Heat Transfer in Radially Rotating Pin-Fin Channel at High Rotation Numbers

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Shyy Woei Chang ◽  
Tong-Miin Liou ◽  
Tsun Lirng Yang ◽  
Guo Fang Hong
Keyword(s):  
Heat Transfer ◽  
Flow Region ◽  
Operating Conditions ◽  
Previous Attempt ◽  
Height Ratio ◽  
Pin Fin ◽  
Nusselt Numbers ◽  
Rotation Numbers ◽  
The Individual ◽  
Selection Of

Endwall heat transfer measurements for a radially rotating rectangular pin-fin channel with the width-to-height ratio (aspect ratio) of 8 are performed at the parametric conditions of 5000≤Re≤20,000, 0≤Ro≤1.4, and 0.1≤Δρ/ρ≤0.21. Centerline heat transfer levels along the leading and trailing endwalls of the rotating pin-fin channel are, respectively, raised to 1.77–3.72 and 3.06–5.2 times of the Dittus–Boelter values. No previous attempt has examined the heat transfer performances for the pin-fin channel at such high rotation numbers. A selection of experimental data illustrates the individual and interactive Re, Ro, and buoyancy number (Bu) effects on heat transfer. Spanwise heat transfer variations between two adjoining pin rows are detected with the averaged Nusselt numbers (Nu) determined. A set of empirical equations that calculates Nu values over leading and trailing endwalls in the developed flow region is derived to correlate all the heat transfer data generated by this study and permits the evaluation of interactive and individual effects of Re, Ro, and Bu on Nu. With the aid of the Nu correlations derived, the operating conditions with the worst heat transfer scenarios for this rotating pin-fin channel are identified.

Heat Transfer in Radially Rotating Pin-Fin Channel at High Rotation Numbers

2008 ◽  
Author(s):  
S. W. Chang ◽  
T. L. Yang ◽  
G. F. Hong ◽  
Tong-Miin Liou
Keyword(s):  
Heat Transfer ◽  
Flow Region ◽  
Operating Conditions ◽  
Previous Attempt ◽  
Height Ratio ◽  
Pin Fin ◽  
Nusselt Numbers ◽  
Rotation Numbers ◽  
The Individual ◽  
Selection Of

Endwall heat transfer measurements for a radially rotating rectangular pin-fin channel with the width-to-height ratio (aspect ratio) of 8 are performed at the parametric conditions of 5000≤Re≤20000, 0≤Ro≤1.4 and 0.1≤Δρ/ρ≤0.21. Centerline heat transfer levels along the leading and trailing endwalls of the rotating pin-fin channel are respectively raised to 1.77–3.72 and 3.06–5.2 times of the Dittus-Boelter values. No previous attempt has examined the heat transfer performances for the pin-fin channel at such high rotation numbers. A selection of experimental data illustrates the individual and interactive Re, Ro and buoyancy number (Bu) effects on heat transfer. Spanwise heat transfer variations between two adjoining pin rows are detected with the averaged Nusselt numbers (Nu) determined. A set of empirical equations that calculates Nu values over leading and trailing endwalls in the developed flow region is derived to correlate all the heat transfer data generated by this study and permits the evaluation of interactive and individual effects of Re, Ro and Bu on Nu. With the aid of the Nu correlations derived, the operating conditions with the worst heat transfer scenarios for this rotating pin-fin channel are identified.

Influence of Radial Rotation on Heat Transfer in a Rectangular Channel With Two Opposite Walls Roughened by Hemispherical Protrusions at High Rotation Numbers

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Shyy Woei Chang ◽  
Tong-Miin. Liou ◽  
Wei-Chun Chen
Keyword(s):  
Heat Transfer ◽  
Infrared Thermography ◽  
Rotation Number ◽  
Rectangular Channel ◽  
Flow Region ◽  
Transfer Data ◽  
Nusselt Numbers ◽  
Rotation Numbers ◽  
Heat Transfer Correlations ◽  
Rotating Channel

Detailed heat transfer distributions over two opposite leading and trailing walls roughened by hemispherical protrusions were measured from a rotating rectangular channel at rotation number up to 0.6 to examine the effects of Reynolds (Re), rotation (Ro), and buoyancy (Bu) numbers on local and area-averaged Nusselt numbers (Nu and Nu¯) using the infrared thermography. A set of selected heat transfer data illustrates the Coriolis and rotating buoyancy effects on the detailed Nu distributions and the area-averaged heat transfer performances of the rotating channel. The Nu¯ for the developed flow region on the leading and trailing walls are parametrically analyzed to devise the empirical heat transfer correlations that permit the evaluation of the interdependent and individual Re, Ro, and Bu effect on Nu¯.

