A Study Of Simulation Modules For Condensation Of Flowing Steam

According to the actual physical process outside the tubes of the shell-and-tube heat exchanger,a two-dimension numerical model for condensation of flowing steam outside a horizontal tube was established.The situation where saturated steam flows vertically across a cylinder and condenses into water on the tube wall was studied in the article.The 2D numerical model of laminar film-condensation outside a horizontal tube for the flowing saturated steam was built based on the one-phase theory of boundary-layer built by Prandtl and the classical two-phase theory built by W.G.Whitman and L.K.Lewis in the article.And the section of the model is perpendicular to the tube axis.The procedure of the simplification and establishment of the laminar film-wise condensation of downward-flowing dry saturated steam outside a single horizontal tube was analyzed in the article,and at last a 2D numerical model was achieved.The partial differential governing equations of conservation of mass,momentum and energy for steam and condensate were established respectively.On the base of Laplace's series solutions for one-phase laminar-flow fluid and the application of similarity in studying laminar film-wise condensation of saturated-vapor on surface plate by Deyi Shang,the scatter simultaneous equations for steam and water were solved with help of the principle of solving matrix equations.Results for the velocity distribution of water and steam in the boundary layer,the temperature distribution of the condensate were achieved.And then,solutions of the local distributions of the thickness of condensate,Nu and the coefficient of heat transfer for laminar film-wise condensation of dry saturated steam were got.The mean values of the thickness of the condensate,Nu and the coefficient of heat transfer from the upper stagnation point to the point of calculating termination for laminar film-wise condensation of dry saturated steam were solved.The solution of laminar film-wise condensation for dry saturated steam outside a single horizontal cylinder was obtained in the Cartesian coordinates along the tube surface,and then characters of flowing and heat transfer for condensate and steam were analyzed.And at last,the influence of oncoming velocity U_?of freedom steam,the temperature _sT of saturated vapor,the diameter D of the cylinder,and the temperature difference?T between saturated vapor and the outside wall of the tube for laminar film condensation of saturated steam was analyzed in the article.