Showing papers in "Industrial & Engineering Chemistry Fundamentals in 1962"

Settling Rates and Sediment Volumes of Flocculated Kaolin Suspensions

Abstract: HE KINETICS of sedimentation of particulate solids in liquid T m e d i a and the structural and rheological characteristics of the resulting sediments are of great importance to a broad segment of the chemicals processing and process metallurgical industries. Although sedimentation phenomena have been subjects of research for many decades, and much insight has been gained into the hydrodynamics of sedimentation processes, relatively little is yet known of the role of particleparticle attractive forces in settling and sediment consolidation. The object of this investigation, therefore, was to study the sedimentation behavior of aqueous suspensions of a solid (kaolin) whose surface characteristics are well enough understood to allow analysis and interpretation of sedimentation data in terms of particle-particle interactions. Most previous studies of settling rates have pertained to suspensions of dispersed, nonattracting particles, rather than to flocculated suspensions. In general, these have been attempts to extend Stokes’ law to cover nonspherical particles (7 , 3, 20), to allow for the effect of particle concentration upon settling rate (70, 77, 77, 20), or to calculate the wall effect for settling in containers of finite size (77). The first general study of flocculated suspensions was by Coe and Clevenger (4), who described the various concentration zones which exist within a settling suspension, and who observed that the upward flow of displaced supernatant was a special case of pore flow. Wadsworth and Cutler (22) studied the effects of flocculating agents upon the settling rates of kaolin suspensions. Smellie and La Mer (72, 79) also studying flocculated kaolin suspensions, sbggested that settling rates could be correlated using the Darcy filtration equation to predict the flow rate of displaced supernatant, and proposed an

Natural Convection in Horizontal Concentric Cylindrical Annuli

Abstract: The problem of steady, laminar natural convection between horizontal concentric circular cylinders was attacked numerically via detailed difference equation approximations for the differential equations of conservation. No terms were eliminated by boundary layer arguments. The problem was solved with machine language on an IBM 650 digital computer for several diameter ratios and several Grashof numbers at a Prandtl number of 0.714. Computed results agree well with experiments reported in the literature. In the appropriate limiting case, the computed results also accord with an analytical derivation for creeping flow.

A Quenching Theory for Transition Boiling

Abstract: A quenching theory of transition boiling is proposed, which is consistent with Berenson's data. An interesting result is that the thermal boundary layer in the liquid contacting the surface is very much larger than the critical bubble radius for nucleation.