John D. Paccione

Modeling and measurement of the effective drag coefficient in decelerating and non-accelerating turbulent gas—solids dilute phase flow of large parti

Abstract The one-dimensional modeling of decelerating and non-accelerating turbulent dilute phase flow has been studied by transporting 1 mm glass spheres with

Effect of particle diameter, particle density and loading ratio on the effective drag coefficient in steady turbulent gas-solids transport

Abstract Extending earlier work [1], effective drag coefficients for particles in steady turbulent gas-solids transport in a 28.45 mm vertical transport pipe 5.49 m long have been determined for 1 and 2 mm glass spheres and 1.99 mm rapeseed. The data are well represented by the equation C dn = 4 3 ∈Ar Re p 2 so that in the range studied, Cdn increases proportionally with dp and (ϱ p −ϱ f ) ϱ f and is essentially independent of loading ratio. Slip Reynolds numbers ranged from 469 to 1847 and pipe Reynolds numbers from 21400 to 33600. Loading ratios were varied from 7.03 to 45.4. The data reported here for Cdn fall below the standard drag curve as the slip velocity is increased due to the effects of freestream turbulence. The effect of neglecting particle-wall friction in our two-fluid model on the calculation of the solids fraction, slip velocity and drag coefficient is discussed.

A pseudo-Stokes representation of the effective drag coefficient for large particles entrained in a turbulent airstream

Abstract Recently published data by Littman et al., Powder Technol., 77 (1993) 267 and Powder Technol., 84 (1995) 49, for the effective drag coefficient in the vertical pneumatic transport of 1 and 2 mm glass and 1.99 mm rapeseed particles are represented by the pseudo-Stokes equation, C d = 24/ R e pc . The effects of freestream turbulence are represented using Lees ( Int. J. Multiphase Flow, 13 (1987) 247) correlation for the apparent turbulent kinematic viscosity of the fluid felt by the particles in a suspension flow. These results not only confirm the importance of freestream turbulence in lowering the drag coefficient for those particles significantly below that on the standard drag curve but suggest that the turbulence intensities are high enough to largely or completely eliminate the particle wake. These low drag coefficients increase corresponding slip velocities above terminal suggesting that solids residence times in the pipe are much higher than predicted by use of the standard drag curve.

Analytical Determination of the Baffle Factor for Disinfection Contact Systems Based on Hydraulic Analysis, Disinfection Kinetics, and Ct Tables

AbstractThe Surface Water Treatment Rule (SWTR) specifies the Ct (disinfectant concentration×time) calculation as the means by which disinfection efficacy, and therefore compliance, is determined. Baffle factors are used to scale the theoretical residence time of the water in a vessel to obtain the amount of time used for the Ct calculation. The baffle factor formulation has been left to guidance and has been a topic of discussion. In this work, an extended baffle factor formulation is developed using disinfection contact system performance models that incorporate the methods imposed by and built into the SWTR. The performance models are based on chemical reactor analyses that have been validated extensively in the literature. A comparison made between the extended baffle factor formulation and methods that use hydraulic considerations alone shows that failing to account for the entire residence time distribution and disinfection kinetics can lead to significant errors. The result of this work is a baffle...

Targeting Maximum Reaction Conversion at Minimum Total Annualized Cost for a Spouted Fluidized Bed with a Draft Tube

The spouted fluidized bed with a draft tube (SFBDT) has been extensively studied and has a number of applications. However, future attention and studies are expected to focus on applications which involve reacting systems. In this work, we present the modeling equations for a SFBDT that describes and characterizes its behavior. These modeling equations, combined with the reaction kinetics and mass balance equations, provide an accurate mathematical description of the phenomenon. Here, we consider contact between a reactant solid-phase, consisting of uniformly sized particles (beads), with an annular reactant liquid phase side stream flowing through the bed. The hydrodynamic patterns between reactant fluid and beads are modeled as back-mixing flow. In addition, we assume the reactions are . A is the bead carrying unreacted chemical. B is the bead carrying desired product. C is the bead carrying product which loses its function. Models characterizing the reactions are presented and combined with modeling equations of SFBDT. Here we present an optimized SFBDT system where we achieve the maximum product concentration for a given set of reactants at the lowest cost. 1 2 k k A B C