Turbulent heat transport phenomena in multiple‐started helically ribbed pipes are investigated. Such structures are applied to enhance heat transfer in various technical systems. A large‐eddy simulation (LES) approach is used to model the turbulent flow field. The simulation results for heat transfer and pressure loss are in good agreement with available experimental data and the simulation model is successfully validated for complex surface geometries. For a better understanding of the impact of the wall structures on the turbulent transport processes, local profiles of the relevant flow variables values are investigated. Thus, the specific mechanism of the heat transfer enhancement can be explained and a knowledge‐based optimization of innovative structures is possible.
Abstract. Evaporation of thin liquid films inside reentrant cavities occurs in several boiling processes where enhanced surfaces are utilized. In this work, evaporation from a single reentrant cavity with an additional thin channel is studied. The channel allows the backflow of liquid from the pool into the cavity during bubble growth. Direct numerical simulations were performed, showing a strong relation between flow to the film inside the cavity and bubble growth at the pore. Additionally, a model was created with a novel modeling approach which is based on solving the Young-Laplace equation. From the model characteristic nondimensional parameters can be obtained and the influence of geometry variations on hydrodynamics can be studied.
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