Condensation of Vapors of Miscible Liquids

Abstract

In the process industry, vapor mixtures are frequently liquefied, or the vapors contain inert gases, which by definition do not condense under the prevailing conditions. Their influence on the heat transfer during condensation was treated together with the deviations from the Nusselt film condensation theory in Sect. 2.2.3. There is yet to be considered how the heat transfer is changed if the condensate consists of a homogeneous phase and all components are essentially liquefied. Depending upon the purpose of the application, the vapor can be completely or partially condensed, so that vapor of a generally different composition than that of the entering vapor leaves the condenser. Such apparatus is designated as partial condenser or in rectification columns as dephlegmator. Because during the condensation of vapor mixtures as a rule the components with the higher boiling point condense first, and because the residual vapor thus becomes poor in these components, there is formed a concentration profile that is variable with the flow path and which influences considerably the heat exchange.