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1
Mutlu, Imren. "Thermal behaviour of heat sinks." Thesis, Staffordshire University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358462.
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2
Lee, Man. "Forced convection heat transfer in integrated microchannel heat sinks /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?MECH%202006%20LEE.
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3
Duan, Zhipeng. "Impingement air cooled plate fin heat sinks /." Internet access available to MUN users only, 2003. http://collections.mun.ca/u?/theses,161910.
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4
Burzynski, Katherine Morris. "Printed Nanocomposite Heat Sinks for High-Power, Flexible Electronics." University of Dayton / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1619702252056433.
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5
Al-Neama, Ahmed Fouad Mahmood. "Serpentine minichannel liquid-cooled heat sinks for electronics cooling applications." Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/20318/.
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The increasing density of transistors in electronic components is leading to an inexorable rise in the heat dissipation that must be achieved in order to preserve reliability and performance. Hence, improving the thermal management of electronic devices is a crucial goal for future generations of electronic systems. Therefore, a complementary experimental and numerical investigation of single-phase water flow and heat transfer characteristics of the benefits of employing three different configurations of serpentine minichannel heat sink (MCHS) designs has been performed, to assess their suitability for the thermal management of electronic devices. These heat sinks are termed single (SPSMs), double (DPSMs) and triple path serpentine rectangular minichannels (TPSMs), and their performance is compared, both experimentally and numerically, with that of a design based on an array of straight rectangular minichannels (SRMs) in terms of pressure drop (ΔP), average Nusselt number (Nuavg) and total thermal resistance (Rth). The results showed that the serpentine channel bends are very influential in improving heat transfer by preventing both the hydrodynamic and thermal boundary layers from attaining a fully-developed state. The SPSM design provides the most effective heat transfer, followed by the DPSM and TPSM ones, both of which out-performed the SRM heat sink. The SPSM heat sink produced a 35% enhancement in Nuavg and a 19% reduction in Rth at a volumetric flow rate (Qin) of 0.5 l/min compared to the conventional SRM heat sink. These improvements in the heat transfer are, however, achieved at the expense of significantly larger ΔP. It was found that the incorporation of serpentine minichannels into heat sinks will significantly increase the heat-removal ability, but this must be balanced with the pressure drop requirement. Therefore, an experimental and numerical investigation of the benefit of introducing chevron fins has been carried out to examine the potential of decreasing pressure drop along with further thermal enhancement. This novel design is found to significantly reduce both the ΔP across the heat sink and the Rth by up to 60% and 10%, respectively, and to enhance the Nuavg by 15%, compared with the SPSM heat sink without chevron fins. Consequently, the design of the SPSM with and without chevron fins was then optimised in terms of the minichannel width (Wch) number of minichannels (Nch) and chevron oblique angle (θ). The optimisation process uses a 30 (without chevron fins) and 50 (with chevron fins) point Optimal Latin Hypercubes Design of Experiment, generated from a permutation genetic algorithm, and accurate metamodels built using a Moving Least Square (MLS) method. A Pareto front is then constructed to enable the compromises available between designs with a low pressure drop and those with low thermal resistance to be explored and appropriate design parameters to be chosen. These techniques have then been used to explore the feasibility of using serpentine MCHS and heat spreaders to cool GaN HEMTs.
6
Crockett, Dean D. "Direct measurement of parallel plate heat sink bypass flow." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Thesis/Fall2006/d_crockett_121206.pdf.
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7
Simionescu, Florentina. "Considerations on optimum design of micro heat pipe sinks using water as working fluid." Auburn, Ala., 2006. http://repo.lib.auburn.edu/Send%2012-15-07/SIMIONESCU_FLORENTINA_33.pdf.
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8
Farnam, Dylan Sean. "Comparative analysis of microchannel heat sink configurations subject to a pressure constraint." Diss., Online access via UMI:, 2007.
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9
Pate, Daniel Thomas Bhavnani S. H. "Experimental investigation of cavity induced two phase flow in silicon microchannels." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Summer/Theses/PATE_DANIEL_19.pdf.
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10
Nagarathnam, Premkumar. "Novel carbon nanotube thermal interfaces for microelectronics." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31720.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010.Committee Chair: Graham, Sam; Committee Member: Joshi, Yogendra; Committee Member: Kalaitzidou, Kyriaki. Part of the SMARTech Electronic Thesis and Dissertation Collection.
11
Kota, Krishna M. "Design and experimental study of an integrated vapor chamber thermal energy storage system." Orlando, Fla. : University of Central Florida, 2008. http://purl.fcla.edu/fcla/etd/CFE0002332.
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12
Turkakar, Goker. "Numerical Simulation And Analytical Optimization Of Microchannel Heat Sinks." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612377/index.pdf.
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This study has two main objectives: The performance evaluation of existing microchannel heat sinks using a CFD model, and the dimensional optimization of various heat sinks by minimizing the total thermal resistance.
For the analyses, the geometric modeling is performed using the software GAMBIT while the thermal analysis is performed with FLUENT. The developed model compares very well with those available in the literature. Eight different metal-polymer microchannel heat sinks are analyzed using the model to find out how much heat could be provided to the systems while keeping the substrate temperatures below 85°C under a constant pumping power requirement. Taking the objective function as the total thermal resistance, the optimum geometries have been obtained for the mentioned metal-polymer heat sinks as well as more conventional silicon ones. The results of the optimization code agreed very well with available ones in the literature. In the optimization study, the Intel Core i7-900 Desktop Processor Extreme Edition Series is considered as a reference processor which is reported to dissipate 130 W of heat and to have chip core dimensions of 1.891 cm ×
1.44 cm. A dimensional optimization study has been performed for various copper and silicon microchannel heat sinks to cool down this processor. To the best of the author&rsquo
s knowledge, this study contributes to the literature in that, as opposed to the available analytical microchannel optimization studies considering constant thermophysical properties at the fluid inlet temperature, the properties are evaluated at the area weighted average of the fluid inlet and iteratively calculated outlet temperatures. Moreover, the effects of the thermal and hydrodynamic entrance regions on heat transfer and flow are also investigated.
13
Woodworth, Ronald Keith. "THE DYNAMIC THERMAL ANALYSIS OF A VOLTAGE REGULATOR CIRCUIT." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275365.
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14
Ulu, Ayse Gozde. "Experimental Investigation Of Uninterrupted And Interrupted Microchannel Heat Sinks." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614227/index.pdf.
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Experimental measurements are conducted on uninterrupted and interrupted aluminum microchannel heat sinks of 300, 500, 600 and 900 &mum channel widths. Two different versions of interrupted channels are tested
with single interruption and with 7 interruptions. Distilled water is used as the working fluid and tests are conducted at volumetric flow rates in a range of 0.5-1.1 lpm. Thermoelectric foils are used to supply uniformly distributed heat load to the heat sinks such that for all the tests the heat removed by water is kept constant at 40 W. Pressure drop and temperature increase are measured along the channels of different configurations for a number of different flow rates. For the interrupted channels thermal boundary layers re-initialize at the leading edge of each interrupted fin, which decreases the overall boundary layer thickness. Also the flow has been kept as developing, which results in better heat transfer performance. Due to the separation of the flow into branches, secondary flows appear which improves the mixing of the stream. Advanced mixing of the flow also enhances the thermal performance. In the experiments, it is observed that interruption of channels improved the thermal performance over the uninterrupted counterparts up to 20% in average Nusselt number, for 600 micron-wide channels. The improvement of average Nusselt number between the single interrupted and multi interrupted channels reached a maximum value of 56% for 500 micron-wide channels. This improvement did not cause a high pressure drop deviation between the uninterrupted and interrupted microchannels even for the maximum volumetric flow rate of 1.1 lpm. Highest pressure drop through the channels was measured as 0.07 bar, which did not require to change the pump. In the tests, maximum temperature difference between the inlet of the fluid and the base of the channel is observed as 32.8°
C, which is an acceptable value for electronic cooling applications.
15
Dietz, Carter Reynolds. "Single-phase forced convection in a microchannel with carbon nanotubes for electronic cooling applications." Thesis, Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-07052007-155623/.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2008.Dr. David Gerlach, Committee Member ; Dr. Samuel Graham, Committee Member ; Dr. Minami Yoda, Committee Member ; Dr. Yogendra Joshi, Committee Chair.
