A Numerical Study of Evaporating Heat Transfer of Nonazeotropic Binary Mixtures Flowing Upward in a Vertical Tube. 2nd Report, The Effect of Nonideality of Mixtures.

Abstract

Taking into account the equilibrium characteristics of nonideal mixtures, numerical analysis has been conducted for an evaporating annular two-phase flow of nonazeotropic binary mixtures flowing upward in a vertical tube. The equations of continuity, momentum, energy and mass conservation for each phase have been solved numerically by a finite volume method. The predicted streamwise distributions of the heat transfer coefficient, wall temperature and quality were examined for three different mixtures, R11-R113, R22-R114 and R22-R11. When the concentration of the more volatile component of a mixture is high, the heat transfer coefficient was found to decrease towards the downstream in some cases as evaporation proceeds. The assumption of ideality of the mixture can affect the heat transfer characteristics by twenty percent. Nonideality of the mixture must be taken into account, especially if all the local values of heat transfer coefficient, temperature and quality are to be predicted. The significance of the nonideality of the mixture cannot be discussed based on only the difference in the boiling temperature of each component.