Direct Numerical Simulation of Modified Heat Transfer in Turbulent Channel Flow With Condensation

Kurzfassung

Flows with condensing components occur in a wide variety of critical technical applications. Developing more accurate models for predicting the heat and mass transfer in such flows is predicated upon a solid understanding of the phenomena found in the interaction between phase transition and turbulence. In this work, Direct Numerical Simulation (DNS) is employed to investigate the effect of condensing vapor on turbulent channel flow with a cooled wall, in parallel to ongoing experimental efforts focused on a similar system. Temperature and vapor pressure are added to the governing equations as active scalars, and condensation is triggered based on a localized oversaturation condition. Both buoyancy due to temperature and concentration differences as well as heat injection due to the release of latent heat at the phase boundary are considered. By investigating a simple geometry using highly resolved simulations, the effects of the phase transition can be isolated and observed across all scales, from the microscopic interaction with turbulent flow structures to the changes to boundary layer growth up to the impact on the overall heat transfer. In this investigation, we observe an increase in heat transfer compared to a similar flow without modeled condensation and in line with results from experiments. Additionally, we show that condensation events close to the channel wall are directly affected by the structures of the turbulent flow.