Fluid Engine and Turbine Efficiency

Fluid engine and turbine efficiency is defined as the inverse of pump or compressor efficiency  

For an incompressible fluid (e.g., water), the common definition of the maximum possible work is the work that would be delivered if the fluid left the system with zero velocity and if the term in Bernoulli s equation were zero. For gases (e.g., steam), the common definition of maximum work is that work which would have been obtained for zero outlet velocity and isentropic operation. Although the forms of these maximum-work definitions are different, they can both be shown to be the same, because the term in Bernoulli s equation is related to the irreversible entropy increase. 

Positive-displacement pumps work by trapping a fluid in a cavity and then squeezing it out at a higher pressure they are generally high-pressure-rise, low-flow-rate devices. 

Centrifugal pumps work by giving the fluid kinetic energy and then converting this to injection work. They are generally high-flow-rate, low-pressure-rise devices. 

The problem of boiling in the inlet line (or cavitation) limits how high any kind of pump may be placed above the reservoir on which it is drawing. 

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