Heat transfer and pressure drop data of three smooth multiport minichannels featuring hydraulic diameters > 1mm are presented. Experiments were conducted under single phase convection of heptane and under convection of condensing R134a. Two specifically designed testing facilities feature a novel measurement setup to register the amount of condensate generated and to measure the temperatures of the refrigerant and minichannel wall. The results for the smallest minichannel geometrie show that the assumption of an increasing heat transfer rate with decrasing hydraulic diameter is not generally valid.