Experiments have been performed with distilled water, methanol, benzene, toluene and ethylene glycol at atmospheric pressure to measure the average heat transfer coefficient under natural convection conditions. Uniform heat flux values have been used in the range of 4.1-43.0 kW/m(2), while inlet liquid subcooling of 0.5-11.6 degrees C. The typical experimental data have been presented graphically. An empirical correlation for the average Nusselt number has also been developed.