I'm trying to calculate the stagnation conditions of a water / steam - two-phase-flow in a horizontal constant diameter pipe.

The object is to calculate the stagnation pressure p_0 and mass flow quality x_dot_0 with given diameter d, mass flow m_dot, inlet pressure p_in and inlet mass flow quality x_dot_in.

I know how to calculate the stagnation mass flow quality x_dot_0 once I've calculated p_0. This ist done with an isentropic flash:

x_dot_0 = (s - s'_0) / (s''_0 - s'_0)

Entropies will be calculated via REFPROP, where s = s(p_in,x_dot_in), but s'_0 and s''_0 are dependent only from stagnation pressure p_0

So far I've found no real formula to calculate stagnation pressure conditions within two-phase-flows.

Hope there's someone out here, who can be of help.

Thanks a lot in advance !