Computational fluid dynamic prediction of the residence time distribution of a prototype hydrodynamic vortex separator operating with a base flow component

Abstract

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.

Development and validation of CFD models for gas phase reactions in biomass grate furnaces considering gas streak formation above the packed bed

“…The approach proved to be valid for use in modelling heating, ventilation, air conditioning and hydraulic systems [18,19].…”

“…For an arbitrary scalar, φ k (here gas residence time), the steady state transport equation to be solved is given by [18,19]:…”

“…The diffusivity of the UDS is defined to be the same as of the flue gas since the residence time is transported and mixed with the gas flow. Therefore, in turbulent combustion flows, the diffusivity of the UDS is a function of the binary diffusivity, the turbulent and laminar viscosities, and the turbulent Schmidt number and is defined as follows [19]:…”

Assessment of residence time in a hydrodynamic vortex separator by applying distribution models

“…This has been shown to be applicable to the prediction of mean residence time of wastewater treatment systems for which details are given in Egarr et al [19]. Simplistically, the transport equation for any scalar, φ k , is given by…”

“…The source term is divided by the cell volume since it is applied on a volumetric basis. However, the time is not known nor is the mass flowrate through the cell; hence, by considering the following relationships, the source term is simplified to [19] …”