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1
Phillips, Richard J. "Forced-convection, liquid-cooled, microchannel heat sinks." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14921.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1987.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Bibliography: v.2, leaves 286-291.
by Richard J. Phillips.
M.S.
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
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.
4
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.
5
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.
6
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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7
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.
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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.
8
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.
9
Ates, Ahmet Muaz. "Experimental Comparison Of Fluid And Thermal Characteristics Of Microchannel And Metal Foam Heat Sinks." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613577/index.pdf.
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Doubling transistor count for every two years in a computer chip, transmitter and receiver (T/R) module of a phased-array antenna that demands higher power with smaller dimensions are all results of miniaturization in electronics packaging. These technologies nowadays depend on improvement of reliable high performance heat sink to perform in narrower volumes. Employing microchannels or open cell metal foam heat sinks are two recently developing promising methods of cooling high heat fluxes. Although recent studies especially on microchannels can give a rough estimate on performances of these two methods, since using metal foams as heat sinks is still needed further studies, a direct experimental comparison of heat exchanger performances of these two techniques is still needed especially for thermal design engineers to decide the method of cooling.
For this study, microchannels with channel widths of 300 µm, 420 µ
m, 500 µ
m and 900 µ
m were produced. Also, 92% porous 10, 20 and 40 ppi 6101-T6 open cell aluminum metal foams with compression factors 1,2, and 3 that have the same finned volume of microchannels with exactly same dimensions were used to manufacture heat sinks with method of vacuum brazing. They all have tested under same conditions with volumetric flow rate ranging from 0,167 l/min to 1,33 l/min and 60 W of heat power. Channel height was 4 mm for all heat sinks and distilled water used as cooling fluid. After experiments, pressure drops and thermal resistances were compared with tabulated and graphical forms. Also, the use of metal foam and microchannel heat sinks were highlighted with their advantages and disadvantages for future projects.
10
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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11
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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12
Bogojević, Dario. "Flow boiling and two-phase flow instabilities in silicon microchannel heat sinks for microsystems cooling." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/3791.
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Flow boiling in microchannels, while very promising as a cooling technology in electronics thermal management, is still a subject being explored that requires further investigation. Before applying this technology for high heat flux computer chip cooling, challenging issues such as fully understanding boiling mechanisms in confined spaces, extending and stabilising the nucleate boiling regime, suppressing flow boiling instabilities, maintaining uniform flow distribution among microchannels, have to be addressed. If flow boiling is to be used as a thermal management method for high heat flux electronics it is necessary to understand the behaviour of a non-uniform heat distribution, which is typically the case observed in a real operating computer chip. In this study, flow boiling of deionised water in a silicon microchannel heat sink under uniform and non-uniform heating has been investigated with particular attention to flow boiling instabilities. An experimental system was designed and constructed to carry out the experimental investigations. The experimental heat sink consisting of forty parallel rectangular microchannels with 194 μm hydraulic diameter together with integrated inlet and outlet manifold was fabricated on a silicon wafer using inductive coupled plasma dry etching, in conjunction with photolithographic techniques. A design with integrated temperature sensors made from a thin nickel film allows local temperature measurements with a much faster response time and smaller thermal resistance as compared to temperature measurements using thermocouples. The integrated heater was designed to enable either uniform or non-uniform heating (hotspot investigation) with a low thermal resistance between the heater and the channels. Numerical simulations for single phase flow in adiabatic conditions were used to assist the design of the manifold geometry in the microchannels heat sink. Microfabricated temperature sensors were used together with simultaneous high speed imaging in order to obtain a better insight related to temperature fluctuations caused by two-phase flow instabilities under uniform and non-uniform heating. Two types of two-phase instabilities with flow reversal were identified and classified into flow stability maps. The effect of inlet water temperature on flow boiling instabilities was experimentally studied, with the influence of different subcooling conditions on the magnitude of temperatures as well as the influence on temperature uniformity over the heat sink being assessed. The effect of various hotspot locations on flow boiling instabilities has been investigated, with hotspots located in different positions along the heat sink. Bubble growth and departure size have been experimentally investigated. The results of this study demonstrate that bubble growth in microchannels is different from that in macroscale channels. Furthermore, the effects of bubble dynamics on flow instabilities and heat transfer coefficient have been investigated and discussed.
13
Kuravi, Sarada. "Numerical Study of Encapsulated Phase Change Material (EPCM) Slurry Flow in Microchannels." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4093.
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Heat transfer and flow characteristics of phase change material slurry flow in microchannels with constant heat flux at the base were investigated. The phase change process was included in the energy equation using the effective specific heat method. A parametric study was conducted numerically by varying the base fluid type, particle concentration, particle size, channel dimensions, inlet temperature, base heat flux and melting range of PCM. The particle distribution inside the microchannels was simulated using the diffusive flux model and its effect on the overall thermal performance of microchannels was investigated. Experimental investigation was conducted in microchannels of 101 [micro]m width and 533 [micro]m height with water as base fluid and n-Octadecane as PCM to validate the key conclusions of the numerical model. Since the flow is not fully developed in case of microchannels (specifically manifold microchannels, which are the key focus of the present study), thermal performance is not as obtained in conventional channels where the length of the channel is large (compared to length of microchannels). It was found that the thermal conductivity of the base fluid plays an important role in determining the thermal performance of slurry. The effect of particle distribution can be neglected in the numerical model under some cases. The performance of slurry depends on the heat flux, purity of PCM, inlet temperature of the fluid, and base fluid thermal conductivity. Hence, there is an application dependent optimum condition of these parameters that is required to obtain the maximum thermal performance of PCM slurry flows in microchannels.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering PhD
14
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.
15
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.
16
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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17
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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18
Tunuguntla, Sri Priyanka. "Numerical Study of Thermal Performance of Two-Layered Microchannel Heat Sink with Nanofluids For Cooling of Microelectronics." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307442807.
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19
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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20
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.
21
Al, Siyabi I. "Enhancing the performance of concentrating photovoltaics through multi-layered microchannel heat sink and phase change materials." Thesis, University of Exeter, 2019. http://hdl.handle.net/10871/35932.
