Stirred tanks are widely used in chemical engineering, which is why there is a large variety of different designs. Numerical fluid dynamics is therefore often used in stirred tank studies that focus on flow behavior. In this work, a generic reaction in a stirred tank is simulated using computational fluid dynamics and the temperature control of the reactor is investigated. Design-critical aspects are derived from the simulation. In addition, the simulation approach is very well suited for a reaction-specific optimization of a stirred tank.