# Model of air–steam flow with condensation into the volume and surface wall

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 February 9, 2022, 23:22 Model of air–steam flow with condensation into the volume and surface wall #1 Member     Angel Penev Join Date: Apr 2016 Location: Bulgaria Posts: 47 Rep Power: 10 Hi, I'm working in the field of thermodynamics properties of humid air and the condensation of water vapor into the volume and surface wall. So before 2 years, I saw one article in Science Direct that contains a condensation model that was developed for the species transport model in Fluent code and it is suitable for both compressible and incompressible flow of air–steam mixture with additional non-condensable gases. The condensation model consists of two parts: condensation in volume and condensation on the wall. Condensation in volume is modeled by “RETURN TO SATURATION IN CONSTANT TIME SCALE” method. Condensation on the wall is calculated from diffusion of steam through a layer of non-condensable gases near the wall. The model was validated with an experiment and you can check the article in the link below. https://www.sciencedirect.com/scienc...ross%20section. Because the Condensation model was implemented into the Fluent code by means of user-defined functions, I'm wondering do you know how can I write this kind of UDF code into the software. Before 1 year we don't have time for this and we public our article that presents a numerical physical-mathematical model for the phase change in fixed counterflow regenerative heat exchanger working with humid air. The model is Eulerian Wall Film including condensation and evaporation process with species mixture transport. The formation of phase change in the honeycomb matrix depends on the interior microclimate in buildings and the outdoor conditions. The results from the computational fluid dynamics model show the evaporation and condensation processes into the channel. The discussions and the conclusions from this simulation include the influence of the phase change on the thermal efficiency of the regenerative heat exchanger. The model doesn't include fog formation and you can see that article in the link below. https://www.researchgate.net/publica..._for_humid_air Now I have time and I really want to include UDF or to try the simulate the fog formation or the condensation into the volume as DPM particles. Can you help me a little with this UDF?

 February 19, 2022, 06:52 #2 Member   Void_CFD-user Join Date: Feb 2022 Posts: 67 Rep Power: 4 Hey! I can't help you much with UDFs but you can use a mixture or Eulerian multiphase model and that'll take care of condensation in the bulk of the fluid. Fluent also has a Lagrangian wall-film model and Eulerian wall-film model and that'll take care of wall condensation I believe.