NDLI: The Effect of Thermal Barrier Coating Roughness Magnitude on Heat Transfer With and Without Flowpath Surface Steps

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Ronald, S. Bunker
Copyright Year	2003
Abstract	An experimental study has been performed to investigate the convective heat transfer coefficients resulting from differing magnitudes of surface roughness for ceramic thermal barrier coatings (TBC) of the type used to protect gas turbine hot section components. A flat plate wind tunnel test is employed with zero freestream pressure gradient, and levels of freestream turbulence from 4.5 to 6.5%. The TBC applied in these tests is an air plasma sprayed, yttriastabalized zirconia-oxide. Average test surface Reynolds numbers are varied from 400,000 to 2,200,000. Average roughness values (RA) for the TBC surfaces are varied by degrees of polishing from 10 μm to 1 μm, resulting in roughness Reynolds numbers of up to 70. Baseline comparison tests use smooth metal surfaces. The changing physical and heat transfer character of the TBC surfaces with polishing is demonstrated. Results show a significant effect of polishing degree on the surface heat transfer coefficients. Such surfaces were also tested with varying magnitudes of forward facing flowpath steps to model the potential interruptions seen at component interfaces. Flowpath steps are shown to produce quite elevated levels of heat transfer for the smooth surfaces, with little or no further additional enhancement due to increased TBC roughness levels.
Sponsorship	Heat Transfer Division
Starting Page	1
Ending Page	10
Page Count	10
File Format	PDF
ISBN	0791837181
DOI	10.1115/IMECE2003-41073
Volume Number	Heat Transfer, Volume 2
Conference Proceedings	ASME 2003 International Mechanical Engineering Congress and Exposition
Language	English
Publisher Date	2003-11-15
Publisher Place	Washington, DC, USA
Access Restriction	Subscribed
Subject Keyword	Turbulence Flat plates Wind tunnels Reynolds number Polishing Surface roughness Ceramics Pressure gradient Plasmas (ionized gases) Convection Gas turbines Metal surfaces Thermal barrier coatings Heat transfer coefficients Heat transfer
Content Type	Text
Resource Type	Article

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