<p>Abstract</p><p>This thesis is studying the heatsinks new designs for copper heatsinks which utilizes modelling and simulation by CFD, construction of prototypes and experimental works. Challenges and complications in manufacturing of copper heatsinks are expressed and finding the solutions to these hindrances involve in this work. Numerical efforts supported by fluent are made to promote investigation and approaching the goal in which serves the new opportunities for wider application of copper material in heat sinks.</p><p>However the thermal conductivity of copper is about double as aluminium but still aluminium heatsinks are commonly used for heat dissipation in computers.</p><p>Comparing of heat performance of two analogous heatsink of different materials, aluminium and copper, is conducted by numerical analysis in the CFD environment.</p><p>In addition to larger surface area and airflow velocity another solution for enhancement of heat dissipation is suggested.</p><p>Manufacturing solutions of copper heatsinks are proposed which will facilitate fabrication of more high performance copper heatsinks than the current heavy and expensive models.</p><p>Our first copper heat sink model is designed exclusively based on the technical observations and analyses of numerical simulation of two identical copper and aluminium heatsinks by CFD and as well as manufacturability concerns.</p><p>This heat sink is fabricated mechanically and is tested by a number of heat sources and high sensitive devices such as adhesive K type thermocouple, data acquisition 34970A in associated with HP Bench Link program.</p><p>An extent experimental work on aluminium heatsinks, integrated with forced convection, is performed in order to measure their thermal capacities.</p><p>Comparison of the heat performance of a typical aluminium heatsink, which was the best among the all aluminium heat sinks and proposed copper heatsink under identical experimental conditions, is performed.</p><p>Also in some numerical efforts, optimizing and predicting of the thermal characterization of the proposed heatsink with inclined free fins is developed. The model is scaled up in the fluent environment to predict its application in the cooling of larger heat generated electronic devices.</p><p>Impingement air-cooling mode of force-convection is adopted for heat dissipation from high power electronic devices in associated with the proposed inclined fin model.</p><p>Components of airflow velocity in the hollow spaces of the heatsink are discussed. Pressure drop and other thermal variables are analyzed analytical and by CFD code.</p><p>Another mechanical manufactured copper heat sink is investigated. A new design of the base and fins is optimized.</p><p>A three-dimensional finite volume method is developed to determine the performance of the proposed heatsink.</p><p>Thermal and hydraulic characterization of the heat sink under air-forced convection cooling condition is studied. The flow behavior around the fins and some other parts of the heat sink is analyzed by utilizing CFD code.</p><p>The hydraulic parameters including velocity profiles, distribution of static pressure, dynamic pressure, boundary layer and fluid temperature between the fins and in the passageway at the middle of the heat sink are analyzed and presented schematically.</p><p>Furthermore the thermal characteristic of the proposed heatsink is studied by contouring the three dimensional temperature distributions through the fins and temperature of the heat source by CFD code.</p>

Abstract This thesis is studying the heatsinks new designs for copper heatsinks which utilizes modelling and simulation by CFD, construction of prototypes and experimental works. Challenges and complications in manufacturing of copper heatsinks are expressed and finding the solutions to these hindrances involve in this work. Numerical efforts supported by fluent are made to promote investigation and approaching the goal in which serves the new opportunities for wider application of copper material in heat sinks. However the thermal conductivity of copper is about double as aluminium but still aluminium heatsinks are commonly used for heat dissipation in computers. Comparing of heat performance of two analogous heatsink of different materials, aluminium and copper, is conducted by numerical analysis in the CFD environment. In addition to larger surface area and airflow velocity another solution for enhancement of heat dissipation is suggested. Manufacturing solutions of copper heatsinks are proposed which will facilitate fabrication of more high performance copper heatsinks than the current heavy and expensive models. Our first copper heat sink model is designed exclusively based on the technical observations and analyses of numerical simulation of two identical copper and aluminium heatsinks by CFD and as well as manufacturability concerns. This heat sink is fabricated mechanically and is tested by a number of heat sources and high sensitive devices such as adhesive K type thermocouple, data acquisition 34970A in associated with HP Bench Link program. An extent experimental work on aluminium heatsinks, integrated with forced convection, is performed in order to measure their thermal capacities. Comparison of the heat performance of a typical aluminium heatsink, which was the best among the all aluminium heat sinks and proposed copper heatsink under identical experimental conditions, is performed. Also in some numerical efforts, optimizing and predicting of the thermal characterization of the proposed heatsink with inclined free fins is developed. The model is scaled up in the fluent environment to predict its application in the cooling of larger heat generated electronic devices. Impingement air-cooling mode of force-convection is adopted for heat dissipation from high power electronic devices in associated with the proposed inclined fin model. Components of airflow velocity in the hollow spaces of the heatsink are discussed. Pressure drop and other thermal variables are analyzed analytical and by CFD code. Another mechanical manufactured copper heat sink is investigated. A new design of the base and fins is optimized. A three-dimensional finite volume method is developed to determine the performance of the proposed heatsink. Thermal and hydraulic characterization of the heat sink under air-forced convection cooling condition is studied. The flow behavior around the fins and some other parts of the heat sink is analyzed by utilizing CFD code. The hydraulic parameters including velocity profiles, distribution of static pressure, dynamic pressure, boundary layer and fluid temperature between the fins and in the passageway at the middle of the heat sink are analyzed and presented schematically. Furthermore the thermal characteristic of the proposed heatsink is studied by contouring the three dimensional temperature distributions through the fins and temperature of the heat source by CFD code.

