4. Relationship between input-output measurements and internal operation

Let's recall the quantities that can be measured at the inlets – outlets, the physical characteristics of the two fluids being known: these are the four temperatures and the two mass flow rates.

Any phase changes are determined by the change in titre between the inlet and outlet of the two-phase fluid(s). Internal operation is characterized by the overall exchange coefficient K, which in turn depends on the two exchange coefficients of each fluid with respect to the exchange wall, as well as its conductive resistance.

We're going to define the classic relationships between measurements at the quadrupole's terminals and its internal operation.