Abstract
Jet velocity is an important parameter affecting the air entrainment rate of plunging liquid jet processes. While the vast majority of researchers have investigated the effect of jet velocity, only a few of them considered the effect of jet length in calculating the jet velocity at impingement point. This study investigates the difference (ΔV) between the jet velocity at the inception of the nozzle (Vj) and the impingement point (VL) for a range of operating conditions. Furthermore, bubble voidage inside the downcomer, another critical parameter in plunging jets, is estimated using three different voidage equations incorporated inside a momentum balance model to predict the two-phase elevation level (HR) inside the downcomer. Results showed that ΔV is significant (VL > Vj), especially at low jet flow rates and high jet lengths. Generally, the momentum balance model predicted the HR well, and its prediction improves with downcomer diameter. Given that, the model still needs to be refined for more accuracy for a wide range of operating conditions.