  We prove the hydrodynamic limit for a one dimensional harmonic chain with a
random flip of the momentum sign. The system is open and subject to two
thermostats at the boundaries and to an external tension at one of the
endpoints. Under a diffusive scaling of space-time, we prove that the empirical
profiles of the two locally conserved quantities, the volume stretch and the
energy, converge to the solution of a non-linear diffusive system of
conservative partial differential equations.
