Mass transfer submerged objects

TABLE 5-24 Mass Transfer Correlations for Flow Past Submerged Objects... 

Mass-Transfer Correlations Because of the tremendous im-ortance of mass transfer in chemical engineering, a veiy large num-er of studies have determined mass-transfer coefficients both empirically and theoretically. Some of these studies are summarized in Tables 5-17 to 5-24. Each table is for a specific geometry or type of contactor, starting with flat plates, which have the simplest geometry (Table 5-17) then wetted wall columns (Table 5-18) flow in pipes and ducts (Table 5-19) submerged objects (Table 5-20) drops and... 

This result suggests diet the mass transfer coefficient varies as Djg, a result intermediate to those of the film theory and tha panetration theory. In fact, the j power dependence of the Sherwood number on the Schmidt number is observed in a number of correlations for mass transfer in turbulent flow in conduits aed for flow about submerged objects. (See Section 2.4-3.)... 

LAMINAR BOUNDARY LAYER MASS TRANSFER AROUND SOLID SPHERES, GAS BUBBLES, AND OTHER SUBMERGED OBJECTS... 

The following information is provided for flow around a spherical submerged object with interphase mass transfer into the passing fluid stream ... 

One should realize that these calculations are based on an expression for Vr which corresponds to potential flow past a stationary nonde-formable bubble, as seen by an observer in a stationary reference frame. However, this analysis rigorously requires the radial velocity profile for potential flow in the Uquid phase as a nondeformable bubble rises through an incompressible liquid that is stationary far from the bubble. When submerged objects are in motion, it is important to use liquid-phase velocity components that are referenced to the motion of the interface for boundary layer mass transfer analysis. This is accomplished best by solving the flow problem in a body-fixed reference frame which translates and, if necessary, rotates with the bubble such that the center of the bubble and the origin of the coordinate system are coincident. Now the problem is equivalent to one where an ideal fluid impinges on a stationary nondeformable gas bubble of radius R. As illustrated above, results for the latter problem have been employed to estimate the maximum error associated with the neglect of curvature in the radial term of the equation of continuity. 

Answer For boundary layer mass transfer across solid-liquid interfaces, = I and y =. In the creeping flow regime, z = - This problem is analogous to one where the solid sphere is stationary and a hquid flows past the submerged object at low Reynolds numbers. 

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