Particles terminal velocity

Temperature rise, centrifugal pump, 207-209 Terminal particle velocity, 228, 230 Particles, different densities, 238 Single spheres, 274 Solids in air, 237 Solids in water, 237 Test pressure, piping, 18 Thickeners and settleix/decanters, Decanter, 242... 

A slip takes place between the gas and the particle as the free space between the gas molecules becomes comparable to the particle size. This is accounted for in the drag law by multipljdng the terminal particle velocity... 

Fig. 14. Drag coefficient for terminal settling velocity correlation (single particle) where A represents Stokes law B, intermediate law and C, Newton s...

Fluidized This is an expanded condition in which the sohds particles are supported by drag forces caused by the gas phase passing through the interstices among the particles at some critical velocity. It is an unstable condition in that the superficial gas velocity upward is less than the terminal setting velocity of the solids particles the gas... 

Dilute This is a fully expanded condition in which the solids particles are so widely separated that they exert essentially no influence upon each other. Specifically, the solids phase is so fuUy dispersed in the gas that the den sity of the suspension is essentially that of the gas phase alone (Fig. 12-29). Commonly, this situation exists when the gas velocity at all points in the system exceeds the terminal setthng velocity of the solids and the particles can be lifted and continuously conveyed by the gas however, this is not always true. Gravity settling chambers such as prilling towers and countercurrent-flow spray diy-ers are two exceptions in which gas velocity is insufficient to entrain the sohds completely. 

Gravity Settlers Gravity can act to remove larger droplets. Set-thng or disengaging space above aerated or boiling liquids in a tank or spray zone in a tower can be very useful. If gas velocity is kept low, all particles with terminal settling velocities (see Sec. 6) above the gas... 

Ut Terminal settling velocity of particle under action of gravity m/s ft/s ft/s... 

From the standpoint of collector design and performance, the most important size-related property of a dust particfe is its dynamic behavior. Particles larger than 100 [Lm are readily collectible by simple inertial or gravitational methods. For particles under 100 Im, the range of principal difficulty in dust collection, the resistance to motion in a gas is viscous (see Sec. 6, Thud and Particle Mechanics ), and for such particles, the most useful size specification is commonly the Stokes settling diameter, which is the diameter of the spherical particle of the same density that has the same terminal velocity in viscous flow as the particle in question. It is yet more convenient in many circumstances to use the aerodynamic diameter, which is the diameter of the particle of unit density (1 g/cm ) that has the same terminal settling velocity. Use of the aerodynamic diameter permits direct comparisons of the dynamic behavior of particles that are actually of different sizes, shapes, and densities [Raabe, J. Air Pollut. Control As.soc., 26, 856 (1976)]. 

Free-falling diameter Also known as sedimentation or Stokes diameter, the diameter of a sphere with the same terminal settling velocity and density as a nonspherical or irregular particle. 

Absolute Gas Temperoture, F ab5.,or R = Terminal Settling Velocity of Particle Under Action of Grovify jff./sec,... 

Terminal Settling Velocity of Particle os Colculoted from Stokes Low, ft./sec. 

Figure 4-9 is convenient for quick checks of terminal settling velocities of solid particles in air and in water [23]. 

Figure 4-8. Terminal settling velocity of particles in water. By permission, Lapple, C. E., Fluid and Particle Mechanics, 1st Ed., University of Delaware, Newark, 1954.

Vo = Average velocity of gas, feet/sec. u, = Terminal settling velocity of particle under action of gravity, feet/sec. gL = 32.2 feet/sec. ... 

Terminal setding velocity determined by Stokes Law, of particle under acuon of gravity, ft/sec... 

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