A hydrodynamic vortex separator (HDVS) has been modelled using computational fluid dynamics (CFD) in order to accurately determine the residence time of the fluid at the two outlets of the HDVS using a technique that was developed for use in heating, ventilation, and air conditioning (HVAC). The results have been compared with experimental data [1]. It is shown that, in using CFD, it is possible to study the response to a variety of inputs, and also to determine the mean residence time of the fluid within the separator. Although the technique used for determining the residence time was developed for use in HVAC, it is shown here to be applicable for the analysis of hydraulic systems, specifically, wastewater treatment systems.
A Hydrodynamic Vortex Separator (HDVS) has been modelled using Computational Fluid Dynamics (CFD) in order to predict the residence time of the fluid at the overflow and underflow outlets. A technique which was developed for use in Heating, Ventilation and Air Conditioning (HVAC) was used to determine the residence time and the results have been compared with those determined experimentally. It is shown that in using CFD, it is possible to predict the mean residence time of the fluid and to study the response to a pulse injection of tracer. It is also shown that it is possible to apply these techniques to predict the mean survival rate of bacteria in a combined separation and disinfection process.
A number of models exist to simulate the residence time distribution (RTD) of a system or process. Four of these models known as the tanks in series model, axial dispersion model (ADM), aggregated dead zone model, and the advection dispersion equation, have been used to assess which is most suitable for representing the RTD of a hydrodynamic vortex separator (HDVS) when compared to RTD measurements taken under laboratory conditions on a full-scale 3.4 m diameter unit. Computational fluid dynamics (CFD) is also used to model the HDVS and compare with the RTD models and experimental measurements. It has been shown that the fit by each of the RTD models to observed RTDs vary quite considerably, with the ADM being the most appropriate for the HDVS studied, based on having the highest R 2 t value. Given the number of model variables that influence CFD predictions, the outputs from the CFD models appear to be reasonable.
Conventional equipment for the transportation of solid-liquid mixtures is often subject to wear-related problems. A recent innovation, which is a fully fluidic non-moving part device, utilizes vortex flows for the mixing and transportation of slurries. Its novelty lies in the fact that it is driven by an external fluid supply and thus contains no moving parts in direct contact with the slurry material. Slurry mixing is an integral part of the process, and thus the need for pre-treatment of slurries is eliminated. An extensive series of studies has been carried out to investigate both the performance aspects of the device and the underlying phenomena involved in its operation. This paper presents experimental results of both performance and operational studies of this novel slurry transportation system.
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