Onset of Flow Stratification in Horizontal RodBundles

Abstract

Experiments have been conducted in a string of horizontal 37-rod bundles to determine the onset of flow stratification, and the conditions under which the top element of the 37-rod bundle becomes completely dry around its periphery (i.e., onset of peripheral dryout or OPD). The experiments were performed for air-water flow at room temperature and atmospheric pressure, and at mass fluxes up to 3000 kg/m%, and qualities up to 3.2%. The flow-regime boundaries were also determined, and the void distributions measured with a miniature fibre - optic probe. The results were analyzed using dimensionless coordinates, and extrapolated to other fluid and flow conditions. The experimental results for 37-sod bundles have been compared with Taitel and Dukler's [l] predictions for pipes, The pipe model tends to overpredict the onset of complete flow stratification in rod bundles when analyzed in terms of tube diameter, and underpredicts the results when analyzed in terms of the hydrodynamic diameter. A goad agreement with the experimental results was obtained at high gas-flow rates when compared with the wedel of Osarnusali and CPlang [2], which accounts for rod-bundle geometry and surface tension effects.