Comparison of Pin Surface Heat Transfer in Arrays of Oblong and Cylindrical Pin Fins

Kirsch, Kathryn L.; Ostanek, Jason K.; Thole, Karen A.

doi:10.1115/1.4025213

Cited by 24 publications

(6 citation statements)

References 18 publications

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“…To validate the sensor measurements, the time-mean Nusselt number was obtained for the heated pin located in a single-row array (no downstream pins), as well as in the first row of a multirow array with six rows of pins downstream (total of seven rows). The results are compared to previously published results (Ames, et al [16], Ostanek and Thole [22], Kirsch, et al [23]) in Figure 4. This figure shows the mean Frossling number, Fr (Nusselt number over the square root of Reynolds number, which is a common scaling for cylinder heat transfer) versus pin circumferential position.…”

Section: Measurement Validationmentioning

confidence: 71%

Unsteady Heat Transfer Around Low Aspect Ratio Cylinders in an Array

Siroka

Shallcross

Lynch

2016

Volume 8: Heat Transfer and Thermal Engineering

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Cylindrical pins, often called pin fins, are used to create turbulence and promote convective heat transfer within many devices, ranging from computer heat sinks to the trailing edge of jet engine turbine blades. Previous experiments have measured the time-averaged heat transfer over a single pin as well as the flow fields around the pin. However, in this study, focus is placed on the instantaneous heat flux around the centerline of a low aspect-ratio pin within an array. Time-mean and unsteady convective heat flux are measured around the circumference of an isothermal heated test pin via a microsensor located at the surface. The pin is positioned at various locations within a staggered array in a large-scale wind tunnel. Reynolds numbers from 3,000 to 50,000, based on pin diameter and maximum velocity between pins, are tested with a streamwise spacing of 1.73 diameters between rows, a spanwise spacing of 2 diameters, and a pin height of 1 diameter. The time-averaged and standard deviation of convective heat flux around the pin is higher over most of the pin surface for pins in downstream row positions of an array relative to the first row pin, except in the wake which has similar levels for all rows. For a given pin position in the array, as the Reynolds number increases, the point of minimum heat transfer moves circumferentially upstream on the pin fin, corresponding to earlier transition of the pin boundary layer. Also, for a given Reynolds number, the minimum heat transfer point on the pin circumference moves upstream for pins further into the array, due to the high turbulence levels within the array which cause early transition. For a single pin row with no downstream pins, heat transfer fluctuations are very high on the backside of the pin due to the significant unsteadiness in the pin wake, but heat transfer fluctuations are suppressed for a pin with downstream rows due to the confining effects of the close spacing. The results from this study can be used to design pin-fin arrays that take advantage of unsteadiness and increase overall convective heat transfer for various industry components.

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Section: Measurement Validationmentioning

confidence: 71%

Unsteady Heat Transfer Around Low Aspect Ratio Cylinders in an Array

Siroka

Shallcross

Lynch

2016

Volume 8: Heat Transfer and Thermal Engineering

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“…On an oblong pin with its long axis parallel to the flow direction, the heat transfer behavior mimics that of the cylindrical pin. One key difference, however, is that the boundary layer on the surface of the oblong transitions to turbulence for Reynolds numbers 1 order of magnitude less than the Reynolds number required for transition on a cylindrical pin [22]. These oblong pins are more severely impacted by spacing variations than cylindrical pins due to the longer surface length over which the boundary layer transitions.…”

Section: Resultsmentioning

confidence: 99%

“…The study represented a continuation of experiments in which surface temperature measurements were taken on an oblong oriented with its long axis 0 deg to the flow. Kirsch et al [22] showed that the heat transfer distribution on an oblong differed significantly from those found on cylindrical pins. These patterns were strongly dependent on spanwise spacing and Reynolds number.…”

