Heat storage materials and heat transfer characteristics in latent heat storage systems상변화 물질을 이용한 축열시스템에서 축열재와 열전달 특성 연구

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The performance for thermal energy storage of the salt hydrates by using a thickener and a nucleating agent has been investigated. A super-absorbent polymer made from an acrylic acid copolymer is proposed as an effective thickener to prevent the undesirable phase separation of the salt hydrates. The addition of 2.9 wt\% of super-absorbent polymer is found to be an effective addition to prevent the phase separation of a sodium sulfate decahydrate (Glauber``s salt = $Na_2SO_4$.$10H_2O$) over 100 thermal cycling tests. The phase separation of disodium phosphate dodecahydrate ($Na_2HPO_4$.$12H_2O$) can be prevented by the addition of 3.4 wt\% super-absorbent polymer. However, the super-absorbent polymer is found to be not an effective thickener to prevent phase separation of calcium chloride hexahydrate ($CaCl_2$.$6H_2O$) and sodium thiosulfate pentahydrate ($Na_2SO_3$.$5H_2O$). The supercooling of thickened Glauber``s salt is reduced from 18$^\circ$C to 3$\sim$4$^\circ$C by using 1.9 wt\% borax as a nucleating agent. Three kinds of powdered forms of carbon (1.3$\sim$6.7$\mu$m), copper (1.5$\sim$2.5$\mu$m) and titanium oxide (2$\sim$200$\mu$ m) reduce the supercooling of thickened disodium phosphate dodecahydrate. However, the phase change of thickened $Na_2HPO_4$.$12H_2O$ with aluminum powders (8.5$\sim$20$\mu$m) takes place in a wide temperature range during the heat storage, and it supercools to 25$^\circ$C during the heat recovery stage. Thermophysical properties have been measured by using a thermal analyzer (Dupont 990) and a differential scanning calorimeter (DSC, Dupont 910). The obtained values of the latent heat, thermal conductivity and heat capacities for the mixture of 94\% sodium sulfate decahydrate, 3\% super-absorbent polymer and 3\% borax by weight, are 227 J/g, 0.64 W/m.K, 3.4 J/g.K in the solid and 4.6 J/g.K in gelded state, respectively. For the mixtures of disodium phosphate dodecahydrate, super-absorbent polymer and the respective nucleating a...
Kim, Sang-DoneresearcherPark, Won-Hoonresearcher김상돈researcher박원훈researcher
한국과학기술원 : 화학공학과,
Issue Date
61484/325007 / 000805537

학위논문(박사) - 한국과학기술원 : 화학공학과, 1990.2, [ xviii, 278 p. ]

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