Heat Transfer in a Rotating Rectangular Channel With Two Opposite Walls Roughened With Spherical Protrusions at High Rotation Numbers

2010 ◽  
Author(s):  
S. W. Chang ◽  
T.-M. Liou ◽  
W. C. Chen
Keyword(s):  
Heat Transfer ◽  
Infrared Thermography ◽  
Rotation Number ◽  
Rectangular Channel ◽  
Flow Region ◽  
Transfer Data ◽  
Nusselt Numbers ◽  
Rotation Numbers ◽  
Rotating Channel ◽  
Spherical Protrusions

Detailed heat transfer distributions over two opposite leading and trailing walls roughened by spherical protrusions were measured from a rotating rectangular channel at rotation number up to 0.6 to examine the effects of Reynolds (Re), rotation (Ro) and buoyancy (Bu) numbers on local and area averaged Nusselt numbers (Nu and Nu) using the infrared thermography. A set of selected heat transfer data illustrates the Coriolis and rotating-buoyancy effects on the detailed Nu distributions and the area-averaged heat transfer performances of the rotating channel. The Nu for the developed flow region on the leading and trailing walls are parametrically analyzed to devise the empirical heat transfer correlations that permit the evaluation of the interdependent and individual Re, Ro and Bu effect on Nu.

Local Heat Transfer Distribution in a Rotating Serpentine Rib-Roughened Flow Passage

1993 ◽  
Vol 115 (3) ◽  
pp. 560-567 ◽  
Author(s):  
N. Zhang ◽  
J. Chiou ◽  
S. Fann ◽  
W.-J. Yang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Performance ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Performance ◽  
Height Ratio ◽  
Nusselt Numbers ◽  
Rayleigh Numbers ◽  
Rib Roughened

Experiments are performed to determine the local heat transfer performance in a rotating serpentine passage with rib-roughened surfaces. The ribs are placed on the trailing and leading walls in a corresponding posited arrangement with an angle of attack of 90 deg. The rib height-to-hydraulic diameter ratio, e/Dh, is 0.0787 and the rib pitch-to-height ratio, s/e, is 11. The throughflow Reynolds number is varied, typically at 23,000, 47,000, and 70,000 in the passage both at rest and in rotation. In the rotation cases, the rotation number is varied from 0.023 to 0.0594. Results for the rib-roughened serpentine passages are compared with those of smooth ones in the literature. Comparison is also made on results for the rib-roughened passages between the stationary and rotating cases. It is disclosed that a significant enhancement is achieved in the heat transfer in both the stationary and rotating cases resulting from an installation of the ribs. Both the rotation and Rayleigh numbers play important roles in the heat transfer performance on both the trailing and leading walls. Although the Reynolds number strongly influences the Nusselt numbers in the rib-roughened passage of both the stationary and rotating cases, Nuo and Nu, respectively, it has little effect on their ratio Nu/Nuo.

Heat Transfer in Reciprocating Planar Curved Tube With Piston Cooling Application

2005 ◽  
Vol 128 (1) ◽  
pp. 219-229 ◽  
Author(s):  
Shyy Woei Chang ◽  
Yao Zheng
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Interactive Effects ◽  
Experimental Conditions ◽  
Nusselt Numbers ◽  
Curved Tube ◽  
The Individual ◽  
Cooling Passage ◽  
Piston Cooling