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Concentrating Photovoltaic technology is considered now as a promising option for solar electricity generation along with the conventional flat plate PV technology especially in high direct normal irradiance areas. However, the concentrating photovoltaic industry sector still struggles to gain market share and to achieve adequate economic returns due to challenges such as the high temperature of the solar cell which causes a reduction its efficiency. The work presented in this thesis is targeted to influence the overall performance of a high concentrated photovoltaic system by integrating both the multi-layered microchannel heat sink technique and a phase change material storage system. The proposed integrated system is composed of a multi-layered microchannel heat sink attached to a single solar cell high concentrated photovoltaic module for thermal regulation purposes. This is expected to reduce the solar cell temperature hence increasing the electrical output power. The high concentrated photovoltaic and multi-layered microchannel heat sink system is then connected to a phase change material thermal storage system to store efficiently the thermal energy discharged by the high concentrated photovoltaic and multi-layered microchannel heat sink system. The first part of the thesis discusses the influence of the multi-layered microchannel heat sink on the high concentrated photovoltaic module using both the numerical and experimental approaches. The multi-layered microchannel heat sink has been integrated for the first time with the single cell receiver and tested successfully. A numerical analysis of the high concentrated photovoltaic and multi-layered microchannel heat sink system shows the potential of the heat sink to reduce the solar cell maximum temperature and its uniformity. The thermal behaviour of the multi-layered microchannel heat sink under non-uniform heat source was experimentally investigated. The results show that in extreme heating load of 30W/cm² and in heat transfer fluid flow rate of 30ml/min, increasing the number of layers from 1-layer to 4-layers reduced the heat source temperature from 88.55°C to 73.57°C, respectively. In addition, the single layer multi-layered microchannel heat sink suffers of the most heat source temperature non-uniform compared to the heat sinks with higher number of layers. Also, the results show that increasing the number of layers from 1-layer to 4-layers reduced the pressure drop from 16.6mm H2O to 3.34 mm H2O. The indoor characterization of the high concentrated photovoltaic and multi-layered microchannel heat sink system investigated the effect of the number of layers, the homogeniser materials, and the heat transfer fluid flow rate and inlet temperature on the electrical and thermal performance of the system. The results show that the maximum power of the high concentrated photovoltaic module with glass homogeniser is 3.46W compared to 2.49W when using the crystal resin homogeniser for the 2-layers multi-layered microchannel heat sink and 30ml/min under 1000W/m² irradiance intensity. Increasing the number of layers from 1-layer to 3-layers on the high concentrated photovoltaic and multi-layered microchannel heat sink system increased the maximum electrical power by 10% and decreased the solar cell temperature 3.15°C for the heat transfer fluid flow rate of 30ml/min. This gives an increase in the maximum electrical power of 98.4mW/°C. The outdoor characterisation of the high concentrated photovoltaic and multi-layered microchannel heat sink system performance was evaluated at the University of Exeter, Penryn Campus, UK. The achieved maximum output electrical power of the system was 4.59W, filling factor of 75.1%, short circuit current of 1.96A and extracted heat of 12.84W which represents of 74.9% of the maximum solar irradiance of 881W/m². In addition, the maximum solar cell temperature reached to 60.25°C. Secondly, the experimental studies were carried out in order to investigate the performance of the phase change material storage system using paraffin wax as the PCM materials. The thermal storage system performance was evaluated in various conditions. The results show that inclination of the phase change material storage influences the melting behaviour of the phase change material where the phase change material storage of 45º inclination position melts faster than the phase change material storages in the 0º and 90º inclination positions. The phase change material melting time is reduced in the PCM storage of 45º inclination position by 13% compared to the 0º inclination position. The last part of the thesis discusses the integration of the phase change material storage with the high concentrated photovoltaic and multi-layered microchannel heat sink system. A 3D numerical model was developed to predict the behaviour of the integrated high concentrated photovoltaic and multi-layered microchannel heat sink system with the phase change material storage system using variable source conditions. The results show a higher heat absorption rate on phase change material storage that uses a lower melting temperature phase change material compared to the higher phase change material melting temperature. The multi-stages storage with different phase change materials melting temperature showed a lower heat absorption compared to the phase change material arrangement with the lower melting temperature. Also, the rate of the absorbed heat fluctuation is less affected by the phase change material arrangement with higher melting temperature.
22
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.
23
Ojada, Ejiro Stephen. "Analysis of mass transfer by jet impingement and study of heat transfer in a trapezoidal microchannel." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0003297.
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Nascimento, Francisco Júlio do. "Estudo teórico-experimental da transferência de calor e da perda de pressão em um dissipador de calor baseado em microcanais." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18147/tde-14082012-113947/.
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A presente dissertação trata de um estudo teórico-experimental sobre escoamento monofásico e bifásico em um dissipador de calor baseado em microcanais. Este tipo de dissipador de calor tem sido usado para a intensificação da troca de calor em sistemas compactos e de alto desempenho. A intensificação da troca de calor promovida pelo escoamento em microcanais é acompanhada de um incremento na perda de pressão, portanto o estudo destes dois parâmetros é essencial para o entendimento dos fenômenos relacionados e fundamental para o desenvolvimento de ferramentas de projeto para dissipadores de calor baseados em microcanais. Inicialmente, um levantamento bibliográfico extenso sobre a ebulição convectiva em microcanais de reduzido diâmetro foi realizado. Este estudo da literatura trata de critérios de transição entre micro- e macro-escala, padrões de escoamento, métodos de previsão do coeficiente de transferência de calor e perda de pressão. Atenção específica foi dada a estudos de dissipadores de calor baseados em microcanais. Com base nesta análise da literatura, uma bancada experimental foi confeccionada para que dados experimentais de transferência de calor e perda de pressão pudessem ser levantados a partir de um dissipador de calor de microcanais. O dissipador de calor fabricado para este estudo é constituído de 50 microcanais retangulares dispostos paralelamente com 15 mm de comprimento, 100 µm de largura, 500 µm de profundidade e espaçados entre si de 200 µm. Experimentos foram executados para o R134a, velocidades mássicas de 400 a 1500 kg/m²s, título de vapor máximo de 0,35 e fluxos de calor de até 310 kW/m². Como conclusão deste trabalho observa-se perda de pressão elevada em relação aos valores fornecidos pelos métodos de previsão da literatura e um coeficiente de transferência de calor próximo ao estimado pelo modelo de três zonas proposto por Thome et al. (2004).This study presents a theoretical and experimental investigation on single and two-phase flows in a microchannel based heat sink. Multi-microchannel heat sinks are able of dissipating extremely high heat fluxes under confined conditions. Such characteristics have attracted the attention of academia and industry and actually several studies are being carried out in order to evaluate and optimize such devices. Initially, an extensive investigation of the literature concerning convective boiling in micro-scale channels was performed. This literature review covers transitional criteria between micro- and macro-scale flow boiling, two phase flow patterns, heat transfer coefficient and pressure drop during convective boiling. Special attention was given to studies concerning microchannels based heat sinks. Based on this investigation, an experimental facility was built for performing heat transfer and pressure drop measurements during single-phase flow and flow boiling in microchannel based heat sinks. For this study, a microchannel based heat sink was also manufactured. The heat sink contains 50 rectangular parallel microchannels, 15 mm long, 100 µm wide by 500 µm deep and separated by 200 µm walls. Experiments were performed for R134a, mass velocity of 400-1500 kg/m²s, maximum vapor quality of 0,35 and heat fluxes up to 310 kW/m². The database obtained in the present study was compared against pressure drop and heat transfer coefficient prediction methods from the literature. It was found that no one method is accurate in predicting heat sink pressure drop while heat transfer coefficient results were accurately predicted by the 3-zone model proposed by Thome et al. (2004).
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Toro, Cristian Alfredo Chávez. "Transferência de calor e perda de pressão durante a ebulição convectiva de hidrocarbonetos em um dissipador de calor baseado em multi-microcanais." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18147/tde-03052017-160433/.
