Vapor–Gas Mixture Condensation in Tubes

Abstract—

A one-dimensional differential model describing condensation of a vapor–gas mixture in tubes and its implementation on a computer in the Visual Basic integrated development environment is presented. The model is intended for studying the operation conditions and parameters of the relevant types of condensing devices and, in the future, for carrying out technical computations and providing information support to design developments and tests. The compute kernel is based on mathematical models that take into account the main significant effects during condensation, such as gravitation (with different tube orientations), friction at the phase interface boundary (taking into account the cross flow of mass and specific roughness of the boundary), availability of noncondensing, admixtures, different external cooling methods, and the possibility of dangerous operation conditions to occur (freezing and flooding). The well-studied limiting models, such as a gravity or shear condensate film, are united by the interpolation method between asymptotes. The mathematical formulation of the problem consists of conservation equations (of momentum, energy, and mass of mixture components) for averaged flows of coolants supplemented with algebraic relations for local coefficients of heat transfer, mass transfer, and friction at the interface boundaries. The remoteness of working fluid thermodynamic parameters from the critical point, which is almost always observed in condensing installations, is the natural limitation of the analysis model’s application field. A special analysis for determining heat transfer and friction in gravity–shear condensate films based on an adequate differential turbulence model is carried out.