16
Wei, Xiaojin. "Stacked Microchannel Heat Sinks for Liquid Cooling of Microelectronics Devices." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4873.
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A stacked microchannel heat sink was developed to provide efficient cooling for microelectronics devices at a relatively low pressure drop while maintaining chip temperature uniformity. Microfabrication techniques were employed to fabricate the stacked microchannel structure, and experiments were conducted to study its thermal performance. A total thermal resistance of less than 0.1 K/W was demonstrated for both counter flow and parallel flow configurations. The effects of flow direction and interlayer flow rate ratio were investigated. It was found that for the low flow rate range the parallel flow arrangement results in a better overall thermal performance than the counter flow arrangement; whereas, for the large flow rate range, the total thermal resistances for both the counter flow and parallel flow configurations are indistinguishable. On the other hand, the counter flow arrangement provides better temperature uniformity for the entire flow rate range tested. The effects of localized heating on the overall thermal performance were examined by selectively applying electrical power to the heaters. Numerical simulations were conducted to study the conjugate heat transfer inside the stacked microchannels. Negative heat flux conditions were found near the outlets of the microchannels for the counter flow arrangement. This is particularly evident for small flow rates. The numerical results clearly explain why the total thermal resistance for counter flow arrangement is larger than that for the parallel flow at low flow rates.
In addition, laminar flow inside the microchannels were characterized using Micro-PIV techniques. Microchannels of different width were fabricated in silicon, the smallest channel measuring 34 mm in width. Measurements were conducted at various channel depths. Measured velocity profiles at these depths were found to be in reasonable agreement with laminar flow theory. Micro-PIV measurement found that the maximum velocity is shifted significantly towards the top of the microchannels due to the sidewall slope, a common issue faced with DRIE etching. Numerical simulations were conducted to investigate the effects of the sidewall slope on the flow and heat transfer. The results show that the effects of large sidewall slope on heat transfer are significant; whereas, the effects on pressure drop are not as pronounced.
17
Jonsson, Hans. "Turbulent forced convection air cooling of electronics with heat sinks under flow bypass conditions /." Stockholm : Tekn. högsk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3127.
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18
Quy, Tiffany Anne. "Characterization of micro-capillary wicking evaporators." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Thesis/Fall2006/T_Quy_081806.pdf.
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19
Thiagarajan, Naveenan Bhavnani S. H. "Experimental investigation of thermo-hydraulic characteristics of two-phase flow of FC72 in microchannel heat sinks." Auburn, Ala., 2009. http://hdl.handle.net/10415/1954.
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20
Al-Waaly, Ahmed. "The effect of heat transfer on temperature measurement and its applications to study microchannel heat sinks." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6781/.
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Analytical, numerical and experimental analyses have been performed to investigate the effects of thermocouple wire electrical insulation on the temperature measurement of a reference surface. Two diameters of K-type thermocouple, 80μm and 200μm, with different exposed stripped wire lengths (0 mm, 5mm, 10mm, 15mm and 20mm) were used to measure various surface temperatures (4oC, 8oC, 15oC, 25oC and 35oC). Measurements were made when the thermocouple probe is in direct contact with the surface and the wires are extended vertically and exposed to natural convection from outside environment. Experimental results confirmed that the thermal effect from the electrical insulation on temperature measurement was within -0.5oC and therefore it can be neglected. Moreover, the experimental results agree well with those obtained by both the analytical and numerical methods and further confirm that the diameter of the thermocouple has an impact on the temperature measurement. Analytical results of the thermocouple wire with insulation confirm that there is no specific value for the critical radius and the rate of heat flux around the thermocouple wire continuously increases with the wire radius even when this is larger than the critical radius. Experimental and numerical analyses have been performed to investigate the heating impact of using thermocouples for the temperature measurement of small volumes of cold water. Two sizes of K-type thermocouple have been used: 80μm and 315μm to measure the temperature of the cold water inside a small chamber while the thermocouple wires were extended vertically in the outside environment. For this study, the chamber temperature was adjusted to 4oC. The results show that the heating effect of the thermocouple decreases for the greater depth measurements and this effect is eliminated when the thermocouple junction is close to the chamber bottom surface. The increase in the thermal resistance between the bottom surface and the thermocouple junction raises the heating effect of the thermocouple impact. Moreover, the exposed length of thermocouple wires to the environment has no effect over a specific length where the wire end temperature is equal to that of the environment. Experimental and numerical analyses have been carried out to study the effect of using subchannels in heat sink to minimise the effect of hotspots generated on a chip circuit. Two devices of heat sink – with and without subchannels – were fabricated in order to investigate this effect. The first device was manufactured with a normal parallel channel while the second one was designed to extract more heat by dividing the main channels above the hotspot into two subchannels. A hotspot heat flux (16.7×104 [W/m2]) was applied at the centre of the channels while a uniform heat flux (4.45×104 [W/m2]) was applied at upstream and downstream of the channels. Five mass flow rates have generated under gravity force to investigate the performance of devices under different operating conditions. The results showed the maximum surface temperature was reduced by 4oC the temperature uniformity was improved. Moreover, thermal resistance was reduced by 25% but the pumping power was increased as a result of the presence of the subchannels.
21
Mehrtash, Mehdi. "Numerical Investigation Of Natural Convection From Plate Finned Heat Sinks." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613530/index.pdf.
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Finned heat sink use for electronics cooling via natural convection is numerically investigated. An experimental study from the literature that is for vertical surfaces is taken as the base case and the experimental setup is numerically modeled using commercial CFD software. The flow and temperature fields are resolved. A scale analysis is applied to produce an order-of-magnitude estimate for maximum convection heat transfer corresponding to the optimum fin spacing. By showing a good agreement of the results with the experimental data, the model is verified. Then the model is used for heat transfer from inclined surfaces. After a large number of simulations for various forward and backward angles between 0-90 degrees, the dependence of heat transfer to the angle and Rayleigh number is investigated. It is observed that the contributions of radiation and natural convection changes with the angle considerably. Results are also verified by comparing them with experimental results available in literature.
22
Eidi, Ali Fadhil. "Experimental Evaluation of an Additively Manufactured Straight Mini-Channel Heat Sink for Electronics Cooling." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/102777.
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The continuous miniaturization of electronic devices and the corresponding increase in computing powers have led to a significant growth in the density of heat dissipation within these devices. This increase in heat generation has challenged conventional air fan cooling and alternative solutions for heat removal are required to avoid overheating and part damage. Micro/Mini channel heat sinks (M/MCHS) that use liquids for heat removal appear as an attractive solution to this problem as they provide large heat transfer area per volume. Mini/microchannels traditionally have suffered from geometrical and material restrictions due to fabrication constraints. An emerging new additive manufacturing technique called binder jetting has the potential to overcome some of those restrictions. In this study, a straight minichannel heat sink is manufactured from stainless steel using binder jetting, and it is experimentally evaluated. The hydraulic performance of the heat sink is tested over a range of Reynolds numbers (150-1200). The comparison between the hydraulic results and standard correlations confirms that the targeted geometry was produced, although the high surface roughness created an early transition from laminar-to-turbulent flow. The heat transfer performance was also experimentally characterized at different heat flux conditions ($3000W/m^2$, $5000W/m^2$, $6500W/m^2$), and a range of Reynolds numbers (150-800). These results indicated that convection heat transfer coefficients on the order of $1000 W/m^2-K$ can be obtained with a simple heat sink design. Finally, the effects of the contact resistance on the results are studied, and contact resistance is shown to have critical importance on the thermal measurements.Master of Science
The continuous miniaturization of electronic devices and the corresponding increase in computing powers have led to a significant growth in the density of heat dissipation within these devices. This increase in heat generation has challenged conventional air fan cooling and alternative solutions for heat removal are required to avoid overheating and part damage. Micro/Mini channel heat sinks (M/MCHS) that use water instead of air for heat removal appear as an attractive solution to this problem as they provide large heat transfer area per volume due to the small channels. Mini/microchannels are distinguished from conventional channels by the hydraulic diameter, where they range from $10mu m$ to $2mm$. M/MCHS are typically manufactured from a highly conductive metals with the channels fabricated on the surface. However, mini/microchannels traditionally have suffered from geometrical and material restrictions due to fabrication constraints. Complex features like curves or internall channels are difficult or even impossible to manufacture. An emerging new additive manufacturing technique called binder jetting has the potential to overcome some of those restrictions. Binder jetting possess unique advantageous as it uses precise control of a liquid binder applied to a bed of fine powder to create complex geometries Furthermore, it does not require extreme heating during the fabrication process. The advantages of binder jetting include that it is low cost, high speed, can be applied to a variety of materials, and the ability to scale easily in size. In this study, a straight minichannel heat sink is manufactured from stainless steel using binder jetting, and this heat sink is experimentally evaluated. The hydraulic performance of the heat sink is tested over different water flow rates (Reynolds numbers between 150-1200). The comparison between the hydraulic results and standard correlations confirms that the targeted geometry was produced, although the high surface roughness created an early transition from laminar-to-turbulent flow. The surface roughness effect should be considered in future designs of additively manufactured minichannels. The heat transfer performance was also experimentally characterized at different heat flux conditions ($3000W/m^2$, $5000W/m^2$, $6500W/m^2$), and different water flow conditions (Reynolds numbers 150-800). These results indicated that convection heat transfer coefficients on the order of $1000 W/m^2-K$ can be obtained with a simple heat sink design. However, a mismatch between the experimental data and the correlation requires further investigation. Finally, the effects of the contact resistance on the results are studied, and contact resistance is shown to have critical importance on the thermal measurements.