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A presente tese envolve um estudo experimental da ebulição convectiva no interior de um dissipador de calor baseado em multi-microcanais. Resultados experimentais para perda de pressão e coeficiente de transferência de calor foram levantados para os hidrocarbonetos R600a (isobutano), R290 (propano) e R1270 (propileno), fluidos com reduzido GWP (Global Warming Potential) e ODP (Ozone Depletion Potential) nulo. O desempenho termo-hidráulico destes fluidos foi avaliado em um dissipador de calor de cobre, contendo cinquenta canais paralelos com seção transversal retangular de 123x494 µm2 , 15 mm de comprimento e área de base de 15x15 mm2. Os experimentos foram realizados para fluxos de calor de até 400 kW/m2, velocidade mássica variando entre 165 e 823 kg/m2s, graus de sub-resfriamento do líquido na entrada da seção de testes de 5, 10 e 15°C e temperaturas de saturação de 21 e 25°C. Os dados experimentais foram amplamente analisados e discutidos, focando o efeito do fluido refrigerante. Oscilações dos sinais de temperatura e pressão foram analisadas parametricamente visando caracterizar efeitos de instabilidades térmicas. Adicionalmente, realizou-se análise comparativa de desempenho dos refrigerantes baseada na 2ª Lei da Termodinâmica. Os dados para hidrocarbonetos foram comparados com resultados de trabalhos prévios para o refrigerante R134a levantados na mesma seção de testes e utilizando a mesma bancada experimental. A partir destes dados, conclui-se que os hidrocarbonetos proporcionam coeficientes de transferência de calor superiores ao R134a. Em geral, o coeficiente de transferência de calor apresenta a seguinte ordem decrescente: R290, R1270, R600a e R134a. No entanto, o R290 necessitou superaquecimentos da parede superiores ao R1270 para iniciar o processo de ebulição. O refrigerante R1270 proporcionou perdas de pressão totais inferiores aos demais fluidos segundo a seguinte ordem decrescente: R600a, R134a, R290 e R1270. O refrigerante R1270 apresentou frequências de oscilação inferiores na temperatura da câmara de saída. Baseado na análise de desempenho da 2ª Lei da Termodinâmica, conclui-se que, as irreversibilidades devido ao processo de transferência de calor foram predominantes quando comparadas àquelas devido à perda de pressão. Através desta análise também constatou-se o melhor desempenho para o refrigerante R290.The present thesis concerns an experimental study on flow boiling inside a microchannel array. Experimental results for two-phase pressure drop and heat transfer coefficient were acquired for the hydrocarbons R600a (isobutane), R290 (propane) and R1270 (propylene). These fluids present low Global Warming Potential (GWP) and null Ozone Depletion Potential (ODP). The cooling performance of these hydrocarbons were evaluated for a copper heat sink containing fifty parallel microchannels. The microchannels are rectangular with cross section of 123x494 µm2, 15 mm length and a footprint area of 15x15 mm2. The experimental evaluation was performed in a test facility located at the Laboratory of Thermal and Fluid Engineering of School of Engineering of São Carlos, University of Sao Paulo. The experiments were performed for heat fluxes up to 400 kW/m2, mass velocities from 165 to 823 kg/m2s, degrees of liquid subcooling at the test section inlet of 5, 10 and 15°C and saturation temperatures of 21 and 25°C. The experimental data were carefully analyzed and discussed focusing on the effects of the fluid on the heat sink thermal hydraulic performance. Fluctuations in the temperature and pressure were analyzed parametrically in order to evaluate thermal instability effects. Additionally, an exergy analysis was performed to evaluate the refrigerant efficiency during convective evaporation. Subsequently, the parametric effects and performance of hydrocarbons were compared with previous results for refrigerant R134a obtained in the same test facility and under the same experimental conditions. The refrigerant R290 provided heat transfer coefficients higher than R600a and R1270. However, R290 needed a degree of wall superheating for the onset of nucleate boiling higher than R1270. Based on the exergy analysis it was concluded that, the irreversibility associated to the heat transfer process are predominant compared with the irreversibility due to the pressure drop. According to the Second Law analyses it was also concluded R290 as the fluid providing the best performance.
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Arroyave, Ortegón Jorge Andrés. "Desenvolvimento de um dissipador de calor compacto para o resfriamento de células fotovoltaicas de alta concentração (HCPV)." Ilha Solteira, 2018. http://hdl.handle.net/11449/154894.
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Orientador: Elaine Maria CardosoResumo: A energia solar pode ser aproveitada como fonte de energia térmica para aquecimento de água, por exemplo, em coletores solares ou como fonte de energia elétrica usando sistemas de células fotovoltaicas. Entretanto, as células fotovoltaicas, geralmente, de custos relativamente altos, têm algumas restrições relacionadas a altas temperaturas de operação e distribuições de temperatura não homogêneas levando a redução da vida útil e eficiência elétrica de tais sistemas. Essas limitações têm sido o foco de pesquisas, a fim de melhorar as eficiências elétricas, regular as temperaturas de operação e reduzir os materiais necessários para fabricação das células. Assim, este projeto de pesquisa tem como objetivo avaliar o desempenho de um dissipador de calor, baseado em microcanais retangulares paralelos, no resfriamento de uma célula fotovoltaica de alta concentração (HCPV-High Concentration Photovoltaic Cell), utilizando-se de análise teórica (modelo térmico), simulação numérica (usando o software comercial CFD ANSYS® Fluent v15) e de uma bancada experimental. Neste trabalho, foram consideradas as condições de máxima radiação (denominado de pior cenário, quando a célula não gera eletricidade e todo o calor deve ser dissipado) e de radiação média ao longo do período considerado. Os dados climatológicos foram obtidos do site Canal Clima - UNESP, com dados historicos do clima na região noroeste paulista. Foi realizada uma revisão do estado da arte a fim de compreender como os sistemas de... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Solar energy can be used as a source of thermal energy in solar collectors, for example, or as a source of electricity using photovoltaic cell systems. However, photovoltaic cells requires high investments having some restrictions related to high operating temperatures and nonhomogeneous temperature distributions, leading to a reduction in the useful life and electrical efficiency. These limitations have been the focus of researches in order to improve electrical efficiencies, to regulate operating temperatures, and to reduce required materials in the cells. Thus, this research project aims to evaluate the performance of a heat sink based on parallel rectangular microchannels for cooling of a high concentration photovoltaic cell (HCPV), using theoretical analysis (thermal model), numerical simulation (using commercial software CFD ANSYS® Fluent v15) and an experimental bench. In this work, it was considered the conditions of maximum radiation (named worst scenario, when the cell does not generate electricity and all the heat must be dissipated) and the average radiation over the period considered. These climatological data were obtained from the Canal Clima – UNESP site, in the northwestern region of São Paulo state. A review on the subject was carried out in order to understand how solar photovoltaic systems can be optimized using solar concentrators and more efficient materials (multiple-junction cells). The influence of temperature and cooling systems were analyzed. An exp... (Complete abstract click electronic access below)
Mestre
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Leão, Hugo Leonardo Souza Lara. "Análise experimental dos efeitos do fluido e da orientação do escoamento no desempenho de dissipadores de calor baseados na ebulição convectiva em microcanais." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18147/tde-19082014-102054/.
