EXPERIMENTAL AND THEORETICAL RESULTS ON UPWARD ANNULAR FLOWS IN THERMAL NONEQUILIBRIUM

Some thermal and flow phenomena occurring in two phase annular dow reg ime have been analyzed by means of a simulation procedure coupled to a n experimental investigation. After a discussion about the closure rel ationships adopted and the validation of the numerical model against a vailable experimental data, some information have been obtained concer ning the thermal behavior of the two phases involved in the non-equili brium annular flow. A characteristic entry length required to reach th e thermal equilibrium between the phases has been defined and the typi cal values have been calculated as a function of the flow operating pa rameters (liquid and gas superficial velocities, inlet temperatures). Finally a simple relationship has been proposed to obtain a first eval uation of this equilibrium entry length in terms of superficial veloci ties and mean values of the physical properties of the fluids involved . (C) 1998 Elsevier Science Inc. All rights reserved.