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.

Multi Layer Micro Pin-Fins Heat Sinks for Better Performance

2010 ◽  
Author(s):  
T. J. John ◽  
B. Mathew ◽  
H. Hegab
Keyword(s):  
Temperature Distribution ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Single Layer ◽  
Heat Sinks ◽  
Substrate Thickness ◽  
Pin Fin ◽  
Micro Channels ◽  
Pin Fins ◽  
Overall Performance

This study numerically investigates the feasibility and advantages of using a multilayer pin-fin heat sink to increase the overall performance of the heat sink. For the purpose of determining overall performance of the pin-fin heat sink a figure of merit (FOM) term is introduced in this paper, which constituted of both the thermal resistance and the pumping power of the heat sink. Higher the FOM of a heat sink better is its overall performance. A computational fluid dynamics software CoventorWARE™ is used for the analysis of micro heat sink performance. A small portion of the entire heat sink is modeled in this study assuming repeatability towards both sides for the ease of analysis. The developed models consist of two sections, the substrate (silicon) and the fluid (water at 278K). A uniform heat flux is applied to the base of the heat sink. A single layer micro pin-fin heat sinks with same dimensions as of the multi layer heat sink was also modeled for the comparison purpose. Temperature distribution at five different locations from the inlet to the outlet section is also analyzed to study the temperature distribution over the heat sink. Circular pin-fins were used in both the multilayer and single layer micro heat sinks. Feasibility of using micro channels as the second layer was also investigated in this paper and it proved to have advantages over using pin-fin structures on both layers. A geometric optimization based on the substrate thickness of the second layer of the double layer heat sink showed that the substrate thickness of the second layer doesn’t have any effect on the overall thermal resistance of the heat sink.

Thermo-Mechanical Fatigue Life Prediction of Orthotropic Composite Pin Fin Heat Sinks for Electronic Packaging

2011 ◽  
Author(s):  
Sulaman Pashah ◽  
Abul Fazal M. Arif
Keyword(s):  
Thermal Performance ◽  
Heat Sink ◽  
Electronic Packaging ◽  
Base Plate ◽  
Heat Sinks ◽  
Metallic Base ◽  
Plate Interface ◽  
Pin Fin ◽  
Pin Fins ◽  
Reliability Performance

Heat sinks are used in modern electronic packaging system to enhance and sustain system thermal performance by dissipating heat away from IC components. Pin fins are commonly used in heat sink applications. Conventional metallic pins fins are efficient in low Biot number range whereas high thermal performance can be achieved in high Biot number regions with orthotropic composite pin fins due to their adjustable thermal properties. However, several challenges related to performance as well as manufacturing need to be addressed before they can be successfully implemented in a heat sink design. A heat sink assembly with metallic base plate and polymer composite pin fins is a solution to address manufacturing constraints. During the service life of an electronic packaging, the heat sink assembly is subjected to power cycles. Cyclic thermal stresses will be important at the pin-fin and base-plate interface due to thermal mismatch. The cyclic nature of stresses can lead to fatigue failure that will affect the reliability of the heat sink and electronic packaging. A finite element model of the heat sink is used to investigate the thermal stress cyclic effect on thermo-mechanical reliability performance. The aim is to assess the reliability performance of the epoxy bond at the polymer composite pin fins and metallic base plate interface in a heat-sink assembly.

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.

Thermal Performance Analysis of Fan-Heat Sinks for CPU Cooling

2003 ◽  
Author(s):  
Seo Young Kim ◽  
Ralph L. Webb
Keyword(s):  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Heat Sinks ◽  
Operating Point ◽  
Pin Fin ◽  
Flow Impedance ◽  
Impedance Curve ◽  
Convective Thermal ◽  
Offset Strip Fin

