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The electrochemical technique was used to investigate the effect of surface corrugations on the rate of mass and heat transfer (by analogy) in a stirred tank reactor. Impeller rotational speed, impeller shape, corrugation peak to valley height, and corrugation orientation (horizontal or vertical) were among the variables investigated. Depending on the operating conditions, surface corrugation increased the volumetric mass transfer coefficient by a factor ranging from 1.16 to 3.7. Mass transfer data were correlated with dimensionless correlations of an average deviation of ±4.2 and ±5.49 for radial and axial flow turbines, respectively. The significance of the dimensionless equations in determining the rate of heat transfer from the corrugated wall to a cooling jacket was emphasized. [ABSTRACT FROM AUTHOR]

The rate of diffusion-controlled corrosion of an annulus under swirl flow was studied by measuring the limiting current of the cathodic reduction of potassium ferricyanide depolarizer in the presence and absence of polyox WSR-301 drag-reducing polymer. It was found that the rate of diffusion-controlled corrosion of the inner cylinder of the annulus increases with increasing swirl flow solution velocity and decreases with increasing the active height of the cylinder. The data in the absence of polymer (blank solution) under swirl flow were fitted by a dimensionless equation. The importance of this equation in predicting the rate of diffusion-controlled corrosion and the corrosion allowance during the design of the swirl flow equipment was highlighted. For a given set of conditions, the rate of accelerated swirl flow corrosion was much higher than that of axial flow. Drag reducing polymer was found to inhibit the rate of diffusion-controlled corrosion by a maximum of 23%, if other benefits of the polymer are considered such as the decrease in the shear stress and the associated decrease in the erosion-corrosion tendency besides the decrease in pressure drop and pumping power requirement it may be concluded that the use of drag-reducing polymers in industry is worthwhile. [ABSTRACT FROM AUTHOR]

Rates of mass and heat transfer (by analogy) at the surface of a helical coil imbedded in a fixed bed of inert cylindrical packing were measured under upward two-phase (gas-liquid) flow by the electrochemical technique. The effects of geometrical and hydrodynamic parameters were considered. The performance of cylindrical packing was compared with that of Raschig rings and spheres. The analogy between heat and mass transfer was discussed and the importance of the present study for the design and operation of heterogeneous reactors that need rapid cooling in case of highly exothermic reactions was highlighted. [ABSTRACT FROM AUTHOR]

Effect of upward two-phase gas-liquid flow on the rate of liquid-solid mass transfer in a bubble column equipped with a horizontal tube bundle was studied by measuring the rate of the diffusion-controlled dissolution of copper in an acidified K2Cr2O solution. Variables studied included gas (nitrogen) flow rate, liquid flow rate, and the number of tube arrays. Data were successfully correlated by a dimensionless equation. The presence of surfactants reduced the rate of mass transfer by 3–17% depending on flow rates. The importance of the tube array as a built-in heat exchanger and a catalyst support was highlighted. [ABSTRACT FROM AUTHOR]

Rates of mass transfer in a spiral coil were measured by a technique involving the diffusion-controlled dissolution of copper in acidified dichromate. The variables studied were solution velocity, spiral tube pitch, and physical properties of the solution. The data were correlated by the equation S h = 0.189 S c 0.33 D e 0.55 P d 0.29 For a given set of conditions, the mass transfer coefficient predicted from the above equation was found to be much higher than that of the straight tube. Comparison of the ratio between the mass transfer coefficient and pressure drop for spiral tubes and straight tubes has revealed that k Δ p for spiral tubes is much higher than that of a straight tube under the present range of conditions. The possibility of using the above equation in predicting the rate of diffusion-controlled corrosion and the corrosion allowance needed to design a spiral tube heat exchanger was noted. Other possible applications in heterogeneous reactor design and membrane processes are reported. [ABSTRACT FROM AUTHOR]