NUMERICAL SIMULATION OF CONDENSATION OF A VAPOR-GAS MIXTURE ON THE SURFACE OF A SPIRAL WOUND FINNED TUBE

To intensify heat transfer, finning of the heat exchange surface is used, which would ensure effective tearing of the condensate film from the pipe surface, which would reduce the thickness of the film and create a drop condensation. The complexity of calculating the heat exchange apparatus consists in changing the ratio of liquid and steam in a vapor-gas mixture during condensation of steam on the heat exchange surface. The aim of the work is the numerical simulation of steam condensation from a vapor-gas mixture on the surface of a spiral-wound finned pipe. The object of the study is the condensation of a vapor-gas mixture on a pipe with spiral-wound ribs. The subject of the study is to determine the coefficient of heat transfer from a vapor-gas mixture to the surface of a pipe with spiral-wound ribs during its condensation on it, depending on the density of the heat flux, its initial velocity and the mass fraction of water in it. To carry out the calculations, a simplified three-dimensional calculation model of a finned pipe in an air duct was created based on the experimental data got. The paper presents the geometric dimensions of the model, information about the grid model, boundary, and initial conditions. In preliminary studies, it was found that grid independence is achieved with the number of 87,928 cells. The results of numerical calculations confirmed the high accuracy of modeling the condensation of a vapor-gas mixture on the surface of a pipe with spiral-wound ribs. The uncertainty between numerical and physical experiments on the coefficient of heat transfer from the vapor-gas mixture to the heat exchange surface during its condensation on it was only 16.8%. The maximum value of the heat transfer coefficient is achieved with a minimum velocity of the vapor-gas mixture equal to 7.4 m/s and the lowest mass fraction of water in it is equal to 0.188.