The paper presents an experimental study of suspension flow patterns and velocity field inside two types of circular settling tanks with continuous operation. The two tanks differ in inlet- and outlet configurations. Research was focused on the influence of flow field on the sedimentation efficiency of both settling tanks. Experiment was carried out on a settling tank sections made of plexi-glass that represented radial slices of prototype circular settling tanks. Kinematic flow properties inside settling tank sections were determined by computer-aided visualization in order to analyse the whole instantaneous flow field at once. Sedimentation efficiency was assessed by measurements of inlet- and effluent suspension concentrations. Pronounced density current evolved in both tanks, which under certain conditions enhanced sedimentation. Flow field showed qualitative changes during operation and proved to be significantly dependent on average suspension density in the inner chamber of the settling tank. Some important properties of the flow field could also be reconstructed from the spatial distribution of the remaining sludge. Centrally fed settling tank with peripheral effluent generally performed better in terms of sedimentation efficiency mainly due to insufficient height of the effluent baffle in the peripherally fed settling tank.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 12106523The quality of the end product in mineral wool production depends on the fiberisation process on the spinning machine. An important process variable is the fluctuation of melt mass flow from the melter. A method for measuring melt mass flow, which is based on the measuring the diameter and flow velocity using computer-aided visualization is presented. The velocity of the molten jet onto the surface is measured by a method based on the advection diffusion equation. A sequence of successive flow images was processed to obtain the required unknown terms. Concentration of the passive tracer was acquired through the greyscale intensity on images at chosen measurement points. Standard numerical procedures were applied to obtain spatial- and time derivatives of the passive tracer concentration. The field measurements were performed by comparison with the weight of the final product. The agreement among field measured values and available comparison method is fair.
F.06 Development of a new product
COBISS.SI-ID: 11999003This paper presents a reliable method for accurate non-contact measurements ofvelocity field and longitudinal water surface profiles at model side weir and should prove valuable in investigations of flood overflow structures, which are being designed within the framework of future hydro power plants on the Sava River in Slovenia. We focused on the influence of downstream main channel weir Zg on the lateral discharge Qs over a sharp-crested rectangular side weir. Quantification of velocity fields using visualization method showed that velocities at side weir were not uniform. Longitudinal components of overflow velocities U were greater than corresponding main channel cross section average velocities V, except in stagnation zone that formed at the downstream end of the side weir. Measured side weir discharges were in good agreement with calculated values, using discharge coefficient Cd from the momentum-approach-based equation by May et al. [7] and the energy-approach-based equation by Singh et al. [11]. As an additional result, a new phenomenological model for Cd is proposed to illustrate the influence ofZg on Qs.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 5541729