A Shielded Hot-Wire Probe for Highly Turbulent Flows and Rapidly Reversing Flows

Günkel, Alfred A.; Patel, Rajni P.; Weber, M.

doi:10.1021/i160040a015

Cited by 11 publications

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“…The parameters measured were the induced current density, magnetic flux and temperature difference. The velocity was then estimated approximately from the"relation 6) ρ…”

Section: Literature Surveymentioning

confidence: 99%

“…For the single channel units four different geometries were tested in a vertical model.The velocities, (calculated from the temperature measurements) showed that the most intense flow around the loop was achieved when the top half of the channel had one sharp corner of an angle, 30° < a < 60°, and the bottom half was at a circular shape (see Fig. (1)(2)(3)(4)(5)(6)…”

Section: Literature Surveymentioning

confidence: 99%

“…Alternatively taking the curl of (2)(3)(4)(5)(6)(7)(8)(9) and substituting equations (2)(3)(4)(5)(6), (2)(3)(4)(5) and (2)(3)(4)(5)(6)(7)(8) As it is seen from the system of equation to (2)(3) and (2)(3)(4)(5) to (2)(3)(4)(5)(6)(7)(8)(9)(10) the following physical values, ω, ρ, ν, gß, ΔΤ, L, B 0 , u Q , ο are the parameters characterising the system. Β is a characteristic flux induced in the channel, ΔΤ -TQ -T B , can be taken as the maximum allowed temperature difference between the metal in the channel and in the bath and L is a characteristic length (say the height of the channel).…”

Section: Literature Surveymentioning

confidence: 99%

“…The physical properties of aluminium at 700° C are: (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13) In this case we assume that the length of the channel W = 26 and the metal (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) This shows that although Joule heating is important the buoyancy is of secondary effect in the 'dynamics of the stirring in the channel crosssection.…”

Section: Literature Surveymentioning

confidence: 99%

“…As demonstrated in Section 3•1.2 equations (3.10) and (3)(4)(5)(6)(7)(8)(9)(10)(11)• the axial and transverse components of the time mean electromagnetic body force (J χ Β),can be expressed in terms of flux densities and their gradients, which can be measured using simple search coils and appropriate instrumentation.…”

Section: H22 Calculations Of the The Electromagnetic Body Force And Its Curlmentioning

confidence: 99%

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Magnetohydrodynamics of Channel Induction Furnaces

Moros¹

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Notation Introduction 1.1 Principal objectives of this research 1.2 Literature Survey Chapter 2 Nature of electromagnetic stirring in a single phase C.I.F. 2.1 Fundamental equations 2.2 Characteristic parameters and Thermal effects 2.3 Electromagnetic forces in the melt 2.4 The Flow field 17 Chapter 3 Instrumentation 3.1 The Electromagnetic field 3.1.1 Introduction 3.1.2 Estimation of (JxB) and Vx (JxB) for the 2-D symmetric model 3.1.3 Estimation of (JxB) and Vx (JxB) for the axisymmetric model 3.1.4 Search coil 3.1.

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“…The parameters measured were the induced current density, magnetic flux and temperature difference. The velocity was then estimated approximately from the"relation 6) ρ…”

Section: Literature Surveymentioning

confidence: 99%

Section: Literature Surveymentioning

confidence: 99%

Section: Literature Surveymentioning

confidence: 99%

Section: Literature Surveymentioning

confidence: 99%

Section: H22 Calculations Of the The Electromagnetic Body Force And Its Curlmentioning

confidence: 99%

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Magnetohydrodynamics of Channel Induction Furnaces

Moros¹

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Flow phenomena in stirred tanks. Part I. The impeller stream