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A pesquisa realizada envolveu a avaliação experimental dos efeitos do fluido e da orientação do escoamento no desempenho de um dissipador de calor baseado na ebulição convectiva em microcanais. Estes dissipadores de calor são usados como uma nova aplicação para a refrigeração dos novos dispositivos eletrônicos que geram altas taxas de calor. Efetuou-se inicialmente uma extensa pesquisa bibliográfica sobre o escoamento monofásico e a ebulição convectiva em microcanais e em multi-microcanais através da qual levantou-se os principais métodos de previsão do coeficiente de transferência de calor e da perda de pressão. Então, utilizando o aparato experimental desenvolvido durante o mestrado de Do Nascimento (2012) avaliou-se a transferência de calor e perda de pressão de um dissipador de calor baseado em multi-microcanais paralelos. O dissipador de calor avaliado possui 50 microcanais retangulares dispostos paralelamente com 15 mm de comprimento, 100 µm de largura, 500 µm de altura e espaçados de 200 µm. Ensaios experimentais foram executados para o R245fa, fluido de baixa pressão utilizado em ciclos frigoríficos de baixa pressão, e R407C, fluido de alta pressão usado para conforto térmico, temperatura de saturação de 25 e 31°C, velocidades mássicas de 400 a 1500 kg/m²s, graus de subresfriamento do líquido de 5, 10 e 15°C, título de vapor máximo de até 0,38, fluxos de calor de até 350 kW/m², e para 3 orientações diferentes do dissipador de calor, horizontal, vertical com os canais alinhados horizontalmente e vertical com escoamento ascendente. Os resultados obtidos foram parametricamente analisados e comparados com métodos da literatura. Coeficientes de transferência de calor médios de até 35 kW/m² °C foram obtidos. Resultados adquiridos para o R245fa e R407C foram inferiores aos levantados por Do Nascimento (2012) para o R134a utilizando o mesmo dissipador. O fluido R407C apresentou frequências e amplitudes de oscilações inferiores aos fluidos R134a e R245fa. Nenhum método para o coeficiente de transferência de calor e perda de pressão proporcionou previsões satisfatórias dos dados experimentais. O modelo Homogêneo com viscosidade da mistura bifásica dada por Cicchitti et al. (1960) apresentou as melhores previsões da perda de pressão, já para o coeficiente de transferência de calor, os métodos de Bertsch et al. (2009) e Liu e Winterton (1991) apresentaram as melhores previsões. O dissipador com sua base posicionada horizontalmente fornece coeficientes de transferência de calor superiores enquanto sua base na vertical e escoamento ascendente verificam-se perdas de pressão inferiores. Imagens do escoamento bifásico foram obtidas com uma câmera de alta velocidade e analisadas.This study presents an experimental investigation on the effect of the fluid and the footprint orientation on the performance of a heat spreader based on flow boiling inside micro-scale channels. This heat spreader is used in an electronics cooling application with high-power density. Initially an extensive investigation of the literature concerning single-phase and two-phase flow inside a single microchannels and multi-microchannels was performed. In this literature review the leading predictive methods for heat transfer coefficient and pressure drop are described. The experimental study was carried out in the apparatus developed by Do Nascimento (2012). The heat sink evaluated in the present study is comprised of fifty parallel rectangular microchannels with cross-sectional dimensions of 100 µm width and of 500 µm depth, and total length of 15 mm. The fins between consecutive microchannels are 200 µm thick. Experimental tests were performed for R245fa, low-pressure fluid used in low pressure refrigeration cycles, and R407C, high-pressure fluid used for heat comfort, saturation temperature of 25 and 31°C, mass velocities from 400 to 1500 kg/m² s, degrees of subcooling of the liquid of 5, 10 and 15°C, outlet vapor quality up to 0.38, heat fluxes up to 350 kW/m², and for the following footprint heat sink orientations: horizontal, vertical with the microchannels aligned horizontally and vertical with upward flow. The results were parametrically analyzed and compared again the predictive methods from literature. Average heat transfer coefficients up to 35 kW/m² °C were obtained. The results for R134a from Do Nascimento (2012) for the same heat sink presented heat transfer coefficients higher than R245fa and R407C. The fluid R407C presented oscillation of the temperature due to thermal instability effects with lower frequency and amplitude lower than R134a, and R245fa. None predictive method provided satisfactory heat transfer coefficient and pressure drop predictions of the experimental data. The Homogeneous model with the viscosity given by Cicchitti et al. (1960) provided the best pressure drop prediction while the heat transfer coefficient was best predicted by Bertsch et al. (2009) and Liu and Winterton (1991). The horizontal orientation of the footprint provided the highest heat transfer coefficients while the vertical footprint orientation with upward flow the lowest pressure drops. Images of the two-phase flow were obtained with a high-speed camera and analyzed.
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Riera, Curt Sara. "Estudi experimental i numèric d’un sistema de refredament híbrid de jet impactant i microcanals a escala micromètrica." Doctoral thesis, Universitat de Lleida, 2015. http://hdl.handle.net/10803/365303.
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En aquesta tesi s’avalua un sistema híbrid de jet impactant/ microcanals, a escala micromètrica.
S’inclou el procediment de dimensionament i la construcció del dissipador mitjançant el procés
de microfabricació. Amb proves experimentals que permeten el càlcul de paràmetres com el
coeficient de resistència tèrmica i la desviació estàndard de la temperatura, s’avalua el
comportament del sistema en comparació amb d’altres de similars a escala mil•limètrica.
Paral•lelament es desenvolupa i valida un model numèric per simular el comportament del
dispositiu. El model permet analitzar l’efecte de la velocitat del fluid refrigerant així com
l’impacte del material d’interfície tèrmica (TIM). També s’estudia l’efecte de la geometria del jet
utilitzant el quocient entre l’amplitud de l’entrada del fluid i la distància entre aquesta i el punt
d’impacte (z/b). La resistència tèrmica, la uniformitat de temperatura i les pèrdues de pressió
s’analitzen en funció d’aquest paràmetre z/b. Finalment, per estudiar l’adaptació del dissipador a
fluxos de calor bidimensionals s’avalua un disseny de matriu d’agulles, comparant-lo amb el
dissipador de microcanals.En esta tesis se evalúa un sistema híbrido de jet impactante/microcanales, a escala micrométrica. Se incluye el procedimiento de dimensionamiento y la construcción del disipador mediante el proceso de microfabricación. Con pruebas experimentales que permiten el cálculo de parámetros como el coeficiente de resistencia térmica y la desviación estándar de la temperatura se evalúa el comportamiento del sistema en comparación con otros de similares a escala milimétrica. Paralelamente se desarrolla y valida un modelo numérico para simular el comportamiento del dispositivo. El modelo permite analizar el efecto de la velocidad del fluido refrigerante así como el impacto del material de interfaz térmica (TIM). También se estudia el efecto de la geometría del jet utilizando el cociente entre la amplitud de la entrada del fluido y la distancia entre ésta y el punto de impacto (z/b). La resistencia térmica, la uniformidad de temperatura y las pérdidas de presión se analizan en función de este parámetro z/b. Finalmente, para estudiar la adaptación del disipador a flujos de calor bidimensionales se evalúa un diseño de matriz de agujas, comparándolo con el disipador de microcanales.
This thesis evaluates a hybrid microchannels/jet impingement system, in a micrometer scale. The work includes the dimensioning process and the heat sink development using a microfabrication process. With the experimental tests that allow to calculate parameters like the thermal resistance coefficient and the temperature standard deviation, the system behaviour is evaluated in comparison to similar ones in a millimeter scale. In parallel a numeric model is developed and validated in order to simulate the behaviour of the device. The model makes possible to analyse the effect of the cooling fluid velocity as well as the impact of the thermal interface material (TIM). In addition the effect of the jet geometry is studied using the nozzle to plate spacing (z/b) . The thermal resistance, temperature uniformity and pressure drop are analysed in function of this z/b parameter. Finally, a pin fins design is evaluated comparing it with the microchannels heat sink, in order to study the adjustment of the heat sink to bidimensional heat fluxes.