In this thesis the sink-effect in indoor materials wasstudied using mathematical modelling and experimental studies.The sink-effect is a concept which is commonly used tocharacterise the ability of different indoor materials to sorbcontaminants present in the indoor air. The sorption process ismore or less reversible, i.e. molecules sorbed in materials athigh contaminant concentrations may again be desorbed at lowerconcentrations. Knowledge of the sorption capacity of materialsand the rate at which sorption and desorption takes place is offundamental importance for mathematical simulation of indoorair quality. The aim of this work is to contribute withknowledge about how the sink-effect can be described inmathematical terms and how the interaction parametersdescribing the sorption capacity and sorption/desorptionkinetics can be determined. The work has been of amethodological nature. The procedure has been to set upphysically sound mathematical models of varying complexity andto develop small-scale chamber experiments. Two differentdynamic chamber methods have been used. One is based on amodified standard FLEC-chamber while the other uses a chamberwith two compartments, one on each side of the material. The"twin-compartment" method was designed due to the observationthat the contaminant readily permeated straight through theselected materials, which resulted in uncontrolled radiallosses in the FLEC-chamber. In order to be useful forcomparison between experiments and calculations and parameterfitting, the boundary conditions in the chambers must beprecisely known and controlled. This matter has shown to be themost crucial and difficult problem in the research. A varietyof mathematical models for the sink-effect have been proposed.In some models advanced fluid simulations were used in order totest the influence ofill-defined flow boundary conditions. Theaim of the modelling is to find a formulation with a minimum ofinteraction parameters, which is generally useful, i.e. both insmall-scale laboratory environments and in full-scale like anoffice room. Estimated model parameters are shown to be able toyield a reasonably good fit to experimental data for thesorption process but a less satisfactory fit for the desorptionprocess. <b>Keywords:</b>sink-effect, sorption, adsorption, diffusion,indoor air quality, volatile organic compounds, VOC,contaminants, building materials

