Static Pressure Characteristics in a Pin-Fin Channel With Shaped Cylindrical Pins

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
H. J. Pretorius ◽  
G. I. Mahmood ◽  
J. P. Meyer
Keyword(s):  
Thermal Performance ◽  
Static Pressure ◽  
Rectangular Channel ◽  
Diameter Ratio ◽  
Streamwise Direction ◽  
Array Configuration ◽  
Pin Fin ◽  
Pressure Distributions ◽  
Pin Fins ◽  
Transfer Channels

Standard pin-fins in the heat transfer channels are shaped to reduce the pressure penalty and increase the thermal performance. The paper presents experimental results of the wall-static pressure distributions in an array of modified cylindrical short pin-fins in a channel. Standard cylindrical pin-fins with a smooth surface and a similar array configuration are also evaluated as a baseline for comparisons. The pin-fins with a height to diameter ratio of 1.28 are arranged in a staggered array consisting of 13 rows in a rectangular channel of aspect ratio 1:7.8. The cylindrical pins are modified by the machined slots at the tips. The slots in the pins are aligned in the streamwise direction. The static pressure distributions are measured on the endwall between the pin-rows and on the pin surface. The Reynolds number based on the channel hydraulic diameter ranges from 10,000 to 50,000. The slots in the pins reduce the friction factor and wall-static pressure drop between the pin-rows by up to 50%. The objectives of the investigation are to reduce the pressure penalty in the cylindrical pin-fin channel to provide increased thermal performance.

Thermal Performance of Pin-Fin Fan-Sink Assemblies

1997 ◽  
Vol 119 (1) ◽  
pp. 26-31 ◽  
Author(s):  
R. A. Wirtz ◽  
R. Sohal ◽  
H. Wang
Keyword(s):  
Cross Section ◽  
Thermal Performance ◽  
Applied Pressure ◽  
Axial Flow ◽  
Pressure Rise ◽  
Diameter Ratio ◽  
Pin Fin ◽  
Pin Fins ◽  
Small Axial Flow Fan ◽  
Square Array

Experiments are reported on the thermal performance of model fan-sink assemblies consisting of a small axial flow fan which impinges air on a square array of pin-fins. Cylindrical, square, and diamond shape cross section pin-fins are considered. The pin-fin heat transfer coefficient is found to be maximum immediately under the fan blades and minimum below the fan hub and near the corners of the array. The overall heat sink thermal resistance, R, decreases with an increase in either applied pressure rise or fan power and fin height. At fixed applied pressure rise, R is minimized when the fin pitch-to-diameter ratiois maximum. At fixed fan power, R is minimized when the pitch-to-diameter ratio is reduced toward unity. Finally, cylindrical pin-fins give the best overall fan-sink performance.

An Experimental Study of Transitional Flow Friction and Heat Transfer Performance of a Channel With Staggered Arrays of Mini-Scale Short Pin Fins

2009 ◽  
Author(s):  
Yu Rao ◽  
Chaoyi Wan ◽  
Shusheng Zang
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Thermal Performance ◽  
Heat Transfer Performance ◽  
Diameter Ratio ◽  
Transitional Flow ◽  
Transfer Performance ◽  
Pin Fin ◽  
Pin Fins

An experimental study was conducted to investigate the friction and heat transfer performance of air transitional flow in a rectangular channel with staggered arrays of short pin fins with transverse spacing-to-diameter of 1.5 and streamwise spacing-to-diameter ratio of 2.5. The friction factor, averaged Nusselt number and the overall thermal performance of the transitional flow have been obtained, and compared with Metzger’s pin fin channel with transverse spacing-to-diameter of 2.5 and streamwise spacing-to-diameter ratio of 2.5. The experimental study has showed that in the Reynolds number range of 1678–8500, the pin fin channel with transverse spacing-to-diameter of 1.5 has a higher convective heat transfer performance, but the enhancement capability decreases with the Reynolds number. For Re <6000, the overall thermal performance of the pin fin channel with transverse spacing-to-diameter of 1.5 is higher than the pin fin channel transverse spacing-to-diameter of 2.5, however for Re >6000 the overall thermal performance of the former is lower than the latter. For both of the pin fin channels, the overall thermal performance gets highest when the flow transition occurs.

