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.

Steady-state heat conduction analysis for two-terminal microwave oscillator devices with rectangular integral heat sinks

1995 ◽  
Vol 451 (1942) ◽  
pp. 375-381 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Steady State ◽  
Temperature Rise ◽  
Heat Sink ◽  
Microwave Oscillator ◽  
Heat Sinks ◽  
Maximum Temperature ◽  
Maximum Temperature Rise ◽  
Steady State Heat

The outline of a theoretical analysis to calculate the steady-state temperature distribution within a rectangular prism mounted on a semi-infinite heat sink is presented. The incident heat flux is uniform over a given centralized circular region on one face of the prism. The thermal conductivity of the material is treated as being dependent on the temperature. The model is used to calculate the maximum temperature rise within a heat sink configuration that is used to package contemporary two-terminal microwave oscillator devices. Results are presented that show how the maximum temperature rise within such commercially available heat sink packages depends on the input heat flux and the dimensions and thermal conductivity of the materials. These results are presented in a generalized form for device design purposes.

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.

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.

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.

Compact Modeling of Unshrouded Plate Fin Heat Sinks

2003 ◽  
Author(s):  
Sridhar Narasimhan ◽  
Avram Bar-Cohen
Keyword(s):  
Thermal Conductivity ◽  
Pressure Drop ◽  
Effective Thermal Conductivity ◽  
Heat Sink ◽  
Heat Sinks ◽  
Compact Modeling ◽  
Base Temperature ◽  
Computational Domain ◽  
Porous Block ◽  
Compact Models

The present work considers the compact modeling of unshrouded parallel plate heat sinks in laminar forced convection. The computational domain includes three heat sinks in series, cooled by an intake fan. The two upstream heat sinks are represented as “porous blocks”, each with an effective thermal conductivity and a pressure loss coefficient, while the downstream heat sink, assumed to be the component requiring the most accurate characterization, is modeled in detail. A large parametric space covering three typical heat sink geometries, as well as a range of common inlet velocities, separation distances between the heat sinks, and bypass clearances is considered in the development and evaluation of the compact models. The current study uses a boundary layer-based methodology, accounting for both the viscous dissipation and form drag losses, to determine the pressure drop characteristics, and an effective conductivity methodology, using a flow bypass model and Nusselt number correlation, to determine the effective thermal conductivity, for the porous block representation of the heat sink. The results indicate that the introduction of compact heat sinks has little influence on the pressure drop of the critical heat sink. Good agreement in pressure drops, typically in the range of 5%, is also obtained between “detailed” heat sink models and their corresponding porous block representation. The introduction of the compact models is found to have little influence (typically less than 1°C) on the base temperature of the critical heat sinks. For the compact heat sinks, the agreement is again within a typical difference of 5% in thermal resistance. Dramatic improvements were observed in the mesh count (factor > 10X) and solution time (factor >20X) required to achieve a high-fidelity simulation of the velocity, pressure, and temperature fields.

The Influence of the Thermal Conductivity on the Heat Transfer Performance in a Heat Sink

2002 ◽  
Vol 124 (3) ◽  
pp. 164-169 ◽  
Author(s):  
H. B. Ma ◽  
G. P. Peterson
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Fluid Flow ◽  
Temperature Distribution ◽  
Heat Sink ◽  
Heat Transfer Performance ◽  
Solid Material ◽  
Heat Sinks ◽  
Transfer Performance ◽  
Desktop Computers

An extensive numerical analysis of the temperature distribution and fluid flow in a heat sink currently being used for cooling desktop computers was conducted, and demonstrated that if the base of a heat sink was fabricated as a heat pipe instead of a solid material, the heat transfer performance could be significantly increased. It was shown that as the heat sink length increases, the effect of the thermal conductivity of the base on the heat transfer performance increases to be a predictable limit. As the thermal conductivity is increased, the heat transfer performance of heat sinks is enhanced, but cannot exceed this limit. When the thermal conductivity increases to 2,370 W/m-K, the heat transfer performance of the heat sinks will be very close to the heat transfer performance obtained assuming a base with infinite thermal conductivity. Further increases in the thermal conductivity would not significantly improve the heat transfer performance of the heat sinks.

