In this paper, a new strategy for temperature control of multipurpose batch reactors using a cascaded model based control is presented. This strategy is based on the use of the thermal flux as the manipulated variable. At each sampling time, the master controller computes the thermal flux to be exchanged between the reactor content and the thermal fluid flowing inside the jacket. This information is then used to determine the right fluid and to evaluate the opening value of the control valve. For this purpose a physical modelling of the thermal system has been developed. Finally, the control valve opening degree is computed and applied to the plant.