The thermal performance of plate fin, round pin-fin and offset strip-fin heat sinks with a duct-flow type fan arrangement was analytically evaluated. Heat sinks of 65mm × 60mm plan area × 50 mm height with a 4300-RPM DC fan (60mm × 15mm) were chosen for the performance comparison. A constant temperature, 6 mm thick heat sink base plate is assumed so that thermal spreading resistance is not involved. The operating point on the fan curve is based on the flow pressure drop impedance curve through a heat sink using the friction factor correlation for the chosen heat sink. The loss coefficients at both the entrance and the exit of heat sink are included in the flow impedance curve. The operating point is defined by the balance point of the flow impedance curve and the fan performance curve. After determining the operating air velocity, the convective thermal resistance of heat sinks is evaluated from the Nusselt number correlation for the chosen heat sink. Results obtained show that optimized round pin-fin heat sinks provide 32.8%-to-46.4% higher convective thermal resistance compared to an optimized plate-fin heat sink. The optimized offset strip-fin heat sink shows a slightly lower convective thermal resistance than the plate-fin heat sink. As the offset strip length decreases, however, thermal performance seriously deteriorates.

Investigation of Cylindrical Pin-Fin Heat Sink Thermal Performance at High Altitude

2006 ◽  
Author(s):  
Melanie Beauchemin ◽  
Jinny Rhee
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
High Altitude ◽  
Friction Factor ◽  
Thermal Performance ◽  
Heat Sink ◽  
Average Nusselt Number ◽  
Maximum Velocity ◽  
Heat Sinks ◽  
Pin Fin

Heat sinks with cross airflow are commonly used for enhancing the cooling of electronic components. When using heat sinks in avionics applications, the primary heat transfer challenges are due to low air densities, which occur when operating at high altitudes, and space and mass constraints. Because of the spatial constraints, heat sinks with a large surface area per unit volume are advantageous. In general, cylindrical pin-fin heat sinks offer such characteristics. The Nusselt number is used as an indication of the thermal performance of the heat sink for a given Reynolds number. At high altitude, we expect the Reynolds number (based on the fin diameter and maximum velocity, Red,max) to be smaller than 1000. Empirical correlations for the Nusselt number of cylindrical pin-fin heat sinks are available in the literature; however, these correlations were obtained for larger values of Red,max. The objective of this work is to correlate the Nusselt number and the friction factor of an in-line cylindrical pin-fin heat sink with its non-dimensional geometric parameters, and the airflow Reynolds number. The emphasis is on Red,max range between 25 and 1000, which allows the evaluation of the thermal performance of the heat sink for altitudes up to 70,000 feet. The results are obtained using three-dimensional numerical simulations with the commercial CFD software Flotherm. The numerical model is validated against experimental data. The results show that for a given Red,max, the average Nusselt number and friction factor are independent of the altitude for a given heat sink configuration. However, for a given air inlet velocity, an important drop in the average Nusselt number is observed as the altitude increases due to the reduction in air density. The effect of the variation of the fin span-wise and stream-wise pitches, as well as height is also studied.

Experimental Investigation of Thermal Performance of Vapor Chamber Heat Sinks

2010 ◽  
Author(s):  
Hung-Yi Li ◽  
Ming-Hung Chiang ◽  
Chih-I Lee ◽  
Wen-Jei Yang
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Base Plate ◽  
Heat Sinks ◽  
Maximum Temperature ◽  
Vapor Chamber ◽  
Lower Reynolds Number

This work experimentally studies the thermal performance of plate-fin vapor chamber heat sinks using infrared thermography. The effects of the fin width, the fin height and the Reynolds number on the thermal performance are considered. The results show that generated heat is transferred more uniformly to the base plate by a vapor chamber heat sink than by a similar aluminum heat sink. Therefore, the maximum temperature is effectively reduced. The overall thermal resistance of the vapor chamber heat sink declines as the Reynolds number increases, but the strength of the effect falls. The effect of the fin dimensions on the thermal performance is stronger at a lower Reynolds number.

