scholarly journals Importance of Melt Flow Direction during Injection Molding on Polymer Heat Sinks’ Cooling Efficiency

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1186
Author(s):  
Michal Guzej ◽  
Martin Zachar ◽  
Jan Kominek ◽  
Petr Kotrbacek ◽  
Robert Brachna
Keyword(s):  
Thermal Conductivity ◽  
Heat Source ◽  
Heat Sink ◽  
Flow Direction ◽  
Conductive Filler ◽  
Heat Sinks ◽  
High Thermal Conductivity ◽  
Cooling Efficiency ◽  
Melt Flow ◽  
Molding Process

Polymers with highly conductive fillers could possibly replace standardly used materials, such as aluminum and copper alloys, for passive cooling purposes. The main problem of the composite polymer-based heat sinks is that their high thermal conductivity is uneven. The orientation of this anisotropy is set according to the position of the highly thermally conductive filler. Its orientation is influenced by the melt flow during the polymer heat sink molding process. This article shows that change of the melt flow inside the mold cavity can improve the overall cooling efficiency of a polymer heat sink, which leads to lower temperatures on the heat source used. Two polymer heat sinks of identical geometries were produced. Their high thermal conductivity was given by the use of graphite flakes as the filler. The only difference between the heat sinks was in the position of the fan gate during their production. Different temperatures of the heat source between the two heat sinks were observed for the same measurement conditions. The measurements were conducted at Heatlab, BUT/Brno.

Study on the Factors Influencing Spreading Resistance of Heat Sinks

2011 ◽  
Vol 301-303 ◽  
pp. 165-169
Author(s):  
Da Yong Gao ◽  
Jian Xin Zhang ◽  
Ping Juan Niu
Keyword(s):  
Heat Source ◽  
Heat Sink ◽  
Electronic Devices ◽  
Great Influence ◽  
Base Plate ◽  
Critical Value ◽  
Area Ratio ◽  
Heat Sinks ◽  
Spreading Resistance ◽  
Factors Influencing

The spreading resistance is a very important parameter in the applications of heat sink. The design of electronic devices will fail without considering the influence of the spreading resistance. In this paper, a simple thermal model was simulated by Computational Fluid Dynamics software. Some factors, which have great influence on the spreading resistance, have been analyzed. The spreading resistance decreases significantly with the increasing of the area ratio between the heat source and the base-plate. While the ratio being 1, the spreading resistance reaches the mix value. The greater the thermal conductivity of heat sink, the lower the spreading resistance. With the increasing of the thickness of base-plate, the spreading resistance reduces. However, if the thickness exceeds the critical value, the spreading resistance will increase. And the spreading resistance reaches the mix value while the centers of heat source and the base-plate are overlapped.

Flexible graphene composites with high thermal conductivity as efficient heat sinks in high-power LEDs

2018 ◽  
Vol 52 (2) ◽  
pp. 025103 ◽  
Author(s):  
J Oliva ◽  
A I Mtz-Enriquez ◽  
A I Oliva ◽  
R Ochoa-Valiente ◽  
C R Garcia ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
High Power ◽  
Heat Sinks ◽  
High Thermal Conductivity

Design and Optimization of a Composite Heat Spreader to Improve the Thermal Management of a 3D Integrated Circuit

2021 ◽  
Author(s):  
Andisheh Tavakoli ◽  
Kambiz Vafai
Keyword(s):  
Thermal Conductivity ◽  
Heat Sink ◽  
Variable Temperature ◽  
Heat Removal ◽  
High Conductivity ◽  
High Thermal Conductivity ◽  
Maximum Temperature ◽  
Optimal Distribution ◽  
Heat Spreader ◽  
The Impact

Abstract The present study analyzes the optimal distribution of a limited amount of high thermal conductivity material to enhance the heat removal of circular 3D integrated circuits, IC. The structure of the heat spreader is designed as a composite of high thermal conductivity (Boron Arsenide) and moderate thermal conductivity (copper) materials. The volume ratio of high-conductivity inserts to the total volume of the spreader is set at a fixed pertinent ratio. Two different boundary conditions of constant and variable temperature are considered for the heat sink. To examine the impact of adding high-conductivity inserts on the cooling performance of the heat spreader, various patterns of the single and double ring inserts are studied. A parametric study is performed to find the optimal location of the rings. Moreover, the optimal distribution of the high-conductivity material between the inner and outer rings is found. The results show that for the optimal conditions, the maximum temperature of the 3D IC is reduced up to 10%; while the size of the heat sink, and heat spreader can be diminished by as much as 200%.

