Countercurrent gas-liquid flow in a rectangular channel simulating a PWR hot leg (3). Evaluation of effects of fluid properties using VOF method

To examine the effects of fluid properties on countercurrent flow limitation (CCFL) in a hot leg of a pressurized water reactor (PWR), experiments are conducted using glycerol-water solutions and a 1/5 scale hot leg model with a rectangular channel. Numerical simulations are also carried out using a VOF (volume of fluid) method implemented in the CFD software, FLUENT 6.3.26. The increase in the liquid viscosity does not change the intercept coefficient C in the Wallis-type CCFL correlation but increases the proportional coefficient m, which indicates that the liquid viscosity does not affect the interfacial drag but influences the wall friction. CCFL predicted for steam-water flow at 5 MPa, corresponding to a high gas density and low liquid viscosity condition, is greatly mitigated, which indicates that the gas density has a significant effect on the interfacial drag. (author)