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The Damköhler numbers (Da) are dimensionless numbers used in chemical engineering to relate chemical reaction timescale to other phenomena occurring in a system. It is named after German chemist Gerhard Damköhler, 1908-1944.
Additional recommended knowledge
There are several Damköhler numbers, and their definition varies according to the system under consideration.
For a general chemical reaction A → B of n-th order, the Damköhler number is defined as
and it represents a dimensionless reaction time. It provides a quick estimate of the degree of conversion (X) that can be achieved in continous flow reactors.
Generally, if Da<0.1 then X<0.1 similarly if Da>10 then X>0.9
In continuous or semibatch chemical processes, the general definition of the Damköhler number is defined as:
For example, in a continuous reactor, the Damköhler number is:
where τ is the mean residence time or space time.
In reacting systems that include also interphase mass transport, the second Damköhler number (DaII) is defined as the ratio of the chemical reaction rate to the mass transfer rate
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Damköhler_numbers". A list of authors is available in Wikipedia.|