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

2003 ◽  
Author(s):  
Mario Urdaneta ◽  
Alfonso Ortega
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Empirical Data ◽  
Heat Sink ◽  
Companion Paper ◽  
Heat Sinks ◽  
One Dimensional ◽  
Pin Fin ◽  
Hydraulic Behavior ◽  
Approach Velocity

The thermal resistance of in-line square-pin fin heat sinks was experimentally investigated. In a companion paper [1], extensive results for the hydraulic behavior of such heat sinks with and without top-bypass were reported. It was shown that the top-bypass, as well as pin pitch, strongly influence the fin flow available for cooling. Systematic measurements of the overall thermal resistance with a uniformly heated base were performed for the same set of twenty aluminum heat sinks. Pin height was varied from 12.5 mm to 22.5 mm, pin pitch was varied from 3.4 mm to 6.33 mm, and base dimensions were kept fixed at 25 × 25 mm. The overall base to ambient thermal resistance was measured as a function of heat sink geometry, approach velocity and by-pass height. Experimental results were compared with predictions based on a simple one-dimensional “two-branch bypass model”. It was found that the overall heat transfer is governed by the fin flow, hence, empirical data for the zero bypass case can be used to predict the decrease of heat sink performance with flow bypass.

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

2002 ◽  
Author(s):  
M. Baris Dogruoz ◽  
Mario Urdaneta ◽  
Alfonso Ortega
Keyword(s):  
Heat Transfer ◽  
Experimental Results ◽  
Heat Sinks ◽  
Transfer Coefficients ◽  
Clearance Ratio ◽  
One Dimensional ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Approach Velocity ◽  
Good Agreement

This paper presents experimental results on the heat transfer characteristics of in-line square pin fin heat sinks with and without top by-pass. A self-consistent set of aluminum heat sinks were utilized, where the pin height was varied from 12.5 mm to 22.5 mm, the pin pitch was varied from 3.4 mm to 5.8 mm and the base dimensions were kept fixed at 25 × 25 mm. The overall base to ambient thermal resistance was measured as a function of Reynolds number and bypass height. Experimental results were then compared with predictions based on a simple one-dimensional “two-branch by-pass model”. Comparisons were made with the data using heat transfer coefficients available in the literature for infinitely long tube bundles. It was shown that there is a good agreement between the temperature predictions based on the model and the experimental data at high approach velocities for tall heat sinks, however the discrepancy between the computations and experiments increases as the approach velocity and heat sink height decrease. The validated model was used to identify optimum pin spacing as a function of clearance ratio.

Pin-Fin Heat Sink With Horizontal Base and Blocked Edges

2008 ◽  
Author(s):  
D. Sahray ◽  
H. Shmueli ◽  
N. Segal ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Contact Resistance ◽  
Cross Section ◽  
Heat Input ◽  
Heat Sink ◽  
Numerical Study ◽  
Heat Sinks ◽  
Transfer Enhancement ◽  
Pin Fin

In the present work, horizontal-base pin fin heat sinks exposed to free convection in air are studied. They are made of aluminum, and there is no contact resistance between the base and the fins. For the same base dimensions the fin height and pitch vary. The fins have a constant square cross-section. The edges of the sink are blocked: the surrounding insulation is flush with the fin tips. The effect of fin height and pitch on the performance of the sink is studied experimentally and numerically. In the experiments, the heat sinks are heated using foil electrical heaters. The heat input is set, and temperatures of the base and fins are measured. In the corresponding numerical study, the sinks and their environment are modeled using the Fluent 6 software. The results show that heat transfer enhancement due to the fins is not monotonic. The differences between sparsely and densely populated sinks are analyzed for various fin heights. Also assessed are effects of the blocked edges as compared to the previously studied cases where the sink edges were exposed to the surroundings.

