"In this work, we propose an outlet temperature control scheme for counterflow heat exchangers, that 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 adaptive controller which does not need to feedback the whole state vector and does not depend on the exact value of the system parameters. Furthermore, positivity and boundedness (nonsaturation) of the input flow rate are additionally guaranteed through the proposed approach, without entailing complex control algorithms or stability proofs. The analytical developments are corroborated through experimental results."