In the derivation of the pressurizer pressure, only the conservation equations of mass and energy…

In the derivation of the pressurizer pressure, only the
conservation equations of mass and energy were used. What is the application of
the momentum equation in the pressurizer?

Consider the mass flow rate due to the condensation of steam
on the wall of the pressurizer. Can we obtain this term from the conservation
equations of mass and energy written for the water and the steam regions?