I can witness liquid NH3 achieving sub 'boiling point' temperatures by simpling removing a thermocouple from a container of liquid, typically around -40 to -60°C.
I see that as the Ammonia evaporates energy is lost from the liquid droplets and I would imagine a loss in density.
With the exception of mathematical explanations from the works of Geoffrey D. Kaiser & Richard F. Griffiths, I am yet to find an explanation that hits home of how this occurs other than terms like entrained air and adiabatic volumetric expansion, partial pressures etc. I would like to find some visualisation of what is exactly going on in this process.