A heat exchanger that is constructed with a heat exchanger shell having inlet and outlet plenums and fluid inlet and outlet ports, and a tube sheet construction disposed in the heat exchanger shell. The tube sheet construction includes at least two separate tube sheets and a plurality of tubes that extend between the separate tube sheets. Each tube sheet includes at least two planar tube sheet segments and an interstitial layer disposed between the at least two tube sheet segments, and at least one sensor element supported by each of the interstitial layers. A control monitor controls flow through the shell by a feedback control from the sensor to an inlet control valve and/or a stimulus device excites the media layer.