[en] Combined free and forced convection in vertical annular passages is important in the design of coolant channels for power transformers, nuclear reactors, double-pipe heat exchangers, certain types of catalytic converters, and modern electronic equipment. Although most such equipment is designed to operate in a turbulent flow regime, laminar flow and heat transfer become important when the equipment operates under reduced power or during accidental pump failure. This paper presents a numerical study of laminar, fully developed mixed convection in vertical eccentric annular ducts. The equations governing the velocity and temperature are solved on a body-conforming grid by using a finite-volume technique. The effects of radius ratio, eccentricity, and Rayleigh number on the friction factor and the Nusselt number are discussed. The buoyancy forces significantly increase both friction and heat transfer. The effect of buoyancy is stronger for configuration with larger eccentricities