Stirred Tank Reactors (STR) are widely used in the chemical industry. When these tanks are used for highly exothermic reactions, a jacket or coils are employed for heat removal. Inner coils are used to supply additional heat transfer surfaces in stirred tanks when the needed heat generation or removal is too great. One major problem associated with inner coils is that they provide resistance or blockage to flow, reducing the effective flow circulation within the reactor. The aim of this work is to obtain a CFD model for these systems in order to improve their design. In the first part of the work a methodology is proposed to obtain a CFD Nusselt correlation according to the work by Oldshue and Gretton (1954). After this step, the design proposed by Pedrosa and Nunhez (2003) will be simulated and compared to the geometry by Oldshue and Gretton (1954). Preliminary results indicate that the CFD model reproduces the correlation by Oldshue and Gretton (1954).