Measurement of Total Air Entrainment, Disentrainment and Net Entrainment Flow Rates Utilizing Novel Downcomer Incorporating Al-Anzi’s Disentrainment Ring (ADR) in a Confined Plunging Jet Reactor

Abstract

Plunging liquid jet reactor (PLJR) has gained popularity as a feasible and efficient aerator and mixer. However, the measurement of air disentrainment rate (Qads), which affects aeration performance, has been overlooked by many researchers. In this work, a newly invented Al-Anzi disentrainment ring (ADR) device was incorporated in CPLJR to experimentally measure Qads and its effect on the net air entrainment rate. Furthermore, the effect of new variables (lADR and ds) and old variables (Lj and VL) on Qanet were also investigated. Results showed that shorter ds and lADR produced higher Qanet for the same ADR device. A new net entrainment jet velocity at the impingement point (VLnet) was measured at about 651 cm/s, above which bubbles left the base of downcomer as Qanet. Qanet increased linearly with VL; however, Qads increased until it reached maximum value, and then decreased. Bubble penetration depth and liquid rise height increased for all VL until they reached maximum, and then leveled off for the same lADR. A significant increase in Qanet values was achieved with this downcomer in comparison with the conventional one. The increase in Qanet was measured to be approximately 2.5–15 times of that measured by the standalone downcomer.

Keywords

• ADR
• air net entrainment rates
• air disentrainment rates
• CPLJR
• downcomer
• entrainment jet velocity