Abstract
The results of theoretical studies of the hydrodynamic laws of fluid flow and changes in the characteristics of the wall layer of the flow in tubular mixing devices, used in technological processes of reagent-based wastewater treatment, are presented. A mathematical relation, which allows determining the critical value of the Reynolds number Re, at which the regime of fluid movement in a tubular mixing device passes into the region of the quadratic resistance law of rough channels with the maximum degree of turbulence of flows, is obtained. It is shown that the main technical characteristics of tubular mixing devices are: the magnitude of the pulsation component of the local velocity ∆υl (m/s) and the value of the turbulent diffusion coefficient DT (m2/s) in the wall region of the turbulent fluid flow. Mathematical relations, which allow calculating the magnitude of the pulsation component of the local velocity and the turbulent diffusion coefficient in the wall region of the fluid flow in the pressure channels of circular cross section, are obtained. Using the proposed calculation technique will allow to optimize the operation regime of tubular mixing devices.
Highlights
Reagent treatment of the fluid flow is widely used in the wastewater treatment technology, in particular, using reagent coagulation of colloidal and fine impurities (Adelshin and Potekhin 1997).In the process of reagent coagulation, a quick and uniform distribution of coagulant reagents in the treated volume of wastewater is required to ensure the contact of the maximum amount of dispersed pollution particles with intermediate products of coagulant hydrolysis
By analogy with formula (9), which is valid in the case of a laminar regime of fluid movement, we assume that using this Reynolds number, the magnitude of the pipe friction factor λCT at the critical point of a turbulent fluid flow transition into the region of the quadratic resistance law can be determined by the following formula: CT =
The first assumption describes the moment of time when the formation of turbulent eddies in the transition sublayer occurred, which leads to its destruction and an increase in the local velocity at the boundary of the wall sublayer
Summary
Reagent treatment of the fluid flow is widely used in the wastewater treatment technology, in particular, using reagent coagulation of colloidal and fine impurities (Adelshin and Potekhin 1997). In the process of reagent coagulation, a quick and uniform distribution of coagulant reagents in the treated volume of wastewater is required to ensure the contact of the maximum amount of dispersed pollution particles with intermediate products of coagulant hydrolysis. There are bladed, turbine or propeller agitators mounted on a vertical shaft in mechanical mixing devices, which are driven by an electric motor (Adelshin and Potekhin 1997). Unlike mechanical ones, do not require the use of additional energy supplied to an electromechanical mixing device; they are distinguished by structural simplicity and operational reliability. In the hydraulic-type mixing devices, there is a principle of utilization of the own energy
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