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ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

CFD calculations of heat transfer in impinging jet flow

Get access (open in a dialog) DOI: 10.1615/IHTC12.2940
5 pages

Аннотация

Several CFD calculations have been performed in order to assess the ability of the turbulence models implemented in FLUENT to predict heat transfer in the flow of a gas jet impinging perpendicularly upon a flat plate.
In these calculations a two dimensional, axisymmetric geometry with a single round nozzle has been used. Apart from the turbulence model the treatment of the wall (logarithmic wall-function or resolving the geometry down to the viscous sublayer) has been varied.
In the first part, the calculations using the Wall-Function approach were compared with a correlation, given in Martin (1977), which is based on experimental data from (Schlünder and Gnielinski, 1967). Integral Nusselt numbers from the stagnation point to a given radius were obtained from the CFD-calculations and compared with the correlation of the experimental data. The best results have been found with the Reynolds Stress Model. The various k-ε-models, which are available in FLUENT, still gave satisfactory results. The calculations included a systematic variation of the Reynolds number and the distance between nozzle exit and wall. For local heat transfer coefficients, the Wall-Function approach gave insufficient results, because no grid-independent solution could be obtained in these cases.
Therefore in the second part the calculations were done using a grid with higher resolution near the wall (the Near Wall Model) that enabled to solve the equations without the use of wall-functions. Local Nusselt numbers in the stagnation region, calculated with the various turbulence models available in FLUENT show deviations in the of up to 40% among each other and differ from the experimental results in their qualitative behavior. The experimental data in this region are partly overpredicted by the CFD calculations by up to 60%. In the wall-jet region the various models give approximately the same results as found from the experiments. Additionally, a calculation concerning the influence of turbulence intensity at the exit of the nozzle has been performed. It shows that the higher the turbulence intensity, the higher the local heat transfer coefficient near the stagnation point. Some distance downstream from the stagnation point, however, the influence of the initial turbulence intensity becomes negligible.