What is mass transfer

Mass transfer and reaction rate

In multi-phase systems, the mass transfer between phases is crucial for scale-up and reactor performance. Equally crucial is the transfer of mechanical force from the stirrer to the fluid; it affects the degree of dispersion of the various phases and the corresponding mass transfer between them.In a process with only one liquid phase, in which a rapid reaction results in the formation of Can cause competition and by-products, the level of fluid turbulence can affect the selectivity and yield of the overall chemical process.

In such systems, the level of turbulence and the process performance are determined by the mechanical performance per unit volume. The general performance curve of the stirrer results from a given stirrer and a specific stirred tank reactor geometry. This characterizes the stirring force transferred to the liquid phase.

Typical performance curves (comparison of the coefficient of performance (Np) and Reynolds number (Re) in the diagram on the right) are independent of the reactor volume and therefore facilitate scale-up and system characterization. The dimensionless Reynolds number indicates whether a reactor fluid flows laminar or turbulent. It indicates the ratio of the inertia forces (stirring forces on the fluid) to the viscosity forces of the process fluid. If the viscosity forces predominate and Re < 10,="" wird="" die="" strömung="" von="" der="" fluidviskosität="" bestimmt="" und="" das="" strömungsmuster="" ist="" laminar.="" überwiegen="" die="" trägheitskräfte="" und="" ist="" re=""> 2,000-10,000, the flow is independent of the viscosity and proportional to the density. Hence the flow pattern is turbulent. The exact transition point to the turbulent flow pattern depends on the reactor geometry and possibly on elements that cause turbulence, for example flow disruptors. With laboratory reactors, fluids and the design of the reactor and stirrer can be tested quickly.