Search results
Results from the WOW.Com Content Network
Mass transfer coefficients can be estimated from many different theoretical equations, correlations, and analogies that are functions of material properties, intensive properties and flow regime (laminar or turbulent flow). Selection of the most applicable model is dependent on the materials and the system, or environment, being studied.
Here, is the overall mass transfer coefficient, which could be determined by empirical correlations, is the surface area for mass transfer (particularly relevant in membrane-based separations), and ˙ is the mass flowrate of bulk fluid (e.g., mass flowrate of air in an application where water vapor is being separated from the air mixture). At ...
Mass transfer is the net movement of mass from one location (usually meaning stream, phase, fraction, or component) to another. Mass transfer occurs in many processes, such as absorption, evaporation, drying, precipitation, membrane filtration, and distillation. Mass transfer is used by different scientific disciplines for different processes ...
This equation permits the prediction of an unknown transfer coefficient when one of the other coefficients is known. The analogy is valid for fully developed turbulent flow in conduits with Re > 10000, 0.7 < Pr < 160, and tubes where L/d > 60 (the same constraints as the Sieder–Tate correlation). The wider range of data can be correlated by ...
For best accuracy, n should be adjusted where correlations have a different exponent. We can take this further by substituting into this equation the definitions of the heat transfer coefficient, mass transfer coefficient, and Lewis number, yielding: = =
This is known as the charge transfer rate. The second is the rate at which reactants are provided, and products removed, from the electrode region by various processes including diffusion, migration, and convection. The latter is known as the mass-transfer rate [Note 1]. These two rates determine the concentrations of the reactants and products ...
For complex systems, such as electrolytic solutions, and other drivers, such as a pressure gradient, the equation must be expanded to include additional terms for interactions. A major disadvantage of the Maxwell–Stefan theory is that the diffusion coefficients , with the exception of the diffusion of dilute gases, do not correspond to the ...
In convective heat transfer, the Churchill–Bernstein equation is used to estimate the surface averaged Nusselt number for a cylinder in cross flow at various velocities. [1] The need for the equation arises from the inability to solve the Navier–Stokes equations in the turbulent flow regime, even for a Newtonian fluid .