The paper presents experimental measurements for the transient profiles of burning rates and liquid temperatures (at different depths below the surface) in methanol and heptane pool fires. Square burners are made of steel walls and have 4 different side lengths: 5.5, 8.0, 10.5 and 15 cm. The burner is 5 cm deep and the initial fuel height is about 4.6 cm. An experimental procedure has been developed to measure the enhancement in heat transfer within the liquid due to convective motion, by estimating the internal Nusselt number, Nui. The results suggest that for heptane Nui = 11.8 ± 3.6 and for methanol Nui = 6.2 ± 2.9. Additionally, based on the experimental data, a two-zone approach for the thermal structure within the liquid has been proposed. This approach will be implemented in a numerical code.