Water transport resistance through the polymer electrolyte membrane was evaluated by measuring the water permeability of it. From the results of a thickness sensitivity evaluation, two types of water transport resistance were found. One was "internal diffusion resistance," which was proportional to the membrane thickness, and the other was "interfacial transport resistance," which was independent of thickness. This interfacial resistance was found not to be negligible. Furthermore, both resistances showed sensitivity to temperature and relative humidity. The internal diffusion coefficient estimated from the results of water permeation experiments correlated well with the results obtained by the pulse field gradient nuclear magnetic resonance (PFG-NMR) method. And, the electro-osmotic drag coefficient was also measured by the proton pump balance method based on the water permeation test system (1) . It was concluded that water permeation experiments are helpful for obtaining a better fundamental understanding of water transport mechanism through the membrane.

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A series of study has been performed on the metal hydride particle beds of Ti 0.15 Zr 0.85 Cr 0.9 Fe 0.6 Ni 0.2 Mn 0.3 Cu 0.05 (MH-1, using for heat source), Ti 0.73 Zr 0.27 Cr 1.2 Fe 0.3 Ni 0.1 Mn 0.4 Cu 0.05 (MH-2, using for cooling load) to measure the effective thermal conductivities. The effective thermal conductivities of activated and oxidized MH particle bed in helium have been examined. Experiment results show that pressure has great influence on effective thermal conductivity in low pressure range (<0.5 MPa). And that influence decreases rapidly with increase of gas pressure. The reason of pressure dependence at low pressure range is that the mean free path of gas becomes greater than effective thickness of gas film which is important to the heat transfer mechanism of particle bed. In order to enhance the poor thermal conductivity of metal hydride particle bed, carbon fiber mixing method has been used in this study. Three types, two insert methods and five mass percentages of carbon fiber have been examined and compared. The highest effective thermal conductivity of MH particle bed has been reached with Type B carbon fiber which has second higher thermal conductivity, and 2 weight percentage. This method has acquired 5-6 times higher thermal conductivity than pure metal hydride particle beds with quite low quantity of additives, only 2 mass% 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.

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