23
Kuan, Wai Keat. "Experimental study of flow boiling heat transfer and critical heat flux in microchannels /." Link to online version, 2006. https://ritdml.rit.edu/dspace/handle/1850/1887.
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Perry, Jeffrey L. "Fouling in silicon microchannel designs used for IC chip cooling and its mitigation /." Online version of thesis, 2008. http://hdl.handle.net/1850/6211.
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25
Chauhan, Anjali. "Hot spot mitigation in microprocessors by application of single phase microchannel heat sink and microprocessor floor planning." Diss., Online access via UMI:, 2009.
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Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineeering, 2009.Includes bibliographical references.
26
Szleper, Michele Lee. "Converging nozzle design for a subsonic wind tunnel to test heat sinks under impinging and parallel airflows." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17124.
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27
Steinke, Mark E. "Single-phase liquid flow and heat transfer in plain and enhanced silicon microchannels /." Link to online version, 2005. http://hdl.handle.net/1850/999.
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28
Al-damook, Amer Jameel Shareef. "Design optimisation and analysis of heat sinks for electronic cooling." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/13427/.
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Since industrial devices create power dissipation in the form of heat created as a by-product, which can have a negative effect on their performance, certain temperature limit constraints are required for almost all these applications to work within suitable conditions. That is, these engineering devices might fail in some way if these limitations are surpassed by overheating. In all the related industries, inexorable increases in power densities are driving innovation in heat exchange techniques. Furthermore, electronic devices are becoming smaller at the same time as their thermal power generation increases. Thus, heat sinks can be applied for cooling critical components in many important applications ranging from aero-engines and nuclear reactors to computers, data centre server racks and other microelectronic devices. The most common cooling technique for heat dissipation for thermal control of electronics is air cooling. Reduced cost, simplicity of design, the easy availability of air, and increased reliability are the main benefits of this cooling method. Heat sinks with a fan/blower are commonly used for air-cooled devices as a forced convection heat transfer. An amount of heat is dissipated from the heat source to environmental air utilising a heat sink as a heat exchanger, which is a vital practice employed in air-cooling systems. This transfer mechanism is easy, simple and leads to reduced cost and increased reliability, and pinned heat sinks are more beneficial than plate fin heat sinks. The main interest of this study is to investigate the benefits of using perforated, slotted, and notched pinned heat sinks with different configurations to reduce CPU temperature and fan power consumption to overcome the pressure drop and maximise a heat transfer rate through the heat sink. An experimental heat sink with multiple perforations is designed and fabricated, and parameter studies of the effect of this perforated pin fin design on heat transfer and pressure drops across the heat sinks are undertaken, to compare it to solid pinned heat sinks without perforations. Experimental data is found to agree well with predictions from a CFD model for the conjugate heat transfer and turbulent airflow model into the cooling air stream. The validated CFD model is used to carry out a parametric study of the influence of the number and positioning of circular perforations, and slotted/notched pinned heat sinks. Then, the multi-objective optimum pinned heat sink designs are tested to obtain CPU temperature and fan power consumption as lowest as possible through the heat sink. In addition, the limitations in application of pinned heat sinks based on the pin density and applied heat flux are reported for active air-cooling electronic systems. An overview of the findings indicates that the CPU temperature, the fan power consumption, and the heat transfer rate in terms of Nusselt number are enhanced with the number of pin perforations and slotted/notched pinned heat sinks, while the locations of the pin perforations are much less influential. These benefits arise due to not only the increased surface area but also to the heat transfer enhancement near the perforations through the formation of localised air jets. Finally, the perforated heat sinks will be lighter in weight compared with solid pinned heat sinks.
29
Gensure, John Reynold. "Extended surface heat sinks for electronic components: a computer optimization." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23672.
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Approved for public release; distribution is unlimitedHeat sinks consisting of individual fins and arrays of fins are used extensively throughout the Navy and industry. The fins serve to increase the surface area thorough which heat is transferred to the surrounding environment by natural convection. Extended surfaces or fins are commonly found on electronic components ranging from power supplies to transformers. The dissipation and subsequent rejection of potentially destructive self produced heat is an important aspect of electronic equipment design. Fin design theory is examined starting with the optimization of individual fin dimensions. The insights obtained are utilized in an investigation of the optimal number and spacing of elements in an array of fins. The results are implemented in a computer program written in ADA and compiled for use on IBM compatible machines. The program takes as inputs thermal and physical data and outputs an optimized fin configuration. Menu driven, the program is easily employed without any amplifying documentation. The program serves to greatly simplify and accelerate the fin design process and should be an invaluable tool to electronic component designers, especially those with a limited background in heat transfer and fin optimization theory.
30
Ozturk, Emre. "Cfd Analyses Of Heat Sinks For Cpu Cooling With Fluent." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605700/index.pdf.
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In this study, forced cooling of heat sinks mounted on CPU&rsquos was investigated. Heat sink effectiveness, effect of turbulence models, effect of radiation heat transfer and different heat sink geometries were numerically analyzed by commercially available computational fluid dynamics softwares Icepak and Fluent. The numerical results were compared with the experimental data and they were in good agreement. Conjugate heat transfer is simulated for all the electronic cards and packages by solving Navier-Stokes equations. Grid independent, well converged and well posed models were run and the results were compared. The best heat sink geometry is selected and it is modified in order to have lower maximum temperature distribution in the heat sink.
31
Chong, Jen Haw. "Modelling of subcooled flow boiling in a rectangular micro-channel heat sink." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/51313/.
