Heat Transfer Measurements of Oblong Pins

2014 ◽  
Author(s):  
Kathryn L. Kirsch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Flow Direction ◽  
Effective Means ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
The Third ◽  
Pin Fins ◽  
Two Peaks ◽  
Pin Fin Arrays

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 mid-span 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.

Heat Transfer Measurements of Oblong Pins

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Kathryn L. Kirsch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Flow Direction ◽  
Effective Means ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
The Third ◽  
Pin Fins ◽  
Two Peaks ◽  
Pin Fin Arrays

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.

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

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
Kathryn L. Kirsch ◽  
Jason K. Ostanek ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Boundary Layer Separation ◽  
Diameter Ratio ◽  
Pin Fin ◽  
The Third ◽  
Spacing Effects ◽  
Pin Fins ◽  
Turbine Airfoils ◽  
Pin Fin Arrays

Pin fin arrays are most commonly used to promote convective cooling within the internal passages of gas turbine airfoils. Contributing to the heat transfer are the surfaces of the channel walls as well as the pin itself. Generally the pin fin cross section is circular; however, certain applications benefit from using other shapes such as oblong pin fins. The current study focuses on characterizing the heat transfer distribution on the surface of oblong pin fins with a particular focus on pin spacing effects. Comparisons were made with circular cylindrical pin fins, where both oblong and circular cylindrical pins had a height-to-diameter ratio of unity, with both streamwise and spanwise spacing varying between two and three diameters. To determine the effect of relative pin placement, measurements were taken in the first of a single row and in the third row of a multirow array. Results showed that area-averaged heat transfer on the pin surface was between 30 and 35% lower for oblong pins in comparison to cylindrical. While heat transfer on the circular cylindrical pin experienced one minimum prior to boundary layer separation, heat transfer on the oblong pin fins experienced two minimums, where one is located before the boundary layer transitions to a turbulent boundary layer and the other prior to separation at the trailing edge.

Effects of Geometry, Spacing, and Number of Pin Fins in Additively Manufactured Microchannel Pin Fin Arrays

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Katharine K. Ferster ◽  
Kathryn L. Kirsch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Pressure Loss ◽  
Reynolds Numbers ◽  
Turbine Engine ◽  
Pin Fin ◽  
Study Results ◽  
Pin Fins ◽  
Turbine Airfoils ◽  
Pin Fin Arrays

The demand for higher efficiency is ever present in the gas turbine field and can be achieved through many different approaches. While additively manufactured parts have only recently been introduced into the hot section of a gas turbine engine, the manufacturing technology shows promise for more widespread implementation since the process allows a designer to push the limits on capabilities of traditional machining and potentially impact turbine efficiencies. Pin fins are conventionally used in turbine airfoils to remove heat from locations in which high thermal and mechanical stresses are present. This study employs the benefits of additive manufacturing to make uniquely shaped pin fins, with the goal of increased performance over conventional cylindrical pin fin arrays. Triangular, star, and spherical shaped pin fins placed in microchannel test coupons were manufactured using direct metal laser sintering (DMLS). These coupons were experimentally investigated for pressure loss and heat transfer at a range of Reynolds numbers. Spacing, number of pin fins in the array, and pin fin geometry were variables that changed pressure loss and heat transfer in this study. Results indicate that the additively manufactured triangles and cylinders outperform conventional pin fin arrays, while stars and dimpled spheres did not.

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

2013 ◽  
Author(s):  
Kathryn L. Kirsch ◽  
Jason K. Ostanek ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Boundary Layer Separation ◽  
Diameter Ratio ◽  
Pin Fin ◽  
The Third ◽  
Spacing Effects ◽  
Pin Fins ◽  
Turbine Airfoils ◽  
Pin Fin Arrays

Pin fin arrays are most commonly used to promote convective cooling within the internal passages of gas turbine airfoils. Contributing to the heat transfer are the surfaces of the channel walls as well as the pin itself. Generally the pin fin cross-section is circular; however, certain applications benefit from using other shapes such as oblong pin fins. The current study focuses on characterizing the heat transfer distribution on the surface of oblong pin fins with a particular focus on pin spacing effects. Comparisons were made with circular cylindrical pin fins, where both oblong and circular cylindrical pins had a height-to-diameter ratio of unity, with both streamwise and spanwise spacing varying between two and three diameters. To determine the effect of relative pin placement, measurements were taken in the first of a single row and in the third row of a multi-row array. Results showed that area-averaged heat transfer on the pin surface was between 30 and 35 percent lower for oblong pins in comparison to cylindrical. While heat transfer on the circular cylindrical pin experienced one minimum prior to boundary layer separation, heat transfer on the oblong pin-fins experienced two minimums, where one is located before the boundary layer transitions to a turbulent boundary layer and the other prior to separation at the trailing edge.

