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.

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.

Effect of Rotation on Heat Transfer in Narrow Rectangular Cooling Channels (AR = 8:1 and 4:1) With Pin-Fins

2003 ◽  
Author(s):  
Lesley M. Wright ◽  
Eungsuk Lee ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Rotation Number ◽  
Rectangular Channel ◽  
Density Ratio ◽  
Pin Fin ◽  
Aspect Ratios ◽  
Rectangular Channels ◽  
Smooth Channel ◽  
Pin Fins

The effect of rotation on smooth narrow rectangular channels and narrow rectangular channels with pin-fins is investigated in this study. Pin-fins are commonly used in the narrow sections within the trailing edge of the turbine blade; the pin-fins act as turbulators to enhance internal cooling while providing structural support in this narrow section of the blade. The rectangular channel is oriented at 150° with respect to the plane of rotation, and the focus of the study involves narrow channels with aspect ratios of 4:1 and 8:1. The enhancement due to both conducting (copper) pin-fins and non-conducting (plexi-glass) pins is investigated. Due to the varying aspect ratio of the channel, the height-to-diameter ratio (hp/Dp) of the pins varies from two, for an aspect ratio of 4:1, to unity, for an aspect ratio of 8:1. A staggered array of pins with uniform streamwise and spanwise spacing (xp/Dp = sp/Dp = 2.0) is studied. With this array, 42 pin-fins are used, giving a projected surface density of 3.5 pins/in2 (0.543 pins/cm2), for the leading or trailing surfaces. The range of flow parameters include Reynolds number (ReDh = 5000–20000), rotation number (Ro = 0.0–0.302), and inlet coolant-to-wall density ratio (Δρ/ρ = 0.12). Heat transfer in a stationary pin-fin channel can be enhanced up to 3.8 times that of a smooth channel. Rotation enhances the heat transferred from the pin-fin channels 1.5 times that of the stationary pin-fin channels. Overall, rotation enhances the heat transfer from all surfaces in both the smooth and pin-fin channels. Finally, as the rotation number increases, spanwise variation increases in all channels.

Turbulent Flow Heat Transfer and Friction in a Rectangular Channel With Varying Numbers of Ribbed Walls

1997 ◽  
Vol 119 (2) ◽  
pp. 374-380 ◽  
Author(s):  
P. R. Chandra ◽  
M. E. Niland ◽  
J. C. Han
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Channel Length ◽  
Diameter Ratio ◽  
Hydraulic Diameter ◽  
Published Data ◽  
Flow Heat ◽  
Turbulent Air Flow

An experimental study of wall heat transfer and friction characteristics of a fully developed turbulent air flow in a rectangular channel with transverse ribs on one, two, and four walls is reported. Tests were performed for Reynolds numbers ranging from 10,000 to 80,000. The pitch-to-rib height ratio, P/e, was kept at 8 and rib height-to-channel hydraulic diameter ratio, e/Dh, was kept at 0.0625. The channel length-to-hydraulic diameter ratio, L/Dh, was 15. The heat transfer coefficient and friction factor values were enhanced with the increase in the number of ribbed walls. The friction roughness function, R(e+), was almost constant over the entire range of tests performed and was within comparable limits of the previously published data. The heat transfer roughness function, G(e+), decreased with additional ribbed walls and compared well with previous work in this area. Friction data obtained experimentally for the case with four ribbed walls compared well with the values predicted by the assumed theoretical relationship used in the present study and past publications. Results of this investigation could be used in various applications of internal channel turbulent flows involving different numbers of roughened walls.

scholarly journals Length to Diameter Ratio and Row Number Effects in Short Pin Fin Heat Transfer

1984 ◽  
Vol 106 (1) ◽  
pp. 241-244 ◽  
Author(s):  
B. A. Brigham ◽  
G. J. VanFossen
Keyword(s):  
Heat Transfer ◽  
Diameter Ratio ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Relative Contribution ◽  
Pin Fins ◽  
Lower Heat ◽  
Tube Banks ◽  
Length To Diameter Ratio

Recently, several experiments concerning heat transfer from short pin fins have been conducted with the results indicating lower heat transfer from short pin fins than from longer pin fins found in tube banks and other similar configurations. Assessments of the effect of the number of pin rows and row geometry have also been made. It was felt that there was a need to determine the relative contribution of pin length to diameter ratio and pin row geometry on the heat transfer. Array-averaged heat transfer coefficients on pin and endwall surfaces were measured for two configurations of staggered arrays of short pin fins (length to diameter ratio of 4). One configuration contained eight streamwise rows of pins, while the other contained only four rows. Results showed that both the eight-row and the four-row configurations for an Lp/D of 4 exhibit higher heat transfer than in similar tests on shorter pin fins (Lp/D of 1/2 and 2). It was also found that for this Lp/D ratio the array-averaged heat transfer was slightly higher with eight rows of staggered pins than with only four rows.

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

2005 ◽  
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 150 deg 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.

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.

Evaluation of Wall Heat Transfer in Blade Trailing-Edge Cooling Passage

2013 ◽  
Vol 284-287 ◽  
pp. 738-742 ◽  
Author(s):  
Yu Feng Yao ◽  
Marwan Effendy ◽  
Jun Yao
Keyword(s):  
Heat Transfer ◽  
Transfer Model ◽  
Internal Cooling ◽  
Wall Heat Transfer ◽  
Trailing Edge ◽  
Pin Fin ◽  
Pin Fins ◽  
Cooling Passage ◽  
End Wall ◽  
Good Agreement

Model configurations of turbine blade trailing-edge internal cooling passage with staggered elliptic pin-fins in streamwise and spanwise are adopted for numerical investigation using computational fluid dynamics (CFD). Grid refinement study is performed at first to identify a baseline mesh, followed by validation study of passage total pressure loss, which gives 2% and 4% discrepancies respectively for two chosen configurations in comparison with experimental measurements. Further investigations are focused on evaluation of wall heat transfer coefficient (HTC) of both pin-fin and end walls, and it is found that CFD predicted pin-fin wall HTC are generally in good agreement with test data for the streamwise staggered elliptic pin-fins, but not the spanwise staggered elliptic pin-fins in which some discrepancies occur. CFD predicted end wall HTC have shown reasonable good agreement for the first three rows, but discrepancies seen in downstream rows are around a factor of 2-3. A ratio of averaged pin-fin and end walls HTC is estimated 1.3-1.5, close to that from a circular pin-fin configuration that has 1.8-2.1. Further study should focus on improving end wall HTC predictions, probably through a conjugate heat transfer model.

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.

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