Heat Transfer Experiments in High Aspect Ratio Rectangular Channel With Epoxied Short Pin Fins

1983 ◽  
Author(s):  
S. C. Arora ◽  
W. Abdel Messeh
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Temperature Drop ◽  
Diameter Ratio ◽  
Heat Transfer Surface ◽  
Published Data ◽  
Pin Fin ◽  
Pin Fins ◽  
The Cost ◽  
End Wall

In an attempt to reduce the cost of testing many configurations of short pin fins in a rectangular channel, a technique has been identified whereby the pins are epoxied to the end wall and can be easily removed to form a new configuration at the end of a test. Analytical and experimental results indicate that the temperature drop across a thin layer of epoxy (∼.005–.006 cm) (K = 22.5 W/m°C) with copper pin and endwalls was less than 1% of the heat transfer surface temperature. The technique was then used to test 4 pin fin configurations of height to diameter ratio of about unity. The heat transfer results showed excellent agreement with earlier published data, thus confirming the validity of this technique.

scholarly journals Systematic Comparison on Convective Heat Transfer Characteristics of Several Pin Fins for Turbine Cooling

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 977
Author(s):  
Jin Xu ◽  
Ke Zhang ◽  
Jingtian Duan ◽  
Jiang Lei ◽  
Junmei Wu
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Thermal Performance ◽  
Rectangular Channel ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Pressure Losses ◽  
Pin Fin ◽  
Nominal Diameter ◽  
Pin Fins

This paper is focused on the heat transfer augment ability and friction factor of different cross-section pin fins. An experimental study is conducted in a wide rectangular channel. The steady-state thermochromic liquid crystals (TLC) method is applied to measure the tested surface temperature. Nine sets of pin fins are employed in the experiment. The nominal diameter of all pin fins is the same value. Nine sets of pin fins have three roundness shapes (Circle, Ellipse and Oblong), three streamline shapes (Dropform, NACA and Lancet) and three quadrangle shapes (Diamond, Diamond-s and Square), respectively. The arrangement parameters of all nine shapes are kept the same. As they have the same nominal diameter and arrangement, the channel blockage ratio is the same for each pin fin set. Reynolds numbers range from 10,000 to 60,000. The pressure losses of pin fin arrays are measured to obtain friction factor. Meanwhile, the overall thermal performances of all nine sets are also considered and compared. The results show heat transfer enhancement abilities of quadrangle shape pin fins are relatively higher than the roundness and streamline shapes. Diamond-s pin fins present the largest averaged Nusselt number and overall thermal performance on the endwall for all the nine pin fins under different Re. Concerning overall thermal performance, the traditional Circle pin fin is the second best. The pressure loss of streamline shape pin fins is the lowest in these three shape types. Moreover, the characteristic of local heat transfer distribution varies substantially for different pin shapes at low Re.

Heat Transfer and Pressure Loss Characteristics of Pin-Fins With Different Shapes in a Wide Channel

2017 ◽  
Author(s):  
Jin Xu ◽  
Jiaxu Yao ◽  
Pengfei Su ◽  
Jiang Lei ◽  
Junmei Wu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Bottom Surface ◽  
Number Range ◽  
Pin Fin ◽  
Nominal Diameter ◽  
Pin Fins

