Preparation And Cold Storage Performance Of Dodecane/fumed Silica Composite Phase Change Material

As an energy saving technology to improve energy efficiency and solve energy mismatch in time and space, cold thermal energy storage(CTES) technology shows broad application prospects under energy shortage and environmental pollution background in China. With its excellent cold thermal energy storage performance and cycle performance, the organic phase change materials(PCM) for cold storage gradually become a research hotspot in CTES. However, few researches concern about the organic phase change material researches with phase change temperature below 0℃. Besides, the leakage and formable problems in ambient temperature of organic phase change material seriously hinder its development. Therefore, to prepare a kind of form-stable phase change materials for cold thermal storage in low temperature has great practical value.In this thesis, different mass fraction of dodecane/hydrophobic fumed silica composite phase change materials(PCM) used for cold thermal energy storage is prepared by absorbing dodecane into the hydrophobic fumed silica(support material). Scanning electron microscopy(SEM), surface area analyzers, and Fourier transform infrared analysis were used to characterize the microstructure and the basic structure of composite PCM. It is suggested that dodecane is locked into fumed silica by the van der Waals’ force and the capillary force of hydrophobic fumed silica. The results of leakage test show the good sealing performance of composite PCM and the PCM can be compressed into various densities to apply in different conditions. Thermal properties were characterized by differential scanning calorimetry, thermal constant analyzer and thermogravimetric analysis. Results show that the composite PCM have relatively large enthalpy. The enthalpy and thermal conductivity of composite PCM increase proportionally and with the growth of dodecane mass fraction. After 500 cycles, the composite PCM still has a good cycling performance.A cold energy storage experiment system were set up to investigate the performance of different mass fraction of dodecane/hydrophobic fumed silica composite PCM. The results of cold energy storage experiment show that the process of temperature rising can be divided into three parts. Sensible heat absorbing dominate in the first and third stage and latent heat absorbing dominate in the second stage. The system is mainly affected by enthalpy and thermal conductivity. After comparison of different mass fractions of materials, it is found that the composite PCM with 85% mass fraction of dodecane has the most excellent performance.The cold energy storage experiment was simulated by using commercial numerical simulation software Fluent. The temperature field and liquid field were obtained. The simulated temperature field and liquid field are consistent with the experimental results with average deviation less than 6% in temperature field. The experimental data is found to have a good agreement with the numerical simulation.Composite PCM with 85% mass fraction of dodecane was applied into the outdoor incubator experiment and the result showed that with 1200 g composite PCM, the system could effectively control the internal temperature of the outdoor incubator for about 470 minutes from-16 ℃ to 0 ℃.