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Perret, Corinne. "Réalisation et optimisation de refroidisseurs à microcanaux en technologie silicium." Phd thesis, Grenoble INPG, 2001. http://tel.archives-ouvertes.fr/tel-00549755.
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Les convertisseurs d'électronique de puissance sont de plus en plus compacts. Les pertes générées dans les différents composants restent sensiblement constantes, voire croissantes, pourune puissance donnée, car l'augmentation des fréquences de travail 'est pénalisante à ce niveau. Les puissances volumiques à évacuer sont donc en augmentation et nécessitent la conception de· refroidisseurs plus efficaces. Les meilleures performances sont actuellement obtenues par des refroidisseurs en cuivre à microcanaux parcourus par un fluide caloporteur. Afin.de limiter les problèmes de fatigue thermique, due à la présence de différents matériaux, et d'augmenter la compacité, nous présentons dans cette thèse une démarche visant à réaliser des refroidisseurs à microcanaux en technologie silicium. Après avoir rappelé une méthode de calcul des pertes et les lois de la thermique et de l'hydraulique, nous présenterons les avantages attendus par notre approche; puis nous décrirons les technologies disponibles et celles retenues pour la réalisation de prototypes. Les deux derniers chapitres sont consacrés aux simulations des dispositifs comparées aux résultats expérimentaux, ainsi qu'à une recherche de conception optimale.
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Shu-ChingLiao and 廖淑菁. "Numerical Optimization of Trapezoidal Microchannel Heat Sinks." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/31243249337984834124.
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Li, Wei-ping, and 李偉平. "Heat Transfer Analysis and Channel Designs of Microchannel Heat Sinks." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/96896024583791424982.
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碩士國立臺南大學
綠色能源科技研究所碩士班
100
In this thesis, the numerical analysis is performed to examine the possible methods to enhance the heat transfer performance of microchannel heat sink (MCHS) by computational fluid dynamics software. The effects of geometric parameters and nanofluids are discussed in details for the enhancement of heat transfer performance in MCHs. For the design of two-layer MCHS, the effects of geometric parameters such as channel number, channel width ratio, channel aspect ratio, and pumping power on the temperature distribution and thermal resistance are discussed in details. For the design of tapered MCHS, the effects of tapered ratios of height and width the thermal performance are discussed. For the nanofluids, the double-layered MCHS with different particle volume fractions, particle sizes, and pumping powers are presented. Predictions show that the heat transfer performance of the two-layered MCHS can be improved for a system. For the triple-layered MCHS, higher performance is found for a system with lower aspect ratio of the middle layer when the aspect ratio of the bottom layer is fixed. As for the tapered MCHS, the tapered channel in MCHS would affect the flow field and pressure drop. The pressure drop increases with both the tapered ratios in height and width. For fixed pumping power, the effects of tapered channel in width on the thermal performance. With fixed pumping power, the nanofluid MCHSs with lower base fluid viscosity have a more effective heat transfer enhancement, relatively to those of pure fluid MCHSs. Besides, the predicted showed that best thermal performance of MCHS is found for a nanofluid with 1% particle volume fraction.
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Chen, YehFeng, and 陳業豐. "Performance of Thermoelectric Cooler Integrated with Microchannel Heat Sinks." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/67271114189859742589.
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碩士國立中興大學
機械工程學系
92
The major goal of the present study is using the thermoelectric cooler(TEC) for cooling a fixed volume of water, the microchannel were fabricated by using IC-based micromachining techniques is employed at the TEC hot side to dissipate heat and discuss effect of six specific geometries of silicon microchannel heat sink performance for TEC cooling. Finally, a theoretical model on lumped system is established and used to predict the transient behavior of water temperature variation with time. The measurements show that temperature of water decreases with time. In this study, due to small channel aspect ratios so that the microchannel geometry does not affect the thermal resistance very much. In fact, the experimental thermal resistance is bigger than theory thermal resistance, because of estimation of theory thermal resistance neglect inlet and outlet port of microchannel heat sink. The theoretical predicted temperature is in good agreement with the measured data. Base on the theoretical model, the relationship between minimum temperature of water, heat sink thermal resistance, and TEC electric current input. When decreases heat sink thermal resistances, it can found minimum temperature decreases as electric current constant. Moreover, the minimum temperature can also be decreased by increasing the electric current as heat sink thermal resistance constant. On the other hand, there is no cooling effect for the large TEC electric current input when poor heat sink is used.
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Lin, Jing-Wei, and 林敬唯. "Optimization of Design Parameters for Fibonacci Spiral Microchannel Heat Sinks." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/p6jndf.
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碩士中原大學
機械工程研究所
105
In this study, the Fibonacci series was adopted in design-optimal of spiral micro channel heat sink. By using Taguchi Method, the performance variation in different channel parameters (such as width, height, flow rate, and fluid media) combinations were thoroughly studied, aimed for producing higher performance spiral micro channel heat sink. There are two phases in this study: Firstly, the ANSYS fluent numerical simulation software and Taguchi Method were used to shorten the design and experiment time. Secondly, the pressure drop and thermal resistance were concerned for validating flow field and heat dissipation performance difference in Fibonacci spiral micro channel heat sink. Therefore, two set of experiments were setup for flow field and heat dissipation separately. In flow field experiment, transparent Poly Methyl MethAcrylate (PMMA) was selected as main material for models; significance among channel parameters has found by Taguchi Method. (Ranked as: flow rate >channel height > channel width > Fluid media) This result shows good agreement with numerical simulation in phase one. In heat dissipation experiment, corrosive-resistive Phosphor bronze (S3000) was selected as main material of models witch was machined by CNC. Optimal parameters combination has taken form flowfield experiments; with 90 Watts ceramic electric heater, and water flow rate ranging from 20 – 90 (ml/min) In conclusion, this research achieved lowest 0.071 (K/W) thermal resistance. This Fibonacci spiral micro channel heat sink could suppress CPU core temperature under 35 ℃ (When subject to 100 Watts server-level CPU), by comparison traditional air-cooling model is ranged from 50 to 70 ℃.
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Huang, Jun-min, and 黃俊閔. "HEAT TRANSFER AND PRESSURE DROP CHARACTERISTICS FOR HFE-7100 WITHIN MICROCHANNEL HEAT SINKS." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/01437923921722950668.
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碩士國立中正大學
機械工程所
97
This study examines the heat transfer and pressure drop characteristics of the dielectric fluid HFE-7100 within multiport microchannel heat sink having a square configuration rectangular with a hydraulic diameter of 460μm and790μm. For a lower mass flux of 100 or 200kg/m2s, it is found that the heat transfer coefficients are roughly independent of heat flux and vapor quality provided that no flow reversal occurs. However, with the presence of flow reversal at an elevated heat flux, appreciable drop of heat transfer coefficient is encountered. The flow reversal also plays a significant role in the overall pressure drop and 790μm not change with vapor quality difference Without flow reversal, the pressure drop for higher heat flux always exceeds that of lower heat flux due to acceleration contribution. However, the presence of flow reversal may offset the contribution of acceleration and results in a negligible effect of heat flux. For a higher mass flux like 300kg/m2?s, the heat transfer coefficients are virtually independent of vapor quality and heat flux. 790μm with the heat transfer coefficient will increase with the different heat flux.
