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.

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.

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 Enhancement by Fins in the Microscale Regime

1999 ◽  
Vol 121 (4) ◽  
pp. 972-977 ◽  
Author(s):  
F.-C. Chou ◽  
J. R. Lukes ◽  
C.-L. Tien
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Size Effect ◽  
Heat Transfer Enhancement ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
Pin Fins ◽  
Microscale Effect ◽  
Fin Thickness ◽  
Micro Pin Fins

The current literature contains many studies of microchannel and micro-pin-fin heat exchangers, but none of them consider the size effect on the thermal conductivity of channel and fin walls. The present study analyzes the effect of size (i.e., the microscale effect) on the microfin performance, particularly in the cryogenic regime where the microscale effect is often appreciable. The size effect reduces the thermal conductivity of microchannel and microfin walls and thus reduces the heat transfer rate. For this reason, heat transfer enhancement by microfins becomes even more important than for macroscale fins. The need for better understanding of heat transfer enhancement by microfins motivates the current study, which resolves three basic issues. First, it is found that the heat, flow choking can occur even in the case of simple plate fins or pin fins in the microscale regime, although choking is usually caused by the accommodation of a cluster of fins at the fin tip. Second, this paper shows that the use of micro-plate-fin arrays yields a higher heat transfer enhancement ratio than the use of the micro-pin-fin arrays due to the stronger reduction of thermal conductivity in micro-pin-fins. The third issue is how the size effect influences the fin thickness optimization. For convenience in design applications, an equation for the optimum fin thickness is established which generalizes the case without the size effect as first reported by Tuckerman and Pease.

Effects of Pin Detached Space on Heat Transfer and Pin-Fin Arrays

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Sin Chien Siw ◽  
Minking K. Chyu ◽  
Tom I.-P. Shih ◽  
Mary Anne Alvin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Rectangular Channel ◽  
Local Heat Transfer ◽  
Internal Cooling ◽  
Hybrid Technique ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
Cooling Passage ◽  
Pin Fin Arrays

Heat transfer and pressure characteristics in a rectangular channel with pin-fin arrays of partial detachment from one of the endwalls have been experimentally studied. The overall channel geometry (W = 76.2 mm, E = 25.4 mm) simulates an internal cooling passage of wide aspect ratio (3:1) in a gas turbine airfoil. With a given pin diameter, D = 6.35 mm = ¼E, three different pin-fin height-to-diameter ratios, H/D = 4, 3, and 2, were examined. Each of these three cases corresponds to a specific pin array geometry of detachment spacing (C) between the pin tip and one of the endwalls, i.e., C/D = 0, 1, 2, respectively. 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 experiment employs a hybrid technique based on transient liquid crystal imaging to obtain the distributions of the local heat transfer coefficient over all of the participating surfaces, including the endwalls and all the pin elements. Experimental results reveal that the presence of a detached space between the pin tip and the endwall has a significant effect on the convective heat transfer and pressure loss in the channel. The presence of pin-to-endwall spacing promotes wall-flow interaction, generates additional separated shear layers, and augments turbulent transport. In general, an increase in detached spacing, or C/D, leads to lower heat transfer enhancement and pressure drop. However, C/D = 1, i.e., H/D = 3, of a staggered array configuration exhibits the highest heat transfer enhancement, followed by the cases of C/D = 0 and C/D = 2, i.e., H/D = 4 or 2, respectively.

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.

Effects of Pin Detached Space on Heat Transfer and From Pin Fin Arrays

2010 ◽  
Author(s):  
Sin Chien Siw ◽  
Minking K. Chyu ◽  
Tom I.-P. Shih ◽  
Mary Anne Alvin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Rectangular Channel ◽  
Local Heat Transfer ◽  
Internal Cooling ◽  
Hybrid Technique ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
Cooling Passage ◽  
Pin Fin Arrays

Heat transfer and pressure characteristics in a rectangular channel with pin-fin arrays of partial detachment from one of the endwalls have been experimentally studied. The overall channel geometry (W = 101.6 mm, E = 25.4 mm) simulates an internal cooling passage of wide aspect ratio (4:1) in a gas turbine airfoil. With a given pin diameter, D = 6.35 mm = 1/4 E, three different pin-fin height-to-diameter ratios, H/D = 4, 3, and 2, were examined. Each of these three cases corresponds to a specific pin array geometry of detachment spacing (C) between the pin-tip and one of the endwalls, i.e. C/D = 0, 1, 2, respectively. The Reynolds number, based on the hydraulic diameter of the un-obstructed cross-section and the mean bulk velocity, ranges from 10,000 to 25,000. The experiment employs a hybrid technique based on transient liquid crystal imaging to obtain distributions of the local heat transfer coefficient over all of the participating surfaces, including the endwalls and all the pin elements. Experimental results reveal that the presence of a detached space between the pin-tip and the endwall have a significant effect on the convective heat transfer and pressure loss in the channel. The presence of pin-to-endwall spacing promotes wall-flow interaction, generates additional separated shear layers, and augments turbulent transport. In general, an increase in detached spacing, or C/D leads to lower heat transfer enhancement and pressure drop. However, C/D = 1, i.e. H/D = 3, of a staggered array configuration exhibits the highest heat transfer enhancement, followed by the cases of C/D = 0 and C/D = 2, i.e. H/D = 4 or 2, respectively.

Elliptical Pin Fins as an Alternative to Circular Pin Fins for Gas Turbine Blade Cooling Applications: Part 1 — Endwall Heat Transfer and Total Pressure Loss Characteristics

2001 ◽  
Author(s):  
Oğuz Uzol ◽  
Cengiz Camci
Keyword(s):  
Heat Transfer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Major Axis ◽  
Total Pressure Loss ◽  
Turbine Blade Cooling ◽  
Pin Fin ◽  
Blade Cooling ◽  
Pin Fins ◽  
Pin Fin Arrays

Detailed experimental investigation of the wall heat transfer enhancement and total pressure loss characteristics for two alternative elliptical pin fin arrays is conducted and the results are compared to the conventional circular pin fin arrays. Two different elliptical pin fin geometries with different major axis lengths are tested, both having a minor axis length equal to the circular fin diameter and positioned at zero degrees angle of attack to the free stream flow. The major axis lengths for the two elliptical fins are 1.67 and 2.5 times the circular fin diameter, respectively. The pin fin arrays with H/D = 1.5 are positioned in a staggered 2 row configuration with 3 fins in the first row and 2 fins in the second row with S/D = X/D = 2. Endwall heat transfer and total pressure loss measurements are performed two diameter downstream of the pin fin arrays (X/D = 2) in a rectangular cross-section tunnel with an aspect ratio of 4.8 and for varying Reynolds numbers between 10000 and 47000 based on the inlet velocity and the fin diameter. Liquid Crystal Thermography is used for the measurement of convective heat transfer coefficient distributions on the endwall inside the wake. The results show that the wall heat transfer enhancement capability of the circular pin fin array is about 25–30% higher than the elliptical pin fin arrays in average. However in terms of total pressure loss, the circular pin fin arrays generate 100–200% more pressure loss than the elliptical pin fin arrays. This makes the elliptical fin arrays very promising cooling devices as an alternative to conventional circular pin fin arrays used in gas turbine blade cooling applications.

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