CG-7 Film Theory Methods for Condensation of Multicomponent Vapors or Vapor-Gas Mixtures

R. G. Sardesai

The Resistance Proration Method has been used for a number of years to calculate heat transfer rates during the condensation of multicomponent mixtures. An important assumption in the Resistance Proration Method is that the condensation process follows the equilibrium condensation curve. This assumption generally is not valid and may give significant errors when condensing mixtures with a wide range of molecular weights. Recent studies have shown that the methods based on film theory of mass transfer (e.g., Colburn-Hougen and Krishna-Standart) are accurate and applicable over a wide range of conditions. This report reviews the film theory methods to establish algorithms and equations for incorporation in HTRI computer programs.

The report first discusses the Resistance Proration Method and improvements made to it using principles of the Film Theory Method. Next, the Colburn-Hougen Film Theory Method for condensation of a vapor in the presence of a noncondensing gas is discussed. This is followed by a discussion on film theory methods for condensation of a binary vapor mixture and multicomponent vapors or vapor-gas mixtures.

Vapor condensation of immiscible liquids poses a unique problem because the vapor-phase mass transfer phenomenon varies significantly depending on whether the vapor mixture is eutectic or noneutectic. The problem is further complicated if a noncondensing gas is present. The report details the calculation methods that should be used for these mixtures when they have different vapor compositions.

Recommendations are made for particular applications.