A simple and general procedure has been developed to determine the thermal behaviour of a reactor based on heat balance, PID temperature control, and jacket behaviour. Using only temperature heating/cooling ramps followed by isothermal stages, such a procedure was tested at laboratory and industrial scale, respectively in a 0.5 L Mettler-Toledo RC1e and a 100 L industrial reactor. The obtained model was demonstrated to be in good accordance with the measurements. The consistency and robustness of the model were assessed by imposing an external heat profile based on an autocatalytic reaction system. The results have proven that even under perturbations, the retrieved parameters remain correct. In summary, the thermal behaviour of a chemical reactor can be defined through the reactor dynamic investigation procedure and can be used to identify the optimal operating conditions.