Measurement and augmentation of effective thermal conductivity of La0.8Ce0.2Ni5hydride bed

Abstract

An experimental set up for measuring Effective Thermal Conductivity (ETC) of Metal Hydride (MH) beds was fabricated using one-dimensional steady-state radial heat transfer absolute method. La0.8Ce0.2Ni5alloy powder and its hydride were considered in the present study. Two types of compacts were fabricated for ETC augmentation of MH bed. First type was made from the mixture of 6 wt% graphite flakes with the La0.8Ce0.2Ni5alloy powder. A three dimensional structure, having six radial fins, uniformly distributed around the outer periphery of a hollow cylinder, made with copper wire mesh, was integrated with the mixture of La0.8Ce0.2Ni5powder and 6 wt% graphite flakes to make the second type of compacts. The ETC of the three types of beds namely loose metal powder bed (LMP), bed of compacts of metal alloy powder mixed with graphite flakes (CMPGF) and bed of compacts of metal alloy powder mixed with graphite flakes and embedded with copper wire mesh structure (CMPGFCu) were measured and compared at different argon and hydrogen pressures, hydrogen concentrations and average bed temperatures. The maximum values of effective thermal conductivity for the bed configurations of LMP/CMPGF/CMPGFCu were 1.3/4.7/6.8 W m−1 K−1. These values of effective thermal conductivity were obtained at 70 bar hydrogen gas pressure and 60 °C average bed temperature. The decrease in mass fraction of hydrogen absorbed by the La0.8Ce0.2Ni5hydride, as a result of implementation of ETC augmentation techniques, was nominal (around 5.7% in case of CMPGF and 4.5% in case of CMPGFCu) when compared to the respective powder bed configurations. © 2016 Elsevier B.V.