INTEGRAL FORMULATION OF BALANCE-EQUATIONS FOR 2-PHASE FLOW-THROUGH A SUDDEN ENLARGEMENT .1. BASIC APPROACH

A general expression of irreversible losses related to two-phase flows through a sudden enlargement is derived from basic balance equations (mass, momentum and energy). The need to take into account void fracti on and quality changes is emphasized for some one-fluid flows. From a comparison with several experimental results, it is concluded that a v oid fraction decrease downstream of the enlargement must be considered in order to predict satisfactorily pressure variations on the basis o f the momentum balance procedure. When expressed in the form of a frac tion of reversible pressure recovery, dissipation losses appear to dep end strongly on the quality. Their minimum value is observed for a lar ger quality value when the pressure of the system is increased.