CFD analysis of three-dimensional thermalhydraulics flow effects on wall concentration gradient profiles for LBE loop fittings

The objective of the thesis is to study the effects of thermalhydraulics flows on the wall concentration gradient profiles in LBE loop fittings. To that end detailed models of the fittings have been constructed to study these effects. These fittings include sudden expansion, sudden contraction, t-joint and elbow. The typical flow rates chosen for these simulations are typical of design criteria chosen for the Loop with Reynolds numbers expected around 200,000 and the usual axial temperature profiles which are being characterized in the DELTA loop at LANL. STAR-CD is the simulation package used to make these predictions, which include detailed 3-D velocity, temperature and concentration gradient profiles of the corrosion/precipitation on the inner surface of these fittings. The different predicted variables from these simulations indicate that special attention needs to be placed when designing loops with these fittings especially in the regions of sudden velocity changes and stagnation zones. These wall gradients can determine eventually the expected longevity of these fittings in an LBE flow environment. Presently though very little experimental data exists that would be suitable to corroborate the simulation results. Graphs of concentration gradient v/s distance from the inlet of these fittings were plotted. Eventually these individual fitting models will become part of an overall closed loop that will yield more realistic core concentration values and hence more realistic wall gradient values, which are dependent on these core values.