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In an attempt to reduce the high computational efforts for dynamic thermal simulations using Computational Fluid Dynamics (CFD) the authors have recently developed an adaptive freeze-flow method (i.e. freezing of flow equations over variable time periods). This paper documents the work that has been carried out to predict the radiative surface heat transfer in dynamic thermal building processes using CFD.The Monte Carlo and Discrete Transfer radiation models were investigated and results compared with analytical solutions. The Discrete Transfer model has shown good performance whereas an unrealistic radiation distribution on the surfaces was observed for the Monte Carlo model. A further investigation of the Discrete Transfer model for the cooling of a solid wall has shown that the adaptive freeze-flow method is an efficient and accurate way to carry out dynamic thermal CFD simulations which involve radiation.

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FachthemenZur Reduktion des Zeitaufwands von dynamisch-thermischen Langzeitsimulationen mit CFD-Programmen wurde in kürzlich veröffent-lichten Studien eine neuartige Freeze-Flow Methode vorgestellt. Diese basiert auf der periodischen Umschaltung zwischen der volldynamischen Lösung aller Gleichungen und der ausschließlichen Lösung der Enthalpie-Gleichungen (eingefrorene Luftströmung