TY - GEN A1 - Reis, Timo A1 - Hanke, Michael T1 - The perturbation and ADAE index of a degenerated hyperbolic system modelling a heat exchanger N2 - The heat exchanger in a heat pump can be modelled by the zero Mach-number limit of the Euler equations of compressible fluid flow. This system turns out to be a coupled hyperbolic/parabolic equation with coupled, time-dependent boundary conditions. Using the theory of abstract differential-algebraic equations it is shown that the frozen coefficient system has ADAE index 1. Moreover, the much stronger result is proven that the system has time-perturbation index one and space-perturbation index two even in the case of time-dependent boundary conditions. The results are stated in terms of the original physical variables. The estimates agree well with numerical experiments. Y1 - 2007 UR - https://opus4.kobv.de/opus4-matheon/frontdoor/index/index/docId/398 UR - https://nbn-resolving.org/urn:nbn:de:0296-matheon-3989 ER -