Simulation technology plays an important role in propulsion test facility design and development by assessing risks, identifying failure modes and predicting anomalous behavior of critical systems. This is true for facilities such as the proposed A-3 that will operate at low pressures in conjunction with steam ejectors and the B-2 facility where flame deflector cooling and plume impingement dynamics become important. Integrated analyses of facility designs that include supersonic diffusers, steam ejectors, valves, cooling spray nozzles and turning ducts will be carried out for both steady state operation and shutdown/startup transients. More importantly, predictions related to thermal and pressure loads on diffuser/deflector walls will be made and transient phenomena such as blow-back during shutdown and start-up blast waves will be studied. The proposed innovation expands on the multi-element unstructured CFD which has been validated for complex valve/feed systems and high pressure propellant delivery systems used in engine and component test stands at NASA SSC. The focus here will be on extending this capability to include advanced models for analysis of non-equilibrium two-phase flow dynamics and heat transfer in water injection systems in the flame deflector, steam loaded plume entrainment, chemical steam generator performance and operation of steam ejectors.