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Ding, Chang-Yi, and 丁章議. "Thermal Flow Field and Cooling Performance of Nanofluids in Microchannel Heat Sinks." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/9dr8f2.
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碩士國立虎尾科技大學
機械與機電工程研究所
97
The objective of this work is to investigate thoroughly the forced convection heat transfer of nanofluid flow through microchannel heat sinks. In view of the small dimensions of the microstructures, the microchannel heat sink is modeled as a fluid-saturated porous medium by using a general non-Darcy model to describe the flow and the two-equation model is used for heat transfer. A numerical study is carried out to solve the flow field and thermal transport problems. Results for the velocity profiles of the coolant flow and the temperature distributions for both the solid and fluid phases are presented to reveal the flow and heat transfer characteristics of nanofluids flowing in microchannel heat sinks. Also, cooling performance of the microchannel heat sink in terms of the thermal resistance is illustrated for different values of the nano-particle volume fraction. Results for the thermal resistance of water-alumina nanofluid are compared to existing experimental data in the literature. It is found that the results of these two sets match very well. Also, cooling performances of various nanofluids are considered in the present study. The present investigation is expected to be useful for the development of the next-generation electronic cooling techniques.
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Dang, Minh Nhat. "A study on two-phase flow characteristics in cross-linked microchannel heat sinks." Thesis, 2007. http://spectrum.library.concordia.ca/975499/1/MR34741.pdf.
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Thermal management for high performance of miniaturized electronic devices using microchannel heat sinks has recently become of interest to researchers and industry. Obtaining heat sink designs with uniform flow distribution is strongly desired. Mal-distribution in a standard straight microchannel heat sink has become a problematic issue in this research area. A cross-linking scheme, introduced in the channel core promises an appropriate solution to this problem due to flow sharing through the cross-links. In the present thesis, a number of experimental and numerical studies have been conducted to seek appropriate designs for microchannel heat sinks. The effects of cross links, introduced in the channel core of an array of parallel scaled microchannels, are investigated, by comparing the flow distribution and pressure drop in six different multi-channel configurations. A standard straight channel test section and five cross-linked test sections are experimentally investigated. All test sections have 45 parallel rectangular channels, with a hydraulic diameter of 1.59 mm. The flow distribution is monitored at four selected channels. The working mixture is air and water with superficial velocities ranging from 0.03 to 9.93 m/s, and 0.04 to 0.83 m/s, respectively. The results show that the cross-linked designs improve the flow distribution between channels compared to the standard straight channel configuration. Flow patterns obtained from flow visualization are presented in terms of fractional time function and a flow pattern map was developed. Compared with a single channel flow regime map, the expected intermittent flow regime is observed 84% to 90% of the time for the cross-linked designs, but only 65% to 80% of that for the straight channel design. A new cross-linked microchannel heat sink is proposed with the support of numerical investigations. The new design shows a significant improvement, up to 55%, on flow distribution when compared to the standard straight channel configuration without a penalty in pressure drop.
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Levac, Marc. "Three-dimensional analysis of two-layered microchannel heat sinks in parallel and counter-flow arrangements." 2008. http://hdl.handle.net/1993/21093.
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Ling, Ling. "Numerical Investigation of the Cooling Performance of Microchannel Heat Sinks under Uniform and Non-Uniform Heating Conditions." Thesis, 2012. http://spectrum.library.concordia.ca/975059/1/Ling_MASc_S2013.pdf.
Full textAbstract:
High-power electronic devices are now widely applied in computer, mechanical and sustainable energy industries. As electronic devices become further more integrated and powerful, more effective cooling is required to remove increasing heat fluxes generated by smaller devices. Microchannel heat sink has been recognized as a very promising cooling technology since it was brought up by Tuckerman and Pease.
The purpose of the present work is to numerically study the cooling performance of microchannel heat sinks under non-uniform heating conditions and to compare to that under uniform heating conditions. Water with temperature-dependent properties is used. The temperature distribution, pressure drop, and total thermal resistance of the heat sink are selected as criteria of their cooling performance. The heat sinks are tested under various inlet velocities and heat fluxes. Firstly, cross-linked microchannel heat sink is used for cooling of heat source with hotspots. Three widths of cross-linked channel which are 0.5 mm, 1 mm, 2 mm are compared to straight channel with different positions and amount of hotspots on the bottom surface of the heat sink. Secondly, straight channel micro heat sinks are studied and optimized
IV
under continuously varying heat flux conditions. Two layouts of the heat sink are proposed on which heat fluxes change perpendicular and along flow direction, respectively. Then, the layout with better cooling performance is optimized with Taguchi method. Finally, a novel swirl channel heat sink is employed for cooling of continuously varying heat flux conditions on a circular plate and is compared to uniform heating. Erenow, four cross sectional geometries of the channel (rectangular, trapezoidal, inverse-trapezoidal, and isosceles triangular) are compared for the heat sink.
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Ighalo, Fervent U. "Optimisation of microchannels and micropin-fin heat sinks with computational fluid dynamics in combination with a mathematical optimisation algorithm." Diss., 2011. http://hdl.handle.net/2263/26207.
Full textAbstract:
In recent times, high power density trends and temperature constraints in integrated circuits have led to conventional cooling techniques not being sufficient to meet the thermal requirements. The ever-increasing desire to overcome this problem has led to worldwide interest in micro heat sink design of electronic components. It has been found that geometric configurations of micro heat sinks play a vital role in heat transfer performance. Therefore, an effective means of optimally designing these heat sinks is required. Experimentation has extensively been used in the past to understand the behaviour of these heat extraction devices. Computational fluid dynamics (CFD) has more recently provided a more cost-effective and less time-consuming means of achieving the same objective. However, in order to achieve optimal designs of micro heat sinks using CFD, the designer has to be well experienced and carry out a number of trial-and-error simulations. Unfortunately, this will still not always guarantee an accurate optimal design. In this dissertation, a design methodology which combines CFD with a mathematical optimisation algorithm (a leapfrog optimisation program and DYNAMIC-Q algorithm) is proposed. This automated process is applied to three design cases. In the first design case, the peak wall temperature of a microchannel embedded in a highly conductive solid is minimised. The second case involves the optimisation of a double row micropin-fin heat sink. In this case, the objective is to maximise the total rate of heat transfer with the effect of the thermal conductivity also being investigated. The third case extends the micropin-fin optimisation to a heat sink with three rows. In all three cases, fixed volume constraint and manufacturing restraints are enforced to ensure industrial applicability. Lastly, the trends of the three cases are compared. It is concluded that optimal design can be achieved with a combination of CFD and mathematical optimisation.Dissertation (MEng)--University of Pretoria, 2011.
Mechanical and Aeronautical Engineering
Unrestricted
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Shiao, Shin-Duan, and 蕭心端. "Experimental Study of Microchannel Geometry on the Microchannel Heat Sink Performance Enhancement." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/77817152086764854254.