Günkel

Weber

1975

AIChE Journal

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Flow parameters were measured in a baffled, turbulent, stirred tank agitated by a six-blade, disk style turbine. The working fluid was air. Mean and fluctuating velocities were measured between the blades of the impeller with a probe mounted on the spinning impeller. Mean velocities, turbulent velocities, one-dimensional energy spectra, and Eulerian autocorrelation functions were measured in the impeller stream by using the shielded hot-wire anemometer of Gunkel et al. (1971) which permits the measurement of turbulence parameters in flows of very high turbulence intensity. Reliable impeller pumping capacities were obtained yielding Q r a d / N D 3 = 1.0 at the impeller periphery. An energy balance on a control volume containing the impeller and the impeller stream showed that the energy put into the tank via the impeller appeared as a net efflux of kinetic energy leaving the control volume. Therefore, most of the energy input to the tank is dissipated in the bulk of the tank. SCOPENo progress in the understanding of mixing operations in stirred tanks can be achieved without a better picture of the flow phenomena in stirred tanks. The main objectives of this study were: to measure flow parameters in a turbulent stirred tank, from them to determine how the energy put into the tank was dissipated, and then to derive theoretically supported scale-up procedures for operations in stirred tanks. The achievement of this last objective is of most immediate importance for practical applications.Previous studies on the flow phenomena in the impeller stream of a stirred tank have reported mean velocities, turbulent velocities, one-dimensional energy spectra, and correlation functions (Kim and Manning, 1964;Bowers, 1965;Cutter, 1966; Sat0 et al., 1967;Mujumdar et al., 1970;Rao and Brodkey, 1972;Cho et al., 1971). The main shortcoming of these studies is the poor precision of the experimental techniques which were not suitable for the high turbulence intensities (up to Svo)found in stirred tanks. Nevertheless, Cutter (1966) concluded that 70% of the energy put into the tank was dissipated within the impeller and the impeller stream, and only 30y0 was dissipated in the bulk of the tank. In the first part of the present paper, accurate flow parameters are reported in the impeller stream from a six-blade, dipk style turbine. An energy balance is then used to determine the amount of energy dissipated in the impeller and the impeller stream. CONCLUSIONS A N D SIGNIFICANCEA very complete picture of the flow pattern in the neighborhood of a six-blade, disk style turbine impeller has been obtained. For the first time velocities between the blades of a rotating impeller have been measured. These measurements indicated that four vortices are present between each pair of blades, two above and two below the disk.Mean velocity profiles in the impeller stream showed a jet like behavior, with the impeller stream entraining fluid as it traveled from the periphery of the impeller to the tank wall. Integration of the velocity profiles yielded ...

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Flow phenomena in stirred tanks. Part II. The bulk of the tank

Günkel

Weber

1975

AIChE Journal

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O r a d p r e sFig. A2. Velocities and angles used for calculating of the energy flux through control surface 1. tropic at any z in the impeller stream at s = 7 cm: Incorporating these simplifications and neglecting fluctuating velocities raised to the power 3, we get 11 = nrlp j'Ila [ ( ~sres + ~v r e s u2r,~) COST -2 T J r e s K s s i n 7 dz (A16)The flux of kinetic energy through control surface 2 was determined similarly by assuming that uraa was negligible and that the flow was isotropic: r e s , a t + m r e s , a t y z r e s , a t ) c0s-C-2f7res,at&es,at sin 71 rdr (A17) CTres,,t is the sum of the velocity components v,, and ntan, and ure7,,,t is the fluctuating velocity in direction of Ures,at. The -/ Fig. A3. Velocities and angles used for calculating the energy flux through control surface 2.angles and velocity components are shown in Figure A3. All the terms in Equations (AlG) and (A17) were obtained from measured velocities. The control surfaces were set at s = 7 cin and z2 = t 3.75 cm for the data presented in Tahle 2 . Part II. T h e Bulk of the TankTurbulence parameters were measured in the bulk of turbulent stirred tanks of 45.7 and 91.4 cm diameter with air as the working fluid. Three types of turbine impellers were studied ranging in diameter from 22.8 to 45.7 cm. The turbulence in the bulk of the tank was essentially homogeneous and isotropic. The normalized one-dimensional energy spectra and the Eulerian autocorrelation functions were approximately the same throughout the tank and for all tanks, impellers, and operating conditions. The space averaged turbulent velocities were correlated by using the turbulent energy equation. A transformation of the measured spectra from the frequency space to the wave number space was accomplished. Integration of the dissipation spectra in the wave number space confirmed that most of the energy input is dissipated in the bulk of the tank through the turbulent motion. The results were extended to low viscosity liquid systems and used to interpret the data on mass transfer from suspended particles.

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A Shielded Hot-Wire Probe for Highly Turbulent Flows and Rapidly Reversing Flows

Cited by 11 publications

References 4 publications

Magnetohydrodynamics of Channel Induction Furnaces

Magnetohydrodynamics of Channel Induction Furnaces

Flow phenomena in stirred tanks. Part I. The impeller stream

Flow phenomena in stirred tanks. Part II. The bulk of the tank

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