Entropy production in flames

Abstract

Thermodynamic foundations of the thermal entropy production are rested on the concept of lost heat, (Q/T) [delta]T. The thermomechanical entropy production is shown to be in terms of the lost heat and the lost work as where the second term in brackets denotes the lost (dissipated) work into heat.The dimensionless number [Pi]s describing the local entropy production s[triple prime] in a quenched flame is found to be [Pi]s~(Ped0)-2, where [Pi]s = s[triple prime]l2/k, l = [alpha]/Su0 (a characteristic length), k thermal conductivity, [alpha] thermal diffusivity, Su0 the adiabatic laminar flame speed at the unburned gas temperature, Ped0 = Su0D/[alpha] the flame Peclet number, and D the quench distance.The tangency condition [part]Ped0/[part][theta]p = 0, where [theta]b = Tb/Tb0, Tb and Tb0 denoting, respectively, the burned gas (nonadiabatic) and adiabatic flame temperatures, is related to an extremum in entropy production. The distribution of entropy production between the flame and burner is shown in terms of the burned gas temperature and the distance from the burner.