Sun Dawen

Study of the heat and mass transfer characteristics of metal hydride beds: A two-dimensional model

Abstract Modelling studies are of a practical importance in understanding and characterizing the behaviour of metal hydride beds. A numerical model for two-dimensional transient heat and mass transfer within metal hydride reaction beds is presented. The model can be used to describe the two-dimensional heat and mass transfer problems in cylindrical or rectangular coordinates and the one-dimensional problems in rectangular, cylindrical or spherical coordinates. Theoretical predictions of temperature distributions within the reaction beds and cumulative reacted hydrogen distributions based on this model are in good agreement with the experimental data obtained in our experiments.

Study of the heat and mass transfer characteristics of metal hydride beds

Abstract Understanding of the heat and mass transfer characteristics of metal hydride beds is very important in studying the enhancement of heat and mass transfer in metal hydride beds and in designing the reactor vessels in an optimum way. Until now, only models with constant hydrogen and metal hydride physical properties have been presented. These models cannot reflect the practical cases well. In the present study, a more practical model is presented. The model not only includes the effects of the effective thermal conductivity in the hydride bed, which is severely affected by the hydrogen pressure and hydrogen-to-metal ratio, but also includes the effects of the physical properties of the metal hydride and other operating parameters. The numerical results of the TiMn 1.5 hydride bed show that the hydriding or dehydriding reaction occurs in the entire hydride bed, but the main reaction occurs in a rather narrow region, and that the enhancement of heat transfer in the metal hydride bed is very important in shortening the reaction time.

Theoretical descriptions and experimental measurements on the effective thermal conductivity in metal hydride powder beds

Abstract An experimental apparatus with a computerized data acquisition system has been constructed and used for measuring the effective thermal conductivity Ke in hydride beds by means of a steady state method. The effective thermal conductivity in an MlNi4.5Mn0.5 (Ml: lanthanum-rich misch metal) hydride bed was measured. The experimental data were compared with theoretical results calculated by using a model (Ke model) which was developed by the authors for calculating Ke in hydride powder beds, and the comparison shows good agreement. Several factors affecting Ke are also discussed.