Full textAbstract:
碩士國立中興大學
機械工程學系所
94
In this study，performances of two types of microscale heat sinks based on the modifications from the conventional parallel channel heat sink (PCHS) are studied experimentally。By referring the walls that separating the channels in PCHS as the plate fins，the first type of modified heat sinks involves placing obstacles alternatively on the plate fins. As a result，the original parallel channels in PCHS become winded。This type of heat sink is referred to as the obstructive channel heat sink (OCHS)。It is intended to enhance the heat transfer coefficient by the flow disruption in this heat sink design。In the second type of heat sink，the plate fins are cut into segments and arranged in staggered form。This results in the plate fins in the original parallel heat sink been modified to a staggered arranged pin fin array and the heat sink is referred as the pin fin heat sink (PFHS)。Since the transverse fluid flow in pin fin array is allowed，the PFHS is designed to have two inlets and two outlets to enhance heat transfer coefficient。The heat sink base plate temperature uniformity，thermal resistance，and pressure drop across the heat sink are the three parameters used to evaluate the performances of the heat sinks studied。For all these three parameters，the experimental results show that the PFHS can provide best temperature uniformity，lowest thermal resistance and lowest pressure drop among the three heat sink designs in this study。
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Lu, Chun-Ting, and 盧俊庭. "Development of a Highly Stable Microchannel Heat Sink." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/97394825354763002963.
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博士國立清華大學
工程與系統科學系
99
With microprocessor performance increasing, the power generation from a microprocessor chip is expected to exceed 180 W/cm2 and the limits of current air-cooling technology will be reached, i.e., forced air heat sinks have become significantly larger with more expensive and noisier. Therefore, there is a need to address the thermal challenge of high-heat-flux for next generation of power electronics. Flow boiling in microchannels, considered as one of the most promising technologies, has the advantages of highest heat fluxes, lowest pumping powers, and the highest efficiency. This study explores experimentally the flow boiling stability, channel-to-channel interactions and convective boiling heat transfer in 10 parallel diverging microchannels with/without ANS. Three types of diverging microchannel heat sinks (named type-1, type-2, and type-3) were designed. Each microchannel had a mean hydraulic diameter of 120 ?慆. Water and FC-72 was used as the working fluid with different mass fluxes, based on the mean cross section area, ranging from 99 kg/m2s to 999 kg/m2s. Type-1 system did not contain any ANS, whereas type-2 system contained ANS distributed uniformly along the downstream half of the channel and type 3 system contained ANS distributed uniformly along the entire channel. The ANS are laser-etched pits on the bottom wall of the channel and have a mouth diameter of 24 μm, as indicated by the heterogeneous nucleation theory. Flow visualization shows that slug and annular flow is the dominant two-phase flow pattern. It may imply the dominant heat transfer mechanism may be convective boiling. During CHF, the dryout of annular liquid film appears near the outlet region with frequent rewetting of liquid film with slug bubble or rewetting of liquid column on the dryout surface, while wavy annular flow is the dominant flow pattern. Moreover, correlations for boiling heat transfer coefficient and the CHF are developed and reviewed, respectively. The proposed correlations for boiling heat transfer coefficient show excellent agreement with the experimental data of the present study. Furthermore, the CHF correlation of Bowers and Mudawar can predict the present CHF data very well with the overall MAE of about 16%. Under boiling condition, a significant improvement in stabilizing the flow boiling, suppressing flow reversals, enhancing heat transfer performance can be obtained by using diverging microchannel heat sinks with ANS. Among three types of microchannels, type-3 system shows the best boiling heat transfer performance. This particular design can be regarded as a highly stable and high-heat-flux microchannel heat sink.
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Yu-PinHsu and 許毓彬. "Thermal Analysis and Optimization of Microchannel Heat Sink." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/37701846224452019201.
Full textAbstract:
碩士國立成功大學
機械工程學系碩博士班
98
Three-dimensional incompressible laminar fluid flow and heat transfer of a rectangular micro-channel heat sink is studied numerically using water as a cooling fluid in a silicon substrate. The control volume approach is developed for solving Navier-Stokes equations with conjugate energy equation for both fluid and solid regions. The QUICK and SIMPLE techniques are used for discretization of momentum and energy equations. In this studied, computations were performed for a range of 50≦Re≦600, 0.05W≦P≦0.25W, 100W/cm2≦q"≦300W/cm2. Solutions are first carefully validated with available experimental results in the literature and the shape of the micro-channel is then optimization using response surface methodology, full factorial design and genetic algorithm method. Ratio of the depth of the micro-channel to the whole depth η(Hc/Hb+Hc) and the width of the micro-channel to the whole width ξ(Wc/Wb+Wc) are selected as design variables. The thermal resistance of a micro-channel is minimized for a constant heat flux and constant pumping power. The different optimum models yielded nearly the same optimum geometries. Based on the results derived by the optimization, the optimum condition is η=0.8 and ξ=0.711. According to the numerical results, the inlet thermal resistance decreases with increasing η but increases with increasing ξ in all cases. In addition, one can observes that averaged Nusselt number increases with increase in Reynolds number or pumping power.
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Kroeker, Christopher J. "Three-dimensional thermal analysis of heat sinks with circular microchannels." 2003. http://hdl.handle.net/1993/19928.
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Chuang, Jason, and 莊志升. "Experimental Study of Heat Transfer in Nanofluid-cooled Microchannel Heat Sink." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/25517146589492126235.
Full textAbstract:
碩士國立中興大學
機械工程學系
93
The major goal of this study is to investigate the microchannel heat sink performance using nanofluids for the coolant. Pure water, nanofluids with volume fraction of 0.204%, 0.25%, 0.294% and 0.4%.and Ethylene glycol- nanofluids with volume fraction of 0.208% are employed in this study. Under the fixed heating power, microchannel heat sink performance in terms of thermal resistance and overall Nusselt number are evaluated bead on the measured with temp variations along the heat sink base plate . The coolant flow rate employed in the rage of 10 to 20 ml/min. As comparedwith the pure water-cooled microchannel heat sink, theexperiment results show the nanofluid-cooled heat sink has better performance when the flow rate is low. At high coolant volume flow rate,nanofluid-cooled microchannel heat sink is worse than pure water–cooled one due to serious nanoparticle agglomeration and deposition. Suitable dispersion agent in nanofluid is required in the heat sink application in order to enhance the device performance.
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Lin, Shih-han, and 林詩涵. "Numerical Study of Microchannel Heat Sink Performance using Nanofluids." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/04893553231914996201.
Full textAbstract:
碩士國立成功大學
機械工程學系碩博士班
96
In this study, microchannel heat sink (MCHS) performance using nanofluids as coolant is analyzed numerically and nanofluids are modeled using the single phase approach and the two phase approach. The numerical predictions are validated with available experimental data in the literature in the laminar flow, then extend to turbulent flow. The turbulent governing equations are solved with the standard turbulence model. An orthogonal non-uniform staggered grid is used for the establishment of mesh grids. The parameters studied include the particle volume fraction, the volumetric flow rate , Reynolds number. The numerical computations indicate that the results of the two phase approach are more accurate than the single phase approach. The heat transfer performance enhances by increasing the particle volume fraction. In the laminar flow, the thermal resistance of nanofluids is smaller than that of water, and which reduces as the particle volume fraction and the volumetric flow rate increases. In turbulent case, a slight increase in the thermal resistance of nanofluids with increasing of the particle volume fraction and the volumetric flow rate. In addition, the pressure drop of both nanofluid-cooled MCHS and pure water-cooled MCHS is discussed. For laminar case, it seems slight increase in pressure drop for nanofluid-cooled MCHS. But in turbulent flow, the pressure drop increases quite significantly.
