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Study on Phase Change Energy Storage of PEG System

Author: ZhuYi
Tutor: WenZuoJiang
School: Suzhou University
Course: Materials Science
Keywords: Phase change material Polyethylene glycol Energy storage Crystallization Non-isothermal crystallization kinetics Graphite
CLC: TB34
Type: Master's thesis
Year: 2010
Downloads: 248
Quote: 1
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Abstract

Of solid - liquid phase change material, whether inorganic or organic, in the process of phase transition liquid phase, so we must encapsulate the material, which will not only increase the heat transfer medium with phase transition the thermal resistance of the material, reducing the heat transfer efficiency, but also increase production costs. Composite phase change material substance of the solid - liquid phase change material and other materials through the composite amorphous, its able to maintain a certain shape (ie solid state) before and after the phase transition, and therefore can be a solid - solid phase change materials . These materials with low requirements for the container, and can even be used directly, thus greatly reducing the cost. Composite phase change material both to overcome the shortcomings of the single phase change material, but also to expand the application range of the phase change material. The this paper prepolymerized synthesized solid - solid phase change material with polyethylene glycol (PEG) as the soft segment, 4,4 '- diphenylmethane diisocyanate (MDI) and the reaction of glycerol segment as a hard segment . Materials Analysis using infrared spectroscopy (FT-IR), differential scanning calorimetry France (DSC), and wide angle X-ray diffraction (WAXD), thermogravimetric (TG), and polarized microscopy (POM), scanning electron microscopy (SEM) technical analysis to study the structural characteristics of PCM phase change behavior, thermal storage performance aggregation structure and thermal properties of factors, such phase change material phase change mechanism. The research results show that the material has a block structure of crosslinked polyurethane. The material has a suitable phase change temperature and phase transition enthalpy, no liquid phase change process is typical of solid - solid phase change, and the phase change process is completely reversible. The essence of the phase change is the soft segment of polyethylene glycol, the process of transition from the crystalline to the amorphous state. Therefore, the material for the market application prospects polymer solid - solid phase change material. The study showed that the material as the cooling rate increases, the Tp and the crystallization onset temperature of the crystallization peak temperature Tc is moved to the low temperature, the crystallization half time t1 / 2 decreases gradually. Ozawa method of processing data obtained by kinetic parameters linear relationship between poor Mo Zhishen rule can be well described by the phase change materials, non-isothermal crystallization kinetics. The apparent activation energy Ea Ozawa kinetic equation to calculate the system than pure PEG apparent activation energy is slightly larger of PEG in the PCM to overcome the hard segment bound to occur from crystalline to amorphous transition. When the PEG molecular weight and content of the material change research to prepare a series of different phase transition temperature and enthalpy PCM. PCM phase change enthalpy and the phase transition temperature as the PEG content reducing sharply; PCM phase change enthalpy of the different molecular weights of the same PEG content with the molecular weight increased significantly increase when a large molecular weight to a certain value, the phase change enthalpy The slight decrease in the trend of the phase transition temperature is consistent with the phase transition enthalpy. Hard segment content increases gradually improve the thermal stability of the material, but also seriously affect the soft segment crystallization integrity sharp decline in the degree of crystallinity of the soft segment. The graphite was added to and not significantly improve the thermal stability of the composite PCM, but the enthalpy decreases with the increase of the added amount, the phase change temperature changes is very small. Compared with the PCM, the addition of graphite significantly improve the composite thermal storage and heat release rate of the PCM.

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