Spherical Agglomerates of Poly(ethylene glycol)/Silica Fume Composites as Phase Change Materials
| Autor: | Chih-Lin Wang, 王智霖 |
|---|---|
| Rok vydání: | 2016 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 104 The aim of this thesis was to prepare a solid-liquid shape-stabilized phase change materials, polyethylene glycol/silica fume (PEG/SF) composite, and study the blends of different PCM composites to broaden application temperature to suit for more applications of PCM, then through spherical crystallization to conglomerate the PCM composites become spherical agglomerates to improve the flowability. PEG 4000 was embedded in a low-cost SF to form the PEG75/SF composite with a PEG wt% of 47.9 wt%. The melting point and crystallization temperature of the PEG75/SF composite or spherical agglomerates were around 55-58ﾟC and 18-24ﾟC as determined by the temperature cycle of DSC with a heating rate of 10ﾟC/min and a cooling rate of 10ﾟC/min, respectively. Blends of PEG75/SF composites with PEG25/SF composites or with low-cost SF having a ratio of 1:1 could be used as a phase change material that had a broad crystallization temperature range. The spherical agglomerates of SF and PEG75/SF were made by the spherical crystallization process. Two agitation speeds in the spherical crystallization process about 400 and 600 rpm were studied. It was found that the particle size distribution of agglomerates prepared from different agitation speeds could vary significantly. There were more than 40 wt% of fine particles (< 250 μm) PEG75/SF composites did not conglomerate to become spherical agglomerates at 400 rpm. The particle size distribution was more uniform at 600 rpm. However, the morphology of agglomerates produced at 400 rpm was more spherical than those made at 600 rpm. The effect of the agitation speed on the particle fracture force of agglomerates in the range of 355-500 μm and 710-1000 μm was not obvious. The particle fracture force of agglomerates of 355-500 μm, and 710-1000 μm were 0.18±0.06, and 0.52±0.02 N by 400 rpm and 0.16±0.03, and 0.53±0.04 N by 600 rpm, respectively. There were similar properties between different size cuts of spherical agglomerates of PEG75/SF. Spherical agglomerates of PEG75/SF produced at 400 rpm and 600 rpm had good homogeneity in thermal properties and low Carr’s index indicating good flowability. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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