The two-zone models are seen as interesting tools for engine simulation. The two-zones, spatially homogeneous, are set during the combustion process. Such models take into account an interface of infinitesimal thickness for the separation between zones. The success of this simulation approach depends on the accuracy of the heat transfer model. Models of heat transfer, in turn, aim to obtain the heat transfer coefficient from the combustion gases in contact with the cylinder walls. Several heat transfer correlations from the literature can be used to obtain the heat transfer coefficient. Eichelberg correlation, which consider natural convection of the combustion gases, along with Woschni, Hohenberg, Sitkei and Annand correlations, which consider forced convection of those gases, were compared in search for the best fit to the experimental data. Comparisons were made using the software Matlab® for an internal combustion engine using different fuel blends: hydrous ethanol fuel (HEF) and mixtures of ethanol and water in the proportions of 90% (E90W10), 80% (E80W20), 70% (E70W30) and 60% (E60W40) by volume of ethanol. This Part A paper shows tests results were performed at fixed spark timing for wet ethanol combustion. The results have shown that correlations of Hohenberg and Annand are most suitable for the type of engine and fuels considered in this study, both being able to predict accurately the pressure curve inside the cylinder.