The aim of this work is focused on the characterization of the behavior of large-capacity multihole industrial twin-fluid atomizers. Sauter mean diameter (SMD), discharge coefficient and air-to-liquid mass flow rate ratio are the parameters that have been selected for the experimental study. Two kinds of nozzles have been tested: a commercial "Y" type and a new-concept twin-fluid nozzle with an internal swirl chamber. This new-concept nozzle, which is specifically designed to atomize crude petroleum in power plants, is made with two different pieces, which eases cleaning and maintenance tasks. The best performance has been obtained for the new-concept nozzle without Y ports in the internal part, yielding smaller droplets with a lower air mass flow rate. A nondimensional relationship between the SMD-to-air core diameter at the exitholes (D-a o) versus the air Reynolds number defined with D-a o has been found. This nondimensional relation reproduces very well the experimental measurements for the whole range of atomizing conditions, which includes the actual power plant operating conditions.