Forced convective boiling of ternary mixtures at high qualities

This paper deals with convective boiling of ternary mixtures in vertical tubes. Experiments were carried out in 8.58 m long, 25.4 mm ID, electrically heated test section using an n-pentane/n-hexane/iso-octane mixture (0.31/0.22/0.47 overall mole fraction). Bulk and wall temperatures as well as local heat transfer coefficients were measured. The results were compared with those obtained using an extension to ternary (and multicomponent) mixtures of the methodology proposed by J.R. Barbosa and G.F. Hewitt [Int. J. Heat Mass Transfer 44 (2001) 1465, 1475] for prediction of forced convective boiling of binary mixtures in upward annular flow. Interphase transfer of heat and mass is dealt with using two formulations: (i) a film method in which the diffusive fluxes are calculated via a linearly generalised Fickʹs Law [H.L. Toor, AIChE J. 10 (4) (1964) 460; W.E. Stewart, R. Prober, Ind. Eng. Chem. Fundam. 3 (3) (1964) 224], and (ii) an effective diffusivity method. Droplet entrainment and deposition are modelled via an interchange model that takes into account the local concentration non-equilibrium between the liquid film and the entrained droplets. As for the binary case, it is claimed that the deterioration in the heat transfer coefficient is due to a combined effect of droplet interchange and mass transfer resistance in the vapour side.