Convective Heat Transfer of Cubic Fin Arrays in a Narrow Channel

1998 ◽  
Vol 120 (2) ◽  
pp. 362-367 ◽  
Author(s):  
M. K. Chyu ◽  
Y. C. Hsing ◽  
V. Natarajan
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Pressure Loss ◽  
Narrow Channel ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
Pin Fins ◽  
Pin Fin Arrays ◽  
Element Shape

The present study explores the heat transfer enhancement induced by arrays of cubic fins. The fin element is either a cube or a diamond in shape. The array configurations studied include both in-line and staggered arrays of seven rows and five columns. Both cubic arrays have the same geometric parameters, i.e., H/D = 1, S/D = X/D = 2.5, which are similar to those of earlier studies on circular pin-fin arrays. The present results indicate that the cube element in either array always yields the highest heat transfer, followed by diamond and circular pin-fin. Arrays with diamond-shaped elements generally cause the greater pressure loss than those with either cubes or pin fins. For a given element shape, a staggered array generally produces higher heat transfer enhancement and pressure loss than the corresponding inline array. Cubic arrays can be viable alternatives for pedestal cooling near a blade trailing edge.

Effects of Geometry and Spacing in Additively Manufactured Microchannel Pin Fin Arrays

2017 ◽  
Author(s):  
Katharine K. Ferster ◽  
Kathryn L. Kirsch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Pressure Loss ◽  
Reynolds Numbers ◽  
Turbine Engine ◽  
Pin Fin ◽  
Study Results ◽  
Pin Fins ◽  
Turbine Airfoils ◽  
Pin Fin Arrays

The demand for higher efficiency is ever-present in the gas turbine field and can be achieved through many different approaches. While additively manufactured parts have only recently been introduced into the hot section of a gas turbine engine, the manufacturing technology shows promise for more widespread implementation since the process allows a designer to push the limits on capabilities of traditional machining and potentially impact turbine efficiencies. Pin fins are conventionally used in turbine airfoils to remove heat from locations in which high thermal and mechanical stresses are present. This study employs the benefits of additive manufacturing to make uniquely shaped pin fins, with the goal of increased performance over conventional cylindrical pin fin arrays. Triangular, star, and spherical shaped pin fins placed in microchannel test coupons were manufactured using Direct Metal Laser Sintering. These coupons were experimentally investigated for pressure loss and heat transfer at a range of Reynolds numbers. Spacing, number of pin fins in the array, and pin fin geometry were variables that changed pressure loss and heat transfer in this study. Results indicate that the additively manufactured triangles and cylinders outperform conventional pin fin arrays, while stars and dimpled spheres did not.

scholarly journals Convective Heat Transfer of Cubic Fin Arrays in a Narrow Channel

1996 ◽  
Author(s):  
M. K. Chyu ◽  
Y. C. Hsing ◽  
V. Natarajan
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Pressure Loss ◽  
Narrow Channel ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
Pin Fins ◽  
Pin Fin Arrays ◽  
Element Shape

The present study explores the heat transfer enhancement induced by arrays of cubic fins. The fin element is either a cube or a diamond in shape. The array configurations studied include both inline and staggered arrays of seven rows and five columns. Both cubic arrays have the same geometric parameters, i.e., H/D=1, S/D=X/D=2.5, which are similar to those of earlier studies on circular pin-fin arrays. The present results indicate that the cube element in either array always yields the highest heat transfer, followed by diamond and circular pin-fin. Arrays with diamond-shaped elements generally cause the greatest pressure loss than those with either cubes or pin fins. For a given element shape, a staggered array generally produces higher heat transfer enhancement and pressure loss than the corresponding inline array. Cubic Arrays can be viable alternatives for pedestal cooling near a blade trailing edge.