Human existence and welfare depend on functional ecosystems. Ecosystems are critical to sustain life-support services for human well-being. One method that visualizes that humanity requires ecosystem services for resource consumption and assimilation of produced waste is ecological footprints. This study focuses on the ecosystem service carbon sequestering. A quantification of this ecosystem service showed the potential for accumulation of carbon in different ecosystems in Stockholm and Norrbotten County for the years of 1995 and 2004. This study also provides an estimate of the ecosystem area that is appropriated to accumulate all carbon from total carbon dioxide emissions in Stockholm and Norrbotten County respectively. The appropriated ecosystem area represents the ecological footprint. The ecological footprint is also calculated for Stockholms läns landsting`s total carbon dioxide emissions in 2004. The total potential for accumulation of carbon is lower in the ecosystems in Stockholm County in 2004 than in 1995 and the corresponding figure for Norrbotten County has increased. The results indicate that the total potential for carbon accumulation in Stockholm County was approximately 427 kton C year-1 in 1995 and 352 kton C year -1 in 2004. In 1995 the ecosystems in Stockholm County could assimilate 26% of the county’s total emissions whereas the figure for 2004 was 21%. In Norrbotten County, the total potential for accumulation was approximately 2 824 kton C year -1 in 1995 and 2 983 kton C year -1 in 2004. The ecosystem area that is appropriated to assimilate total emissions of carbon dioxide was smaller in 2004 than in 1995 in Stockholm County and larger in Norrbotten County. The ecological footprint for total carbon dioxide emissions in Stockholm County was 12 696 km2 in 1995 and 12 506 km2 in 2004. The corresponding estimate for Norrbotten County indicate that the ecological footprint for total carbon sequestering was 14 457 km2 in 1995 and 32 146 km2 in 2004. The result shows that both regions require large areas of ecosystem to absorb total emissions of carbon dioxide. Stockholms läns landsting´s ecological footprint was 409 km2, which corresponds to 3.3 % of the County’s total ecological footprint. Stockholm County depends on ecosystem areas outside the region for assimilation of the region’s total emissions of carbon dioxide. According to the results Norrbotten County is self-sufficient with regard to the ecosystem service carbon accumulation. This study also includes a discussion of the advantages and limitations of the ecological footprint as a methodology. The received results serve as the starting point for this discussion. Ecological footprints are pedagogic and communicative indicators and can therefore reach out to a broad audience which is a great advantage with the method. It is a static measure and is therefore incapable of giving any presages. Ecological footprints do not take the dynamics and complexity of ecosystems into account and can therefore not provide any information about the possibilities for ecosystems to deliver ecosystem services at the same quality and quantity in the future. The method does not take socio-economic factors into consideration. For these reasons, ecological footprint should not be used as an indicator for sustainability. On the other hand, ecological footprint can illustrate why an ecologically sustainable development is necessary by visualizing that human welfare and existence rely on functional ecosystems.

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.

Population-level dynamics are affected by temporal variation in individual vital rates of survival and reproduction, which are in turn influenced by habitat-specific processes. Variation in habitat quality within a population’s range can drive movement of individuals between different areas, and so there may be a relationship between variation in vital rates and spatial heterogeneity in population growth (λ). I investigated this relationship for the feral horses (Equus ferus caballus) of Sable Island, Nova Scotia, Canada, from 2008−2010. The horses (n = 484 in September 2010) form a closed population that is free from human interference and predation. I analyzed annual population growth using age-structured projection matrix models parameterized with survival and fertility data collected from almost every female (98.7% of females). I found some evidence of temporal variation in growth during the two years I studied the population (λ2008−2009 = 1.065, λ2009−2010 = 1.117). Age structure appears to have converged to a stable age distribution, suggesting this growth rate has been sustained in the years leading up to the end of my study. Variation in vital rates of adult fertility and foal survival made the largest contribution to annual variation in population growth. Future growth is predicted to be most influenced by proportional changes in adult survival, which remained relatively unchanged between 2008 and 2010. The population can be stratified into three spatially distinct subunits found across a west−east longitudinal gradient of water resources (access to permanent ponds vs. ephemeral water sources and holes dug in sand). I assessed the existence of source-sink dynamics to determine if individual movements between subunits could explain spatial heterogeneity in population growth. I found that spatial heterogeneity in growth appears to be most influenced by immigration and emigration events between subunits. Evidence suggests that current growth of the overall Sable Island horse population is made possible by individual emigration from more productive into less productive subunits; in particular, a source presented in the west of the island where permanent water ponds are located.

