How does a NRV function? It has a flap, disc(s), springs, counterweights, dashpots, etc. The flap/disc(s) close onto a seat when the flow reverses. Different styles of valves behave differently. refer to the presentation attached. Read the notes.
How do we measure accuracy? Manufacturter should provide dv/dt vs. Vr data. What other accuracy are you talking about? It is repeatability that you need in a NRV.
What will be its estimated loss? Depends on your fluid whether it is viscous or not, contains solids, temperature, density, viscosity etc etc. This is provided by the manufacturer for water and depends upon the style of check valve and its appetanances. Also ARD Thorley provides this information in the reference text. You have to compute the losses based on the process conditions. Please dont ask here how to do that. Go see you boss or professor.
Under what pressure difference it operates? This is provided by the manufacturer and depends upon the style of check valve. Also ARD Thorley & Ellis provides this information in the reference text.
Does it hold the water hammer thrust? This depends on the pressure transient level, the pipework design and how it is supported. Some rubber flap or duckbill valves may be inverted on reverse flow.
Please throw some light in it . Look to the heavens and there shall be light but only if you believe. Our creator gave us the wonder of sight, a brain to interpret and understand and intelligence to apply so go forth and read, understand and apply.
“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