Numerical Analysis of Impinging Air Flow and Heat Transfer in Plate-Fin Type Heat Sinks

1999 ◽  
Vol 123 (3) ◽  
pp. 315-318 ◽  
Author(s):  
Keiji Sasao ◽  
Mitsuru Honma ◽  
Atsuo Nishihara ◽  
Takayuki Atarashi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Numerical Analysis ◽  
Numerical Method ◽  
Heat Sink ◽  
Flow Resistance ◽  
Air Flow ◽  
Heat Sinks ◽  
Flow And Heat Transfer ◽  
Conventional Methods

A numerical method for simulating impinging air flow and heat transfer in plate-fin type heat sinks has been developed. In this method, all the fins of an individual heat sink and the air between them are replaced with a single, uniform element having an appropriate flow resistance and thermal conductivity. With this element, fine calculation meshes adapted to the shape of the actual heat sink are not needed, so the size of the calculation mesh is much smaller than that of conventional methods.

scholarly journals Temperature Control at DBS Electrodes Using Heat Sinks: Experimentally Validated FEM Model of DBS Lead Architecture

2009 ◽  
Vol 3 (2) ◽  
Author(s):  
M. Elwassif ◽  
A. Datta ◽  
M. Bikson
Keyword(s):  
Thermal Conductivity ◽  
Temperature Field ◽  
Temperature Rise ◽  
Heat Sink ◽  
Magnetic Coupling ◽  
Heat Sinks ◽  
Peak Temperature ◽  
Normal Operation ◽  
Driving Voltage ◽  
Control Temperature

There is a growing interest in the use of Deep Brain Stimulation (DBS) for the treatment of medically refractory movement disorders and other neurological and psychiatric conditions. The extent of temperature increases around DBS electrodes during normal operation (joule heating and increased metabolic activity) or magnetic coupling (e.g., MRI) remain poorly understood, and methods to mitigate temperature increases are actively investigated. Indeed, brain function is especially sensitive to the changes in temperature including neuronal activity, metabolic functions, blood-brain barrier integrity, molecular stability, and viability. We developed technology to control tissue heating near DBS leads by modifying the thermal properties of lead materials. A micro-thermocouple was used to measure the temperature near DBS electrodes immersed in a saline bath. 3387 and 3389 Leads were energized using Medtronic DBS stimulators. The RMS of the driving voltage was monitored. Peak steady-state temperature was determined under different RMS values. A micro-positioning system was used, which allowed the generation of temperature field map. We developed and solved a finite element method (FEM) bio-heat transfer model of DBS incorporating realistic DBS lead architecture. The model was first validated using the experimental results (by matching saline thermal conductivity and electrical conductivity) and was then applied to develop methods to control temperature rises in the brain using heat-sink technology. Experimental measurements are consistent with theoretical predictions including: 1) Peak temperature increases directly with the RMS square of the applied voltage, such that different waveforms with the same RMS induce the same peak temperature rise; 2) Peak temperatures increases with contact proximity such the maximal temperature rise was observed using adjacent contacts of lead 3389; 3) Temperature decayed over ∼2 mm distance away from energized contacts. FEM results demonstrated the central role of lead materials (material properties and geometry) in controlling temperature rise by conducting heat: namely by acting as passive heat sinks. We report that the relatively high thermal conductivity of exiting DBS lead wiring affects the temperature field, indicating the importance of detailed lead architecture. We then demonstrate how modifying lead design to optimize heat conduction can effectively control temperature increases; the manifest advantages of this approach over complimentary heat-mitigation technologies is that heat-sink controls include: 1) insensitive to the mechanisms of heating (e.g., nature of magnetic coupling); 2) does not interfere with device efficacy (e.g., the electric fields induced in the tissue during stimulation are unaffected); and 3) can be practically implemented in a broad range of implanted devices (cardiac/neuro-prothethics, pumps...) without modifying device operation or implant procedure.

