CFD Analysis for the Hydrodynamics and Heat Transfer in Packed Pebble Bed

Abstract

Lithium titanate (Li2TiO3) and lithium orthosilicate (Li4SiO4) are the promising solid breeder materials for the fusion reactors. Packed bed of Li2TiO3 or Li4SiO4 pebbles is considered in the fusion reactor blanket for in situ production of tritium and for this a good effective thermal conductivity of the pebble bed is necessary. In recent past, Mandal et al. [26] studied the hydrodynamics and heat transfer properties of bed of lithium titanate pebbles at different operating conditions viz., gas flow rates, pebble sizes, bed wall temperatures, etc. In the present study laminar, k – ε and low Reynolds k – ε model have been used to simulate the hydrodynamics and heat transfer data of Li2TiO3 pebble bed. The computational fluid dynamics (CFD)-simulated hydrodynamics results have been compared with hydrodynamics and heat transfer results of bed of Li2TiO3 pebbles reported by Mandal et al. [26] and others. It was found that k – ε and low Reynolds number k – ε model shows better agreement with experimental results. The CFD study were carried out using low Reynolds k – ε model for pebble bed of different materials viz. Li2TiO3, Li4SiO4 and alumina (Al2O3). The effect of flow rate, pebble size, wall temperature, solid properties viz. thermal conductivity and specific heat on effective thermal conductivity and overall heat transfer coefficient has been discussed in this paper.