# steam flow in a pipe driven by a pressure gradient between inlet and outlet

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 March 11, 2010, 07:52 steam flow in a pipe driven by a pressure gradient between inlet and outlet #1 New Member   Salvatore Catalano Join Date: Mar 2010 Location: Italy Posts: 1 Rep Power: 0 Sponsored Links Hi All, i'm a new user of Comsol 3.5. In this moment i'm experiencing some problems of convergence to solve a steam flow in a pipe of 4.75 mm. The flow is driven by a gradient pressure between the inlet and the outlet: - inlet 500 kPa - outlet 100 kPa (approx. atmospheric pressure) I'm using the chemical engineering module>flow with variable density>non-isothermal flow>k-w turbulence model>steady state analysis because i'm interested on looking into also the temperature in the pipe as the steam's temperature at the inlet is 121°C. I set as initial condition of temperature for the gas domain 298K. I used the material library of comsol to set the properties of the steam (there is exactly steam in it). Boundary condition for the turbulent weakly compressible flow model are -inlet: pressure> no viscous stress 500 kPa (default settings k0 turbulent kinetic energy 0.005 m^2/s^2 and w0 specific turbulent dissipation rate 10 1/s) -outlet: pressure> no viscous stress 100kPa -walls of the pipe: wall> logarithmic wall function (default setting deltaw=h/2) Boundary condition for the convection and conduction model are: -inlet: 394,15 K -outlet: convective flux -walls of the pipe: -1 W/m^2 The simulation does not converge. I've tried in different way...also with a lower pressure as 150 kPa doesn't converge! It converges only deactivating turbulence model and setting as inlet condition a low velocity inflow i.e. 0.1 m/s. Does anybody know how to do? Maybe k0, w0, h/2 for the wall setting are wrong? To be honest I don't know how to set them. Thanks in advance for anybody could support me! Salvo

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