I have selected a lot of pumps/fans/compressors, but for low to medium vacuum (~1000Pa) the kinetic theory of gasses dominates and additionally there are many different types of less encountered pump technologies to select from.
How would you select a pump for pure water vapor (steam) at 500Pa being pumped at 1 liter/second up to 1500Pa?
Starting temperature can be STP 273K. I don't need to know an exact pump, I just need some background on the thought process from someone with experience working in this pressure regime.
This Vac Aero website has a good overview of some pump types.
Here are some pumps I have considered that don't have high oil emissions:
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