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Proceedings of Symposium on Energy Engineering in the 21<sup>st</sup> Century (SEE2000) Volume I-IV

ISSN:
1-56700-132-7 (Print)

STUDY OF THE REACTION RATE OF MHHigh (MHTAL HYDRIDE: Ti0.18Zr0.84Cr1.0Fe0.7Mn0.3Cu0.057) TO BE USED FOR COMPACT MH REFRIGERAION SYSTEMS

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

Shinsuke Takeguchi
Department of Mechanical Engineering Waseda University, Graduate School of Science and Engineering

Takahiro Yabe
Department of Mechanical Engineering Waseda University, Graduate School of Science and Engineering

Masahumi Katsuta
Waseda University, Graduate School of Environment and Energy Engineering, Tokyo, Japan

Abstract

Our purpose is to develop the compact MH refrigeration system for the vending machine and the show case, and to attain a refrigeration temperature of 243 K by using a heat source of about 423K. The reaction rate of the MH to use for the heat source, MHHigh is studied first though the MH refrigeration system consists of two MHs, one is used for the heat source and the other is used for the cooling load extracting. As for the reaction rate in the hydriding process, initially, a rapid surface reaction, governed by the relation 1−(1−F)1/3 =kht. After the MH surface has been covered by hydride, the reaction becomes diffusion controlled with the relation 1−3(1−F')2/3 +2(1−F') = k'h t. The reaction rates, kh, k'h are exponentially proportional to the pressure difference and increase with temperature. And, As for the dehydriding process, it is found out that the rate-controlling step is uniquely diffusion reaction. The dehydriding reaction rate is exponentially proportional to the pressure difference and the initial reacted fraction, and increases with temperature. Finally, on the basis of these experimental results, the brand new rate correlations are reasonably derived. The calculated results are in agreement with the experimental ones.