Experimental Study of the Effect of External Pressure on Particle Bed Effective Thermal Properties

Abstract

Accurate prediction of the thermomechanical responses of particle beds in fusion blankets depends strongly on the availability of experimental data on their thermal properties as a function of the blanket operating conditions. In this study, a series of experiments is conducted to measure the effective thermal conductivity and interface conductance of single-size aluminum, beryllium, and lithium zirconate particle beds as a function of applied external load in the 0- to 1.6-MPa range. Experiments are carried out with both helium and air as cover gas over a pressure range of 30 to 760 Torr. In both the aluminum and beryllium beds, as the applied load is increased to 1.5 MPa, the effective thermal conductivity increases by a factor of ∼3 to 7 in an air cover gas and by a factor of ∼2 to 3 in helium. With 1.2-mm lithium zirconate particles and air or helium as the cover gas, changes in the bed thermal conductivity when the applied load is varied in the 0 to 1.6-MPa range are small and within the experimental error. The increase in the interface conductance values with applied external load shows variations similar to those of the thermal conductivity. Based on the Hertz elastic equation and finite element models, the particle-to-particle contact areas as a function of the applied external load are evaluated and used in a predictive model by Bauer, Schlunder, and Zehner to calculate the effective thermal conductivity of a beryllium particle bed as a function of external pressure. The experimental results are in good agreement with the model predictions.

Additional information

Notes on contributors

Fatollah Tehranian

Fatollah Tehranian (PhD, University of California, Berkeley, 1983) is a senior development engineer in the Fusion Engineering Program at the University of California, Los Angeles (UCLA) with experimental and analytical research interests in the areas of thermomechanics, heat transfer, and tritium transport as related to fusion nuclear technology.

Mohamed A. Abdou

Mohamed A. Abdou (PhD, University of Wisconsin, 1973) is a professor in the Department of Mechanical, Aerospace, and Nuclear Engineering at UCLA. He is also the leader of the Fusion Engineering Program. His research interests include fusion neutronics, thermal hydraulics, blanket technology, fusion reactor design, and system studies.