In Situ Local Parameter Measurements for CFD Modeling to Optimize Aeration
Authors: Fayolle, Yannick; Gillot, Sylvie; Cockx, Arnaud; Roustan, Michel; Héduit, Alain
Source: Proceedings of the Water Environment Federation, WEFTEC 2006: Session 41 through Session 50 , pp. 3314-3326(13)
Publisher: Water Environment Federation
Abstract:Measurement methods to determine in situ local parameters were developed, in order to optimize design and operating parameters impacting oxygen transfer in aeration tanks equipped with EDPM membrane diffusers and slow speed mixers. New tools to measure bubble sizes and gas hold-ups were coupled with the traditional ones used to determine liquid velocities and oxygen transfer coefficients. These methods have been developed and applied to an annular loop reactor (1493 m3).
Using an immersed camera, 100 bubbles are sufficient to determine the local Sauter diameter by image analysis. Obtained results are reproducible and independent of the operator. The gas hold-up, deduced from water level measurements with the help of a magnetostrictif level meter, can be determined with a confidence interval of ± 5% using an integration time of 380 s.
The obtained increase in the oxygen transfer coefficient (+ 29%) with the horizontal liquid velocity (from 0 to 0.42 m/s) is mainly due to the increase of the global gas hold-up, the bubble size varying only slightly (from 0.46 to 0.43 cm). These results will be used as input data and validation data to model hydrodynamics and mass transfer, in order to set up a simulation methodology for aeration tanks using computational fluid dynamics.
Document Type: Research Article
Publication date: January 1, 2006
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