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Research Papers

# High Rotation Number Effects on Heat Transfer in a Rectangular $(AR=2:1)$ Two-Pass Channel

[+] Author and Article Information
Michael Huh

Department of Mechanical Engineering, University of Texas at Tyler, Tyler, TX 75799mhuh@uttyler.edu

Jiang Lei

Department of Mechanical Engineering, Turbine Heat Transfer Laboratory, Texas A&M University, College Station, TX 77843

Yao-Hsien Liu1

Department of Mechanical Engineering, Turbine Heat Transfer Laboratory, Texas A&M University, College Station, TX 77843

Je-Chin Han2

Department of Mechanical Engineering, Turbine Heat Transfer Laboratory, Texas A&M University, College Station, TX 77843jc-han@tamu.edu

1

Present address: Department of Mechanical Engineering, National Chiao Tung University, Hsinchu, Taiwan 30010.

2

Corresponding author.

J. Turbomach 133(2), 021001 (Oct 05, 2010) (11 pages) doi:10.1115/1.4000549 History: Received July 10, 2009; Revised July 13, 2009; Published October 05, 2010; Online October 05, 2010

## Abstract

This paper experimentally investigated the rotational effects on heat transfer in a smooth two-pass rectangular channel $(AR=2:1)$, which is applicable to the cooling passages in the midportion of the gas turbine blade. The test channel has radially outward flow in the first passage and radially inward flow in the second passage after a 180 deg sharp turn. In the first passage, the flow is developing and heat transfer is increased compared with the fully developed case. Rotation slightly reduces the heat transfer on the leading surface and increases heat transfer on the trailing surface in the first pass. Heat transfer is highly increased by rotation in the turn portion of the first pass on both leading and trailing surfaces. Rotation increased heat transfer enhancement in the tip region up to a maximum Nu ratio $(Nu/Nus)$ of 1.83. In the second passage, under rotating conditions, the leading surface experienced heat transfer enhancements above the stationary case while the trailing surface decreased. The current study has more than four times the range of the rotation number previously achieved for the 2:1 aspect ratio channel. The increased range of the rotation number and buoyancy parameter reached in this study are 0–0.45 and 0–0.8, respectively. The higher rotation number and buoyancy parameter have been correlated very well to predict the rotational heat transfer in the two-pass, 2:1 aspect ratio flow channel.

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## Figures

Figure 1

Gas turbine blade internal cooling channels and their applicable aspect ratios

Figure 2

Rotating arm assembly used to perform heat transfer experiments with the 2:1 aspect ratio test section

Figure 3

Drawing showing the flow channel geometry of the 2:1 aspect ratio test section

Figure 4

(a) Test section tip view showing location of heaters and wall naming convention. (b) Test section view showing the copper plate region numbering convention.

Figure 5

Comparison of stationary streamwise averaged Nus/Nuo ratios for different entrance geometries

Figure 6

Conceptual view of (a) rotation induced secondary flow inside a two-passage rectangular channel (AR=2:1) and (b) turn induced secondary flow

Figure 7

Streamwise Nu ratio (Nu/Nuo) distribution at Re=10,000 and Re=20,000 at all rotational speeds (0–400 rpm)

Figure 8

Streamwise Nu ratio (Nu/Nuo) distribution at Re=30,000 and Re=40,000 at all rotational speeds (0–400 rpm)

Figure 9

Nu ratio (Nu/Nuo) as a function of Re for the tip cap at all rotational speeds (0–400 rpm)

Figure 10

Regional leading and trailing Nu ratio (Nu/Nus) distribution as a function of rotation number (Ro)

Figure 11

Tip region 6 and region 7 Nu ratio (Nu/Nus) distributions as a function of rotation number (Ro)

Figure 12

Region 1 to region 4 (leading, trailing, outer, and inner) Nu ratio (Nu/Nus) distribution as a function of buoyancy parameter (Bo)

Figure 13

Region 5 to region 8 (leading, trailing, outer, and inner) Nu ratio (Nu/Nus) distributions as a function of buoyancy parameter (Bo)

Figure 14

Tip region 6 and region 7 Nu ratio (Nu/Nus) distributions as a function of buoyancy parameter (Bo)

Figure 15

Region 9 to region 12 (leading, trailing, outer, and inner) Nu ratio (Nu/Nus) distributions as a function of buoyancy parameter (Bo)

Figure 16

First and second pass averaged Nu ratio (Nu/Nus) distributions as a function of buoyancy parameter (Bo)

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