Turbulent convection in molten pools

In this presentation we summarize the research activities directed towards investigation on the natural convection heat transfer and mixing phenomena in single and two-fluid density stratified pools at NPS/RIT. First, the turbulent characteristics of the natural convection in a single fluid layer is considered. The applicability and shortcomings of existing turbulence models are discussed. The important turbulence characteristics of the Rayleigh-Benard convection and convection with uniform volumetric heat sources are illustrated by direct numerical simulation (DNS). Next, natural convection heat transfer in a two-fluid stratified system with uniform internal heat sources is investigated both numerically and experimentally. The results of and major findings from the SIMECO experimental program are reviewed. The major objective of the SIMECO tests is to determine the role of the interface and stratification on the heat transport characteristics (e.g. fraction of total heat generated within the pool that is transferred upwards, local heat ux distribution etc.). Several sets of experiments have been performed with different simulants and for different geometry configuration. Immiscible (paraffin oil/water) and miscible (salt water/water) systems have been considered with heat being generated in the lower layer or in both layers. The effect of the metal layer on top of oxidic pool has been investigated in an integral fashion. The eutectic salt and the Cerrobend alloy have been employed as simulants. The experiments have shown that the presence of crust at the interface affects much the heat transfer and in such a case, both layers are uncoupled and can be considered separately. In case of no crust, the system should be considered in an integral manner. The top surface cooling eliminates focusing effect which is considerable otherwise. (author)