Thermal Conductivity Enhancement Phase Change Materials And Its Application

Nowadays, the development of the industrialization、urbanization、modernization are becoming faster and faster, thus, the proportion of the total energy consumption is growing more and more, so we have to face a reality,the reducing energy reserves, the low utilization rate, the big supply contradictions, the serious environmental pollution, all these problem bring influence to sustainable development. The pHase change energy storage technology is a new technology which can solve the energy supply and demand contradictions, improving energy efficiency and protecting environment.Paraffin is one kinds of the pHase change materials, but it has some disadvantages, such as easy to leak、low thermal conductivity. To solve this problem,this paper used methyl methacrylate which has good stability、strength、environmental protection、good film-forming property、good encapsulation as the wall material; used three emulsification system:Tween-80、SDBS/Span-80、Tween-80/Span-80; used microencapsulation technology to clad paraffin. The result shows that:the MEPCM used Tween-80/Span-80 emulsification system has high enthalpy value of 91.76 J/g、thermal conductivity of 0.1226 W/(m-K), also it has a good dispersibility, small and uniform particle size, we can see the spHerical morpHology without the adhesion in the surface, no matter the preparation of microcapsule process were different. The thermal conductivity had no difference, this is mainly because of the wall material for the organic polymer, it’s structure affected the coefficient of thermal conductivity room for growth.Methyl methacrylate can obviously reduce the leakage rate of core material, but at the same time it still has some disadvantages:the poor heat conduction performance, low strength.. thermal stability-. easy aging faults.Inorganic wall’s thermal conductivity、 mechanical strength、chemical stability.etc is superior to the organic wall material, in order to improve the heat conduction performance of microcapsule, this paper used inorganic wall SiO2 for secondary coating. It turned out that:MEPCM with SiO2 had the smooth surface、good dispersibility、uniform particle size,and the enthalpy is 72.51 J/g,thermal conductivity is 0.1724 W/(m·K), which increased 40.62% compared with the methyl methacrylate/paraffin pHase change microcapsule.In order to move forward a single step to improve the performance of thermal conductivity of pHase change microcapsules, this paper used the modified carbon nanotubes as thermal conductive additives. Results indicated that PMMA-SiO2/Paraffin/CNTs-C18 pHase change microcapsules’s thermal conductivity respectively increased by 56.25%, 129.52%,63.22%, which compared with Paraffin. PMMA/Paraffin、PMMA-SiO2/Paraffin microcapsules, and reach the level of 0.2814 W/(m·K), when added CNTs-COOH, coefficient of thermal conductivity is 0.3024 W/(m·K).To solve the problem of cooling of electronic chips, this paper combined the pHase change microcapsules with electronic temperature control device, the results show that when the value of thermal conductivity of pHase change microcapsules were increased by 15.97%, 22.09%, temperature control time increased by 40.11%,22.22%, so the existence of the microcapsules can greatly improve the heat efficiency of heat sink. Due to the heat dissipation area、high thermal conductivity, the chip’s temperature rise rate was greatly reduced with the existence of pHase transition metallic paint, from the surface of the heat sink infrared rendering we can found that the surface temperature rise rate was slowed, and after 30 min temperature reach the stage of 41℃, which suggested pHase change microcapsules can be used in the field of electronic temperature control.