Convective heat transfer enhancement and pressure loss characteristics in a wide rectangular channel (AR = 4) with staggered pin fin arrays are investigated experimentally. Six sets of pin fins with the same nominal diameter (Dn = 8mm) are tested, including: Circular, Elliptic, Oblong, Dropform, NACA and Lancet. The relative spanwise pitch (S/Dn = 2) and streamwise pitch (X/Dn = 4.5) are kept the same for all six sets. Same nominal diameter and arrangement guarantee the same blockage area in the channel for each set. Reynolds number based on channel hydraulic diameter is from 10000 to 70000 with an increment of 10000. Using thermochromic liquid crystal (R40C20W), heat transfer coefficients on bottom surface of the channel are achieved. The obtained friction factor, Nusselt number and overall thermal performance are compared with the previously published data from other groups. The averaged Nusselt number of Circular pin fins is the largest in these six pin fins under different Re. Though Elliptic has a moderate level of Nusselt number, its pressure loss is next to the lowest. Elliptic pin fins have pretty good overall thermal performance in the tested Reynolds number range. When Re>40000, Lancet has a same level of performance as Circular, but its pressure loss is much lower than Circular. These two types are both promising alternative configuration to Circular pin fin used in gas turbine blade.

Thermal performance enhancement in a wedge duct with in-line pin fins combined with vortex generators

2019 ◽  
Vol 29 (8) ◽  
pp. 2545-2565
Author(s):  
Safeer Hussain ◽  
Jian Liu ◽  
Lei Wang ◽  
Bengt Ake Sunden
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Thermal Performance ◽  
Performance Enhancement ◽  
Numerical Study ◽  
Vortex Generators ◽  
Content Type ◽  
Pin Fin ◽  
Pin Fins ◽  
Cooling Enhancement

Purpose The purpose of this paper is to enhance the heat transfer and thermal performance in the trailing edge region of the vane with vortex generators (VGs). Design/methodology/approach This numerical study presents the enhancement of thermal performance in the trailing part of a gas turbine blade. In the trailing part, generally, pin fins are used either in staggered or in-line arrangements to enhance the heat transfer. In this study, based on the idea from heat exchangers, pin fins are combined with VGs. A pair of VGs is embedded in the boundary layer upstream of each pin fin in the first row of the pin fin array having an in-line configuration. The effects of the VG angle relative to the streamwise direction and streamwise distance between the pin fin and VGs are investigated at various Reynolds numbers. Findings The results indicated that the endwall heat transfer is enhanced with the addition of VGs and the heat transfer from the surfaces of the pin fins. The level of heat transfer enhancement compared to the case without VGs is more significant at high Reynolds number. The surfaces of the VGs also show a significant amount of heat transfer. Study of the angle of the attack suggested that a high angle of attack is more appropriate for pin fin cooling enhancement whereas an intermediate gap between the VGs and pin fins shows considerable improvement of thermal performance compared to the small and large gaps. The phenomenon of heat transfer augmentation with the VGs is demonstrated by the flow field. It shows that the enhancement of heat transfer is governed by the mixing of the flow as a result of the interaction of vortices generated by the VGs and pin fins. Originality/value VGs are used to disturb the thermal boundary layer. It shows that heat transfer is augmented as a result of the interaction of vortices associated with VGs and pin fins.

Experiments and Modeling of the Hydraulic Resistance of In-Line Square Pin Fin Heat Sinks With Top By-Pass Flow

2003 ◽  
Author(s):  
Mario Urdaneta ◽  
Alfonso Ortega ◽  
Russel V. Westphal
Keyword(s):  
Static Pressure ◽  
Heat Sinks ◽  
Pressure Measurements ◽  
Pin Fin ◽  
Pressure Distributions ◽  
Full Development ◽  
Background Data ◽  
Physical Insight ◽  
Loss Coefficients ◽  
Insight Into

Extensive experiments were performed aimed at obtaining physical insight into the behavior of in-line pin fin heat sinks with pins of square cross-section. Detailed pressure measurements were made inside an array of square pins in order to isolate the inlet, developing, fully developed, and exit static pressure distributions as a function of row number. With this as background data, overall pressure drop was measured for a self-consistent set of aluminum heat sinks in side inlet side exit flow, with top clearance only. Pin heights of 12.5 mm, 17.5 mm, and 22.5 mm, pin pitch of 3.4 mm to 6.33 mm, and pin thickness of 1.5 mm, 2 mm and 2.5mm were evaluated. Base dimensions were kept fixed at 25 × 25 mm. In total, 20 aluminum heat sinks were evaluated. A “two-branch by-pass model” was developed, by allowing inviscid acceleration of the flow in the bypass section, and using pressure loss coefficients obtained under no bypass conditions in the heat sink section. The experimental data compared well to the proposed hydraulic models. Measurements in the array of pins showed that full development of the flow occurs after nine rows, thus indicating that none of the heat sinks tested could be characterized as fully-developed.

