Study On Dispersion Stability And Thermal Properties Of Nano-composites Phase Change Material For Cold Storage Of Conventional Air Conditioning Conditions

With the development of industry and the continuous exploitation of non-renewable energy, the energy crisis is increasingly a challenge worldwide over the past few decades. As a result of the abundant and extensive use of conventional central air-conditioning, seeking a energy saving solution is particularly important, which could adjust the gap between energy supply and demand. Cold storage air conditioning technology is the most economical and the most effective way in peaking technology. Vigorously develop the cold storage technology, not only can play the role of achieving load balancing, open the new mode of power, but also to optimize the allocation of power resources, full use of energy.The preparation of phase change material for conventional air-conditioning is studied in this paper. A new organic PCM whose phase change temperature is 5-9? is developed. The further research of using nanocomposite technology to the organic PCM was made to improve thermal conductivity performance. The main research results were as follows:(1) In this paper, a variety of organic phase change materials is prepared in different proportions, phase change materials with suitable temperature are initially determined by step cooling curve measurement. Then latent heat of these phase change materials are measured by differential scanning calorimetry. Final, an organic PCM SSW-4 (base fluid) with suitable phase change temperature, no obvious supercooling and high latent heat is chosen.(2) In order to improve the thermal conductivity of organic phase change thermal storage medium, the two step method is used to add nano particles into the organic phase change material SSW-4 to modify the thermal conductivity. Based on the DLVO theory, electrostatic stabilization, space static stabilization, space static and electrostatic stabilization, exhaustion of stable mechanism is studied. Surfactant SDBS is selected as dispersant by UV spectrophotometric method, the adsorption method and mechanism of SDBS are analyzed. Dispersion stability test is experimented by using uv-visible absorption spectrum experiment and laser particle size test method, the effect of TiO2 concentration, ultrasonic time, ultrasonic bath temperature and surfactant concentration on dispersion stability is investigated. The optimal stability dispersion conditions for preparation of nano PCM were confirmed.(3) Thermophysical property of nanocomposite cold storage medium is measured by Differential Scanning Calorimetry. Meanwhile thermal stability of nanocomposite phase change cold storage medium is studied. After 50 freezing/melting cycles, the latent heat and phase transition temperature of SSW-8 still remain constant, basically unchanged, which showing good dispersion and no off-phase. The thermal conductivity of the nanocomposite phase change materials SSW-8 were measured by laser scattering method. Compared with the base liquid SSW-4, its thermal performance is enhanced.