Semenov number

Semenov number 1 physchem A dimensionless number used in reaction kinetics, equal to a mass transfer constant divided by a reaction rate constant. Symbolized S . Formerly known as Schmidt number 2. se-m3,n6f nom-bor won ... 

In Section 2.5.2, the Semenov diagram was used to show the critical cooling medium temperature. In the same way it allows discrimination of a stable operation conditions from a runaway situation. A stable operation is achieved for a limit value of the Semenov criterion / (also called Semenov number) ... 

In the specific case of chemical drums with a height equal to three times the radius, the Frank-Kamenetskii criterion is 8cri, = 2.37 [1]. A cube with a side length 2ro, can be converted to its thermally equivalent sphere. The Semenov number then becomes... 

In Fig. 4.6, the critical Semenov number given by (4.28) is reported versus the coolant temperature 7[ for different values of 12. Operation is safe when Se < Sec, provided that condition (4.23) is also satisfied. The critical Semenov number decreases as 7j increases, with a slope that increases with 12, and, in the limit S2 -> oo, it reduces to the vertical line Tj = 1 in this case, operation is safe whenever Tto < 7j < 1. Moreover, all curves nearly cross each other at 7] = 1, where their value can be approximated by... 

Fig. 4.6 Critical Semenov number as a function of 7] for different values of Q...

Tr(C) reported in Fig. 4.8, and corresponding to safe operative conditions according to the Adler and Enig criterion, are obtained with the Semenov number Se = 0.47, which is well above the maximum critical value provided by the Semenov criterion, Sec = 0.377, as given by (4.28). This difference mainly arises from the inclusion into the mathematical model of the terms accounting for consumption of reactant A. 

The Lewis number (or Lewis-Semenov number) is a measure of the ratio of the energy transported by conduction to that transported by diffusion namely. 

As a matter of fact, however, the SADT may be regarded as the critical (or the lowest) temperature below which the thermal explosion of a chemical of the AC type, including every powdery chemical of the quasi-AC type, cannot occur. Semenov number [dimensionless] (Se = 1/e = 0.367879 ). Second. 

The ratio between N and S is an important parameter for the general discussion of the stability and parametric sensitivity of chemical reactors. N /S corresponds to the reciprocal Semenov number [26]... 

Figure 2. Normalized objective sensitivity, S(v ), as a function of the Semenov number, l/ for various input parameters,

Tarantola (2008). Different importance rankings were found depending on whether moment-independent or variance-based techniques were used. The enthalpy of reaction was found to influence the entire output distribution the most, whereas its variance was most influenced by the Semenov number. However, non-important model inputs were found to be the same in both cases. Hence, if the aim of the study were to identify important and non-important parameters for the purpose of model improvement, the outcome would have been the same. 

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