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Dong, Xin-Xian, and 董信賢. "Heat Transfer Enhancement of Microchannel Heat Sink with Rib Shape Vortex Generators." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/5764k8.
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碩士國立虎尾科技大學
航空與電子科技研究所
103
The microchannel heat sink is considered to be the one of effective methods for the electric chip cooling. This study aims to investigate the cooling performance enhancement for the microchannel heat sink by utilizing longitudinal vortex generators. The physical system is a 10 mm x 10 mm x 1 mm silicon substrate. The microchannel has a width of 142 μm and a height of 500 μm. Liquid water is used as the coolant. The ribs are designed onto the channel walls to induce the longitudinal vortices for the liquid water flow. The governing equations for the conjugate conduction-forced convection heat transfer in silicon-based microchannel heat sink are solved by the SIMPLE and SIMPLEC techniques. The numerical simulation is rigorously performed. The results indicate that the temperatures for the cases with ribs constructed on the channel walls are significantly lower than those without ribs. The pressure drop increases with the increasing in rib numbers. It is noted that there exists optimal rib height and rib number for considering the hot spot temperature of heat sink and pressure drop of coolant. Comparing the results for situations with and without the design of rib shape vortex generator, the maximum difference in hot spot temperature of heat sink is up to 54.26% for the investigated cases.
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Chen, Chih-wei, and 陳誌偉. "OPTIMUM THERMAL ANALYSIS OF A HEAT SINK WITH VARIOUS FIN CROSS-SECTIONS AND A MICROCHANNEL HEAT SINK." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/18320670183646478503.
Full textAbstract:
博士大同大學
機械工程學系(所)
96
In the first topic of this study, a theoretical analysis of a heat sink is presented to pursue the purpose of maximum thermal dissipation and the least material cost. Due to the general derivation, the longitudinal fin arrays on a heat sink can have either square, rectangular, equilaterally triangular, or cylindrical cross section. By input the Biot number, Bi*, heat transfer coefficient ratio Hb* and He*, the heat transfer equation is derived in transcendental form which can be solved by iterative method to calculate the optimum fin length. Meanwhile, the thermal resistance of a heat sink can be obtained to illustrate the cooling performance under various design conditions. The second topic of this study presents a mathematical approach to calculate the total heat loss from a heat sink by sum up the fin spacing on the heat sink surface and the surface of rectangular fins, with each of them able to have its specified thermal conductivity and heat transfer coefficient. Meanwhile, the optimum equation with maximum heat dissipation is derived and solved to find the optimum configuration of fins in a heat sink by inputting the values of dimensionless parameters, (Bi*)i, (Hb*)i , (He*)i, and number of fins, n. Finally, several examples including fin arrangements with various distributions of thermal conductivity and heat transfer coefficients have been successfully explored for practical application. In the last topic of this study, a three-dimensional numerical simulation of the microchannel heat sink is presented to study the heat transfer characteristics and then find the optimum configuration. Based on the theory of a fully developed flow, the pressure drop in the microchannel is analytically derived under the requirement of the flow power for a single channel. In the first part of this topic, the effects of one design variables representing the channel width, channel height, the ratio of fin width to the channel width, and the ratio of substrate thickness to the channel height on the thermal resistance of a microchannel heat sink are investigated, separately. In addition, the constraint of the same flow cross section is carried out to find the optimum dimension. Then, the minimum thermal resistance and optimal channel width with various flow powers and channel heights are obtained by using the simulated annealing method. As to the second part of the present topic, the fin width and channel width are chosen as the design variables to find their optimum sizes. For the third part, the depths of the microchannel heat sink in this study are fixed at either 1 cm and 2 cm, separately, Three design variables including channel height, fin width and channel width are individually prescribed in a suitable range to search for their optimum geometric configuration when the other specifications of the micrechannel heat sink are fixed by 24 different cases.
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劉坤穎. "Effect of Discrete Heat Source on the Thermal Characteristics of Microchannel Heat Sink." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/00868702768359722816.
Full textAbstract:
碩士國立交通大學
機械工程學系
100
In electronics cooling, the junction temperature must be kept as low as possible to ensure the safe operation and stability of the electronic components. The problem becomes more severe since the electronic components always has discrete and concentrated heat source feature that accentuates the associated phenomenon. Therefore, microchannel employing liquid cooling is a good solution to eliminate the gigantic heat resistance caused by high flux concentrated heat sources. This study investigates the effect of configuration for microchannel heat sink on the overall performance both experimentally and numerically. The influence of the configurations of the manifolds is also examined. It is found that the forced convection is the main heat transfer mechanism but thermal conduction effect also plays essential role. The temperature distribution of the heat source becomes more non-uniform when the supplied heat is increased. To examine the influence of discrete heat source, the supplied heat source is divided into three separate heating sources. The results show a significant effect of the concentrated heat source. It is found that the deviation of temperature is also related to the supplied heat and the location of supplied heat source.
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Lin, Yu-Chun, and 林昱均. "Entropy Generation Analysis due to Pumping Power and Heat Source of a Microchannel Heat Sink." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/35055450368819137961.
Full textAbstract:
碩士大同大學
機械工程學系(所)
100
In this study, the three-dimensional heat transfer in a micro-channel heat sink is analyzed numerically. Entropy generation is applied to analyze the overall efficiency of the heat sink, and to compare with the overall performance by thermal resistance. The entropy generation caused by the thermal resistance of a heat sink and the pressure loss of fluid flow in a flow passage is calculated. Base on the balance between thermal performance and fluid flow, an optimum geometry of microchannel heat sink is found. This method is an integrated approach for performance of a microchannel heat sink accompanied with the problem of pressure drop. The effects of channel-width ratio and inlet velocity on thermal resistance, pressure drop and entropy generation are studied by setting fixed flow rate, pressure drop and inlet velocity. Through the entropy generation, optimum geometric configuration for different channel number, it is found that case of number of channel N=100 is better than the other case for fixed flow rate. When pressure drop is chosen to be a fixed value, inappropriate over range of pressure drop can be excluded. The entropy generation is calculated for comparison with pressure drop. In addition, the effects due to the mean velocity on both flow resistance and thermal resistance are also calculated. Under the range of the present study, it is found that velocity of 2m/s has the minimum entropy generation than others. The goal of design on microchannel heat sink is to save fluid flow energy and get best heat dissipation. Therefore, entropy generation is a good indicator for analyzing the performance and efficiency of a microchannel heat sink.
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Syu, Tan-Fang, and 徐檀芳. "Effect of Length on Heat Transfer Performance of Liquid Cooling Heat sink with Microchannels." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/26215017004825727460.
Full textAbstract:
碩士北臺灣科學技術學院
機電整合研究所
99
The present study analyzes the effect of length on the heat transfer of liquid cooling heat sink containing microchannels. Both computer simulation and experiments were conducted to investigate the heat transfer of heat sinks with various channel lengths and channel widths. CNC machine center and wire-cut machine were used to prepare aluminum (6161-T6) prototypes for experimental tests. During experiment, pressure drop, volume flow rate, and temperatures were measured. The studied channel length ranges between 10 and 18mm, and the channel width ranges between 0.26 and 0.6mm. The experimental results show that the heat transfer performance of heat sink with channel length 10mm is better than others. In addition, the channels of 0.26 in width performs lower thermal resistance.