This research presents an experimental study of transient heat transfer phenomena between the wall of a tank and the incoming gas during a storage tank charging process. A simple theoretical model of convective heat transfer between the gas and the cylinder is described. Experiments with the high pressure gas (ΔP = 14.5−16.5MPa) charging process to a vehicle supply tank were carried out. Data of gas temperature stratification inside the tank was obtained from low mass thermocouples in the strategic locations inside the tank during runs. The whole charging process can be divided into three phases: forced convection, free convection and conduction. Correlation equations for convection between the gas and the tank are presented for both the forced and free convection phases.