Study On Enhancement Conductivity Factor Of The Organic Phase Change Materials

With the ever sterious enemy problem, the phase change materials, especially organic phase change materials, are given much interest by people. But conductivity factor of the organic phase change materials is very small, which limits its progress and use, and, becomes "bottleneck problem" of its use wide-rangingly.This article choosed out organic phase change materials, and, the solid-liquid-equilibrium of eleven binary system including Fatty alcohol/Fatty acid , n-Octadecane/Fatty acid , n-Octadecane/Fatty alcohol system were determined by cooling curve, and, T-X phase diagrams of these systems were drawn. The result shows that all these systems are simple eutectic, at the same time, the entropy of phase change of every system in the eutectic point is determined by using differential scanning calorimetry (DSC). And n-Octadecane/Fatty acid systems were calculated theoretically.Because of the small conductivity factor of organic phase change materials, All kinds of copper grids , gas SiO2 and organic bentonite were added to organic phase change materials in order to heighten its conductivity factor. The conductivity factors were maesured by using time -temperature curve and comparison curve, and, the conductivity factor curves were drawn. At the same time, the entropy of phase change of every system was determined by using DSC. The result shows the conductivity factor of organic phase change materials was heightened, the temperature of phase change was changeless, and, the entropy of phase change was reduced after adding these additives.Because of the difference of density, the particle with big conductivity factor will subside in the organic phase change materials, so the orginic phase change materials were solided. The best technology was determined, which the solidation Fatty alcohol was made by two steps, the solidation temperature is at 80℃, and the proportion of Fatty alcohol:Fatty acid:sodium hydroxide is 96:3:1. At the same time, the conductivity factor and the entropy of phase change of the solidation Fatty alcohol were measured separately by using the time-temperature curve and DSC. The result shows that the conductivity factor of solidation Fatty alcohol is 0.147 W/(mK), the temperature of phase change is 21-23 ℃, and the entropy of phase change is 198.4j/g.