DOI: 10.1615/ICHMT.1982.AdvCourHeatTransfNucReactSaf
ISBN Print: 978-0-89116-223-0
2.10 A Review on Gas-Liquid Countercurrent Flow through Multiple Paths
RESUMO
Gas-liquid countercurrent flow through multiple paths occurs in PWR and BWR bundle upper structures during the reflood process of a reactor core in a loss-of-coolant accident. In a less dramatic situation, gas-liquid counter-current flow can be found inside chemical distillation equipments as well as other practical flow systems. By extrapolating the present knowledge of single-channel countercurrent flow, it was concluded that multiple-path flow will exhibit similar characteristics as that of single-channel flow for low liquid-holdup cases. Existing experimental investigations on countercurrent flow through perforated plates are summarized and found to support this notion of similitude. These results also show that, for large liquid-holdup, multiple-path flow is strongly governed by the gas-liquid mixing action above the path inlets. This mixing action depends very much on the path geometry and arrangement. There are four distinct flow regimes associated with the mixing behaviors: free draining, bubbling and foaming, oscillating foam, and fluidization. Studies on bubble formation at a single orifice are briefly reviewed, but the state of knowledge is still quite inadequate. Flooding experiments in simulated full-size PWR and BWR upper bundle structures are also discussed.