熱駆動型冷凍機利用金属水素化物層の有効熱伝導率測定と伝熱促進

抄録

A series of study has been performed on the metal hydride beds of Ti_0.15Zr_0.85Cr_0.9Fe_0.6Ni_0.2Mn_0.3Cu_0.05 (MH-1, using for heat source), Ti_0.73Zr_0.27Cr_1.2Fe_0.3Ni_0.1Mn_0.4Cu_0.05 (MH-2, using for cooling load) to measure the effective thermal conductivities. The effective thermal conductivities of MH alloy bed in hydrogen and helium have been examined. Experiment results show that pressure has great influence on effective thermal conductivity in low pressure range. 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. Then, carbon fiber has been used to try to enhance the poor thermal conductivity of MH alloy bed. Three types, two insert methods and three weight percentages of carbon fiber have been examined and compared. The highest effective thermal conductivity has been reached with carbon fiber which has second higher thermal conductivity, and highest weight percentage. This method has acquired 5.4 times higher thermal conductivity than pure metal hydride beds with quite low quantity of additives, only 1.7 wt % 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.