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Attaching micro-channel heat sinks operating under flow boiling conditions on heat sources of electronic components is an efficient cooling technique which still requires further improvements of designs. When developing this system, the efficient heat transfer performance is essential, however, this development often entangles with difficulties. The difficulties arise as existing prediction approaches are underdeveloped and inadequate to perform the accurate prediction in wide ranges of operating conditions. This inadequacy persists due to incomplete discoveries of involved mechanisms that involve fluid and dynamics for the heat transfer during the flow boiling. Also, the mechanisms involved in the flow boiling process are complicated, hindering the development of more reliable approaches. By addressing this issue, this study explores and investigates the relating mechanisms. The mechanisms of fluids during the flow boiling of subcooled liquids in micro-channel heat sinks immediately before and during the nucleation of first bubbles were explored in this study. This study then addressed the mechanisms of heat transfer enhancement of flow boiling. Later, this study repeated with different substrate materials of micro-channel heat sinks and working fluids. This study serves the purpose to better understand the involved mechanisms during the flow boiling of subcooled liquids in micro-channel heat sinks for the development of more reliable approaches to predict the heat transfer. This study regarding the mechanisms during the flow boiling in micro-channel heat sinks implemented the numerical model associated with the Volume of Fluid (VOF) in which corresponding governing equations were solved using a computational fluid dynamics (CFD). In this model, computational domains of micro-channel heat sinks in three dimensions that include the sub-domains of solids and fluid were created to consider the conjugate heat transfer for better estimation of data. The data collected in this study were from operating parameters of heat flux, mass flux, and inlet temperature of the micro-channel at 500-3197 kW/m2, 115-389 kg/m2 s, and 23-53°C, respectively. The micro-channel heat sinks operated at the atmospheric pressure, and the corresponding substrate materials chosen were steel, silicon, aluminium and copper, and working fluids selected were water and ethanol. The numerical results agree well with the experimental data from the previous study. The results show that although the bubble nucleation is absent, the heat transfer mechanisms in micro-channels possesses the nucleate boiling characteristic involving the transient conduction with the existence of the phase change process. The heat transfer mechanisms from the phase change process with the incomplete evaporation induce the ascending and descending flows and liquid-vapour mixture on the heating surfaces. From the results, four different modes of heat transfer mechanisms from the phase change process associated with ascending and descending flows and liquid vapour mixture become apparent. The ascending and descending flows on the heating surfaces appear with local increases of pressure gradients near to the heating surfaces facilitating the heat transfer enhancement due to phase change. On the other hand, the liquid-vapour mixture produced from the phase change process impeding the heat transfer. In overall, the heat transfer enhancement due to the phase change at the side surfaces in the micro-channel is more extensive as compared to the bottom surface for each condition tested in this study. Meanwhile, the amount of the liquid-vapour mixture accumulating on the bottom surface is more massive as compared to the side surfaces, leading to the impedance of the heat transfer. These heat transfer mechanisms also persist during flow boiling in micro-channels. The heat transfer enhancement due to phase change from the side and bottom surfaces also varies when employing different operating conditions before and during flow boiling. This study provides better insights for researchers and designers in industries regarding the local mechanisms for the heat transfer during the flow boiling in micro-channel heat sinks. These understandings assist the researchers to develop the more reliable prediction methods to design new and better heat transfer performance of micro-channel heat sinks and avoid repeating experiments which are costly and tedious in procedures.
32
Hossain, Md Rakib. "Optimization of Heat Sinks with Flow Bypass Using Entropy Generation Minimization." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/896.
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Forced air cooling of electronic packages is enhanced through the use of extended surfaces or heat sinks that reduce boundary resistance allowing heat generating devices to operate at lower temperatures, thereby improving reliability. Unfortunately, the clearance zones or bypass regions surrounding the heat sink, channel some of the cooling air mass away from the heat sink, making it difficult to accurately estimate thermal performance. The design of an "optimized" heat sink requires a complete knowledge of all thermal resistances between the heat source and the ambient air, therefore, it is imperative that the boundary resistance is properly characterized, since it is typically the controlling resistance in the path. Existing models are difficult to incorporate into optimization routines because they do not provide a means of predicting flow bypass based on information at hand, such as heat sink geometry or approach velocity. A procedure is presented that allows the simultaneous optimization of heat sink design parameters based on a minimization of the entropy generation associated with thermal resistance and fluid pressure drop. All relevant design parameters such as geometric parameters of a heat sink, source and bypass configurations, heat dissipation, material properties and flow conditions can be simultaneously optimized to characterize a heat sink that minimizes entropy generation and in turn results in a minimum operating temperature of an electronic component.
An analytical model for predicting air flow and pressure drop across the heat sink is developed by applying conservation of mass and momentum over the bypass regions and in the flow channels established between the fins of the heat sink. The model is applicable for the entire laminar flow range and any type of bypass (side, top or side and top both) or fully shrouded configurations. During the development of the model, the flow was assumed to be steady, laminar, developing flow. The model is also correlated to a simple equation within 8% confidence level for an easy implementation into the entropy generation minimization procedure. The influence of all the resistances to heat transfer associated with a heat sink are studied, and an order of magnitude analysis is carried out to include only the influential resistances in the thermal resistance model. Spreading and material resistances due to the geometry of the base plate, conduction and convection resistances associated with the fins of the heat sink and convection resistance of the wetted surfaces of the base plate are considered for the development of a thermal resistance model. The thermal resistance and pressure drop model are shown to be in good agreement with the experimental data over a wide range of flow conditions, heat sink geometries, bypass configurations and power levels, typical of many applications found in microelectronics and related fields. Data published in the open literature are also used to show the flexibility of the models to simulate a variety of applications.
The proposed thermal resistance and pressure drop model are successfully used in the entropy generation minimization procedure to design a heat sink with bypass for optimum dimensions and performance. A sensitivity analysis is also carried out to check the influence of bypass configurations, power levels, heat sink materials and the coverage ratio on the optimum dimensions and performance of a heat sink and it is found that any change in these parameters results in a change in the optimized heat sink dimensions and flow conditions associated with the application for optimal heat sink performance.
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Koyuncuoglu, Aziz. "Design, Fabrication, And Experimental Evaluation Of Microchannel Heat Sinks In Cpu Cooling." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612430/index.pdf.
Full textAbstract:
A novel complementary metal oxide semiconductor (CMOS) compatible microchannel heat sink is designed, fabricated, and tested for electronic cooling applications. The proposed microchannel heat sink requires no design change of the electronic circuitry underneath. Therefore, microchannels can be fabricated on top of the finished CMOS wafers by just adding a few more steps to the fabrication flow. Combining polymer (parylene C) and metal (copper) structures, a high performance microchannel heat sink can be easily manufactured on top of the electronic circuits, forming a monolithic cooling system.
In the design stage, computer simulations of the microchannels with several different dimensions have been performed. Microchannels made of only parylene showed poor heat transfer performance as expected since the thermal conductivity of parylene C is very low. Therefore an alternative design comprising structural parylene layer and embedded metal layers has been modeled. Copper is selected as the metal due to its simple fabrication and very good thermal properties. The results showed that the higher the copper surface area the better the thermal performance of the heat sinks. Based on the modeling results, the final test structures are designed with full copper sidewalls with a parylene top wall.
Several different microchannel test chips have been fabricated in METU-MEMS Research &Application Center cleanroom facilities. The devices are tested with different flow rates and heat loads. During the tests, it was shown that the test devices can remove about 126 W/cm2 heat flux from the chip surface while keeping the chip temperature at around 90°
C with a coolant flow rate of 500 &mu
l/min per channel.
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Sahu, Vivek. "Hybrid solid-state/fluidic cooling for thermal management of electronic components." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45817.
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A novel hybrid cooling scheme is proposed to remove non-uniform heat flux in real time from the microprocessor. It consists of a liquid cooled microchannel heat sink to remove the lower background heat flux and superlattice coolers to dissipate the high heat flux present at the hotspots. Superlattice coolers (SLC) are solid-state devices, which work on thermoelectric effect, and provide localized cooling for hotspots. SLCs offer some unique advantage over conventional cooling solutions. They are CMOS compatible and can be easily fabricated in any shape or size. They are more reliable as they don't contain any moving parts. They can remove high heat flux from localized regions and provide faster time response. Experimental devices are fabricated to characterize the steady-state, as well as transient performance, of the hybrid cooling scheme. Performance of the hybrid cooling scheme has been examined under various operating conditions. Effects of various geometric parameters have also been thoroughly studied. Heat flux in excess of 300 W/cm² has been successfully dissipated from localized hotspots. Maximum cooling at the hotspot is observed to be more than 6 K. Parasitic heat transfer to the superlattice cooler drastically affects its performance. Thermal resistance between ground electrode and heat sink, as well as thermal resistance between ground electrode and superlattice cooler, affect the parasitic heat transfer from to the superlattice cooler. Two different test devices are fabricated specifically to examine the effect of both thermal resistances. An electro-thermal model is developed to study the thermal coupling between two superlattice coolers. Thermal coupling significantly affects the performance of an array of superlattice coolers. Several operating parameters (activation current, location of ground electrode, choice of working fluid) affect thermal coupling between superlattice coolers, which has been computationally as well as experimentally studied. Transient response of the superlattice cooler has also been examined through experiments and computational modeling. Response time of the superlattice cooler has been reported to be less than 35 µs.
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Gerty, Donavon R. "Fluidic driven cooling of electronic hardware." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31722.