Thermal Optimization of Microchannel Heat Sink With Pin Fin Structures

2003 ◽  
Author(s):  
Duckjong Kim ◽  
Sung Jin Kim
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Fluid Flow ◽  
Heat Sink ◽  
Volume Averaging ◽  
Heat Sinks ◽  
Pumping Power ◽  
Heat Transfer Characteristics ◽  
Pin Fin ◽  
Flow And Heat Transfer

In the present work, a novel compact modeling method based on the volume-averaging technique and its application to the analysis of fluid flow and heat transfer in pin fin heat sinks are presented. The pin fin heat sink is modeled as a porous medium. The volume-averaged momentum and energy equations for fluid flow and heat transfer in pin fin heat sinks are obtained using the local volume-averaging method. The permeability, the Ergun constant and the interstitial heat transfer coefficient required to solve these equations are determined experimentally. To validate the compact model proposed in this paper, 20 aluminum pin fin heat sinks having a 101.43 mm × 101.43 mm base size are tested with an inlet velocity ranging from 1 m/s to 5 m/s. In the experimental investigation, the heat sink is heated uniformly at the bottom. Pressure drop and heat transfer characteristics of pin fin heat sinks obtained from the porous medium approach are compared with experimental results. Upon comparison, the porous medium approach is shown to predict accurately the pressure drop and heat transfer characteristics of pin fin heat sinks. Finally, surface porosities of the pin fin heat sink for which the thermal resistance of the heat sink is minimal are obtained under constraints on pumping power and heat sink size. The optimized pin fin heat sinks are shown to be superior to the optimized straight fin heat sinks in thermal performance by about 50% under the same constraints on pumping power and heat sink size.

Cryogenic Single-Phase Heat Transfer in a Microscale Pin Fin Heat Sink

2013 ◽  
Author(s):  
Eric D. Truong ◽  
Erfan Rasouli ◽  
Vinod Narayanan
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
Single Phase ◽  
Flow Direction ◽  
Heat Sinks ◽  
Variable Cross ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients

A combined experimental and computational fluid dynamics study of single-phase liquid nitrogen flow through a microscale pin-fin heat sink is presented. Such cryogenic heat sinks find use in applications such as high performance computing and spacecraft thermal management. A circular pin fin heat sink in diameter 5 cm and 250 micrometers in depth was studied herein. Unique features of the heat sink included its variable cross sectional area in the flow direction, variable pin diameters, as well as a circumferential distribution of fluid into the pin fin region. The stainless steel heat sink was fabricated using chemical etching and diffusion bonding. Experimental results indicate that the heat transfer coefficients were relatively unchanged around 2600 W/m2-K for flow rates ranging from 2–4 g/s while the pressure drop increased monotonically with the flow rate. None of the existing correlations in literature on cross flow over a tube bank or micro pin fin heat sinks were able to predict the experimental pressure drop and heat transfer characteristics. However, three dimensional simulations performed using ANSYS Fluent showed reasonable (∼7 percent difference) agreement in the average heat transfer coefficients between experiments and CFD simulations.

An Experimental Study of Pin Fin Heat Sinks and Determination of End Wall Heat Transfer

2003 ◽  
Author(s):  
Massimiliano Rizzi ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Sink ◽  
Optimization Methods ◽  
Heat Sinks ◽  
Base Region ◽  
Transfer Coefficients ◽  
Media Type ◽  
Pin Fin ◽  
Heat Transfer Coefficients

An experimental study of a pin fin heat sink was carried out in support of the development of heat sink optimization methods requiring more detailed measurements be made. Measurements of heat flux and temperature are used to separately determine heat transfer coefficients for the pins and the base region between the pins. Three pitch to diameter ratios (distance from pin center to pin center measured diagonally) were studied: P/d = 3/1, 9/4, 3/2. Heat generation was accomplished using cartridge heaters inserted into a copper block. The high thermal conductivity of the copper ensured that the surface beneath the heat sink would be at a constant temperature. The cooling fluid was air and the experiments were conducted with a Reynolds numbers based on a porous media type hydraulic diameter ranging from 500 to 25000. The channel had a shroud that touches the fin tips, eliminating any flow bypass. The pin surface heat transfer coefficients match the values reported by Kays and London and by Zukauskas. The base region heat transfer coefficients were, surprisngly, larger than the pin values.

