Jet pumps or venturi pumps are often stated as having a "terribly low" efficiency, steam jet pumps specifically are usually describes as "only justifiable when there's an abundant steam supply anyway" - however, I hardly find any numbers, and no formulas.
My question: Is there a general form to describe the work done by a (non-steam) jet pump an the pumped medium as a function of the work used to pump the working fluid (gas or liquid)
Is there a general form to describe the work done by a steam pumpe as a function of the thermal energyinput into the workng fluid?
While real-world numbers are interesting, I'm mostly after the limits posed to jet pumps by thermodynamics, not engineering.
EDIT: Can a jet pump be describes meaningfully in a p - V diagram? Put another way, can the changes of impulse in the media be expressed solely as functions of the pressures (before/after)?
Thus, can a (steam-)jet pump be described as a thermal (steam-)engine?