HEAT TRANSFER AND PRESSURE LOSS PERFORMANCE FOR FAMILIES OF PARTIAL LENGTH PIN FIN ARRAYS IN HIGH ASPECT RATIO RECTANGULAR DUCTS

1986 ◽  
Author(s):  
G. D. Steuber ◽  
D. E. Metzger
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Pressure Loss ◽  
Pin Fin ◽  
Partial Length ◽  
Pin Fin Arrays

Influence of the 180° Bend Geometry on the Pressure Loss and Heat Transfer in a High Aspect Ratio Rectangular Smooth Channel

2004 ◽  
Author(s):  
Detlef Pape ◽  
Herve´ Jeanmart ◽  
Jens von Wolfersdorf ◽  
Bernhard Weigand
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Cross Section ◽  
High Aspect Ratio ◽  
Pressure Loss ◽  
Rectangular Cross Section ◽  
Flow Structures ◽  
Cooling Channel ◽  
Smooth Channel

An experimental and numerical investigation of the pressure loss and the heat transfer in the bend region of a smooth two-pass cooling channel with a 180°-turn has been performed. The channels have a rectangular cross-section with a high aspect ratio of H/W = 4. The heat transfer has been measured using the transient liquid crystal method. For the investigations the Reynolds-number as well as the distance between the tip and the divider wall (tip distance) are varied. While the Reynolds number varies from 50’000 to 200’000 and its influence on the normalized pressure loss and heat transfer is found to be small, the variations of the tip distance from 0.5 up to 3.65 W produce quite different flow structures in the bend. The pressure loss over the bend thus shows a strong dependency on these variations.

Heat Transfer and Pressure Drop Measurements in a High Aspect Ratio Channel With Circular Pins and Strip Fins

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Metapun Nuntakulamarat ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Heat Transfer Enhancement ◽  
High Aspect Ratio ◽  
Thickness Effect ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Pin Fin

Abstract This paper focuses on the measurements of heat transfer enhancement and pressure drop of different pin or fin configurations in a high aspect ratio (AR = 9.57/1.2) channel. Two different pin-fin shapes including circular pins and strip fins were studied. Different pin-fin spacings for circular pins (S/D = 2, 4) and strip fins (S/W = 8, 16) were investigated, respectively. In addition, the thickness effect of the strip fin was included in this study. The regionally averaged heat transfer measurement method was used to acquire the heat transfer coefficients on two opposite featured surfaces within the test channel. For each configuration, the tested Reynolds number was ranging from 20,000 to 80,000. The results indicate that the channel with circular pins has better heat transfer enhancement and higher pressure loss than their strip fins counterparts. However, the strip fins are considered better designs in terms of thermal performance. For the gas turbine designers aim at developing an improved internal cooling feature, this work demonstrates the great potential of the strip fins as a novel and effective cooling design compared with the conventional circular pins.

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.

scholarly journals Flow and Mass Transfer Performance in Short Pin-Fin Channels with Different Fin Shapes

1998 ◽  
Vol 4 (2) ◽  
pp. 113-128 ◽  
Author(s):  
R. J. Goldstein ◽  
S. B. Chen
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Flow Velocity ◽  
Pressure Loss ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Flow Characteristics ◽  
Pin Fin ◽  
Pin Fin Arrays

The mass transfer (analogous to heat transfer) and pressure loss characteristics of staggered short pin-fin arrays are investigated experimentally in the range of Reynolds number 3000 to 18,000 based on fin diameter and mean approach-flow velocity. Three different shapes of fins with aspect ratio of 2 are examined: one uniform-diameter circular fin (UDCF) and two stepped-diameter circular fins (SDCF1 and SDCF2). Flow visualization using oil-lampblack reveals complex flow characteristics associated with the repeated production of horseshoe vortices and fin wakes, and the interactions among these. The SDCF1 and SDCF2 arrays show flow characteristics different from the UDCF array due to downflow from the steps. For all arrays tested, the near-endwall flow varies row by row in the initial rows until it reaches a stable pattern after the third row. The row-averaged Sherwood numbers obtained from the naphthalene sublimation experiment also show a row-by-row variation pattern similar to the flow results. While the SDCF2 array has the highest mass transfer rate, the SDCF1 array has the smallest pressure loss at the same approach-flow velocity. The fin surfaces have higher array-averaged Sherwood number than the endwall and the ratio between these changes with fin shape and Reynolds number. The performance of the pin-fin arrays is analyzed under two different constraints: the mass[heat transfer rate at fixed pumping power, and the mass/heat transfer area and pressure loss to fulfill fixed heat load at a fixed mass flow rate. In both cases, the SDCF2 array shows the best performance.

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.

