Dissertations / Theses: 'Cooling mechanism'

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Jawor-Baczynska, Anna. "Nucleation mechanism of crystal formation during antisolvent or cooling induced crystallisation." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=22626.

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This project studied the nucleation mechanism of crystal formation during antisolvent or cooling crystallisation of simple amino acids: D,L-valine and glycine. These amino acids can co-precipitate with proteins to form Protein Coated Microcrystals (PCMCs) in which the crystals create a solid support and the biomacromolecules cover their surface while remaining in a native state. The understanding of the formation mechanism of small microcrystals would help to better control and manage the process which leads to ordered attachment of biomacromolecules on their surfaces. Spectrophotometry, 1H nuclear magnetic resonance (NMR), dynamic light scattering (DLS) and optical microscopy were used to probe the evolution of the system from the transparent solution to a suspension of microcrystals. The nucleation mechanism of antisolvent crystallisation was found to involve formation of a transparent nanoemulsion composied of sub-micron valine-rich liquid nanodroplets with an average size and size distribution depending on supersaturation and the mixing conditions used during sample preparation. The supersaturated solutions prepared by cooling crystallisation, without agitation produced smaller nanodroplets and resulted in formation of only a few large crystals with an extremely slow crystallisation rate compared to samples with identical composition prepared by antisolvent crystallisation. The following nucleation mechanism of amino acids crystals is proposed: dissolution of amino acid into an aqueous/2-propanol mixture at concentration close to saturation results in spontaneous formation of a thermodynamically stable system consisting of amino acid rich liquid nanodroplets dispersed in amino acid solution; above a particular amino acid composition (consistent with the crystal solubility limit) the dispersed nanodroplets become metastable and shear induced coalescence of nanodroplets can provide access to a fast crystallisation pathway (non-classical); in the absence of shear the nanodroplets are colloidally-stable and crystallisation follows a much slower pathway (classical). The spontaneous formation of solute-rich nanodroplets below the crystalline saturation limit as well as formation of metastable solute-rich nanodroplets above this limit provides a paradigm shift which can be potentially used to develop fundamental understanding of nonclassical crystallisation phenomena. It will be crucial for better design and control of crystallisation processes in pharmaceutical applications.

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Popoola, Olubunmi Tolulope. "Numerical, Analytical, and Experimental Studies of Reciprocating Mechanism Driven Heat Loops for High Heat Flux Cooling." FIU Digital Commons, 2017. https://digitalcommons.fiu.edu/etd/3505.

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The Reciprocating Mechanism Driven Heat Loop (RMDHL) is a novel heat transfer device that utilizes reciprocating flow, either single-phase or two-phase flow, to enhance the thermal management in high tech inventions. The device attains a high heat transfer rate through a reciprocating flow of the working fluid inside the heat transfer device. Although the concept of the device has been tested and validated experimentally, analytical or numerical studies have not been undertaken to understand its working mechanism and provide guidance for the device design. The objectives of this study are to understand the underlying physical mechanisms of heat transfer in internal reciprocating flow, formulate corresponding heat transfer correlations, conduct an experimental study for the heat transfer coefficient, and numerically model the single-phase and two-phase operations of the RMDHL to predict its performance under different working conditions. The two-phase flow boiling model was developed from the Rensselaer Polytechnic Institute (RPI) model, and a virtual loop written in C programming language was used to eliminate the need for fluid structure interaction (FSI) modelling. The accuracy of several turbulence formulations, including the Standard, RNG, and Realizable k-ɛ Models, Standard and SST k-ω Models, Transition k - - ω Model, and Transition SST Model, have been tested in conjunction with a CFD solver to select the most suitable turbulence modelling techniques. The numerical results obtained from the single-phase and two-phase models are compared with relevant experimental data with good agreement. Three-dimensional numerical results indicate that the RMDHL can meaningfully reduce the peak temperature of an electronic device and result in significantly more uniform temperature across the device. In addition to the numerical study, experimental studies in conjunction with analytical studies are undertaken. Experimental data and related heat transfer coefficient as well as practically useful semi-empirical correlations have been produced, all of which provide archival information for the design of heat transfer devices involving a reciprocating flow. In particular, this research will lead to the development of more powerful RMDHLs, achieve a heat flux goal of 600 W/cm2, and significantly advance the thermal management at various levels. Considering the other advantages of coolant leakage free and the absence of cavitation problems, the RMDHL could also be employed for aerospace and battery cooling applications.

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Alfasfos, Rami. "Cavern Thermal Energy Storage for District Cooling. Feasibility Study on Mixing Mechanism in Cold Thermal Energy Storage." Thesis, KTH, Kraft- och värmeteknologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-219932.