A Study on Polymer Pin Fin Based Heat Sinks

2007 ◽  
Author(s):  
Ajmal Ansari
Keyword(s):  
Thermal Conductivity ◽  
High Power ◽  
Heat Sink ◽  
Heat Sinks ◽  
Polymer Additives ◽  
Pin Fin ◽  
Recent Developments ◽  
Engineering Polymers

Recent developments in polymer additives and formulations have made available resins that have thermal conductivity that is one to two orders of magnitude higher than that of typical engineering polymers. Such polymers can be potentially used for designing heat sinks. There are two primary advantages of polymer heat sinks: ability to form shapes that may not be feasible with metal and flexibility that allows the heat sink to be bent in various shapes. This paper presents results from a study that was conducted to determine the suitability of commercially available Flexible Heat Sink Material for use in cooling high power LED’s.

scholarly journals Experimental analysis of effect of base with different inner geometries filled nano PCM for the thermal performance of the plate fin heat sink

2021 ◽  
pp. 243-243
Author(s):  
Periyannan Lakshmanan ◽  
Saravanan Periyasamy ◽  
Mohan Raman
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Reynolds Number ◽  
Phase Shift ◽  
Experimental Research ◽  
Thermal Performance ◽  
Heat Sink ◽  
Electronic Devices ◽  
Base Plate ◽  
Heat Sinks

Experimental research demonstrates the performance of electronic devices on plate fin heat sinks in order to guarantee that operating temperatures are kept as low as possible for reliability. Paraffin wax (PCM) is a substance that is used to store energy and the aluminum plate fin cavity base is chosen as a Thermal Conductivity Enhancer (TCEs). The effects of PCM material (Phase shift material), cavity form base (Rectangular, Triangular, Concave and Convex) with PCM, Reynolds number (Re= 4000-20000) on heat transfer effectiveness of plate fin heat sinks were experimentally explored in this research. The thermal performance of concave base plate fin heat sink with PCM is increased up to 7.8% compared to other cavity base heat sinks.

Numerical Evaluation of Clearance Requirements Around Obstructions in Finned Heat Sinks

2017 ◽  
Author(s):  
Steven Miner
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Temperature Rise ◽  
Heat Sink ◽  
Operating Temperature ◽  
Flow Distribution ◽  
Local Heat ◽  
Heat Sinks ◽  
Electronic Components

This study uses CFD to consider the effects of obstructions (bosses) on the fluid flow and heat transfer in finned heat sinks used for cooling electronic components. In particular, the effect of bosses, used for mounting components, on the fluid flow distribution and temperature distribution in the heat sink are evaluated. A typical heat sink has fins sandwiched between top and bottom plates, with electronic components mounted on the plates. The top and bottom plates spread the heat generated in the components to reduce the local heat flux. The fins substantially increase the heat transfer area, reducing the temperature rise from the coolant to the top and bottom plates. In this case a uniform distribution of flow across the heat sink can be achieved and there will be no localized hot spots. Ideally there are no protrusions into the finned portion of the heat sink which would cause disruptions in the uniform flow through the heat sink. However, a boss may be needed to bolt a component to the heat sink. The presence of the boss has three effects on the heat sink performance. The boss disrupts the flow in its immediate vicinity, increasing the thermal resistance. This will cause an increase in operating temperature at that location. In addition, the boss will change the flow distribution in the heat sink. Locations upstream and downstream of the boss may see reduced flow due to the obstruction, which in turn will cause an increase in operating temperature for these areas of the heat sink. Finally, the change in flow distribution may increase the pressure drop through the entire heat sink, increasing the power required to operate the system. The purpose of this study is to numerically evaluate the clearance requirements around circular bosses. Comparisons between an unobstructed heat sink and a heat sink with an obstruction are made for the maximum component temperature rise, the pressure drop and the flow distribution. Clearance ratios, diameter of the fin cut out to boss diameter, were varied from 1.1 to 3.3. The Reynolds number for the flow was varied from roughly 3000 to 70,000 based on the hydraulic diameter of flow passage.

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.

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