Experimental measurement and numerical modeling of the effective thermal conductivity of lithium meta-titanate pebble bed

The effective thermal conductivity (k_eff) of lithium meta-titanate (Li₂TiO₃) pebble beds under fusion relevant environments is an important property for the design of IN LLCB TBM (Indian Lead Lithium Ceramic Breeder Test Blanket Module). The transient hot wire technique was used to examine the thermal property of the Indian made Li₂TiO₃ material. The hot wire is used as both the heating element as well as for the temperature measurement. The k_eff of Li₂TiO₃ pebble bed has been investigated from room temperature to 800 °C. Experiments were performed on uncompressed Li₂TiO₃ pebble bed in stagnant helium gas filled at ambient pressure. A clear dependence of the k_eff on the temperature of the pebble bed was observed. The pebble bed has pebbles of 1 ± 0.15 mm diameter and packing fraction of 63%. The experimental results showed that the k_eff increased from 0.903 W/m°C to 1.204 W/m°C with the increase of bed temperature from 34.3 °C to 785.4 °C. The random close packing of poly dispersed Li₂TiO₃ pebble bed has been generated using discrete element method and then numerical modeling has been performed using finite element method to estimate k_eff. The numerically determined k_eff of the Li₂TiO₃ pebble bed agrees reasonably well with the obtained experimental data. The experimentally achieved k_eff results are also compared with the reported experimental results elsewhere and also with Zehner–Schlunder correlation.