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A commonly-used method to cool rotating cylinders involves spraying water on the surface to cool its internal particles. This paper conducted a numerical investigation of heat transfer from a rotary cylinder cooled with sprayed water. A 3-D numerical model was generated, and the distributions of the wall temperatures and liquid films were analyzed. Then, the heat transfer characteristics for different parameters were obtained and compared. The results showed that the best location for a single spray nozzle was directly above the cylinder, where it had the most uniform liquid film and highest heat exchange efficiency. With increased rotation speeds, the cylinder wall temperature increased and the distribution of wall temperature and liquid film became more uniform, which improved heat transfer. Because of the influence of gravity, the slope of the cylinder had a negative influence on the distribution of the liquid film. When the cylinder material had lower thermal conductivity, the system needed a much longer period of time before it was stable and had lower heat flux. Furthermore, with the same heat source, the system heat flux could not be determined with only the outer surface temperature, but with the temperature difference between inner surface and outer surface. [ABSTRACT FROM AUTHOR]