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Research Papers

Heat Transfer and Pressure Drop Measurements in Constant and Converging Section Pin and Diamond Pedestal Arrays

[+] Author and Article Information
I. Jaswal, F. E. Ames

Department of Mechanical Engineering, University of North Dakota, Grand Forks, ND 58202

J. Thermal Sci. Eng. Appl 1(1), 011006 (Jul 21, 2009) (7 pages) doi:10.1115/1.3159498 History: Received February 21, 2009; Revised May 11, 2009; Published July 21, 2009

High solidity pin and pedestal arrays are beneficial in reducing temperature gradients and distributing stress across double wall cooling channels such as trailing edge regions. In this study two high solidity (45%) cooling channel geometries were selected and tested in both constant channel height and converging channel configurations. One geometry consisted of a high solidity round pin fin array and the other geometry consisted of a rounded diamond pedestal array designed to minimize pressure drop. Heat transfer rates for both geometries were determined on a row by row basis for both the constant channel and converging channel configurations. Heat transfer and pressure drop measurements were acquired in a bench scale test rig. Reynolds numbers ranged from approximately 3000 to 60,000 for the constant channel arrays and 3500 to 100,000 for the converging arrays based on the characteristic dimension of the pin or pedestal and the local maximum average velocity across a row. The high solidity pin fin array had an axial spacing (X/D) of 1.043 and a cross channel spacing (Z/D) of 1.674. The high solidity diamond pedestal array had an axial spacing of 1.00 and a cross channel spacing of 1.93. The constant section pin fin array had a channel height to diameter of 0.95 while the constant section diamond pedestal array had a height to characteristic dimension of 0.96. The converging pin fin array had an inlet to exit convergence ratio of 2.87 over five heated rows while the converging pedestal array had an inlet to exit convergence ratio of 3.53 over seven heated rows. The constant channel height internal cooling schemes have shown that the high solidity pin fin and the rounded diamond pedestal arrays produce comparable heat transfer and array pressure drop. Both the converging channel arrays show a noticeable (5–7%) reduction in heat transfer compared with the constant height channels. Array pressure drop for the two converging geometries was found to be quite consistent.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Small internal heat transfer and flow rig used in heat transfer testing of high solidity round pin and diamond shaped pedestal arrays

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Figure 2

Schematic of preconditioning and heat transfer array test section with plenum, acrylic pins, and heat transfer array and exit

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Figure 3

ABS plastic preconditioning rows for the constant height rounded diamond pedestal array made using a rapid prototyping machine

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Figure 4

Constant height rounded diamond pedestal array without the top endwall plate

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Figure 5

Converging rounded diamond pedestal array assembly before installation of the top endwall plates

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Figure 6

Instrumented bottom endwall with thermofoil heater strips and thermocouples installed

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Figure 7

Nusselt number distribution for a high solidity staggered array of round pins with a constant channel height

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Figure 8

Nusselt number distributions for a high solidity staggered array of rounded diamond pedestals with a constant channel height

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Figure 9

Nusselt number distributions for a high solidity staggered array of round pins for a converging channel

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Figure 10

Nusselt number distributions for a high solidity staggered array of rounded diamond pedestals in a converging channel

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Figure 11

High solidity round pin constant channel height array flow friction factor, f

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Figure 12

Flow friction factor (f) for constant channel height high solidity rounded diamond pedestal array

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Figure 13

Dimensionless array pressure drop for converging high solidity pin and rounded diamond pedestal arrays

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