Hi Everyone

I've joined the forum in the hope someone can help me understand if it is possible to generate a liquid vapour exhaust flow from a gaseous entry in a De Laval subsonic to supersonic nozzle.  Using methane as a working fluid with a relatively low entry temperature (about 200 K, but it's on my other computer) and reasonable 4 bara entry and 0.25 bara exit pressures, the standard formula calculate exit temperature below 95 K that puts methane in its liquid phase.  However, I'm guessing a shock wave would exist in real life at the gas-liquid transition part way down the diverging nozzle at which the working fluid decelerates to subsonic, rises in temperature (kinetic to thermal energy) and comes out the exhaust as a gas at pretty much entry conditions.

Anyway of avoiding this, perhaps by removing kinetic energy just before the gas-liquid interface, and having the exhaust in a liquid phase?  I think the only way to do it is to remove the kinetic energy, otherwise what comes out the back would be the same state as what goes in the front.

The reason for the interest is because De Laval nozzles generate supercooled exhaust flow with the right entry conditions.  A nice supercooled liquid sounds ideal for an inflow of thermal energy from low grade temperature sources.

The theoretical way of generating a cold sink for use in an ambient Organic Rankine Cycle engine without voilating the second law of thermodynamics - ie entropy of the system increases.