioned in literature^[64],the phase enthalpy of KCl solution is...