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TARRAMERA, GISBERT ANGEL. "OPTOMECHANICAL COLLECTIVE EFFECTS USING COLD ATOMS IN FREE SPACE: COLLECTIVE ATOMIC RECOIL LASING & OPTICAL BINDING." Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/797082.

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This theoretical doctoral thesis investigates the collective effects that emerge in cold atomic systems caused by light-scattering in free space. Two specific cases are investigated: the collective atomic recoil laser (CARL) effect in a cold gas, without optical cavity, and a novel cooperative cooling effect via optical binding (OB) with cold atoms. As a main objective, this theoretical project investigates the spatial grating structures and the backward radiation that appears in a cold atomic cloud when it is irradiated by a single far-detuned laser beam, also known as CARL effect. While this effect has traditionally been described using a ring cavity, the study is performed here in free space, in the absence of such a cavity. Both 2D and 3D clouds show a transition from single-atom isotropic scattering to collective directional scattering. The effect is shown by the derivation and numerical solution of a set of multi-particle motion equations coupled by a self-consistent optical field, which is inspected with both a scalar model and a vectorial model. New original approaches are used to address the numerical study of the dynamics of the atomic system, such as molecular dynamics (MD) algorithms. A second system emerged, from the attempt to understand the main objective, where a few atoms rearrange themselves into crystalline atomic structures, with a periodicity between particles close to the optical wavelength. The atomic system is initially confined into a 2D plane (or 1D string) using two (or four) counter-propagating laser beams. Due to the multiple scattering experienced by all the particles in the system, a dipole-dipole force arises among them, generating a non-trivial dynamical trapping potential landscape that compels the atoms, to self-organize at distances multiple of the light wavelength. When atoms are rearranged into an atomic crystal, the force acting on each particle depends on the position of the others, thus allowing to study the stability of such optically bound structures. In addition, it turns out that a non-conservative force is generated from the dipole-dipole interaction, allowing the system to be cooled by controlling the value of certain parameters. This new phenomenon arises as a direct consequence of the use of cold atoms instead of dielectric nanoparticles in an OB system. Therefore, besides the atomic external motion, internal degrees of freedom (DOF) of the atoms are considered by treating each atom as a dipole. This latter aspect is investigated using the coupled dipole equations. When multiple atoms are set in line, the cooling mechanism is collectively enhanced, generating a novel cooperative cooling effect.

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Sjölund, Peder. "Laser cooling mechanisms and Brownian motors in optical lattices." Doctoral thesis, Umeå universitet, Institutionen för fysik, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1127.

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Denna avhandling innefattar såväl experimentella som numeriska studier av laserkylda atomer i optiska kristallgitter. Bland annat har laserkylningsprocesser studerats, där atomers rörelser i optiska kristallgitter har uppvisat andra typer av bakomliggande mekanismer än de som tidigare förutsågs genom “Sisyfoskylningsmodellen”. Sedan atomer kylda till några mikrokelvin först realiserades (sent 60-tal) så har Sisyfoskylningsmodellen varit hörnstenen för förståelsen av laserkylda och lokaliserade atomer i dissipativa optiska kristallgitter. I dissipativa optiska kristallgitter finns det en balans mellan den uppvärmande diffusionen och den kylande friktionen. Studier i denna avhandling visar att laserkylningsprocesser är mer komplexa än vad denna modell innefattar. Både experimentella och numeriska resultat visar att atomer i optiska kristallgitter har två hastighetsfördelningar där en “kallare” och en “varmare” mod av atomer omfördelas mellan moderna. Speciellt så visar det sig att varma atomer dels värms och diffunderar ut ur gittret, men samtidigt populeras den kalla moden med en tidsutveckling som inte förändrar dess temperatur nämnvärt. I detta arbete presenteras också resultat från den första realiserade tredimensionella Brownska motorn baserad på ljus-atom-växelverkan. Det unika med denna Brownska motor är att den är kontrollerbar både vad gäller dess hastighet som dess riktning. Den underliggande principen för denna Brownska motor är tämligen generell och den kan därför vara applicerbar inom andra vetenskapliga discipliner såsom nanoteknik, biologi, kemi och elektronik. Generellt så är förståelsen av Brownska motorer viktigt eftersom de återfinns i vår omgivning, från exempelvis härkomsten av muskelsammandragningar och materialtransporter i levande celler till rörelsen hos bakterier och mindre organismer. Det flesta av de experimentella resultaten presenterade i denna avhandling har varit möjliga genom utveckling och förbättringar av den experimentella uppställningen. Framförallt så har kvaliten och reproducerbarheten vid de olika mätningar som gjorts blivit avsevärt förbättrade jämfört med tidigare vilket utgör en bra grund för framtida studier av ultrakalla atomer.
In this thesis, detailed experimental studies and numerical simulations are presented of laser cooling mechanisms in dissipative optical lattices and results of the first realized three dimensional Brownian motor in optical lattices. A dissipative optical lattice is a periodic light shift potential, created in the interference patterns of laser beams. In this, atoms can be both cooled and trapped, and the most important relaxation mechanism is generally considered to be “Sisyphus cooling”. However, careful experimental and theoretical investigations indicate the presence of other cooling processes as well. This is studied by varying different parameters such as irradiance and frequency of the lattice light. The time evolution of atoms in optical lattices show strong evidence of a bimodal velocity distribution, where a population transfer between one mode containing “hot” atoms and one mode containing “cold” atoms is evident. The normal diffusion of atoms in optical lattices is characterized by isotrop random fluctuations and exhibit the nature of Brownian motion. We have realized a technique where this motion is rectified and controlled. This is done in a three dimensional double optical lattice. This Brownian motor has control properties for both its speed and its direction in three dimensions. Our three dimensional double optical lattice is created by using laser light, exploiting two transitions, in the D2 line of cesium. Two three dimensional optical lattices are spatially overlapped; each optical lattice traps atoms in one of two hyperfine ground states. The controllability comes about by inducing phase shifts in the lattice laser beams, which displace the lattices relative to each other. This type of highly controlled Brownian motor is of fundamental interest since Brownian motion is present in almost all systems and for the role they play in protein motors and the function of living cells, and for the potential applications in nanotechnology. Brownian motors of this kind also open the way to possible studies of quantum Brownian motors and quantum resonances that are predicted for atomic ratchets. Optical lattices, and especially double optical lattices, have also been suggested as a platform for quantum state manipulations due to the good isolation from environment and ambient effects. Most of the work in this thesis is a first step towards the implementation of quantum manipulation schemes in a double optical lattice.

