Spout nozzle velocity

Figure 19. Solids circulation rate as a function of spout nozzle velocity for various entrainment lengths...

Velocity in a down spout Characteristic velocity Velocity through an orifice or nozzle... 

Uy superficial jet nozzle velocity (w) bed voidage at the wall in conical spouted... 

Ahos - Isentropic total-to-total enthalpy drop D2 - Diameter of turbine wrtieel U2 - Blade tip speed = x N D2 Co - Spouting fluid velocity (nozzle outlet)... 

It has been claimed that the magnitude of this stress in some blood vessels is similar to the shear stress at the nozzle of the famous water fountain in Lake Geneva. The fountain spouts 500 litres of water per second with a mean velocity of 200 km/hr which reaches a height of about 140 m the shear stress at the nozzle is about 40 dynes/cm . 

A spouted bed process is similar to the Wurster process. The principal difference is that an air velocity differential needed to properly circulate particles through the nozzle spray zone is created by a tapered coat chamber design rather than an air distribution pattern created by the fluidization plate. An illustration of a spouted bed is provided in Figure 7.5. Process ciir entering through the fluidization plate passes upward past the nozzle, Ccurying particles with it as they feed in from the periphery of the plate and lower chamber. Spray is directed upward with the direction of pmticle flow. Vertical increase in cross-sectional area reduces the air and particle velocity to allow pmticles... 

Similar values were attained in a spouted bed of industrial scale. For example industrial-scale drying of 200 kg/h Z-type black dye resulted in 11.8 kg gas/kg water and 4600 kJ/kg water the diameter of the dryer was 1.6 m. The inlet temperature of 330°C in the spouted bed decreased to 100°C in the process of drying. The initial moisture coutent of the wet material was 5%. Gas velocity in the gas inlet nozzle was 30 and 0.75 m/s in the annulus. Pressure drop over the 400-mm bed at this velocity was 5 kPa... 

Drying of liquid and pasty materials on the surface of heated inert particles is one of the newer drying techniques. The inert material serves not only as a carrier for the liquid film but also as a heat transfer medium. The size of the inert particles may be from 20 to 40 times larger than that of the dispersed material dried, which allows for higher gas velocity and thus increased dryer productivity. Moreover, intensive motion of the inert particles (e.g., in fluid or spouted beds) results in good dispersion of the liquid feed, so coarse spray nozzles can be used. As compared to the standard spray dryer, the use of a fluid bed of inert particles to dry slurries results in 15- to 17-fold higher volumetric ev oration rates under identical thermal conditions. Table... 

Not all beds are spoutable. For beds with the ratio of nozzle diameter to column diameter D JD, above a certain critical value, there is no spouting regime. The bed transfers from the fixed bed directly into the fluidized state with increasing gas velocity. To achieve a stable nonpulsating spouted bed, the nozzle-to-parti-cle-diameter ratio, DJd, should be less than 25 or 30. There are also the so-called minimum spouting... 

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