Boiling Heat Transfer of Binary Mixture in a Tube

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1. Boiling heat transfer of Freon R11-R113 mixture flowing a uniformly heated vertical tube was experimented under various combinations of composition of mixture, pressure, mass velocity, heat flux and inlet condition. The test tube was heated by passing direct current through the tube which resulted in an excessive voltage drop across thermocouple junctions welded on the outer surface of the tube. Correcting method for this voltage drop was proposed and found to provide accurate wall temperature.2. Both the tube wall temperature and the bulk fluid temperature increase linearly in parallel along the tube length before the incipience of boiling. Heat Transfer coefficients in this non-boiling forced convection region are correlated well with Dittus and Boelter's Formula.3. At the point where boiling is initialed, wall temperature abruptly falls and hence heat transfer coefficient abruptly rises from the level of forced convection without phase change.4. Heat transfer coefficients in nucleate boiling regime at relatively low quality are independent to mass velocity. Heat transfer coefficients of mixture in this regime are found to become lower compared to the coefficients linearly interpolated by weighing the mole fraction on their single-component values. Proposed correlating methods for pool boiling of binary mixture are found to fail to correlate the data for flow boiling.Heat transfer coefficients in two-phase forced convection regime at relatively high quality are rather a weak function of local quality.6. For further detailed consideration to be performed on heat transfer characteristics of binary mixture, there are urgently required not only thermodynamic properties but transport properties for binary mixture.