On the Cooling of Electronics With Nanofluids

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
W. Escher ◽  
T. Brunschwiler ◽  
N. Shalkevich ◽  
A. Shalkevich ◽  
T. Burgi ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermophysical Properties ◽  
Heat Sink ◽  
Relative Viscosity ◽  
Volumetric Flow Rate ◽  
Silica Nanoparticle ◽  
Particle Morphology ◽  
Heat Sinks ◽  
Conductivity Enhancement ◽  
Microchannel Heat Sinks

Nanofluids have been proposed to improve the performance of microchannel heat sinks. In this paper, we present a systematic characterization of aqueous silica nanoparticle suspensions with concentrations up to 31 vol %. We determined the particle morphology by transmission electron microscope imaging and its dispersion status by dynamic light scattering measurements. The thermophysical properties of the fluids, namely, their specific heat, density, thermal conductivity, and dynamic viscosity were experimentally measured. We fabricated microchannel heat sinks with three different channel widths and characterized their thermal performance as a function of volumetric flow rate for silica nanofluids at concentrations by volume of 0%, 5%, 16%, and 31%. The Nusselt number was extracted from the experimental results and compared with the theoretical predictions considering the change of fluids bulk properties. We demonstrated a deviation of less than 10% between the experiments and the predictions. Hence, standard correlations can be used to estimate the convective heat transfer of nanofluids. In addition, we applied a one-dimensional model of the heat sink, validated by the experiments. We predicted the potential of nanofluids to increase the performance of microchannel heat sinks. To this end, we varied the individual thermophysical properties of the coolant and studied their impact on the heat sink performance. We demonstrated that the relative thermal conductivity enhancement must be larger than the relative viscosity increase in order to gain a sizeable performance benefit. Furthermore, we showed that it would be preferable to increase the volumetric heat capacity of the fluid instead of increasing its thermal conductivity.

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.

Numerical Simulation of Heat Sink Performance With Interrupted and Staggered Fins

2009 ◽  
Author(s):  
Suabsakul Gururatana ◽  
Xianchang Li
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Heat Transfer Rate ◽  
Heat Sink ◽  
Pressure Loss ◽  
Transfer Rate ◽  
Flow Direction ◽  
Heat Sinks ◽  
High Heat Transfer

Extended surfaces (fins) have been used to enhance heat transfer in many applications. In electronics cooling, fin-based heat sinks are commonly designed so that coolants (gas or liquid) are forced to pass through the narrow straight channel. To improve the overall heat sink performance, this study investigated numerically the details of heat sinks with interrupted and staggered fins cooled by forced convection. Long and narrow flow passages or channels are widely seen in heat sinks. Based on the fundamental theory of heat transfer, however, a new boundary layer can be created periodically with interrupted fins, and the entrance region can produce a very high heat transfer coefficient. The staggered fins can take advantage of the lower temperature flow from the upstream. The tradeoff is the higher pressure loss. A major challenge for heat sink design is to reduce the pressure loss while keeping the heat transfer rate high. The effect of fin shapes on the heat sink performance was also examined. Two different shapes under study are rectangular and elliptic with various gaps between the interrupted fins in the flow direction. In addition, studies were also conducted on the parametric effects of Reynolds number and gap length. It is observed that heat transfer increases with the Reynolds number due to the feature of developing boundary layer. If the same pressure drop is considered, the heat transfer rate of elliptic fins is higher than that of rectangular fins.

Improvement of Heat Sink Effect Using Zinc Oxide Nanostructure

2020 ◽  
Vol 20 (11) ◽  
pp. 6980-6984
Author(s):  
Yun Guang Li ◽  
Hyun Jin Yoo ◽  
Changyoon Baek ◽  
Junhong Min
Keyword(s):  
Thermal Conductivity ◽  
Zinc Oxide ◽  
Reaction Time ◽  
Surface Area ◽  
Heat Sink ◽  
Heat Sinks ◽  
Zno Nanostructures ◽  
X Ray Diffraction ◽  
Precision Temperature ◽  
Polymerase Chain

Heat sinks that dissipate heat effectively play a significant role in devices with high-precision temperature control, such as thermal cyclers for polymerase chain reaction (PCR). This study was carried out to develop a heat sink with a high thermal conductivity to dissipate heat effectively. To increase the surface area of the heat sink, zinc oxide (ZnO) nanostructures were fabricated on an aluminum plate. ZnO nanostructures were fabricated by hydrothermal method and confirmed by scanning electron microscopy and X-ray diffraction. With the increase in the concentration of the precursors, the length of the nanorods increased, and with longer reaction time, nanostructures connected with higher stability and larger surface area. Thermal conductivity is increased by ZnO nanostructures and is affected by the concentration of precursors and the reaction time. Thermal conductivity of an optimal ZnO-coated Al plate is 2 times higher than that of a bare one. This technology can be applied to portable PCR devices to reduce weight, size, and power consumption.

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