Two-group phase distribution characteristics for air-water flow in 5 × 5 vertical rod bundle channel with mixing vane spacer grids

Abstract

The phase distribution in rod bundle channel was associated with the heat transfer coefficient, flow resistance and critical heat flux, which was of great significance for the design and safe operation of nuclear reactor and steam generator. In order to clarify the phase distribution characteristics and reveal the effect of mixing vane spacer grid (MVSG) in two-group air-water flow in rod bundle channel, the adiabatic upward air-water two-phase flow experiments were conducted in 5 × 5 rod bundles with MVSGs and the detailed local two-phase flow parameters were acquired with miniaturized four-sensor conductivity probe (MFSCP). Some interesting phenomena were reported: Group I and II void fraction profiles showed the core-peak features; Group I void fraction almost stayed at the region from 0.2 to 0.3 for two-group air-water flow at current flow conditions; the dissipation length of MVSG was larger than 32.1 L/D at current two-group flow conditions; and the influencing region of MVSG was divided into at least three regions along the axial direction with the flow development for current flow conditions.