Stanton number, definition

For tubes the ratio of volume to surface area is geometrically fixed and equal to a quarter of the tube s diameter. Taking this into consideration a special definition is obtained for the Stanton number of the PFTR... 

When setting up the mass balance the Damkoehler number was referenced to the final reaction volume, this way enabling an easier comparison with other ideal reactors and a convenient calculation of SBR phase and post reaction batch phase. This shall be adopted for the definition of the Stanton number. 

At this point it proves to be helpful to make use of the special definition of the Stanton number for cooled tube reactors introduced in Section 4.1, Equ. (4-54), in order to describe the second requirement for T. ... 

The major problem is determination of heat and mass transfer coefficients. Similitude theory allows the definition Of two dimensionless coefficients including h. and h. These are the so called Nusselt and Stanton numbers given by ... 

Forms of the Peclet number are shown with both column length L and particle diameter dp because both forms are used. It is obviously inportant to know whether L or dp is being enployed in the definition of Pe. Sometimes a dimensionless group called the Stanton number St, the ratio of mass-transfer velocity to flow velocity, is used. 

Heat and mass transfer coefficients are usually reported as correlations in terms of dimensionless numbers. The exact definition of these dimensionless numbers implies a specific physical system. These numbers are expressed in terms of the characteristic scales. Correlations for mass transfer are conveniently divided into those for fluid-fluid interfaces and those for fluid-solid interfaces. Many of the correlations have the same general form. That is, the Sherwood or Stanton numbers containing the mass transfer coefficient are often expressed as a power function of the Schmidt number, the Reynolds number, and the Grashof number. The formulation of the correlations can be based on dimensional analysis and/or theoretical reasoning. In most cases, however, pure curve fitting of experimental data is used. The correlations are therefore usually problem dependent and can not be used for other systems than the one for which the curve fitting has been performed without validation. A large list of mass transfer correlations with references is presented by Perry [95]. 

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