Study On Modification And Application Of Phase Change Cool Storage Material For Air-conditioning

With the development of national economy, the electric power industry is developing rapidly, but the power still can’t satisfy people’s demand. The central air-conditioning system is regarded as the biggest energy-consumption equipment in public building, which has been a key object of energy saving. Cool storage air-conditioning technology is one of the effective measures to solve this problem. At present, the ice-ball cool storage system is more widely applied, but the water freezing point is low, which make the evaporation temperature> COP and cool capacity of cool-storage air-conditioning is lower than conventional air-conditioning system. In addition, the system is more complex than conventional air-conditioning system. Thererfore, it is significant to research suitable cool storage material for conventional air-conditioning and improve the heat exchange efficiency of cool storage system.This paper develops several groups of organic phase change cool storage material, whose phase change temperature meets with air-conditioning condition, with high latent heat value, stable property, and small super-cooling. This paper establishes a 3-dimensional (3D) model of direct contact latent heat thermal energy storage tank to simulate the dynamic characteristics of the solidification process of cool storage material, providing technical support for the application of phase change cool storage system for use in air-conditioning system.This paper selects several organic phase change material to prepare some binary compounds and tri-compounds with different ratios, and finds the eutectic temperature and the optimal proportion with the help of phase transition temperature curve and different scanning calorimetry (DSC), and measures a range of physical parameters such as the phase change latent heat and the specific heat, and then develops a variety of organic mixed phase change cool storage material with good performance.The methyl methacrylate and maleic anhydride are used to graft onto simple substance^ binary compounds and tri-compounds cool storage material, to improve the material’s property. Characterizing the thermal physical property of the grafted cool storage material using DSC and fourier transform infrared spectroscopy (FTIR) and then infer the possible molecular structure of the grafted product according to the principle of free radical polymerization. The results show that the phase change latent heat value of cool storage material can be improved by extending the carbon chain, changing the molecular structure and increasing the molecular weight. When using MMA as grafting monomer, every product only has one molecular structure, in the condition that the quantity of cool storage material and the grafting monomers are the same respectively, and the phase change latent heat value of simple substance increases more than the mixture’s condition. When using MAH as grafting monomer, products may appear three kinds of structures, and all these sturctures can increase the molecular inter-atomic forces to improve the phase change latent heat value.This paper presents a 3D model of direct contact latent heat thermal energy storage tank to simulate the dynamic performance of the cold storage process. The study shows that at the start of the cold storage process, the temperature in the storage tank distributes uniformly, with the increase of cool storage material the outlet temperature of the heat transfer fluid (HTF) rises faster, the outlet tempetature keeps constant after a period of time. The volume fraction of solidified cool storage material increases over time, in the same time, the lower the inlet tempeatture of HTF becomes, the more the cool storage material freezes, but the total storage capacity does not have appreciable different. The charging capacity increases more rapidly when the cool storage material flow rate is greater with other conditions unchanged, however, the flow rate of the liquid cool storage material cannot be too great, otherwise, the liquid material will not freeze completely. The complete charging time can be reduced by increasing the flow rate of the liquid material and decreasing inlet temperature of the HTF when charging the same quality of phase change material.