This paper describes an experimental study of heat transfer in a reciprocating planar curved tube that simulates a cooling passage in piston. The coupled inertial, centrifugal, and reciprocating forces in the reciprocating curved tube interact with buoyancy to exhibit a synergistic effect on heat transfer. For the present experimental conditions, the local Nusselt numbers in the reciprocating curved tube are in the range of 0.6–1.15 times of static tube levels. Without buoyancy interaction, the coupled reciprocating and centrifugal force effect causes the heat transfer to be initially reduced from the static level but recovered when the reciprocating force is further increased. Heat transfer improvement and impediment could be superimposed by the location-dependent buoyancy effect. The empirical heat transfer correlation has been developed to permit the evaluation of the individual and interactive effects of inertial, centrifugal, and reciprocating forces with and without buoyancy interaction on local heat transfer in a reciprocating planar curved tube.

scholarly journals Experimental Investigation of Embedded Micropin-Fins for Single-Phase Heat Transfer and Pressure Drop

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
Chirag R. Kharangate ◽  
Ki Wook Jung ◽  
Sangwoo Jung ◽  
Daeyoung Kong ◽  
Joseph Schaadt ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Friction Factor ◽  
Integrated Circuit ◽  
Single Phase ◽  
Absolute Error ◽  
Heat Fluxes ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pin Fin

Three-dimensional (3D) stacked integrated circuit (IC) chips offer significant performance improvement, but offer important challenges for thermal management including, for the case of microfluidic cooling, constraints on channel dimensions, and pressure drop. Here, we investigate heat transfer and pressure drop characteristics of a microfluidic cooling device with staggered pin-fin array arrangement with dimensions as follows: diameter D = 46.5 μm; spacing, S ∼ 100 μm; and height, H ∼ 110 μm. Deionized single-phase water with mass flow rates of m˙ = 15.1–64.1 g/min was used as the working fluid, corresponding to values of Re (based on pin fin diameter) from 23 to 135, where heat fluxes up to 141 W/cm2 are removed. The measurements yield local Nusselt numbers that vary little along the heated channel length and values for both the Nu and the friction factor do not agree well with most data for pin fin geometries in the literature. Two new correlations for the average Nusselt number (∼Re1.04) and Fanning friction factor (∼Re−0.52) are proposed that capture the heat transfer and pressure drop behavior for the geometric and operating conditions tested in this study with mean absolute error (MAE) of 4.9% and 1.7%, respectively. The work shows that a more comprehensive investigation is required on thermofluidic characterization of pin fin arrays with channel heights Hf < 150 μm and fin spacing S = 50–500 μm, respectively, with the Reynolds number, Re < 300.

Flow and Heat Transfer Characteristics in Rectangular Channels With Staggered Transverse Ribs on Two Opposite Walls

2007 ◽  
Vol 129 (12) ◽  
pp. 1732-1736 ◽  
Author(s):  
Rong Fung Huang ◽  
Shyy Woei Chang ◽  
Kun-Hung Chen
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Turbulence Intensity ◽  
Flow Characteristics ◽  
Channel Height ◽  
Primary Concern ◽  
Height Ratio ◽  
Nusselt Numbers ◽  
Characteristic Flow ◽  
Rectangular Channels

The flow characteristics and the heat transfer properties of the rectangular channels with staggered transverse ribs on two opposite walls are experimentally studied. The rib height to channel height ratio ranges from 0.15 to 0.61 (rib height to channel hydraulic diameter ratio from 0.09 to 0.38). The pitch to rib height ratio covers from 2.5 to 26. The aspect ratio of the rectangular channel is 4. The flow characteristics are studied in a water channel, while the heat transfer experiments are performed in a wind tunnel. Particle image velocimetry (PIV) is employed to obtain the quantitative flow field characteristics. Fine-wire thermocouples imbedded near the inner surface of the bottom channel wall are used to measure the temperature distributions of the wall and to calculate the local and average Nusselt numbers. Using the PIV measured streamline patterns, various characteristic flow modes, thru flow, oscillating flow, and cell flow, are identified in different regimes of the domain of the rib height to channel height ratio and pitch to rib height ratio. The vorticity, turbulence intensity, and wall shear stress of the cell flow are found to be particularly larger than those of other characteristic flow modes. The measured local and average Nusselt numbers of the cell flow are also particularly higher than those of other characteristic flow modes. The distinctive flow properties are responsible for the drastic increase of the heat transfer due to the enhancement of the momentum, heat, and mass exchanges within the flow field induced by the large values of the vorticity and turbulence intensity. Although the thru flow mode is conventionally used in the ribbed channel for industrial application, the cell flow could become the choice if the heat transfer rate, instead of the pressure loss, is the primary concern.

