At Reactor Engineering Division of Jožef Stefan Institute a new experiment is being designed in the THELMA laboratory to study temperature fluctuations at the heated foil cooled by turbulent flow. Detailed design of the experiment is based on Computational Fluid Dynamics (CFD) studies which are described in the present work.
The flow and heat transfer in the new experiment predicted with a wall-resolved Large Eddy Simulation (LES) using a wall-adapting local eddy-viscosity (WALE) model in OpenFOAM computer code. Foil was modeled with approximation of the constant heat flux. Simulations assumed incompressible, fully developed turbulent flow of Newtonian fluids with Reynolds number of 10000. In the first part of the study, heat transfer has been included to the study using temperature as a passive scalar, so there is no feedback loop on mass and momentum conservation equation. The second part of the simulations took into account the influence of the temperature on the water viscosity and density. We have identified the power of the foil in the experiment and the maximum foil temperatures at which the water temperature can be described with the passive scalar approximation.
The most relevant result of our simulations were temperature fluctuations on the foil. With observation and analysis of coherent thermal structures in simulations we have predicted the required resolution and frequency needed by thermographic high-speed camera at given Reynolds and Prandtl numbers.
In the Conclusions we present the comparison of our simulations with the preliminary measurements.
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