Experimental measurements and general conclusions on the effective thermal conductivity of powdered metal hydrides

E. Suissa, I. Jacob, Z. Hadari

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61 Scopus citations

Abstract

The effective thermal conductivity Ke of Mg2NiH4 and MmNi4FeH5.2 (Mm ≡; misch metal) was measured under steady state conditions as a function of the hydrogen pressure and the temperature. The effective thermal conductivity of the two hydrides increases significantly as a function of the hydrogen pressure up to approximately 40 atm and then remains almost constant. The Ke values for Mg2NiH4 and MmNi4FeH5.2 are 0.83 W m-1 K-1 and 1.05 W m-1 K-1 at 373 K and 273 K respectively and a hydrogen pressure of 40 atm. The results were analysed using the Yagi-Kunii model for the effective thermal conductivity in powder-fluid beds. The solid thermal conductivity Ks of the above two hydrides was then estimated. The most important and significant result of the present work is the conclusion that Ke "saturates" at relatively low values of Ks. For example, the maximum Ke values (above the hydrogen breakaway pressure) at 300 K and a typical hydride void fraction (ε{lunate} = 0.5) change from about 0.4 to about 1.5 W m-1 K-1 for a corresponding Ks change between 1 and 500 W m-1 K-1. A survey of the existing data in the literature for the effective thermal conductivities of powdered metal hydrides supports the above conclusion. The practical meaning of this result is that, in engineering applications of hydrides in which a knowledge of Ke is necessary, it can safely be assumed that Ke ≈ 1-2 Wm-1K-1.

Original languageEnglish
Pages (from-to)287-295
Number of pages9
JournalJournal of the Less-Common Metals
Volume104
Issue number2
DOIs
StatePublished - 17 Dec 1984

ASJC Scopus subject areas

  • Engineering (all)

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