S-Shaped Pin-Fins for Enhancement of Overall Performance of the Pin-Fin Heat Sink

2010 ◽  
Author(s):  
T. J. John ◽  
B. Mathew ◽  
H. Hegab
Keyword(s):  
Reynolds Number ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Heat Sinks ◽  
Uniform Heat Flux ◽  
Pumping Power ◽  
Pin Fin ◽  
Pin Fins ◽  
Overall Performance

In this paper the authors are studying the effect of introducing S-shaped pin-fin structures in a micro pin-fin heat sink to enhance the overall thermal performance of the heat sinks. For the purpose of evaluating the overall thermal performance of the heat sink a figure of merit (FOM) term comprising both thermal resistance and pumping power is introduced in this paper. An optimization study of the overall performance based on the pitch distance of the pin-fin structures both in the axial and the transverse direction, and based on the curvature at the ends of S-shape fins is also carried out in this paper. The value of the Reynolds number of liquid flow at the entrance of the heat sink is kept constant for the optimization purpose and the study is carried out over a range of Reynolds number from 50 to 500. All the optimization processes are carried out using computational fluid dynamics software CoventorWARE™. The models generated for the study consists of two sections, the substrate (silicon) and the fluid (water at 278K). The pin fins are 150 micrometers tall and the total structure is 500 micrometer thick and a uniform heat flux of 500KW is applied to the base of the model. The non dimensional thermal resistance and nondimensional pumping power calculated from the results is used in determining the FOM term. The study proved the superiority of the S-shaped pin-fin heat sinks over the conventional pin-fin heat sinks in terms of both FOM and flow distribution. S-shaped pin-fins with pointed tips provided the best performance compared to pin-fins with straight and circular tips.

Optimization of Pin-Fin Heat Sinks in Bypass Flow Using Entropy Generation Minimization Method

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
W. A. Khan ◽  
J. R. Culham ◽  
M. M. Yovanovich
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Entropy Generation ◽  
Heat Sink ◽  
Heat Sinks ◽  
Entropy Generation Rate ◽  
Bypass Flow ◽  
Minimization Method ◽  
Pin Fin ◽  
Entropy Generation Minimization

An entropy generation minimization method is applied to study the thermodynamic losses caused by heat transfer and pressure drop for the fluid in a cylindrical pin-fin heat sink and bypass flow regions. A general expression for the entropy generation rate is obtained by considering control volumes around the heat sink and bypass regions. The conservation equations for mass and energy with the entropy balance are applied in both regions. Inside the heat sink, analytical/empirical correlations are used for heat transfer coefficients and friction factors, where the reference velocity used in the Reynolds number and the pressure drop is based on the minimum free area available for the fluid flow. In bypass regions theoretical models, based on laws of conservation of mass, momentum, and energy, are used to predict flow velocity and pressure drop. Both in-line and staggered arrangements are studied and their relative performance is compared to the same thermal and hydraulic conditions. A parametric study is also performed to show the effects of bypass on the overall performance of heat sinks.

Parametric Study of Heat Sink Performance at High Altitudes With Air Impingement Cooling

2006 ◽  
Author(s):  
Robert E. Seidel ◽  
Jinny Rhee
Keyword(s):  
Reynolds Number ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Air Flow ◽  
Heat Sinks ◽  
Temperature Measurements ◽  
Test Apparatus ◽  
High Altitudes ◽  
Pin Fin ◽  
Hypobaric Chamber