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Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Glezer, Ari; Committee Member: Alben, Silas; Committee Member: Joshi, Yogendra; Committee Member: Smith, Marc; Committee Member: Webster, Donald. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Mehra, Bineet. "Design and optimisation of innovative electronic cooling heat sinks with enhanced thermal performances using numerical and experimental methods." Thesis, Ecole nationale supérieure Mines-Télécom Lille Douai, 2019. http://www.theses.fr/2019MTLD0005/document.
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Cette thèse de doctorat s’intéresse aux mécanismes d’amélioration des transferts dans des géométries de dissipateurs thermiques à plaques et ailettes. Une première partie est consacrée à l’étude d’une configuration académique à l’aide de simulations numériques visant à obtenir une amélioration du transfert de chaleur conjugué en modifiant uniquement par des découpes la forme géométrique des ailettes planes conductrices. Une analyse locale approfondie de l’écoulement et des champs thermiques a été effectuée avec notamment le principe de synergie locale, des champs de vitesse et de gradients thermiques, pour comprendre l’effet des modifications géométriques. Ce mémoire présente également le développement de dissipateurs aux performances thermo-aérauliques augmentées pour des applications de refroidissement de coffrets électronique embarqués. L’intensification des transferts thermiques est obtenue par la génération d’écoulements secondaires qui provoquent un brassage de fluide et réduisent la résistance thermique à la paroi en perturbant le développement de la couche limite thermique. Différentes configurations de dissipateurs avec deux types de générateurs d’écoulements secondaires, paires d’ailettes Delta et protrusions, ont été étudiées numériquement, en employant une modélisation de type « RANS ». Les performances thermo-aérauliques des géométries munies de générateurs de vorticité ont été comparées à celle d’un dissipateur thermique de référence « lisse ». Des prototypes ont également été fabriqués et testés sur un banc expérimental spécifiquement développé pour réaliser des mesures des performances globales en termes de puissance thermique et de pertes de charge. Les résultats expérimentaux et numériques ont été confrontés afin de qualifier les simulations réalisées. Par la suite, une étude d’optimisation employant l’analyse factorielle Taguchi a été utilisée afin d’optimiser les paramètres géométriques des dissipateurs retenus. Deux fonctions objectif ont été considérées : la maximisation du facteur de performance thermique à iso puissance de ventilation (PEC) et la réduction de la température moyenne de paroi du dissipateur par rapport au cas de référence. L’analyse des performances thermo-aérauliques globales des géométries étudiées a été complétée par une analyse qualitative locale des champs thermiques et d’écoulement notamment avec le principe de synergieThis doctoral thesis focuses on mechanisms of heat transfer enhancement in plate and fin heat sink geometries. First part of the thesis is dedicated to study an academic configuration using numerical simulations to achieve an improvement in conjugate heat transfer by modifying only the geometrical shape (through punching) of the conductive plane fins. An in-depth local analysis of the flow and thermal fields was carried out with the local synergy principle, velocity and thermal gradients, to understand the effect of geometric modifications. This thesis also presents the development of heat sinks with increased thermo-hydraulic performance for on-board electronic box cooling applications. The intensification of the heat transfer is obtained by the generation of secondary flows which cause an intensive mixing of fluid and reduces the thermal resistance to the wall by disrupting the development of the thermal boundary layer. Different heat sink geometries with two types of secondary flow generators : delta winglet pair and protrusions were numerically studied using RANS approach. The thermo-hydraulic performances of the geometries equipped with vortex generators were compared with that of a smooth reference heat sink. The prototypes were also manufactured and tested on an experimental bench specifically designed to perform global performance measurements in terms of thermal power and pressure drops. Experimental and numerical results were compared to qualify the simulations performed. Subsequently, an optimization study using Taguchi factorial analysis was used to optimize the geometrical parameters of the chosen dissipaters. Two objective functions were considered : maximization of either iso-pumping power performance criteria (PEC) or average wall temperature of the dissipaters compared to the reference case. The global thermo-hydraulic performance analysis of the studied geometries was completed by a qualitative analysis of local flow and thermal fields, in particular with the local field synergy principle
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Jagannatha, Deepak. "Heat transfer and fluid flow characteristics of synthetic jets." Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/2437.
Full textAbstract:
This thesis presents a fundamental research investigation that examines the thermal and fluid flow behaviour of a special pulsating fluid jet mechanism called synthetic jet. It is envisaged that this novel heat transfer enhancement strategy can be developed for high-performance heat sinks in electronic cooling applications.The study considers a unique arrangement of a periodic jet induced by diaphragm motion within a cavity and mounted on a confined flow channel with a heated wall upon which the jet impingement occurs. The operation of this jet mechanism is examined as two special cases for unravelling its parametric influences. In Case (a), the jet impingement is analysed in a channel with stagnant fluid permitting clear view of the pure synthetic jet process and its controlling variables. In Case (b), jet impingement is considered with fluid flow in the channel to establish the nature of synthetic jet and cross-flow interaction.The unsteady flow of this jet mechanism is simulated as a time-dependant two-dimensional numerical model with air as the working fluid. The current model considers a solution domain in its entirety, comprising the confined flow regions of the jet impinging surface, the cavity and the orifice. With a User Defined Function (UDF), the model accounts for the bulk fluid temperature variations during jet operation, which has been grossly ignored in all published work. Overcoming previous modelling limitations, the current simulation includes flow turbulence for realistic representation of pulsed jet characteristics and cross-flow interference.Computations are performed with applicable boundary conditions to obtain the heat transfer and fluid flow characteristics of the synthetic jet along with cross-flow interaction for the diaphragm amplitude ranging from 0.5 mm to 2 mm and the diaphragm frequency varying from 250 Hz to 1000 Hz. The numerical simulation yields stable solutions and aptly predicts the sequential formation of synthetic jet and its intrinsic vortex shedding process while accurately portraying the flow within the cavity.It is identified that the diaphragm amplitude primarily determines the jet velocity while the diaphragm frequency governs the rate of vortex ejection and the fluid circulation in the vicinity of the heater. The synthetic jet thermal performance is improved with high amplitude that gives rise to stronger jet impingement and reduced bulk fluid temperature arising from high frequency leading to better fluid circulation. The fluid flow in the channel or cross flow drags the jet downstream affecting jet’s ability to reach the heated wall. The relative strengths of jet velocity and channel flow determine the combined thermal performance. The fluid compressibility is seen to have insignificant effect on the synthetic jet behaviour within the examined range of parameters. As for geometrical parameters, reduced orifice width increases jet velocity improving heat transfer rates while the optima is identified for the heater -to- orifice distance within 6 to 10 times the orifice width.Results conclusively show that in a stagnant fluid medium, the proposed synthetic jet mechanism delivers 40 percent higher heat transfer rates than an equivalent continuous jet. It also thermally outperforms pure natural convection at the heated channel wall by up to 120 times within the parametric range. Under cross-flow conditions, the synthetic jet can provide 2-fold improvement in heat transfer compared to an equivalent continuous jet. By adding this synthetic jet mechanism to a flow channel, the overall thermal performance of the hybrid system is enhanced up to about 18 times the pure forced convection heat transfer rates in a channel without this jet mechanism.The observed outstanding thermal performance of the pulsed jet-cross flow hybrid mechanism surpasses the heat removal potential of current conventional techniques for electronic component cooling. It operates with a unique ability of not causing flow pressure drop increases and not requiring additional fluid circuits, which are recognised as key advantages that set this method apart from other techniques. Thus, the proposed synthetic jet-cross flow hybrid mechanism is envisaged to be potentially regarded as an outstanding thermal enhancement strategy in the development of heat sinks for future high-capacity electronic cooling needs.
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Gdhaidh, Farouq A. S. "Heat Transfer Characteristics of Natural Convection within an Enclosure Using Liquid Cooling System." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/7824.
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In this investigation, a single phase fluid is used to study the coupling between natural convection heat transfer within an enclosure and forced convection through computer covering case to cool the electronic chip. Two working fluids are used (water and air) within a rectangular enclosure and the air flow through the computer case is created by an exhaust fan installed at the back of the computer case. The optimum enclosure size configuration that keeps a maximum temperature of the heat source at a safe temperature level (85℃) is determined. The cooling system is tested for varying values of applied power in the range of 15−40𝑊.
