Simplifying the calculation of mass flow

The mass flow for a convergent-only nozzle is given by equation (14.63), repeated below  

A simplification may be introduced as a result of the fact that all the nozzle efficiencies are likely to be near unity, at least near the design point. Hence we may use the approximation  

In a similar way, the simplified equations for mass flow through a convergent-divergent nozzle are  

Equation (16.85) possesses the advantage that it is independent of efficiency calculations. Hence p criii/PoT may now be computed off-line from the main simulation in all cases where y i constant. The only exception is the case of wet steam, where the effective value of y depends on the dryness fraction, x. 

---