Thermal diffusivity measurements of recirculating flows to validate model tests for liquid metal reactors

Before data from water model tests can be applied to sodium-cooled reactors, a lower limit for Reynolds number to give thermal similarity must be established. A route for determining this is to infer the turbulent diffusivity of heat for water and sodium in the relevant geometry by comparing measured temperature profiles to those predicted by a numerical code. Such a code has been developed, based on the finite element method, and its predictions of velocity and temperature fields compared with measurements made in a simple axisymmetric pipe expansion. Initial results are encouraging, but show the need for further refinement of the turbulence model