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978-3-86853-811-3, Reihe Thermodynamik

Sebastian Spring
Numerical Prediction of Jet Impingement Heat Transfer

189 Seiten, Dissertation Universität Stuttgart (2010), Softcover, A5

Zusammenfassung / Abstract

Jet impingement represents a highly effective cooling technology due to the high heat transfer coefficients that can be achieved. In the present work, aspects on the numerical prediction of jet impingement heat transfer for turbomachinery applications are considered. The motivation is to evaluate the use of Computational Fluid Dynamics (CFD) for these types of flow and to assess the numerical accuracy of the results.

In the framework of this thesis, different configurations of impinging jets are investigated numerically. High Reynolds number flows (up to 100,000) are considered due to their relevance for turbomachinery applications. First, the single impinging jet serves to conduct a detailed analysis of the predictions of flow and heat transfer. This is important as it constitutes the basis for an understanding of the phenomena occurring in complex impingement configurations. The results obtained by different turbulence models are evaluated. The models included represent current state of the art with respect to two-equation type models and Reynolds stress type models. Next, the configuration of a single jet impinging through a defined cross-flow is considered. This allows for an isolated analysis of the effects of cross-flow, which are of high importance for the flow within arrays of multiple impinging jets, where cross-flow is one main influencing factor. Different jet Reynolds numbers are investigated in combination with different blowing ratios. The study continues with the simulation of large-scale arrays of multiple impinging jets. The numerical results are discussed in detail by means of extensive comparison with experimental data in the form of both average and local heat transfer coefficients. The effects of cross-flow scheme, Reynolds number, jet arrangement, and separation distance are considered. In the following chapters, macro-scale surface ribs as well as micro-size structures are applied to the target plate for the purpose of heat transfer enhancement. The numerical results are again validated by comparison with experimental data. In this context, it is also demonstrated how the numerical results may be used as an additional source of data for the design of such surface enlarging structures and for the quantification of the effects of conjugate heat transfer.