The calculation of pressure drop in a condenser is ai best only an approximation because of the changing velocities and flow patterns. (See also Section 29.) The overall pressure drop is

\[\label{eq1} \Delta p = \Delta p_{e} + \Delta p -{G} + \Delta p_{A} + \Delta p_{F}\tag{1}\]

where Δp_e represents the various inlet and exit lasses due to nozzles and headers, Δp_G is the static head, Δp_A is the momentum change, and Δp_F is the two-phase friction loss.

The expansion and contraction losses are calculated using the homogeneous flow model, that is, assuming equal liquid and vapor velocities.

The static head is usually insignificant in condensers, but would be calculated as