Preparation And Thermal Performance Of Alkane-Alcohol Phase Change Materials For Cold Storage

Phase Change materials have become the research hot spot as a new energy saving materials. However, there are little research reports about alkane-alcohol organic hybrid system as phase change materials(PCMs) for cold storage. Moreover, organic PCMs suffer from low thermal conductivity and leakage during the phase change process. In this thesis, based on the current research of organic PCMs for cold storage, we main studied on alkane-alcohol organic hybrid system.In this thesis, binary alkane-alcohol organic hybrid system of mixed n-tetradecane(TD) and 1-dodecanol(DD) as phase change materials(PCMs) for cold storage was studied. The eutectic mass ratio, the phase change temperature and latent heat of the binary alkane-alcohol organic system were characterized by DSC. Experimental results show that the eutectic mass ratio of n-tetradecane and 1-dodecanol was 8:2, while the freezing temperatures was-3.931 oC and the freezing enthalpy was 213.961 J/g.However, the application of organic PCMs could be inhibited by both of its leaking during the phase change process and low thermal conductivity. In order to solve these problems, form-stable binary alkane-alcohol organic eutectic PCMs(TD-DD)/ expanded graphite(EG) composite PCMs was prepared. The EG has outstanding thermal conductivity and capillary effect. The experimental results show that the highest loading percent of TD-DD in the form-stable composite phase change materials was 85%, and the melting and freezing temperatures as well as latent heats of the form-stable composite PCMs were 10.566 oC,-2.802 oC and 180.191 J/g, 178.032 J/g, respectively. The phase change temperature and latent heat of the form-stable composite PCMs maintained well in 12 thermal cycles, indicating its superior thermal stability. The thermal conductivity was 0.78 W/(m?k), which is 5 times as that of pure binary alkane-alcohol organic eutectic PCMs(TD-DD). Therefore, expanded graphite as adsorption substrate can not only prevent the leakage of organic PCMs during the phase change process, but also greatly improve the thermal conductivity of PCMs.Additionally, binary alkane-alcohol organic eutectic PCMs(TD-DD)/polymethyl methacrylate(PMMA) microcapsules PCMs for cold storage was prepared, in which TD-DD was the core material and polymethyl methacrylate(PMMA) was the shell material. Effects of emulsifier amounts and the ratio of core and shell to the thermal performance of microcapsules were studied. The surface morphology, structure and thermal capability of microcapsules were characterized by DSC, SEM, TG and FT-IR. Results show that when the emulsifier was 1.0 g and the ratio of core and shell was 1.5:1, the microcapsules exhibit good thermal performance, that the microencapsulation ratio can be reached 61.88% with melting and freezing temperatures of-5.747 oC and 5.116 oC, and the corresponding phase change latent heat were 132.397 J/g and 129.138 J/g, respectively. The microcapsules PCMs show superior thermal reliability in 14 thermal cycling. Moreover, TG test showed that the thermal stability of binary alkane-alcohol organic eutectic PCMs(TD-DD) is also improved after being encapsulated.