There doesn't seem to be any proper online source that describe these flows properly. Please explain the following points that i read about on wikipedia: 1. "The heat addition causes a decrease in stagnation pressure, which is known as the Rayleigh effect and is critical in the design of combustion systems"...why is this so important? 2. " unlike Fanno flow, the stagnation temperature is a variable"-- is this because we're considering uniform cross-sectional area and no mass change, so due to heat addition/removal the net energy at any point will vary? 3. Can anyone tell me where I could find a derivation of the formulae related to Rayleigh flow found in the wikipedia article http://en.wikipedia.org/wiki/Rayleigh_flow?...similarly for Fanno flow. Thanks a lot!