Because flow velocity and reactor channel diameter are typically 2 cm/s and 2 mm in the weak flame regime of MFR, chemical enthalpy of an incoming flow is quite small (e.g., less than 0.3 W for a stoichiometric methane/air mixture). The small reactor channel also results in dominant heat transfer between gas phase and wall surface so that an increase in gas-phase temperature becomes quite small even in a reaction zone. An increase of the gas-phase temperature in the reaction zone for a weak flame in MFR is only less than 10-20 K [61] whereas that for a typical normal flame in a channel may be more than several hundreds K. Note that the 10-20 K is an example of the largest temperature increase for an stoichiometric methane/air weak flame in MFR. We mostly focus on fuels having multi-stage oxidation [67] and/or lower heating values [106] in studies using MFR so that the temperature increases in most cases in our papers are much smaller than the 10-20 K.

We frequently get a comment like "a heat convection term for a laminar flow channel is inappropriate in a reaction zone where gas-phase temperature jumps." but it is indeed a misunderstanding. The gas-phase temperature in the weak flame regime of MFR is governed by a given wall temperature profile even in a reaction zone.