Annals of the Assembly for International Heat Transfer Conference 13

ISBN 1-56700-225-0 / CD 1-56700-226-9

Year 2006

S. C. Bae
Institute of Ocean Energy, Saga University, Saga, Japan

Y. Yang
Institute of Ocean Energy, Saga University, Saga, Japan

Y. Ikegami
Institute of Ocean Energy, Saga University, Saga, Japan

A series of study has been performed on the hydrides of Mm(La_0.6−0.8)Ni_0.4Co_0.6Mn_0.2Al_0.2 (TL-492 ) to acquire the PCT relationship and thermal conductivities. Experimental data of TL-492 has been collected and analyzed at temperature from 50 to 80°C. Based on the collected data, PCT relationship has been established and analyzed.
The effective thermal conductivities of TL-492 with hydrogen and helium have been examined. Experiment results show that pressure has great influence on effective thermal conductivity in low pressure range (<0.3MPa). And that influence decreases rapidly with increase of gas pressure. The reason is at low pressure, the mean free path of gas becomes greater than effective thickness of gas film, which is important to the heat transfer mechanism in this research. The authors have suggested a set of factors for Yagi and Kunii model based on experiment results to predicate the effective thermal conductivity. At the same time, the ingot thermal conductivity of TL-492 has been derived from experiment as 17.91 W/m K. And the accuracy of these coefficients is quite high. For hydrogen, errors between experiment and calculation are lower than 8%; while for helium errors are limited with 3% margin, except for vacuum status.
Carbon fibers have been used to try to enhance the poor thermal conductivity of TL-492. The carbon fibers have been made into brushes to mix with metal hydrides. Three types of carbon fibers and three weight percentages have been examined and compared. Naturally, the highest effective thermal conductivity has been reached with carbon fiber, which has highest thermal conductivity, and highest weight percentage. This method has acquired 5.4 time higher thermal conductivity than pure metal hydrides with quite low quantity of additives, only 0.99% of carbon fiber. This is a good result comparing to other method, which can reach higher effective thermal conductivity but needs much higher percentage of additives too.

ENR-12 pages DOI: 10.1615/IHTC13.p24.120 Download article

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