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Local heat/mass transfer and pressure drop in a two-pass rib-roughened channel for turbine airfoil coolingThe heat transfer characteristics of turbulent air flow in a multipass channel were studied via the naphthalene sublimation technique. The naphthalene-coated test section, consisting of two straight, square channels joined by a 180 deg turn, resembled the internal cooling passages of gas turbine airfoils. The top and bottom surfaces of the test channel were roughened by rib turbulators. The rib height-to-hydraulic diameter ratio (e/D) were 0.063 and 0.094, and the rib pitch-to-height ratio (P/e) were 10 and 20. The local heat/mass transfer coefficients on the roughened top wall and on the smooth divider and side walls of the test channel were determined for three Reynolds numbers of 15, 30, and 60, thousand, and for three angles of attack (alpha) of 90, 60, and 45 deg. Results showed that the local Sherwood numbers on the ribbed walls were 1.5 to 6.5 times those for a fully developed flow in a smooth square duct. The average ribbed-wall Sherwood numbers were 2.5 to 3.5 times higher than the fully developed values, depending on the rib angle of attack and the Reynolds number. The results also indicated that, before the turn, the heat/mass transfer coefficients in the cases of alpha = 60 and 45 deg were higher than those in the case of alpha=90 deg. However, after the turn, the heat/mass transfer coefficients in the oblique-rib cases were lower than those in the transverse rib case. Correlations for the average Sherwood number ratios for individual channel surfaces and for the overall Sherwood number ratios are reported. Correlations for the fully developed friction factors and for the loss coefficients are also provided.
Document ID
19880002657
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Han, J. C. (Texas A&M Univ. College Station, TX, United States)
Chandra, P. R. (Texas A&M Univ. College Station, TX, United States)
Date Acquired
September 5, 2013
Publication Date
September 1, 1987
Subject Category
Fluid Mechanics And Heat Transfer
Report/Patent Number
NAS 1.26:179635
AVSCOM-TR-87-C-14
AD-A191003
NASA-CR-179635
Accession Number
88N12039
Funding Number(s)
PROJECT: DA PROJ. 1L1-62209-AH-76
CONTRACT_GRANT: NAS3-24227
PROJECT: RTOP 505-31-4K
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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