Theoretical and experimental study on effective thermal conductivity of pebble bed for fusion blanket

Abstract

The effective thermal conductivity of breeder pebble bed as an important thermal physical parameter directly affects the thermal and mechanical properties of solid blanket. Theoretical and experimental studies on effective thermal conductivity of Li4SiO4 pebble bed were introduced in this paper. First, a theoretical model coupling the contact areas with bed strains was presented to predict the effective thermal conductivity of mono-sized pebble bed. Taken into account in this theoretical model is the influence of factors, such as properties of pebbles and gas, bed porosity, pebble size, gas flow, contact areas, thermal radiation and contact resistance. Second, experimental platforms were built up to measure the effective thermal conductivity of Li4SiO4 pebble bed. One is based on transient thermal probe method and the other is based on transient plane source method. The effective thermal conductivity of Li4SiO4 pebble bed with pebbles in a diameter of around 1mm were measured in the temperature range of RT∼550°C. The helium at 0.1MPa and air at atmospheric pressure were used as filling gas respectively to assess the influence on effective thermal conductivity of pebble bed. The comparison between the experimental results and calculation results by theoretical model was also discussed.