Characteristic Study on the Optimization of Pin-Fin Micro Heat Sink

2009 ◽  
Author(s):  
T. J. John ◽  
B. Mathew ◽  
H. Hegab
Keyword(s):  
Pressure Drop ◽  
Thermal Resistance ◽  
Flow Rate ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Heat Sinks ◽  
Low Flow ◽  
Pumping Power ◽  
Flow Rates ◽  
Pin Fin

The need for dissipating heat from microsystems has increased drastically in the last decade. Several methods of heat dissipation using air and liquids have been proposed by many studies, and pin-fin micro heat sinks are one among them. Researchers have developed several effective pin-fin structures for use in heat sinks, but not much effort has been taken towards the optimization of profile and dimensions of the pin-fin. In this paper the authors studied the effect of different pin-fin shapes on the thermal resistance and pressure drop in a specific micro heat-sink. Optimization subjected to two different constraints is studied in this paper. The first optimization is subjected to constant flow rate and the second one is subjected to constant pressure drop. Both optimization processes are carried out using computer simulations generated using COVENTORWARE™. Two of the best structures from each of these optimization studies are selected and further analysis is performed for optimizing their structure dimensions such as width, height and length. A section of the total micro heat-sink is modeled for the initial optimization of the pin-fin shape. The model consists of two sections, the substrate and the fluid. Six different shapes: square, circle, rectangle, triangle, oval and rhombus were analyzed in the initial optimization study. Preliminary tests were conducted using the first model described above for a flow rate of 0.6ml/min. The non dimensional overall thermal resistance of the heat sink, and the nondimensional pumping power was calculated from the results. A figure of merit (FOM) was developed using the nondimensional thermal resistance and nondimensional pumping power for each structure with different pin-fin shapes. Smaller the value of FOM better the performance of the heat sink. The study revealed that the circle and ellipse structures have the best performance and the rectangle structure had the worst performance at low flow rates. At high flow rates rectangular and square structures have the best performance.

scholarly journals Numerical investigation of using different arrangement of fin slides on the plate-fin heat sink performance

2021 ◽  
pp. 65-65
Author(s):  
Mostafa Abdelmohimen ◽  
Khalid Almutairi ◽  
Mohamed Elkotb ◽  
Hany Abdelrahman ◽  
Salem Algarni
Keyword(s):  
Reynolds Number ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Parallel Flow ◽  
Heat Sinks ◽  
Pumping Power ◽  
Staggered Arrangement ◽  
Flow Directions ◽  
High Reynolds ◽  
Impinging Flow

Cutting fins of the plate heat sinks into multi-numbers of slides instead of one slide fin is a technique to improve the performance of the heat sink. One, two, three, and four slides have been studied numerically. The slides have been arranged in staggered arrangement. The study has been carried out on two different flow directions (impinging and parallel). The performance of the heat sink under the studied conditions has been represented through calculation of heat sink effectiveness, thermal resistance, pressure drop, pumping power, and Nusselt number. The studied range of Reynolds number is from 1333 to 5334. The results show that parallel flow gives lower thermal resistance than impinging flow for all studied cases. The pumping power required for high Reynolds number in case of parallel flow increases by around 155% with case-4 (four slides) as compared by case-1 (one slide). While it is slightly affected in case of impinging flow, using three slides with impinging flow represents an acceptable decrement in thermal resistance with low change in the required pumping power. In case of parallel flow, the resulting change in the heat sink performance, as the number of slides increases, is not proportional to the large increase in the pumping power.

Hydoroil-Based Micro Pin Fin Heat Sink

2006 ◽  
Author(s):  
Ali Kosar ◽  
Chih-Jung Kuo ◽  
Yoav Peles
Keyword(s):  
Heat Sink ◽  
Hydraulic Performance ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
Pin Fins ◽  
Micro Pin Fins

An experimental study on thermal-hydraulic performance of de-ionized water over a bank of shrouded NACA 66-021 hydrofoil micro pin fins with wetted perimeter of 1030-μm and chord thickness of 100 μm has been performed. Average heat transfer coefficients have been obtained over effective heat fluxes ranging from 4.0 to 308 W/cm2 and mass velocities from 134 to 6600 kg/m2s. The experimental data is reduced to the Nusselt numbers, Reynolds numbers, total thermal resistances, and friction factors in order to determine the thermal-hydraulic performance of the heat sink. It has been found that prodigious hydrodynamic improvement can be obtained with the hydrofoil-based micro pin fin heat sink compared to the circular pin fin device. Fluid flow over pin fin heat sinks comprised from hydrofoils yielded radically lower thermal resistances than circular pin fins for a similar pressure drop.

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.

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