An experimental investigation of the rib surface-averaged heat transfer coefficient in a rib-roughened square passage
- Northeastern Univ., Boston, MA (United States). Dept. of Mechanical Engineering
Turbine blade cooling is accomplished, among other methods, by passing the cooling air through an often serpentine passage in the core of the blade. Furthermore, to enhance the heat transfer coefficient, these passages are roughened with rib-shaped turbulence promoters. Considerable data are available on the heat transfer coefficient on the passage surface between the ribs. However, the heat transfer coefficients on the surface of the ribs themselves have not been investigated to the same extent. Therefore, an accurate account of the heat transfer coefficient on the rib surfaces is critical in the overall design of the blade cooling system. The objective of this experimental investigation was to conduct a series of 13 tests to measure the rib surface-averaged heat transfer coefficient, h{sub rib} in a square duct roughened with staggered 90 deg ribs. To investigate the effects that blockage ratio, e/D{sub h}, and pitch-to-height ratio, S/e, have on h{sub rib} and passage friction factor, three rib geometries corresponding to blockage ratios of 0.133, 0.167, and 0.25 were tested for pitch-to-height ratios of 5, 7, 8.5, and 10. Comparisons were made between the rib average heat transfer coefficient and that on the wall surface between two ribs, h{sub floor}, reported previously. It is concluded that: The rib average heat transfer coefficient is much higher than that for the area between the ribs; similar to the heat transfer coefficient on the surface between the ribs, the average rib heat transfer coefficient increases with the blockage ratio; a pitch-to-height ratios of 8.5 consistently produced the highest rib average heat transfer coefficients amongst all tested; under otherwise identical conditions, ribs in upstream-most position produced lower heat transfer coefficients than the midchannel positions; the upstream-most rib average heat transfer coefficients decreased with the blockage ratio; and thermal performance decreased with increased blockage ratio.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 511914
- Report Number(s):
- CONF-940626-; ISSN 0889-504X; TRN: IM9736%%40
- Journal Information:
- Journal of Turbomachinery, Vol. 119, Issue 2; Conference: 39. international gas turbine and aeroengine congress and exposition, The Hague (Netherlands), 13-16 Jun 1994; Other Information: PBD: Apr 1997
- Country of Publication:
- United States
- Language:
- English
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