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Experimental and Numerical Investigation of Conjugate Heat Transfer in Rib-roughened Duct

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Final rept. 1 Aug 2008-1 Aug 2011

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The final report for this effort is divided into two parts. The first is the Experimental activity and the second the numerical activity. Each of these parts is covered separately in this report. The purpose of the experimental project is to have a deeper understanding of the conjugate heat transfer phenomenon by conducting experiments for the fundamental understanding, as well as creating a baseline database for numerical investigations. The targeted application is the ribbed internal cooling channels used in turbine blades. A test section is built to model the underlying physics of the conjugate heat transfer phenomena in a turbine blade. The investigation focuses on measurements conducive to turbulence characterization of the channel by means of a hotwire, and local heat flux calculations over flat, ribbed and ribbedfilm cooled slab configurations through local temperature measurements made by Infrared Thermography. The turbulence characterization of the channel is not only important for the interpretation of the experimental based local heat flux calculations, but also crucial for the conjugate numerical models that predict the cooling performance in parallel to the experimental work conducted. The numerical part of this project has be executed investigating a generic configuration, namely a straight duct of square test section roughened by square sharp angled ribs. A metallic slab simulates one of the rib-roughened cooling duct walls. An uniform heat flux is applied at the bottom face of this slab, allowing the conduction heat transfer through its thickness at the interface solid-fluid this heat flux is removed and transported by the cooling flow. In a further phase cooling holes was introduced to investigate film cooling. This approach simulates the heat transfer occurring from the freestream hot gas side, through the blade thickness, towards the internal cooling channels and it can be considered to be similar to internal cooling channels in turbine blades.

Subject Categories:

  • Thermodynamics
  • Jet and Gas Turbine Engines

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