A NEW APPROACH TO PREDICT VOID FRACTION, FLOW REGIME AND HEAT TRANSFER ACCOUNTING FOR NON-EQUILIBRIUM IN CONDENSERS WITH SUPERHEATED INLETS

摘要

A new approach to predict the void fraction, flow regime and heat transfer in a condenser with superheated inlet by accounting for the effects of non-equilibrium is introduced. The paper presents evidence (by visualization and temperature and heat transfer measurements) of condensation while the specific enthalpy of the bulk flow indicates superheated vapor because of the temperature gradient causing the wall temperature to drop below saturation temperature. The presence of liquid film induces discrepancies between the void fractions, flow regimes and heat transfer coefficients in a real condenser and the predictions from a model assuming thermal equilibrium. The new approach attempts to address this issue by bringing new predictions of void fractions, flow regimes and heat transfer coefficients from thermodynamic quality one and zero to the real onset and end of the condensation. From extensive measurements and flow characterizations based on visualization in diabatic conditions, the new approach of predicting void fraction, flow regime and heat transfer coefficient is specifically explained and validated.