Packed bed

About: Packed bed is a research topic. Over the lifetime, 8996 publications have been published within this topic receiving 158610 citations.

Viscous flow in multiparticle systems: Slow motion of fluids relative to beds of spherical particles

Abstract: A mathematical treatment is developed on the basis that two concentric spheres can serve as the model for a random assemblage of spheres moving relative to a fluid The inner sphere comprises one of the particles in the assemblage and the outer sphere consists of a fluid envelope with a “free surface” The appropriate boundary conditions resulting from these assumptions enable a closed solution to be obtained satisfying the Stokes-Navier equations omitting inertia terms This solution enables rate of sedimentation or alternatively pressure drop to be predicted as a function of fractional void volume Comparison of the theory is made with other relationships and data reported in the literature Of special interest is its close agreement with the well known Carman-Kozeny equation which has been widely used to correlate data on packed beds as well as sedimenting and fluidized systems of particles This is remarkable in view of the fact that the force on each particle in a packed bed can be up to several hundred times that exerted on a single particle in an undistrubed medium

Mechanical Packing of Spherical Particles

Abstract: An idealized experimental study of particle packing was made. Spherical metal shot of several discrete, narrow size ranges was efficiently packed in glass containers by mechanical vibration. Packing arrangements and the dynamic process of packing were studied visually. One-size spheres packed in an orthorhombic arrangement with a density 62.5% of theoretical density. Forming of high-density multicomponent packings was shown to require at least a sevenfold difference between sphere sizes of the individual components. A quaternary packing with a density 95.1% of theoretical density was formed from spheres with diameter ratios 1:7:38:316 and volume compositions 6.1:10.2:23.0:60.7%, respectively. Such packings could be poured from their glass containers, thus proving that effective mechanical packing is simply an efficient arrangement of spheres of prescribed sizes and proportions. The significance and utility of this work to the ceramic and other industries is discussed.

Studies on effective thermal conductivities in packed beds

Abstract: Applying both their own assumptions and the mechanism of lateral mixing proposed by Ranz (20), the authors obtained theoretical formulas for effective thermal conductivities ke in packed beds. Previously reported experimental data were analyzed with these equations, and the usable data for predicition of ke were shown. In order to see the influence of both packing characteristics and temperature on the effective thermal conductivities, experimental data were obtained with air for beds with various kinds of packing, i.e., iron spheres, porcelain packings, cement clinker, insulating fire brick, and Raschig rings. Correlation of these data with Equation (15) showed that this equation adequately expressed the heat transfer mechanisms in packed beds with motionless gases, especially at hight temperatures.

Ultrahigh-pressure reversed-phase liquid chromatography in packed capillary columns.

Abstract: The use of extremely high pressures in liquid chromatography can improve the efficiency and reduce analysis time for columns packed with small particles. In this work, fused-silica capillaries with inner diameters of 30 μm are slurry packed with 1.5 μm nonporous octadecylsilane-modified silica particles. These columns are prepared in lengths up to 66 cm with packing pressures as high as 4100 bar (60 000 psi). Near the optimum flow rate, columns generate as many as 300 000 theoretical plates for lightly retained compounds (k‘ < 0.5) and over 200 000 plates for more retained compounds (k‘ ≈ 2). These translate to plate heights (Hmin) as low as 2.1 μm. The pressures required to run at optimum flow rates are on the order of 1400 bar (20 000 psi). Analysis times at these pressures are on the order of 30 min (k‘ ≈ 2) and can be reduced to less than 10 min at higher than optimum flow rates. Capacity factors are observed to increase linearly with applied pressure.