Packings void fraction

Reynolds number for gas S = length of corrugation side Uge = effective velocity of gas Ug = superficial velocity of gas Ui = superficial velocity of liquid Ap = pressure drop per unit packed height e = packing void fraction 0 = angle of flow channel (from horizontal) fi = viscosity p = density... 

Catalyst particle size 0.5-1 mm Packing void fraction 0.75... 

Packing void fraction and porosity Experiment + moment analysis + parameter estimation e and et Experiment + moment analysis et, set e et (from manufacturer), set e... 

Values of a and Ch are characteristic of the particular type and size of packing, as listed together with packing void fraction, e, and other packing constants in Table 4.1. Because the specific liquid holdup in the preloading region is constant, equation (4-3) does not involve gas-phase properties or gas velocity. 

Packing Void Fraction Bulk Weight Ib/te Single Phase Pressure Drop (in. H20/ft) Gt = 900 Gt = 1600 ... 

E - packing void fraction, m /m raiual to the free column cross-SKtion, m /m K - enhancement factor (coefficient of acceleration as a results of chemical reacticMi) ... 

Several densities and void fractions are commonly used. For adsorbents, usually the bulk density p, the weight of clean material per unit bulk volume as packed in a column, is reported. The dry particle density Pp is related to the (external) void fraction of packing by... 

Crushing, selective particle size packing or hydraulic compaction can be used to reduce interparticle void space and increase the bulk density within the storage tank to approach the particle density of the carbon. Even with these extreme methods of packing, the fraction of the vessel which is micropore is never greater than 0.50 for any commercial carbon, considerably short of the 0.70 which is necessary for 170 V/V storage. 

Besides the void fraction a very important parameter is the size of the particles. Using a simple cubic model for packing spherical balls, which represent the particles, we get the following expression for the void fraction... 

A typical packed tower design has more than 50% of open tower cross-section, with the void fraction of a packed tower being higher at around 90% of tower volume, resulting in the following ... 

These data are t aluable for determining the total weight of liquid held in the packing, and also the void fraction, in an operating column, e is the void fraction of the dry packing minus the total hold-up, hj. 

Void fraction of packing under operating conditions = void fraction of dry packing minus the total hold-up (not the free volume of dry-packing)... 

The other important factor is a, the geometric surface area exposed to gas per volume of reactor, which depends on the void fraction and the dimension of the packing. The product of the transfer coefficient and the surface-to-volume ratio governs the rate of heat and mass transfer per... 

The void fraction should be the total void fraction including the pore volume. We now distinguish Stotai from the superficial void fraction used in the Ergun equation and in the packed-bed correlations of Chapter 9. The pore volume is accessible to gas molecules and can constitute a substantial fraction of the gas-phase volume. It is included in reaction rate calculations through the use of the total void fraction. The superficial void fraction ignores the pore volume. It is the appropriate parameter for the hydrodynamic calculations because fluid velocities go to zero at the external surface of the catalyst particles. The pore volume is accessible by diffusion, not bulk flow. 

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