A bounded positive non-linear PI control law for double-pipe heat exchangers

In this work, a PI-type control scheme for the outlet temperature regulation of double-pipe heat exchangers is proposed. Compared to previously proposed approaches, the algorithm developed here guarantees positivity and boundedness of the input flow rate. Moreover, the proposed approach takes into account and actually exploits the analytical-stability features inherent to the open-loop dynamics. As a result, outlet temperature regulation is achieved through a simple controller which does not need to feedback the whole state vector, does not depend on the exact value of the system parameters, and whose stabilization character is global in the closed-loop system state-space domain. The analytical developments are corroborated through experimental results.