Thermal conductivity of composite materials: Alkali carbonate-based melts filled with fine α-Al2O3. (April 2018)

• Record Type: Journal Article
• Authors: Dokutovich, Vasiliy N.; Khokhlov, Vladimir A.; Zakir'yanova, Irina D.
• Is Part Of: International journal of heat and mass transfer. Volume 119(2018)
• Page Start: 365
• Page End: 371
• Publication Date: 2018-04
• Subjects: Thermal conductivity -- Composite material -- Salt melts -- α-Al2O3 -- Modelling; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2017.11.132
• Languages: English
• ISSNs: 0017-9310

Abstract

Graphical abstract: Highlights: The thermal conductivity (λ) of molten salt-Al2 O3 composites is first measured. The thermal conductivity grows as the temperature and α-Al2 O3 concentration rise. The temperature coefficient dλ/dT decreases sharply as the oxide content increases. A correlation between the λ and the mean thickness of the molten salt gap is found. A model is proposed for describing the heat transfer in the composites under study. Abstract: The thermal conductivity of composite materials, specifically alkali carbonate-based melts filled with fine α-Al2 O3, was measured in relation to the temperature and thickening agent content using the steady-state coaxial cylinder method. The thermal conductivity was found to be a linear function of the temperature in the range from 670 K to 930 K for salt melts and all of the thickened melt-oxide mixtures that were studied, while this value increased non-linearly as the α-Al2 O3 volume fraction increased showing a tendency to be unchanged at α-Al2 O3 volume concentrations greater than 15%. The thermal conductivity of the (Li2 CO3 - Na2 CO3 - K2 CO3 )eut + α-Al2 O3 composites measured was adequately described by the Maxwell-Wagner equations derived for two-phase heterogeneous materials. The alternating sign of the temperature coefficients of the composites thermal conductivity and peculiarities of its concentration dependency point to the existence of "ionic heat conductor - oxide heat insulator" transaction in alkali carbonate-based melts thickened with fine α-Al2 O3 .