Computational Analysis of Pin-Fin Arrays Effects on Internal Heat Transfer Enhancement of a Blade Tip Wall

2009 ◽  
Vol 132 (3) ◽  
Author(s):  
Gongnan Xie ◽  
Bengt Sundén ◽  
Esa Utriainen ◽  
Lieke Wang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Computational Models ◽  
Internal Heat ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
Flow And Heat Transfer ◽  
Pin Fins ◽  
Blade Tip ◽  
Pin Fin Arrays

Cooling methods are strongly needed for the turbine blade tips to ensure a long durability and safe operation. Improving the internal convective cooling is therefore required to increase the blade tip life. A common way to cool the tip is to use serpentine passages with 180-deg turns under the blade tip cap. In this paper, enhanced heat transfer of a blade tip cap has been investigated numerically. The computational models consist of a two-pass channel with a 180-deg turn and various arrays of pin fins mounted on the tip cap, and a smooth two-pass channel. The inlet Reynolds number is ranging from 100,000 to 600,000. The computations are 3D, steady, incompressible, and nonrotating. Details of the 3D fluid flow and heat transfer over the tip walls are presented. The effects of pin-fin height, diameter, and pitches on the heat transfer enhancement on the blade tip walls are observed. The overall performances of ten models are compared and evaluated. It is found that due to the combination of turning, impingement, and pin-fin crossflow, the heat transfer coefficient of the pin-finned tip is a factor of 2.67 higher than that of a smooth tip. This augmentation is achieved at the expense of a penalty of pressure drop around 30%. Results show that the intensity of heat transfer enhancement depends upon pin-fin configuration and arrangement. It is suggested that pin fins could be used to enhance the blade tip heat transfer and cooling.

Heat Transfer Enhancement of Internal Cooling Passage With Triangular and Semi-Circular Shaped Pin-Fin Arrays

2012 ◽  
Author(s):  
Sin Chien Siw ◽  
Minking K. Chyu ◽  
Mary Anne Alvin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
Pin Fins ◽  
Cooling Passage ◽  
Internal Cooling Passage ◽  
Pin Fin Array ◽  
Pin Fin Arrays

A systematic experimental study has been conducted to explore the heat transfer behavior of triangular and semicircular shaped pin-fin arrays as compared to the circular shaped pin-fin array, that serve as a baseline case. The main advantage of using triangular and semi-circular shaped pin-fin arrays will results in reduced component weight and potentially increases in heat transfer performance. Three staggered arrays with different inter-pin spacing in both transverse and longitudinal are explored in order to determine the optimal configuration for these three dimensional element. Both semi-circular and circular shaped pin-fin arrays are based on typical inter-pin spacing of 2.5 times the pin diameter. The channel geometry (width, W = 76.2mm, height, E = 25.4mm) simulates an internal cooling passage of wide aspect ratio (3:1) in a gas turbine airfoil. All pin-fin elements are fully bridged from one endwall to the opposite endwall. The Reynolds number, based on the hydraulic diameter of the unobstructed cross-section and the mean bulk velocity, ranges from 10,000 to 25,000. The heat transfer measurement employs a hybrid liquid crystal imaging technique, which combined one-dimensional, transient conduction model and lumped heat-capacitance model. Triangular pin-fin arrays produce the highest heat transfer enhancement, while the semi-circular pin-fin array yields the lowest heat transfer enhancement. Sharp edges at each triangular pin-fin generated more wake and turbulence, resulting in more mixing, induces greater heat transfer enhancement by approximately 10%–20% as compared to the typical pin-fins of circular cross-section. More uniform heat transfer is also observed on the endwall and neighboring pin-fins in all triangular shaped pin-fin arrays. However, triangular pin-fin arrays give the highest pressure loss due to the largest induced form drag among all cases, while circular pin-fin array exhibits the lowest pressure loss.

Row Removal Heat Transfer Study for Pin Fin Arrays

2014 ◽  
Author(s):  
Kathryn L. Kirsch ◽  
Jason K. Ostanek ◽  
Karen A. Thole ◽  
Eleanor Kaufman
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
High Reynolds Number ◽  
Pin Fin ◽  
Heat Transfer Augmentation ◽  
Aspect Ratios ◽  
Pin Fins ◽  
High Reynolds ◽  
Pin Fin Arrays ◽  
Transfer Study

Arrays of variably-spaced pin fins are used as a conventional means to conduct and convect heat from internal turbine surfaces. The most common pin shape for this purpose is a circular cylinder. Literature has shown that beyond the first few rows of pin fins, the heat transfer augmentation in the array levels off and slightly decreases. This paper provides experimental results from two studies seeking to understand the effects of gaps in pin spacing (row removals) and alternative pin geometries placed in these gaps. The alternative pin geometries included large cylindrical pins and oblong pins with different aspect ratios. Results from the row removal study at high Reynolds number showed that when rows four through eight were removed, the flow returned to a fully-developed channel flow in the gap between pin rows. When larger alternative geometries replaced the fourth row, heat transfer increased further downstream into the array.

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