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ISSN Online: 2377-424X

ISBN Print: 0-85295-345-3

International Heat Transfer Conference 10
August, 14-18, 1994, Brighton, UK

EFFECTIVE THERMAL CONDUCTIVITY OF METAL HYDRIDE POWDERS: MEASUREMENT AND THEORETICAL MODELLING

Get access (open in a dialog) DOI: 10.1615/IHTC10.790
pages 373-378

Аннотация

Desorption of hydrogen from metal hydrides requires a supply of reaction enthalpy, absorption requires the removal of this enthalpy. Therefore, the effective thermal conductivity λe of the powdered metal hydride strongly influences the velocity of absorbing and desorbing hydrogen.
Based on the cellular-model by Zehner, Bauer and Schlunder (1970, 1972, 1978) for porous media with inert void gases, an extended model is developed to calculate λe of powdery materials with a reaction between gas and solid. This reaction causes an elastic expansion of the particles. The extended model also takes into account methods of increasing λe such as a built-in metallic matrix.
Experimental investigations have been carried out on the low temperature hydride HWT 5800 (Ti0.98Zr0.02V0.43Fe0.09Cr0.05Mn1.5Hx, xmax = 3) and on the medium temperature hydride LaNi4.7Al0.3Hx (xmax = 6) within the temperature ranges of -80 < ν < 20°C and -20 < ν < 140°C respectively and in the pressure range of 10-6 < p < 6 MPa. The porosity of the pure metal powder is originally 44.5 and 53.1 %. The measurement principle used is the transient hot-wire method.
The paper concludes with a comparison of measured and calculated values of the effective thermal conductivity of different metal hydrides. The design of chemical hydrogen storage devices can thus be based on improved predictions of λe.