In this paper we study the frequency andtime domain behaviour of a heat exchanger network system.The system is governed by hyperbolic partial differentialequations. Both the control operator and the observation operator are unbounded but admissible. Using the theoryof symmetric hyperbolic systems, we prove exponentialstability of the underlying semigroup for the heat exchangernetwork. Applying the recent theory of well-posedinfinite-dimensional linear systems, we prove that thesystem is regular and derive various properties of itstransfer functions, which are potentially useful forcontroller design. Our results remain valid for a wide classof processes governed by symmetric hyperbolic systems.