Turbulent Augmentation of Internal Convection Over Pins in Staggered-Pin Fin Arrays

Abstract

The objective of this research was to investigate pin fin midline heat transfer in terms of our understanding of stagnation region heat transfer for cylinders in cross flow and turbine airfoils. An experimental investigation was conducted in a staggered-pin fin array at Reynolds numbers of 3000, 10,000, and 30,000 based on the maximum velocity between cylinders. Midline distributions of static pressure and heat transfer were acquired for rows 1 through 8 at the three Reynolds numbers. Turbulence measurements and velocity distributions were acquired at the inlet and in between adjacent pins in rows using hot wire anemometry. One-dimensional power spectra were calculated to determine integral and energy scales. Midline heat transfer distributions are reported as the Nusselt number divided by the square root of the Reynolds number as a function of angle. In these terms, heat transfer was found to increase through row 3 for a Reynolds number of 30,000. After row 3, heat transfer diminished slightly. The Reynolds number for each row was recast in terms of an effective approach velocity, which was found to be highest in row 3 due to the upstream blockage of row 2. Based on this effective velocity the Nusselt number divided by the square root of the Reynolds number increased through row 4. These data indicate that heat transfer is highest in row 3 pins due to the highest effective velocity, while heat transfer augmentation due to turbulence is highest in row 4 and beyond. Hot wire measurements show higher turbulence intensity and dissipation rates upstream of row 4 compared to upstream of row 3. Generally, pressure, heat transfer, and turbulence measurements were taken at all rows, providing a better understanding of turbulent transport from pin fin arrays.

Heat Transfer From Low Aspect Ratio Pin Fins

“…Chyu et al [1998a] predicts 10% to 20% lower heat transfer over the present testing range. The results from Ames et al [2004] are similar to Chyu et al [1998a] geometry is similar to the predictions given by Zukauskas [1972], and Chyu et al [1998a].…”

“…Both Ames et al [2004] andChyu et al [1998a] give lower results. The combined pin and endwall heat transfer result shown in Table 5-2 from my study agrees well with Metzger et al [1982a].…”

“…As an example, Table 5 Table 5-2 from Metzger and Haley [1982b] and Ames et al, [2004] were obtained from numerically integrating circumferential pin fin data at the given Reynolds numbers. The data from Yeh and Chyu [1998] was obtained directly from a plot.…”

Heat Transfer From Low Aspect Ratio Pin Fins

“…The Reynolds number dependency is unclear for Metzger and Haley [1982b] and Ames et al [2004]. Both only presented three data points across the Reynolds number range.…”

Experimental Study of Performance of Pin Fin Heat Sink under Forced Convection

“…are crucial parameters in determining the heat transfer and friction factor. Ames et al [6] studied the local Nusselt number and turbulent flow structure characteristics in a pin fin channel and their study revealed that the unsteadiness in the wakes, the shear layers formed between the wake and the high speed main stream flow. Sara [7] presented the characteristics of heat transfer and friction and analyzed the convective heat transfer through a rectangular channel with pin fins of square cross sectional and attached over a flat surface; the pin fins were arranged in a staggered manner, with varied clearance ratios C/H.…”