Effects of Partial Inlet Blockages on High-Velocity Flow Through a Thin Rectangular Duct: Experimental and Analytical Results

The Advanced Neutron Source (ANS) reactor was designed to provide a research tool with capabilities beyond those of any existing reactors. One portion of its state-of-the-art design required high velocity fluid flow through narrow channels between the fuel plates in the core. Experience with previous reactors had shown that fuel plate damage could occur if debris became lodged at the entrance to these channels. Such debris disrupts the fluid flow to the plate surfaces and could prevent adequate cooling of the fuel. Preliminary ANS designs addressed this issue by providing an unheated entrance length for each fuel plate so that any flow disruption would have time to recover before reaching the heated portions of the fuel plates further downstream. As part of the safety analysis, the adequacy of this unheated entrance length was assessed using both analytical models and experimental measurements. The Flow Blockage Test Facility (FBTF) was designed and built to conduct experiments in an environment closely matching the ANS channel geometry. The FBTF permitted careful measurements of both heat transfer and hydraulic parameters. In addition to these experimental efforts, a thin rectangular channel was modeled using the FLUENT computational fluid dynamics computer code. The numerical results were compared to the experimental data to benchmark the hydrodynamics of the model. After this comparison, the model was extended to include those elements of the safety analysis difficult to measure experimentally. These elements included the high wall heat flux pattern and variable fluid properties.