Effects of Perpendicular Flow Entry on Convective Heat/Mass Transfer From Pin-Fin Arrays

1999 ◽  
Vol 121 (3) ◽  
pp. 668-674 ◽  
Author(s):  
M. K. Chyu ◽  
Y. Hsing ◽  
V. Natarajan ◽  
J. S. Chiou
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Convective Heat ◽  
Mass Transfer Rate ◽  
Flow Distribution ◽  
Pin Fin ◽  
Through Flow ◽  
Staggered Arrangement ◽  
Naphthalene Sublimation ◽  
Pin Fin Arrays

Convective heat transfer with pin-fin arrays have been studied extensively in laboratory experiments where flow is introduced to the array uniformly over the channel span. However, the flow path in actual cooling designs is often serpentine-shaped with multiple turns, and the pin-fin array section is often located immediately downstream of a turn. The present study, using an analogous mass transfer technique based on naphthalene sublimation, investigates the effects of three different, nonaxial flow entries on array heat transfer for both an inline and a staggered arrangement of pins. The measurement acquires the mass transfer rate of each individual pin in a five row by seven column array for the Reynolds number varying from 8000 to 25,000. The mass transfer and associated flow visualization results indicate that the highly nonuniform flow distribution established at the array entrance and persisting through the entire array can have significant effects on the array heat transfer characteristics. Compared to the conventional case with axial-through flow entrance, the overall array heat transfer performance can be either enhanced or degraded, depending on the actual inlet arrangements and array configurations.

Experiments on In-line Pin Fin Arrays and Performance Comparisons with Staggered Arrays

1980 ◽  
Vol 102 (1) ◽  
pp. 44-50 ◽  
Author(s):  
E. M. Sparrow ◽  
J. W. Ramsey ◽  
C. A. C. Altemani
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Pressure Drop ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Naphthalene Sublimation Technique ◽  
Line Array ◽  
Naphthalene Sublimation ◽  
And Performance ◽  
Pin Fin Arrays

Heat transfer and pressure drop experiments were performed for in-line pin fin arrays to obtain basic data to complement available information for staggered arrays. The experimental data were utilized as input to analyses aimed at establishing performance relationships between in-line and staggered arrays. In the experiments, mass transfer measurements via the naphthalene sublimation technique were employed to determine the row-by-row distribution of the heat (mass) transfer coefficient. Fully developed conditions prevailed for the fourth row and beyond. In general, the fully developed heat transfer coefficients for the in-line array are lower than those for the staggered array, but the pressure drop is also lower. The deviations between the two arrays increase with increasing fin height. With regard to performance, the in-line array transfers more heat than the staggered array under conditions of equal pumping power and equal heat transfer area. On the other hand, at a fixed heat load and fixed mass flow rate, the staggered array requires less heat transfer surface than the in-line array.

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.

Influences of the Non-Uniform Pin-Fin Array on Heat Transfer Distribution in a Rotating Rectangular Channel

2018 ◽  
Author(s):  
Shuo-Cheng Hung ◽  
Szu-Chi Huang ◽  
Yao-Hsien Liu
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Stationary Case ◽  
Pin Fin ◽  
Liquid Crystal Thermography ◽  
Staggered Arrangement ◽  
Channel Orientation ◽  
Pin Fin Array ◽  
Pin Fin Arrays

The liquid crystal thermography was used to investigate the heat transfer of non-uniform pin-fin arrays in a rotating rectangular channel (AR = 4:1) at a channel orientation of 135°. The pin-fin array consisted of four and three pins in a staggered arrangement. The different sized pins were inserted at the rows exhibiting four pins, which produced a non-uniform distribution of the pin-fin array. The experiments were operated at Reynolds numbers of 10,000 and 20,000 for both stationary and rotating conditions. The rotation number varied from 0 to 0.33 and the buoyancy parameter ranged from 0 to 0.27. Results indicated that various heat transfer contours were observed as a result of flow separation and vortices caused by non-uniform pins. Compared to the stationary case, rotation increased heat transfer on both trailing and leading surfaces. The pin-fin array consisted of 6 and 9 mm pins produced the highest heat transfer and frictional losses under rotation condition.

Heat Transfer on Rotating Channel With Various Heights of Pin-Fin

2008 ◽  
Author(s):  
Jun Su Park ◽  
Kyung Min Kim ◽  
Dong Hyun Lee ◽  
Hyung Hee Cho ◽  
Minking K. Chyu
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Naphthalene Sublimation Technique ◽  
Pin Fins ◽  
Naphthalene Sublimation ◽  
Pin Fin Array

Pin-fins have been used to enhance the heat transfer near the trailing edge of a turbine airfoil. Previous pin-fin heat transfer studies focused mainly on the array geometry of pin height-to-diameter equal to unity in a stationary frame. This study experimentally examines the effects of pin height-to-diameter ratio (Hp/Dp) from 2 to 4 and rotation number (Ro) from 0 to 0.2. The tested model used a staggered pin-fin array with an inter-pin spacing of 2.5 times the pin-diameter (S/D = 2.5) in both longitudinal and transverse directions. Detailed heat/mass transfer coefficients were measured using the naphthalene sublimation technique with a heat-mass transfer analogy. The data measured suggest that an increase in Hp/Dp increases the level of array heat/mass transfer. Array averaged Sherwood numbers for Hp/Dp = 3 and Hp/Dp = 4 are approximately 10% and 35% higher than that of Hp/Dp = 2. The effect of rotation induces notable difference in heat/mass transfer between the leading surface and the trailing surface. The heat transfer coefficients change a little although the rotating number increases in the tested range because the pin-fins break the rotation-induced vortices.

Turbulent Transport in Pin Fin Arrays: Experimental Data and Predictions

2005 ◽  
Author(s):  
F. E. Ames ◽  
L. A. Dvorak
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Boundary Layers ◽  
Fluid Dynamic ◽  
Turbulent Transport ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Velocity Profiles ◽  
Pin Fin ◽  
Pin Fin Arrays

The objective of this research has been to experimentally investigate the fluid dynamics of pin fin arrays in order to clarify the physics of heat transfer enhancement and uncover problems in conventional turbulence models. The fluid dynamics of a staggered pin fin array have been studied using hot wire anemometry with both single and x-wire probes at array Reynolds numbers of 3000; 10,000; and 30,000. Velocity distributions off the endwall and pin surface have been acquired and analyzed to investigate turbulent transport in pin fin arrays. Well resolved 3-D calculations have been performed using a commercial code with conventional two-equation turbulence models. Predictive comparisons have been made with fluid dynamic data. In early rows where turbulence is low, the strength of shedding increases dramatically with increasing in Reynolds numbers. The laminar velocity profiles off the surface of pins show evidence of unsteady separation in early rows. In row three and beyond laminar boundary layers off pins are quite similar. Velocity profiles off endwalls are strongly affected by the proximity of pins and turbulent transport. At the low Reynolds numbers, the turbulent transport and acceleration keep boundary layers thin. Endwall boundary layers at higher Reynolds numbers exhibit very high levels of skin friction enhancement. Well resolved 3-D steady calculations were made with several two-equation turbulence models and compared with experimental fluid mechanic and heat transfer data. The quality of the predictive comparison was substantially affected by the turbulence model and near wall methodology.

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