The Mechanism And Application Of Phase Change Latent Heat

Based on the research of the structure of phase change material and the mechanism(s) of phase transition, the effects and the microscopic nature of latent heat were studied to meet the application demands of phase change materials in the thermal infrared decoy camouflage field. Further experiments were carried out to study the factors that determine the decoy capabilities of the phase change materials, the research results provided practical protocols for the application of phase change materials in the thermal infrared decoy camouflage.The relationship between inter-molecular interaction and latent heat was studied by oxidation and the graft copolymerization reaction. How the molecular weight, polar group, and molecular structure affect the latent heat of the organic materials were studied in detail by danamic analyze. The quantitative relationships between latent heat and variable were established. The novel result was found: The latent heat was not always increased when inter-molecular interaction was increased, and it had the maximum.Experiments were designed to determine the composition of the phase change latent heat of inorganic salts. A novel solid-liquid phase change form was also observed when solid materials melt at the phase change temperature. The thermodynamics calculation of the obtained results demonstrated that the latent heat of inorganic salts consists of three parts, which are dehydration enthalpy, solution enthalpy, concentration enthalpy. A quantitative correlation between the number of crystal water and the molar latent heat of inorganic salt was established. The molar latent heat was determined to be 7 kJ·mol^-1 when phase change occurred after the crystal water was missed, while a 12 kJ·mol^-1latent heat was detected when inorganic material melted at the phase change temperature.The effects of different factors including phase change latent heat, thermal conductivity, environment temperature, wind velocity, material thickness, and shape on decoy camouflage were quantitatively analyzed using ANSYS programs and Genetic Programming Design for single-factor and multi-factor analysis, respectively. The predicted results were further confirmed by experiments. It was concluded that the decoy capabilities was dramatically affected by thermal conductivity whereas the shape demonstrated subtle effect on decoy capabilities. The emprical formula was successfully applied to the design of thermal infrared decoy.The infrared exposure profile of typical object was determined to provide critical information on the design of thermal infrared decoy and the selection of phase change materials. An improved self-heating material was developed based on the previously reported materials to meet the outdoor heating requirements. A three-layer material consisting of self-heating, temperature-keeping, and phase change materials was designed to solve the technical problems that prevent thermal infrared decoy from being practically applied.