Submerged jets

Morinda citrifolia submerged jet turbulent membrane integrity morphology non-growth [59, 129,130]... 

Fig. 3. Schematic diagram of the submerged jet apparatus. From reference [59], reproduced with permission. 1998, Wiley-Liss, Inc, a subsidiary of John Wiley Sons, Inc...

Fig. 6. Variation in chain death rates with energy dissipation rate in submerged jet flow [130]...

The attrition rate, i.e., the rate of generation of fines, 0-d microns, at the submerged jets in a fluidized bed, tends to fall off asymptotically with time to a steady-state rate as shown in Fig. 9. Initially the attrition rate is high due to the wearing off of angular comers. Typically, it takes long time, hours to days, for the particles to reach steady-state (equilibrium) where the particles tend to be more rounded. For most catalytic fluidized bed processes, the bed operates at equilibrium. That means the most significant part of the attrition rate curve is the steady-state rate. 

Figure 9. Typical attrition rate curve for submerged jets.

Example 2. For the conditions of Example 1 of perforated plate design, estimate the submerged jet height and particle-attrition rate in the fluidized bed. 

Figure 2. Time dependence of catalyst attrition in a submerged jet test (D, = 0.05 m, uor = 100 ms-1, dor = 2 mm, HA-HPV is a fresh catalyst whereas FCC is a spent cracking catalyst from a commercial unit. (From Werther and Xi, 1993.)...

Friability tests can be used for various purposes. They are widely used in quality control. Here, samples of produced material are subjected to a more or less arbitrary but well defined stress. The attrition extent is assessed by comparison with a standard value and a decision is reached whether the material meets the standard. Moreover, friability tests are often used for comparison of different materials to select the most attrition-resistant one. This is a usual procedure in the case of catalyst development. For example, Contractor et al. (1989) tested anew developed fluidized bed VPO-catalyst in a submerged-jet attrition test (described below). Furthermore, the specific attrition rate of a material in a certain process can be roughly estimated by friability tests. In this case the stress must be similar to that occurring in the process and the obtained degradation extent must be compared with those of other materials from which the process attrition rate is known. 

Both devices described above were developed in order to test the friability of fluid-cracking catalysts. Nowadays the application of these or similar tests is a common procedure in the development of fluidized bed catalysts. Contractor et al. (1989), for example, used a submerged-jet test to compare the attrition resistance of newly developed VPO catalysts. In fact, such tests can be applied to any type of fluidized bed processes. Sometimes they have to be slightly modified to adapt them to the process under consideration. The drilled plate may, for example, be substituted by... 

Case 2 Constant Rayleigh Cross Section - In this case, variations in the Rayleigh scattering intensity are attributed to variations in temperature. A natural compliment to the isothermal mixing investigations identified in Case 1 would be to measure the time-resolved temperature in a submerged jet of heated air. For premixed flames, the variation of Rayleigh intensity is primarily due to variation in temperature, which can vary by a factor of 7. 

Fig. 31. Interfacial area related to jet conditions in the submerged-jet reactor (B30).

P. K. Shukla, Stationary Hemispherical Electrode under Submerged Jet Impingement and Validation of the Measurement Model Concept for Impedance Spectroscopy, Ph.D. dissertation. University of Elorida, Gainesville, FL (2004). 

Bin A.K., Mass transfer into a free liquid surface effected by submerged jets,... 

Now visualize the action of a submerged jet of air in liquid. At very low air flow velocities, the bubbles are large. They rise as independent bubbles at the orifice. When the velocity of air through the orifice increases, the air projects as a cone into the liquid and small bubbles shear off. The maximum velocity is reached when the ratio of absolute hydrostatic pressure outside the orifice divided by the absolute air pressure in the orifice is 0.528. This determines sonic velocity. Four regions of the air cone or jet are conceptually drawn in Fig. 11. Region I is called the potential core of air with a uniform velocity. The outermost annular cone, Region II, is an intermittency zone in... 

Jet flows form a wide class of frequently encountered motions of viscous fluids. In this section we restrict our consideration to steady jet flows of an incompressible liquid in the space filled with a liquid with the same physical properties (such flows are known as submerged jets). We consider the problem about a jet-source in infinite space [26,260] and give some practically important information about the wake structure past moving bodies [3, 427, 501]. 

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