In this study, an entropy generation minimization procedure is employed to optimize the overall performance (thermal and hydrodynamic) of isolated fin geometries and pin-fin heat sinks. This allows the combined effects of thermal resistance and pressure drop to be assessed simultaneously as the heat sink interacts with the surrounding flow field. New general expressions for the entropy generation rate are developed using mass, energy, and entropy balances over an appropriate control volume. The formulation for the dimensionless entropy generation rate is obtained in terms of fin geometry, longitudinal and transverse pitches, pin-fin aspect ratio, thermal conductivity, arrangement of pin-fins, Reynolds and Prandtl numbers. It is shown that the entropy generation rate depends on two main performance parameters, i. e. , thermal resistance and the pressure drop, which in turn depend on the average heat transfer and friction coefficients. These coefficients can be taken from fluid flow and heat transfer models. An extensive literature survey reveals that no comprehensive analytical model for any one of them exists that can be used for a wide range of Reynolds number, Prandtl number, longitudinal and transverse pitches, and thermal conductivity. This study is one of the first attempts to develop analytical models for the fluid flow and heat transfer from single pins (circular and elliptical) with and without blockage as well as pin-fin arrays (in-line and staggered). These models can be used for the entire laminar flow range, longitudinal and transverse pitches, any material (from plastic composites to copper), and any fluid having Prandtl numbers (&ge;0. 71). In developing these models, it is assumed that the flow is steady, laminar, and fully developed. Furthermore, the heat sink is fully shrouded and the thermophysical properties are taken to be temperature independent. Using an energy balance over the same control volume, the average heat transfer coefficient for the heat sink is also developed, which is a function of the heat sink material, fluid properties, fin geometry, pin-fin arrangement, and longitudinal and transverse pitches. The hydrodynamic and thermal analyses of both in-line and staggered pin-fin heat sinks are performed using parametric variation of each design variable including pin diameter, pin height, approach velocity, number of pin-fins, and thermal conductivity of the material. The present analytical results for single pins (circular and elliptical) and pin-fin-arrays are in good agreement with the existing experimental/numerical data obtained by other investigators. It is shown that the present models of heat transfer and pressure drop can be applied for a wide range of Reynolds and Prandtl numbers, longitudinal and transverse pitches, aspect ratios, and thermal conductivity. Furthermore, selected numerical simulations for a single circular cylinder and in-line pin-fin heat sink are also carried out to validate the present analytical models. Results of present numerical simulations are also found to be in good agreement.

In this study, an entropy generation minimization procedure is employed to optimize the overall performance (thermal and hydrodynamic) of isolated fin geometries and pin-fin heat sinks. This allows the combined effects of thermal resistance and pressure drop to be assessed simultaneously as the heat sink interacts with the surrounding flow field. New general expressions for the entropy generation rate are developed using mass, energy, and entropy balances over an appropriate control volume. The formulation for the dimensionless entropy generation rate is obtained in terms of fin geometry, longitudinal and transverse pitches, pin-fin aspect ratio, thermal conductivity, arrangement of pin-fins, Reynolds and Prandtl numbers. It is shown that the entropy generation rate depends on two main performance parameters, i. e. , thermal resistance and the pressure drop, which in turn depend on the average heat transfer and friction coefficients. These coefficients can be taken from fluid flow and heat transfer models. An extensive literature survey reveals that no comprehensive analytical model for any one of them exists that can be used for a wide range of Reynolds number, Prandtl number, longitudinal and transverse pitches, and thermal conductivity. This study is one of the first attempts to develop analytical models for the fluid flow and heat transfer from single pins (circular and elliptical) with and without blockage as well as pin-fin arrays (in-line and staggered). These models can be used for the entire laminar flow range, longitudinal and transverse pitches, any material (from plastic composites to copper), and any fluid having Prandtl numbers (&ge;0. 71). In developing these models, it is assumed that the flow is steady, laminar, and fully developed. Furthermore, the heat sink is fully shrouded and the thermophysical properties are taken to be temperature independent. Using an energy balance over the same control volume, the average heat transfer coefficient for the heat sink is also developed, which is a function of the heat sink material, fluid properties, fin geometry, pin-fin arrangement, and longitudinal and transverse pitches. The hydrodynamic and thermal analyses of both in-line and staggered pin-fin heat sinks are performed using parametric variation of each design variable including pin diameter, pin height, approach velocity, number of pin-fins, and thermal conductivity of the material. The present analytical results for single pins (circular and elliptical) and pin-fin-arrays are in good agreement with the existing experimental/numerical data obtained by other investigators. It is shown that the present models of heat transfer and pressure drop can be applied for a wide range of Reynolds and Prandtl numbers, longitudinal and transverse pitches, aspect ratios, and thermal conductivity. Furthermore, selected numerical simulations for a single circular cylinder and in-line pin-fin heat sink are also carried out to validate the present analytical models. Results of present numerical simulations are also found to be in good agreement.

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 &amp / 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&deg / C with a coolant flow rate of 500 &mu / l/min per channel.

Experimental measurements are conducted on uninterrupted and interrupted aluminum microchannel heat sinks of 300, 500, 600 and 900 &mu / m 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&deg / C, which is an acceptable value for electronic cooling applications.