The flaming mode efficiency g0 of the stove is the ratio of the heat transferred to the vessel to the energy put into the stove in the flaming mode.
This is a product of the gasification efficiency gg and the convective heat transfer efficiency gcon from the gas phase combustion to the vessel (the heat transfer by radiation from the stove wall to the vessel is included in this).
Apart from this, the hot char bed transfers heat to the vessel by radiation and this efficiency is denoted by nrad.