Transformer Oil coolers are heat exchangers used to cool the dielectric oil in a transformer. The cooling medium is typically air or water. Transformer designers, rather than heat exchanger manufacturers, drove the evolution of transformer oil coolers, so the approach or terminology is slightly different than typical heat exchanger applications.

The air cooled oil coolers are designed to dissipate heat from the oil of generator Transformer, Distribution Transformer, Smoothing Reactors and Locomotive Transformers. Specially designed internal turbulators are provided for effective heat transfer from the viscous oil.