The study is based on both numerical models and experimental observations. The numerical work was developed using the commercial software (ANSYS-Icepak) to simulate the flow and temperature fields for the desktop computer and the cooling system. The numerical simulation has the same physical geometry as those used in the experimental investigations. The experimental work was aimed to gather the details for temperature field and use them in the validation of the numerical prediction.
The results showed that, the cavity size variations influence both the heat transfer process and the maximum temperature. Furthermore, the experimental results
ii
compared favourably with those obtained numerically, where the maximum deviation in terms of the maximum system temperature, is within 3.5%. Moreover, it is seen that using water as the working fluid within the enclosure is capable of keeping the maximum temperature under 77℃ for a heat source of 40𝑊, which is below the recommended electronic chips temperature of not exceeding 85℃. As a result, the noise and vibration level is reduced. In addition, the proposed cooling system saved about 65% of the CPU fan power.
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Gdhaidh, Farouq Ali S. "Heat transfer characteristics of natural convection within an enclosure using liquid cooling system." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/7824.
Full textAbstract:
In this investigation, a single phase fluid is used to study the coupling between natural convection heat transfer within an enclosure and forced convection through computer covering case to cool the electronic chip. Two working fluids are used (water and air) within a rectangular enclosure and the air flow through the computer case is created by an exhaust fan installed at the back of the computer case. The optimum enclosure size configuration that keeps a maximum temperature of the heat source at a safe temperature level (85°C) is determined. The cooling system is tested for varying values of applied power in the range of 15-40W. The study is based on both numerical models and experimental observations. The numerical work was developed using the commercial software (ANSYS-Icepak) to simulate the flow and temperature fields for the desktop computer and the cooling system. The numerical simulation has the same physical geometry as those used in the experimental investigations. The experimental work was aimed to gather the details for temperature field and use them in the validation of the numerical prediction. The results showed that, the cavity size variations influence both the heat transfer process and the maximum temperature. Furthermore, the experimental results ii compared favourably with those obtained numerically, where the maximum deviation in terms of the maximum system temperature, is within 3.5%. Moreover, it is seen that using water as the working fluid within the enclosure is capable of keeping the maximum temperature under 77°C for a heat source of 40W, which is below the recommended electronic chips temperature of not exceeding 85°C. As a result, the noise and vibration level is reduced. In addition, the proposed cooling system saved about 65% of the CPU fan power.
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Lacombe, Guillaume. "Rôle des paramètres d'élaboration sur les propriétés physico-chimiques de matériaux composites élaborés par métallurgie des poudres : études théoriques et expérimentales." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2011. http://tel.archives-ouvertes.fr/tel-00681508.
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Les fréquences de fonctionnement élevées des puces semi-conductrices génèrent des flux de chaleurs importants qu'il est nécessaire d'évacuer pour éviter la destruction de la puce. Un module standard dans le domaine de l'électronique de puissance est composé d'une puce en silicium, d'un isolant électrique (substrat) et d'un dissipateur thermique (drain) permettant l'évacuation de la chaleur. Cette chaleur induit des contraintes thermomécaniques dues à la dilatation différentielle des matériaux.Deux concepts nouveaux proposés permettent de palier ces problèmes et d'augmenter la fiabilité générale des systèmes électroniques. Le premier est la conception et l'élaboration d'un drain composite à propriétés thermiques adaptatives (coefficient de dilatation thermique et conductivité thermique). Dans le deuxième, une nouvelle méthode d'assemblage est présentée. Elle permet, au moyen d'un film métallique Sn ou Au, de créer des composés intermétalliques stables dans le temps.
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Souza, Valter Cesar de. "Dissipadores termicos de placas paralelas com influxo de topo." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264120.
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Orientador: Carlos Alberto Carrasco AltemaniTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-08-06T09:32:44Z (GMT). No. of bitstreams: 1 Souza_ValterCesarde_D.pdf: 4532174 bytes, checksum: 07cf885bb91505cb080fc4a067621191 (MD5) Previous issue date: 2005
Resumo: Os dissipadores térmicos de placas paralelas com entrada de topo e saída lateral constituem uma alternativa para intensificar a remoção da potência elétrica dissipada em microprocessadores. Neste trabalho, três dissipadores térmicos de placas paralelas foram construídos e testados com escoamento variável de ar sob condições de entrada de topo e saída lateral. Os resultados experimentais foram comparados com correlações da literatura e com resultados de simulações numéricas tridimensionais. Após a validação com os resultados experimentais, o modelo numérico foi utilizado num procedimento para obter o número de aletas do dissipador para a máxima troca térmica convectiva. Dois casos foram considerados, um deles baseado numa velocidade média do ar constante na entrada do dissipador, e o outro, numa relação linear da curva de operação de um ventilador
Abstract: The parallel plates heat sinks with top inlet and side exit constitute an enhanced heat transfer alternative for the local removal of electric power dissipation in microprocessors. In the present work, three parallel plates heat sinks were built and tested with variable airflow under the conditions of top inlet and side exit. The experimental results were compared with correlations from the literature and with results from three-dimensional numerical simulations. After the validation with the experimental results, the numeric model was used in an optimization procedure to obtain the heat sink number of fins for the maximum convective heat transfer. Two cases were considered, one based on a constant average inlet air velocity, and the other, on an assumed linear fan curve
Doutorado
Termica e Fluidos
Doutor em Engenharia Mecânica
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Harajli, Zeinab. "Synthesis, characterisation and thermal evaluation of a new generation of metalised ceramic materials." Thesis, Lyon, 2022. http://www.theses.fr/2022LYSEI016.
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Une gestion thermique efficace est souvent considérée comme une étape clé vers un système technologique réussi. L'élimination rapide de l'excès de chaleur, des systèmes électroniques exposés à des températures extrêmes, améliore la fiabilité et empêche la défaillance prématurée de ces systèmes. De nos jours, les approches habituelles, pour évacuer la chaleur et maintenir le système à une température souhaitée, consistent à utiliser un dissipateur thermique à semi-conducteur ou un système complexe de contrôle de vitesse de ventilateur qui repose sur une mesure continue de la température. Cependant, l'optimisation d'un dissipateur thermique à semi-conducteur très efficace nécessite le contrôle de diverses propriétés intrinsèques et extrinsèques à différentes échelles, car le flux thermique macroscopique et le transport de chaleur dépendent des propriétés vibrationnelles microscopiques. En outre, l'utilisation généralisée de dissipateurs thermiques à semi-conducteurs hautement efficaces nécessite la capacité de les métalliser et de former des structures multicouches. En raison de ses vitesses de groupe de phonons élevées, le nitrure d'aluminium (AlN) semble être l'un des meilleurs candidats pour la fabrication de dissipateurs thermiques à semi-conducteurs efficaces. Dans cette thèse, nous avons comme objectif de développer une nouvelle technologie d’un substrat à base de la structure Métal/AlN/Métal à haute diffusivité thermique pour des applications à haute température (>300°C). Cette thèse vise à développer des technologies d'électronique de puissance hautement efficaces, intégrées et fiables fonctionnant à haute température pour l'automobile, l'aéronautique et l'énergie. Dans un premier temps, nous avons élaboré des films minces de molybdène pour métalliser le nitrure d'aluminium et synthétiser nos nouveaux substrats de dissipateur thermique pour les modules de puissance. Ensuite, nous avons optimisé les dispositifs établis en étudiant leurs propriétés physico-chimiques et en mettant l'accent sur leurs performances thermiques. Enfin, nous avons étudié les performances des échantillons en utilisant une imagerie souterraine et tout en augmentant la température afin de surveiller la formation de défauts. La caractérisation thermique et l'imagerie souterraine des échantillons ont été effectuées à l'aide de notre nouvelle configuration de déviation de faisceau photo-thermique, dans laquelle nous installons un laser IR pour chauffer les échantillons et qui génère des bosses thermiques qui sont mesurées par des faisceaux de sonde déviant à différents endroits de l'échantillonEfficient thermal management is often considered a key step towards a successful technological system. The fast removal of excess heat from electronic systems exposed to temperature extremes improves the reliability and prevents the premature failure of these systems. Nowadays, the usual approaches to evacuate heat and maintain the system at the desired temperature consist in using a semiconductor heat sink or a complex fan speed control system that relies on continuous temperature measurement. However, the optimization of a highly efficient semiconductor heat sink requires the control of diverse intrinsic and extrinsic properties at different scales because the macroscopic thermal flow and heat transport depend on microscopic vibrational properties. Besides, widespread use of highly efficient semiconductor heat sinks requires the ability to metalize them and form multilayer structures. Due to its high phonon group velocities, Aluminium Nitride (AlN) appears to be one of the best candidates for the manufacturing of efficient semiconductor heat sinks. In this PhD. thesis work, we intend to develop a new substrate technology Metal/AlN/Metal structures with high thermal diffusivity for integrated power systems for high-temperature applications (>300°C). This PhD. Aims at developing highly efficient, integrated and reliable power electronics technologies operating at high temperatures for automotive, aeronautic, and energy applications
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Lee, Scott W. C. H. "Thermal and hydraulic performance of single-phase and two-phase micro-channel heat sinks." Thesis, 2007. http://hdl.handle.net/10125/20697.