Heat Transfer, Pressure Loss and Flow Field Measurements Downstream of Staggered Two-Row Circular and Elliptical Pin Fin Arrays

2005 ◽  
Vol 127 (5) ◽  
pp. 458-471 ◽  
Author(s):  
Oguz Uzol ◽  
Cengiz Camci
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Pressure Loss ◽  
Total Pressure ◽  
Local Heat Transfer ◽  
Field Measurements ◽  
Local Heat ◽  
Wake Flow ◽  
Pin Fin ◽  
Pin Fin Arrays

This paper presents the results of heat transfer, total pressure loss, and wake flow field measurements downstream of two-row staggered elliptical and circular pin fin arrays. Two different types of elliptical fins are tested, i.e., a Standard Elliptical Fin (SEF) and a fin that is based on NACA four digit symmetrical airfoil shapes (N fin). The results are compared to those of a corresponding circular pin fin array. The minor axis lengths for both types of elliptical fins are kept equal to the diameter of the circular fins. Experiments are performed using Liquid Crystal Thermography and total pressure probe wake surveys in a Reynolds number range of 18 000 and 86 000 as well as Particle Image Velocimetry (PIV) measurements at ReD=18 000. The pin fins had a height-to-diameter ratio of 1.5. The streamwise and the transverse spacings were equal to one circular fin diameter, i.e., S/D=X/D=2. For the circular fin array, average Nusselt numbers on the endwall within the wake are about 27% higher than those of SEF and N fin arrays. Different local heat transfer enhancement patterns are observed for elliptical and circular fins. In terms of total pressure loss, there is a substantial reduction in case of SEF and N fins. The loss levels for the circular fin are 46.5% and 59.5% higher on average than those of the SEF and N fins, respectively. An examination of the Reynolds analogy performance parameter show that the performance indices of the SEF and the N fins are 1.49 and 2.0 times higher on average than that of circular fins, respectively. The thermal performance indices show a collapse of the data, and the differences are much less evident. Nevertheless, N fins still show slightly higher thermal performance values. The wake flow field measurements show that the circular fin array creates a relatively large low momentum wake zone compared to the SEF and N fin arrays. The wake trajectories of the first row of fins in circular, SEF and N fin arrays are also different from each other. The turbulent kinetic energy levels within the wake of the circular fin array are higher than those for the SEF and the N fin arrays. The transverse variations in turbulence levels correlate well with the corresponding local heat transfer enhancement variations.

Numerical Investigation of Heat Transfer in a High Aspect Ratio Double Wall Channel With Pin Fin and Jet Array Impingement

2016 ◽  
Author(s):  
Rui Kan ◽  
Shuqing Tian
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Cfd Simulation ◽  
Cooling Effectiveness ◽  
Pin Fin ◽  
Pin Fins ◽  
Double Wall ◽  
Jet Array

A combined impingement-pedestal geometry for turbomachinery double wall cooling application is studied numerically with the shear stress transport turbulence model. Conjugated CFD simulation is performed to investigate the cooling effectiveness distribution. The configuration consists of a high aspect ratio cooling duct, with jet array impinging onto the pin fin-roughed wall. The jet Reynolds number varies from 8,000 to 80,000, jet-to-target wall spacing is kept constant at Z/Dj=0.8. Three main parameters are investigated, including the jet Reynolds number, pin fin shapes (circular and elongated) and the relative location between jets and pin fins (the jet placed uniformly inside the duct or more densely at the front of the duct). For more detailed investigations, the pin fin diameter and impingement hole diameter are varied independently, and a total of 26 configurations are studied. The results show that the double wall configuration with pin fins significantly increases the heat transfer coefficients, compared to that with only impingement. Non-uniform jet arrangement results in a stronger crossflow and enhances heat transfer on the pins, which brings an increase of cooling effectiveness and more uniform temperature distribution.

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.

Topology Optimization of High Aspect Ratio Internal Cooling Channels As a Design for Additive Manufacturing

2020 ◽  
Author(s):  
Shinjan Ghosh ◽  
Jayanta S. Kapat
Keyword(s):  
Heat Transfer ◽  
Topology Optimization ◽  
Additive Manufacturing ◽  
Aspect Ratio ◽  
Gas Turbine ◽  
High Aspect Ratio ◽  
Design Parameters ◽  
Internal Cooling ◽  
Computational Domain ◽  
Pin Fin

Abstract High aspect ratio channels are a common internal cooling feature in Gas Turbine blades, mostly suitable for the trailing edge region or mid-chord regions. Traditionally such channels are fitted with rib-turbulators and/or pin-fin turbulators to augment heat transfer and prevent material failure. Highly efficient internal cooling of blades can improve the efficiency of a real Gas Turbine power cycle by tolerating higher Turbine Inlet Temperatures (TIT). Multi-physics Topology optimization (TO) has been employed in the current study to find optimized shape of these ducts, with an aim to increase heat transfer, while constraining the pressure drop across the channel. This method, commonly used in structural problems, is a novel topic of research when applied to fluid-thermal studies. Material distribution in the computational domain is varied by changing porosity value in each cell and thereby altering the fluid path and creating a conjugate heat transfer problem. Each cell has a value of Brinkmann porosity factor which either simulates a blockage, or a fluid region depending on a low or high value of this design variable. Hence the degree of freedom is high in this method, and there is no manual bias introduced, unlike in parametric shape optimization which is limited to a few design parameters. The unconventional geometries obtained as an end product of this optimization process can thus be an alternative to existing rib/pin-fin type of cooling geometries. The recent progress in additive manufacturing can now facilitate the manufacturing of complicated shapes. An in-house Open-FOAM solver has been used to carry out the process in only twice the amount of time compared to a regular RANS-CFD. 3-Dimensional rectangular channels with inlet aspect ratios of 4:1 and 8:1 have been considered as baselines with a constant inlet velocity. Resulting optimum geometries were found to have organic tree like branching arrangements of rib-like wall roughness and v-shaped structures.

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