Section: Previous Studiesmentioning

confidence: 98%

Heat Transfer Measurements of Oblong Pins

Kirsch

Thole

2015

Journal of Turbomachinery

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Pin fin arrays are employed as an effective means for heat transfer enhancement in the internal passages of a gas turbine blade, specifically in the blade's trailing edge. Various shapes of the pin itself have been used in such arrays. In this study, oblong pin fins are investigated whereby their long axis is perpendicular to the flow direction. Heat transfer measurements were taken at the pin midspan with unheated endwalls to isolate the pin heat transfer. Results show important differences in the heat transfer patterns between a pin in the first row and a pin in the third row. In the third row, wider spanwise spacing allows for two peaks in heat transfer over the pin surface. Additionally, closer streamwise spacing leads to consistently higher heat transfer for the same spanwise spacing. Due to the blunt orientation of the pins, the peak in heat transfer occurs off the stagnation point.

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“…A maximum appeared at a Reynolds number of 80,000. Kirsch et al (2013) presented the flow characteristics around oblong-shaped and circular pin fins as a function of the Reynolds number varying from 10,000 to 30,000, for SD = 2.25 and 3, as well as HD = 1. The investigation reported that oblong-shaped pin fins implied a complete development of the boundary layer, i.e.…”

Section: Lamilloy Cooling Structure In Turbine Vanesmentioning

confidence: 99%

On the heat transfer characteristics of a Lamilloy cooling structure with curvatures with different pin fins configurations

Luo

Zhang

Wang

et al. 2020

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Purpose The pin fin is applied into a Lamilloy cooling structure which is broadly used in the leading edge region of the modern gas turbine vane. The purpose of this paper is to investigate effects of the layout, diameter and shape of pin fins on the flow structure and heat transfer characteristics in a newly improved Lamilloy structure at the leading edge region of a turbine vane. Design/methodology/approach A numerical method is applied to investigate effects of the layout, diameter and shape of pin fins on the flow structure and heat transfer characteristics in a newly improved Lamilloy structure at the leading edge of a turbine vane. The diverse locations of pin fins are Lp = 0.35, 0.5, 0.65. The diameter of the pin fins varies from 8 mm to 32 mm. Three different ratios of root to roof diameter for pin fins are also investigated, i.e. k = 0.5, 1, 2. The Reynolds number ranges from 10,000 and 50,000. Results of the flow structures, heat transfer on the target surface and pin fin surfaces, and friction factor are studied. Findings The heat transfer on the pin fin surface gradually decreases and then increases as the location of the pin fins increases. Increasing the diameter of the pin fins causes the heat transfer on the pin fin surface to gradually increase, while a lower value of the friction factor occurs. Besides, the heat transfer on the pin fin surface at a small root diameter increases remarkably, but a slight heat transfer penalty is found at the target surface. It is also found that both the Reynolds analogy performance and the thermal performance are increased compared to the baseline whose diameter and normalized location of pin fins are set as 16 and 0.5 mm, respectively. Social implications The models provide a basic theoretical study to deal with nonuniformity of the temperature field for the turbine vane leading edge. The investigation also provides a better understanding of the heat transfer and flow characteristics in the leading edge region of a modern turbine vane. Originality/value This is a novel method to adopt pin fins into a Lamilloy cooling structure with curvature. It presents that the heat transfer of the pin fin surface in a pin-fin Lamilloy cooling structure with curvature can be significantly increased by changing the parameters of the pin fins which may lead to various flow behavior. In addition, the shape of the pin fin also shows great influence on the heat transfer and flow characteristics. However, the heat transfer of the target surface shows a small sensitivity to different layouts, diameter and shape of pin fin.

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Comparison of Pin Surface Heat Transfer in Arrays of Oblong and Cylindrical Pin Fins

Cited by 24 publications

References 18 publications

Unsteady Heat Transfer Around Low Aspect Ratio Cylinders in an Array

Unsteady Heat Transfer Around Low Aspect Ratio Cylinders in an Array

Heat Transfer Measurements of Oblong Pins

On the heat transfer characteristics of a Lamilloy cooling structure with curvatures with different pin fins configurations

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