Full text
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CHEN, HAN-TING, and 陳漢廷. "Thermal Optimal Design for Generalized Heat Sinks in Electronics Cooling Applications." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/93293535278331764683.
Full textAbstract:
博士國立清華大學
動力機械工程學系
94
The increasing power requirement for electronics industry, combined with ever-shrinking size and weight allowances, is creating a greater need for optimal design of generalized heat sinks. In this study, the thermal and hydrodynamic models for confined heat sinks with various fin types have been successfully developed. Comparisons between the predicted heat transfer and fluid flow characteristics for both fully-confined and partially-confined generalized heat sinks with existing data are made with satisfactory agreements. In addition, a series of parametric studies, including effects of the size of heat source, power of heating load, the fin structures of heat sink, the conductivity of heat sink, inlet velocity, and the flow bypass conditions, for thermal design of heat sinks have been performed. To conduct the experimental investigation on the fluid flow and heat transfer characteristics for confined generalized heat sinks, an experimental system has been successfully established with an adjustable test section. From the experimental data, the generalized correlations for both the thermal performance and the pressure drop of confined heat sinks are proposed as the functions of Reynolds number, top-bypass ratio, and the side-bypass ratio. Besides, for further validation of the present theoretical results, a comparison between the present predictions with the experimental data was made with a reasonable agreement. The maximum and average deviations are 25.8% and 11.7%, respectively, for the pressure drop; and 14.3% and 6.1%, respectively, for the thermal resistance. In addition, a systematical design optimization method, which allow the thermal engineer to meet several design objectives and constraints simultaneously and effectively, has been successfully presented and applied to the optimal designs for generalized heat sinks in this study. First of all, a statistical method for the sensitivity analysis is performed to determine the key factors that are critical to the design; and a response surface methodology (RSM) is applied to establish explicit regression models for the thermal resistance and the pressure drop in terms of the design factors with an well-organized design of experiments (DOE). By employing the gradient-based numerical optimization technique, a series of constrained optimal designs can be efficiently performed. Comparisons between these predicted optimal designs and those evaluated by the theoretical calculations are also made with satisfactory agreements. With the developed design optimization method, optimal designs for generalized heat sinks, includes the parallel-plate fin (ppf), pin-fin array (pfa), and strip-fin array (sfa), were successfully explored with multiple design constraints of pressure drop, mass, and space limitations. Furthermore, an effective and user-friendly optimal computer-aided design (CAD) system for automatically predicting the optimal thermal performance for confined generalized heat sinks has been successfully developed. In the pre-processor, a user-friendly interface for problem definition has been constructed in order to efficiently collect the required data for the thermal analyzer and optimizer. And a thermal analyzer for confined heat sink has been successfully developed according to the present theoretical calculations. The performances studied include the pressure drop, local and average heat transfer coefficients, local temperature distribution, and the overall thermal resistance. Besides, corresponding to the presented design optimization method, the design optimizer has been established with the functions of the design of experiments, the construction of response surface models, and the programming of numerical optimization. After obtaining the optimal design, the real-time 3-D model, predicted color isotherms, and all the predicted performances can be displayed in the developed post-processor. Moreover, an interactive function has been applied for providing a direct communication between the user and the computer for the detailed information about the optimal design. Finally, to demonstrate the superiorities of the present developed optimal CAD system, two sample applications of thermal optimal designs for generalized heat sinks under multiple constraints have been effectively performed.
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Alharbi, Ali Y. "A study of micro-scale, fractal-like branching flow networks for reduced pumping power and improved temperature uniformity." Thesis, 2001. http://hdl.handle.net/1957/29574.
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A first generation, one-dimensional predictive model is proposed for
designing heat sinks with fractal flow networks. A three-dimensional
computational fluid dynamics (CFD) model is analyzed as a means for validating
the model and identifying areas for improvement.
Two separate CFD models were developed. One was analyzed with
conjugate heat transfer whereas the other was not. For the conjugate heat transfer
model, heat flux was provided at a single surface, simulating a heat source. Energy
addition to the latter model, referred to as the non-conjugate model, was uniform to
all surfaces and was developed to assess the assumptions employed in the one-dimensional
model.
Both CFD models were run with and without variable properties and are
compared to results with a series of parallel channels with identical convective
surface areas. In all cases, with and without conjugate heat transfer and with and
without variable fluid properties, the fractal flow network showed lower maximum
surface temperatures than the straight channel network for identical pumping
powers. The pumping power, however, was determined assuming constant fluid
properties.
The variation in fluid viscosity with temperature was determined to have a
significant impact on the pressure distribution, which indicates that variable fluid
viscosity needs to be included in the one-dimensional model.
Also varied in the analyses were heat sink material, heat flux and flow rate.
Qualitative results show that temperature variations within the copper substrate are
less significant than in the stainless steel substrate. All analyses, including the one-dimensional
model, were restricted to laminar flow conditions.Graduation date: 2002
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Coetzer, C. B. "The development of a new compact model for prediction of forced flow behaviour in longitudinal fin heat sinks with tip bypass." Diss., 2001. http://hdl.handle.net/2263/26228.
Full textAbstract:
Increasing power dissipation and chip densities in the rapidly evolving electronics cooling industry are causing an ever increasing need for the tools and methods necessary for electronic systems design and optimisation. Modern electronic systems have the capacity to produce significant amounts of heat which, if not removed efficiently, could lead to component failure. The most common technique of heat removal is by making use of a heat spreader, or so¬-called heat sink. These devices are excellent heat conductors with a large surface area to volume ratio, and cooled through either natural or forced convection. Despite the advantages of these devices, there are serious consequences involved in the application of heat sinks. The required size of a heat sink may limit the miniaturisation of a product, while inadequate design, due to a lack of understanding of the flow physics, may lead to premature component failure. It is therefore crucial that an optimal heat sink design is achieved for every particular application. In the past, both heat sink design and optimisation have occurred mostly through experimental characterisation of heat sinks, which was not always particularly successful or accurate. Recent rapid developments in computer technology have led to the availability of various computational fluid dynamics or CFD software packages, with the capability of solving the discretized form of the conservation equations for• mass, momentum, and energy to provide a solution of the flow and heat fields in the domain of interest. This method of using the fundamental flow physics is currently the most complete way to determine the solution to the heat sink design and optimisation problem. It does unfortunately have the drawback of being computationally expensive and excessively time consuming, with commercial software prices being financially restrictive to the average designer. The electronics cooling community has subsequently identified the need for so-called "compact models" to assist in the design of electronic enclosures. Compact models use available empirical relations to solve the flow field around a typical heat sink. Current models require significantly less computational power and time compared to CFD analysis, but have the drawback of reduced accuracy over a wide range of heat sink geometries and Reynolds numbers. This is one of the reasons that compact modelling of heat sinks remain an international research topic today. This study has focused on the CFD modelling of a variety of forced flow longitudinal fin heat sinks with tip clearance. Tip clearance allows the flow to bypass the heat sink and downgrade its thermal performance. The flow bypass phenomenon, general flow behaviour, and pressure loss characteristics were investigated in detail. Thermal modelling of the heat sinks was left for future study. The flow information provided by the CFD analysis was combined with data available from literature to develop an improved compact flow model for use in a variety of practical longitudinal fin heat sinks. The new compact model leads to a 4.6 % improvement in accuracy compared to another leading compact model in the industry, and also provides more localised flow information than was previously available from compact modelling. Dissertation (M Eng (Mechanical Engineering))--University of Pretoria, 2007.