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.

Computation of Flow and Heat Transfer in Rotating Rectangular Channels (AR=4:1) With Pin-Fins by a Reynolds Stress Turbulence Model

2006 ◽  
Vol 129 (6) ◽  
pp. 685-696 ◽  
Author(s):  
Guoguang Su ◽  
Hamn-Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rotation Number ◽  
Rectangular Channel ◽  
Density Ratio ◽  
Three Dimensional ◽  
Diameter Ratio ◽  
Mean Velocity ◽  
Flow And Heat Transfer ◽  
Pin Fins

Computations with multi-block chimera grids were performed to study the three-dimensional turbulent flow and heat transfer in a rotating rectangular channel with staggered arrays of pin-fins. The channel aspect ratio (AR) is 4:1, the pin length to diameter ratio (H∕D) is 2.0, and the pin spacing to diameter ratio is 2.0 in both the stream-wise (S1∕D) and span-wise (S2∕D) directions. A total of six calculations have been performed with various combinations of rotation number, Reynolds number, and coolant-to-wall density ratio. The rotation number and inlet coolant-to-wall density ratio varied from 0.0 to 0.28 and from 0.122 to 0.20, respectively, while the Reynolds number varied from 10,000 to 100,000. For the rotating cases, the rectangular channel was oriented at 150deg with respect to the plane of rotation to be consistent with the configuration of the gas turbine blade. A Reynolds-averaged Navier-Stokes (RANS) method was employed in conjunction with a near-wall second-moment turbulence closure for detailed predictions of mean velocity, mean temperature, and heat transfer coefficient distributions.

Shape Optimization of a Rotating Rectangular Channel With Pin-Fins by Kriging Method

2010 ◽  
Author(s):  
Mi-Ae Moon ◽  
Afzal Husain ◽  
Kwang-Yong Kim
Keyword(s):  
Heat Transfer ◽  
Objective Function ◽  
Rectangular Channel ◽  
Latin Hypercube Sampling ◽  
Weighting Factor ◽  
Diameter Ratio ◽  
Reference Case ◽  
Pin Fins ◽  
Meta Modeling ◽  
Rans Analysis

This paper presents numerical optimization of a rotating rectangular channel design with the staggered arrays of pin-fins using Kriging meta-modeling technique. In the reference case, the channel aspect ratio (AR) is 4:1, the pin length to diameter ratio (H/D) is 2.0, and the pin spacing to diameter ratio is 2.0 in both the streamwise and spanwise directions. The rotation number is 0.15, while the Reynolds number based on hydraulic diameter is fixed at 10,000. Rotation of the channel slightly reduces the heat transfer on the leading surface and increases it on the trailing surface due to Coriolis effects. Two non-dimensional variables, the ratio of the height to diameter of the pin-fin and the ratio of the spacing between the pin-fins to diameter of the pin-fins, are chosen as design variables. The objective function defined as a linear combination of heat transfer and friction loss related terms with a weighting factor is selected for the optimization. Twenty training points generated by Latin hypercube sampling (LHS) are evaluated by three-dimensional Reynolds-averaged Navier-Stokes (RANS) analysis with the shear stress transport (SST) model for the turbulence closure. The predictions of objective function by Kriging meta-modeling at optimum point show reasonable accuracy in comparison with the values calculated by RANS analysis. The results of optimization show that the cooling performance of the optimized shape is enhanced significantly through the optimization.

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