Heat sinks are one of the primary mechanisms today for thermal management of electronics. In the high altitudes reached by modern military aircraft, the capacity for air cooling is reduced due to the rarefied atmosphere. With an increase in altitude there is a subsequent decrease in the density of air. A review of the literature shows a lack of research done on pin-fin heat sinks with impingement flows at low Reynolds number conditions. Experimental testing will determine the thermal resistance of a pin-fin heat sink with impingement flow at low absolute pressures. A test apparatus will be constructed, and experiments will be conducted within a hypobaric chamber. In a hypobaric chamber, it is possible to simulate altitudes up to 30 000 meters by reducing the absolute pressure using a vacuum pump. Temperature is regulated and air is circulated within the chamber. The test apparatus, which is to be completely enclosed within the hypobaric chamber, consists of a centrifugal blower forcing air through a duct. Air is impinged upon a pin-fin heat sink heated with uniform flux on the base. Incident air flow is along the axis of each circular pin-fin, and exhaust from the heat sink will be transverse to the pins. Feedthroughs are available in the chamber wall for supplying electrical power to the blower, for taking temperature measurements with embedded thermocouples, and for measuring blower shaft speed. Temperature measurements are made in the base of the heat sink, in the air, and at other points to characterize other heat losses from the apparatus. Blower speed is monitored with an optical tachometer, and by similarity laws for turbomachinery it will be possible to determine the air flow impinging upon the heat sink. Pressure in the chamber will be varied in several steps up to the equivalent of a 30 000-meter altitude, and at each step a correlation will be made between heat sink thermal resistance and Reynolds number of the impinging air.

The Thermal Resistance of Pin Fin Heat Sinks in Transverse Flow

2003 ◽  
Author(s):  
Sukhvinder Kang ◽  
Maurice Holahan
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Building Blocks ◽  
Heat Sinks ◽  
Cfd Simulations ◽  
Pin Fin ◽  
Thermal Wake

This paper presents a physics based analytical model to predict the thermal behavior of pin fin heat sinks in transverse forced flow. The key feature of the model is the recognition that unlike plate fins, streamwise conduction does not occur in pin fin heat sinks. Thus, the heat transfer from each fin depends on its local air temperature or adiabatic temperature and the local adiabatic heat transfer coefficient. Both experimental data and simplified CFD simulations are used to develop the two building blocks of the model, the thermal wake function and the adiabatic heat transfer coefficient. These building blocks are then used to include the effect of the thermal wake from upstream fins on the adiabatic temperature of downstream fins in determining the fin-by-fin heat transfer within the pin fin array. This approach captures the essential physics of the flow and heat transport within the fin array and yields an accurate model for predicting the thermal resistance of pin fin heat sinks. Model predictions are compared with existing experimental data and CFD simulations. The model is expected to provide a sound basis for a consistent performance comparison with plate fin heat sinks.

Thermo-hydraulic performance of modified plate fin and pin fin heat sinks

2021 ◽  
pp. 095765092110240
Author(s):  
Anil Kumar Patil ◽  
Vishwjeet Choudhary ◽  
Ayush Gupta ◽  
Manoj Kumar
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Heat Sink ◽  
Hydraulic Performance ◽  
Heat Sinks ◽  
Forced Flow ◽  
Transfer Rates ◽  
Pin Fin ◽  
Pitch Ratio

Extended surfaces are widely investigated for their ability to enhance the heat transfer rates in different applications. Pin-fin and plate-fin heat sinks are used in a variety of cases involving a miniaturized to the large systems. The present study compares the performance of the pin-fin and the plate-fin heat sink under similar forced flow conditions. The experimental data for a modified pin fin heat sink with wings and a plate-fin heat sink with dimples are collected for the Reynolds number in the range of 6800–15100. The Nusselt number, friction factor, and thermo-hydraulic performance (THP) are examined for different geometries of the heat sink and the enhancements brought out in the heat transfer and friction are gauged relative to the smooth plate. The pin fin heat sink yields two-fold enhancement in heat transfer as compared to the plate-fin heat sink. The maximum thermo-hydraulic performance of the pin-fin heat sink with wings is found to be 4.52 at a pitch ratio (S/Df) of 2 and Wing length ratio (Lw/Df). For the plate fin heat sink with dimples, the maximum thermo-hydraulic performance is found to be 4.67 at dimple diameter ratio (D/d) of 0.5 and dimple pitch ratio (s/d) of 2.5. The correlations of the Nusselt number and friction factor are proposed for different geometries of fins.

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