Abstract Most of the studies on gas turbine blade internal channels have focused on constant cross-sectional areas from entrance to turn. Gas turbine blades are typically tapered from hub to tip to reduce thermal loading. These channels exist inside high-performance turbine blades for providing effective cooling to the blade external surface, which is exposed to high-temperature gas flow. Heat transfer measurements are presented for both the straight and tapered square channels including the turn region with and without rib turbulators. The straight channels will have a uniform square cross-section area of 5.08×5.08 cm 2 . For the tapered channels, the square cross-sectional area reduces from entrance into the first pass ( 5.08×5.08 cm 2 ) to the 180° turn ( 2.54×2.54 cm 2 ) and then expands from turn to exit in the second pass (5.08×5.08 cm 2 ) . The heat transfer results for tapered channels are compared with results for straight channels. Results show that heat transfer in tapered smooth channels is enhanced significantly due to flow acceleration in the first pass, a combination of taper and turn and flow deceleration in the second pass. Overall, the tapered channels significantly produce higher heat transfer enhancements compared to the Dittus–Boelter correlation for fully developed flow especially in the after-turn region. Based on the results from this study, the heat transfer inside tapered channels in the after-turn region cannot be predicted by calculating local Reynolds numbers and using straight channel heat transfer correlations. However, the first pass Nusselt number enhancement distributions are similar for both straight and tapered channels when normalized using the local Nusselt number based on local Reynolds number. The difference in the after-turn region between the straight and tapered channels is reduced with the addition of rib turbulators.
[1]
D. Nikitopoulos,et al.
Heat Transfer in a Two-Pass Internally Ribbed Turbine Blade Coolant Channel With Cylindrical Vortex Generators
,
1995
.
[2]
D. E. Metzger,et al.
Heat Transfer Around Sharp 180-deg Turns in Smooth Rectangular Channels
,
1985
.
[3]
Je-Chin Han,et al.
Local heat/mass transfer distributions around sharp 180 deg turns in two-pass smooth and rib-roughened channels
,
1988
.
[4]
Je-Chin Han,et al.
LOCAL HEAT TRANSFER DISTRIBUTIONS NEAR A SHARP 180° TURN OF A TWO-PASS SMOOTH SQUARE CHANNEL USING A TRANSIENT LIQUID CRYSTAL IMAGE TECHNIQUE
,
1995
.
[5]
R. Boyle.
Heat transfer in serpentine passages with turbulence promoters
,
1984
.
[6]
S. J. Kline,et al.
Describing Uncertainties in Single-Sample Experiments
,
1953
.
[7]
Je-Chin Han,et al.
Detailed heat transfer distributions in two-pass square channels with rib turbulators
,
1997
.
[8]
D. E. Metzger,et al.
Use of Melting Point Surface Coatings for Local Convection Heat Transfer Measurements in Rectangular Channel Flows With 90-deg Turns
,
1984
.
[9]
M. Chyu.
Regional heat transfer in two-pass and three-pass passages with 180-deg sharp turns
,
1991
.
[10]
Je-Chin Han,et al.
Effect of rib angle on local heat/mass transfer distribution in a two-pass rib-roughened channel
,
1987
.
[11]
Sumanta Acharya,et al.
Heat Transfer in a Two-Pass Internally Ribbed Turbine Blade Coolant Channel With Cylindrical Vortex Generators
,
1998
.