Heterogeneity of heat transfer was studied in a packed bed of 8 mm spheres cooled by a two-phase flow composed of air and fine (8 mum diameter) water droplets. Local heat fluxes in the packed bed were measured in both single- and two-phase flow and analyzed as a function of water mass flow rate, the surface temperature of the spheres and air velocity. Heat transfer was enhanced in the two-phase flow: the maximum value rose to 2.8 under experimental conditions. The study shows that heat transfer depends on several factors: axial position, temperature difference, water mass flow rate and air velocity. A marked heterogeneity of heat transfer was demonstrated and was correlated with the local mass flow rate of the collected water.