This paper is concerned with the problem of reachability of parallel-flow heat exchanger equations with boundary inputs. It is shown that the system with boundary inputs is formulated as a boundary control system which is well-defined in the sense of Curtain and Zwart (1995), and further that it is reachable through a concrete expression of the solution. In addition, the reachable subspace is given for the case where only one boundary input is added to the system.
Hideki Sano. "On reachability of parallel-flow heat exchanger equations with boundary inputs." Proc. Japan Acad. Ser. A Math. Sci. 83 (1) 1 - 4, January 2007. https://doi.org/10.3792/pjaa.83.1