Single-Phase Heat Transfer in Mems-Based Pin Fin Heat Sink

2005 ◽  
Author(s):  
Ali Kosar ◽  
Yoav Peles
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Reynolds Numbers ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Pin Fins ◽  
Micro Pin Fins

An experimental study has been performed on single-phase heat transfer of de-ionized water over a bank of shrouded micro pin fins 243-μm long with hydraulic diameter of 99.5-μm. Heat transfer coefficients and Nusselt numbers have been obtained over effective heat fluxes ranging from 3.8 to 167 W/cm2 and Reynolds numbers from 14 to 112. The results were used to derive the Nusselt numbers and total thermal resistances. It has been found that endwalls effects are significant at low Reynolds numbers and diminish at higher Reynolds numbers.

Analysis of the Fin Performance of Offset Strip Fins Used in Plate-Fin Heat Exchangers

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Yujie Yang ◽  
Yanzhong Li ◽  
Biao Si ◽  
Jieyu Zheng ◽  
Rui Kang
Keyword(s):  
Heat Transfer ◽  
Mass Flux ◽  
Heat Exchangers ◽  
3D Models ◽  
Geometrical Parameters ◽  
Height Ratio ◽  
Fin Efficiency ◽  
Fin Thickness ◽  
Offset Strip Fin ◽  
Selection Of

As an important consideration in the design of plate-fin heat exchangers, the selection of plate-fin surfaces is associated with the estimation of the fin performance in many cases. The fin performance of offset strip fin (OSF) and plain fin is numerically investigated with well-validated 3D models in the present study. The comparative analysis shows that the conventional fin efficiency and fin effectiveness concepts provide an incomplete assessment of the fin performance of the fins, and lead to impractical suggestions of using OSF fin. Further investigation indicates that the idealization of uniform heat transfer coefficient over all the surfaces in fin channel, which runs through the conventional concepts, is untenable, and strongly restricts the fin performance analysis. An actual fin effectiveness is then proposed to measure the fin performance. It physically represents the ratio of the heat flux over the fin surfaces and that over the primary surfaces in the fin channel. With this method, the effects of the geometrical parameters of the OSF are discussed carefully. The results show that there exists a specific fin thickness-to-height ratio α and fin density γ, which contribute to the highest fin performance for a given mass flux, and the optimal γ (or α) increases (or decreases) as mass flux increases. The OSF fins with relatively large fin thickness-to-length ratio δ perform better in low Re region and the optimum δ decreases with the increasing Re number.

COOLING PERFORMANCE OF ADDITIVELY MANUFACTURED PIN FINS IN STACKED MICROCHANNELS FOR THE INSIDE-OUT CERAMIC TURBINE SHROUD-COOLING RING

2021 ◽  
pp. 1-26
Author(s):  
Patrick K. Dubois ◽  
Alexandre Landry-Blais ◽  
Rym Gazzah ◽  
Sani Sivic ◽  
Vladimir Brailovski ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Rectangular Cross Section ◽  
Minimal Amount ◽  
Radial Temperature ◽  
Pin Fin ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
Pin Fins ◽  
Significant Performance ◽  
Inside Out

Abstract The Inside-out ceramic turbine (ICT), a novel microturbine rotor architecture, has an air-cooled ring which keeps its composite rotating structural shroud within operating temperature. The cooling ring must achieve a significant radial temperature gradient with a minimal amount of cooling. The cooling ring is made through additive manufacturing, which opens the design space to tailored cooling geometries. Additively manufactured pin fin heat transfer enhancers are explored in this work to assess whether they hold any significant performance benefit over current rectangular cross-section open channels. Experimental friction factors and Nusselt numbers were determined for small, densely-packed pin fins over an asymmetrical thermal load. Results indicate that pressure loss is similar to what can be expected for additively manufactured pin fins, whereas heat transfer is lower due to the extremely tight streamwise pin spacing, in both in-line and staggered pin configurations. A design study presented in this paper suggests that pin fins are beneficial to an ICT for reducing cooling mass flow rate up to 40 %, against an increase in cooling ring mass of roughly 50%.

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