Mechanical and Aeronautical Engineering
unrestricted
47
Sanyal, Anuradha. "Numerical Study Of Heat Transfer From Pin Fin Heat Sink Using Steady And Pulsated Impinging Jets." Thesis, 2006. https://etd.iisc.ac.in/handle/2005/351.
Full textAbstract:
The work reported in this thesis is an attempt to enhance heat transfer in electronic devices with the use of impinging air jets on pin-finned heat sinks. The cooling per-formance of electronic devices has attracted increased attention owing to the demand of compact size, higher power densities and demands on system performance and re-liability. Although the technology of cooling has greatly advanced, the main cause of malfunction of the electronic devices remains overheating. The problem arises due to restriction of space and also due to high heat dissipation rates, which have increased
from a fraction of a W/cm2to 100s of W /cm2. Although several researchers have at-tempted to address this at the design stage, unfortunately the speed of invention of
cooling mechanism has not kept pace with the ever-increasing requirement of heat re-
moval from electronic chips. As a result, efficient cooling of electronic chip remains a
challenge in thermal engineering.
Heat transfer can be enhanced by several ways like air cooling, liquid cooling, phase
change cooling etc. However, in certain applications due to limitations on cost and
weight, eg. air borne application, air cooling is imperative. The heat transfer can be increased by two ways. First, increasing the heat transfer coefficient (forced convec-
tion), and second, increasing the surface area of heat transfer (finned heat sinks). From previous literature it was established that for a given volumetric air flow rate, jet im-pingement is the best option for enhancing heat transfer coefficient and for a given volume of heat sink material pin-finned heat sinks are the best option because of their high surface area to volume ratio. There are certain applications where very high jet velocities cannot be used because of limitations of noise and presence of delicate components. This process can further be improved by pulsating the jet. A steady jet often stabilizes the boundary layer on the surface to be cooled. Enhancement in the convective heat transfer can be achieved if the boundary layer is broken. Disruptions in the boundary layer can be caused by pulsating the impinging jet, i.e., making the jet unsteady. Besides, the pulsations lead to chaotic mixing, i.e., the fluid particles no more follow well defined streamlines but move unpredictably through the stagnation region. Thus the flow mimics turbulence at low Reynolds number. The pulsation should be done in such a way that the boundary layer can be disturbed periodically and yet adequate coolant is made available. So, that there is not much variation in temperature during one pulse cycle. From previous literature it was found that square waveform is most effective in enhancing heat transfer. In the present study the combined effect of pin-finned heat sink and impinging slot jet, both steady and unsteady, has been investigated for both laminar and turbulent flows. The effect of fin height and height of impingement has been studied. The jets have been pulsated in square waveform to study the effect of frequency and duty cycle. This thesis attempts to increase our understanding of the slot jet impingement on pin-finned heat sinks through numerical investigations. A systematic study is carried out using the finite-volume code FLUENT (Version 6.2) to solve the thermal and flow fields. The standard k-ε model for turbulence equations and two layer zonal model in wall function are used in the problem Pressure-velocity coupling is handled using the SIMPLE algorithm with a staggered grid.
The parameters that affect the heat transfer coefficient are: height of the fins, total
height of impingement, jet exit Reynolds number, frequency of the jet and duty cycle
(percentage time the jet is flowing during one complete cycle of the pulse).
From the studies carried out it was found that:
a) beyond a certain height of the fin the rate of enhancement of heat transfer becomes
very low with further increase in height,
b) the heat transfer enhancement is much more sensitive to any changes at low Reynolds
number than compared to high Reynolds number,
c) for a given total height of impingement the use of fins and pulsated jet, increases
the effective heat transfer coefficient by almost 200% for the same average Reynolds
number,
d) for all the cases it was observed that the optimum frequency of impingement is around 50 − 100 Hz and optimum duty cycle around 25-33.33%,
e) in the case of turbulent jets the enhancement in heat transfer due to pulsations is very less compared to the enhancement in case of laminar jets.
48
Sanyal, Anuradha. "Numerical Study Of Heat Transfer From Pin Fin Heat Sink Using Steady And Pulsated Impinging Jets." Thesis, 2006. http://hdl.handle.net/2005/351.
Full textAbstract:
The work reported in this thesis is an attempt to enhance heat transfer in electronic devices with the use of impinging air jets on pin-finned heat sinks. The cooling per-formance of electronic devices has attracted increased attention owing to the demand of compact size, higher power densities and demands on system performance and re-liability. Although the technology of cooling has greatly advanced, the main cause of malfunction of the electronic devices remains overheating. The problem arises due to restriction of space and also due to high heat dissipation rates, which have increased
from a fraction of a W/cm2to 100s of W /cm2. Although several researchers have at-tempted to address this at the design stage, unfortunately the speed of invention of
cooling mechanism has not kept pace with the ever-increasing requirement of heat re-
moval from electronic chips. As a result, efficient cooling of electronic chip remains a
challenge in thermal engineering.
Heat transfer can be enhanced by several ways like air cooling, liquid cooling, phase
change cooling etc. However, in certain applications due to limitations on cost and
weight, eg. air borne application, air cooling is imperative. The heat transfer can be increased by two ways. First, increasing the heat transfer coefficient (forced convec-
tion), and second, increasing the surface area of heat transfer (finned heat sinks). From previous literature it was established that for a given volumetric air flow rate, jet im-pingement is the best option for enhancing heat transfer coefficient and for a given volume of heat sink material pin-finned heat sinks are the best option because of their high surface area to volume ratio. There are certain applications where very high jet velocities cannot be used because of limitations of noise and presence of delicate components. This process can further be improved by pulsating the jet. A steady jet often stabilizes the boundary layer on the surface to be cooled. Enhancement in the convective heat transfer can be achieved if the boundary layer is broken. Disruptions in the boundary layer can be caused by pulsating the impinging jet, i.e., making the jet unsteady. Besides, the pulsations lead to chaotic mixing, i.e., the fluid particles no more follow well defined streamlines but move unpredictably through the stagnation region. Thus the flow mimics turbulence at low Reynolds number. The pulsation should be done in such a way that the boundary layer can be disturbed periodically and yet adequate coolant is made available. So, that there is not much variation in temperature during one pulse cycle. From previous literature it was found that square waveform is most effective in enhancing heat transfer. In the present study the combined effect of pin-finned heat sink and impinging slot jet, both steady and unsteady, has been investigated for both laminar and turbulent flows. The effect of fin height and height of impingement has been studied. The jets have been pulsated in square waveform to study the effect of frequency and duty cycle. This thesis attempts to increase our understanding of the slot jet impingement on pin-finned heat sinks through numerical investigations. A systematic study is carried out using the finite-volume code FLUENT (Version 6.2) to solve the thermal and flow fields. The standard k-ε model for turbulence equations and two layer zonal model in wall function are used in the problem Pressure-velocity coupling is handled using the SIMPLE algorithm with a staggered grid.
The parameters that affect the heat transfer coefficient are: height of the fins, total
height of impingement, jet exit Reynolds number, frequency of the jet and duty cycle
(percentage time the jet is flowing during one complete cycle of the pulse).
From the studies carried out it was found that:
a) beyond a certain height of the fin the rate of enhancement of heat transfer becomes
very low with further increase in height,
b) the heat transfer enhancement is much more sensitive to any changes at low Reynolds
number than compared to high Reynolds number,
c) for a given total height of impingement the use of fins and pulsated jet, increases
the effective heat transfer coefficient by almost 200% for the same average Reynolds
number,
d) for all the cases it was observed that the optimum frequency of impingement is around 50 − 100 Hz and optimum duty cycle around 25-33.33%,
e) in the case of turbulent jets the enhancement in heat transfer due to pulsations is very less compared to the enhancement in case of laminar jets.
49
Chiu, Wei-Cheng, and 邱偉誠. "Study of Heat Transfer Characteristics of Electronic Porous Heat Sinks." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/92634083722754716269.
Full text
50
Shu-Ju, Lin. "Plane Plate Fin Heat Sinks in Electronic Cooling." 2005. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-0108200510482400.
Full text