In Figs. ) and 11(C), 12(B) and 12(C), and 13(B) and 13(C), it is observed that the particle temperature and conversion results using the SAS, are within the results of the FD. Even so, in Fig. , at low conversions, the relative conversion error is very high. Other aspects to be observed in Figs. 11(D), 12(D) and 13(D) are as follows: the profiles of 𝐵 and 𝑇 1 are qualitatively similar, which is due to the dependence of ℎ $ on 𝑇 1 ; the profile of |Da ef | has exponential behavior, which is due to the Arrhenius law for the rate constant. From the results in Figures , it can be concluded that for small Bi, small |Da ef | and small Th M , the present model, Eqs. ( )-( ), is as accurate as the DM -as predicted by the scale analysis -and therefore the SAS can be used. However, in the calculations in Figs. 12 and 13, the large variation of |Da ef | and Th M , makes it extremely difficult to evaluate the effect of these dimensionless numbers on the observed errors (the same holds for Py 7 in Figs. and). Furthermore, not only the ranges of variation must be considered, but also the way in which it occurs. Thus, the analysis proves to be complex and therefore, this question is addressed to future studies.