Accelerated Cycle Test Of Binary Mixture Organic PCMs For The Study Of Thermal Stability

The phase change materials possess the character that they could storage theuntapped energy and release them when needed. This kind of materials hasbecame a focus in the field of energy saving materials.960accelerated thermalcycling tests have been conducted to study the thermal stability of1-hexadecanol/1-tetradecanol binary organic phase change materials and lauricacid(LA)-capric acid(CA) binary organic phase change materials. Thetemperature and the latent heats of phase change were measured by thedifferential scanning calorimetry (DSC) analysis technique with respect torepeated thermal cycles. Laser Raman spectrometer was used to complement thecharacterization for a understanding of the microstructure. The thermal stabilitiesof the different samples were evaluated by the experimental results, and thephase change behavior was investigated in depth.The latent heats of phase change of1-hexadecanol,1-tetradecanol, lauricacid and capric acid are243.54kJ/kg,205.62kJ/kg,178.77kJ/kg and198.07kJ/kg. The change was from-21.65%to6.46%in480cycles. From480to960cycles, the melting temperatures of alcohol monomers decrease, but the changeof the acid monomers express in the reduction of latent heats of the phasechange.The phase change process of1-hexadecanol/1-tetradecanol binary materialsinclude crystal form transition and solid-liquid phase change. The latent heats ofsome samples reduced after480cycles. The analysis shows that the decrease ofcrystal form transition enthalpy is the main reason. The samples present stablethermal properties when the mass fraction of1-hexadecanol in mixture is20%,50%and80%, respectively. The sample, the mass fraction of LA in mixture is30%, has the best thermal stability. In960cycles, the melting temperature is inrange of-0.25℃to1.12℃, and the change in latent heat of phase change isfrom-4.39%to3.46%.The microstructures of the fatty alcohols indicate that the thermal cycleshave an influence on the conformation of alkyl chain, result in decrease inordering degree of molecular chain. For fatty acids system, the hydrogen bondsare destroyed between the molecules, and the result is original dimer structurewas changed. There were no new groups in all samples.