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Sjölund, Peder. "Laser cooling mechanisms and Brownian motors in optical lattices /." Umeå : Physics Fysik, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1127.

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Strange, Michael Edward. "The effect of surface cooling on compressible boundary-layer instability." Thesis, University of Hull, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296279.

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Lekakh, Boris. "Mechanisms and limitations for water-cooling of high heat flux surfaces." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10890.

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Jagannatha, Deepak. "Heat transfer and fluid flow characteristics of synthetic jets." Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/2437.

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This thesis presents a fundamental research investigation that examines the thermal and fluid flow behaviour of a special pulsating fluid jet mechanism called synthetic jet. It is envisaged that this novel heat transfer enhancement strategy can be developed for high-performance heat sinks in electronic cooling applications.The study considers a unique arrangement of a periodic jet induced by diaphragm motion within a cavity and mounted on a confined flow channel with a heated wall upon which the jet impingement occurs. The operation of this jet mechanism is examined as two special cases for unravelling its parametric influences. In Case (a), the jet impingement is analysed in a channel with stagnant fluid permitting clear view of the pure synthetic jet process and its controlling variables. In Case (b), jet impingement is considered with fluid flow in the channel to establish the nature of synthetic jet and cross-flow interaction.The unsteady flow of this jet mechanism is simulated as a time-dependant two-dimensional numerical model with air as the working fluid. The current model considers a solution domain in its entirety, comprising the confined flow regions of the jet impinging surface, the cavity and the orifice. With a User Defined Function (UDF), the model accounts for the bulk fluid temperature variations during jet operation, which has been grossly ignored in all published work. Overcoming previous modelling limitations, the current simulation includes flow turbulence for realistic representation of pulsed jet characteristics and cross-flow interference.Computations are performed with applicable boundary conditions to obtain the heat transfer and fluid flow characteristics of the synthetic jet along with cross-flow interaction for the diaphragm amplitude ranging from 0.5 mm to 2 mm and the diaphragm frequency varying from 250 Hz to 1000 Hz. The numerical simulation yields stable solutions and aptly predicts the sequential formation of synthetic jet and its intrinsic vortex shedding process while accurately portraying the flow within the cavity.It is identified that the diaphragm amplitude primarily determines the jet velocity while the diaphragm frequency governs the rate of vortex ejection and the fluid circulation in the vicinity of the heater. The synthetic jet thermal performance is improved with high amplitude that gives rise to stronger jet impingement and reduced bulk fluid temperature arising from high frequency leading to better fluid circulation. The fluid flow in the channel or cross flow drags the jet downstream affecting jet’s ability to reach the heated wall. The relative strengths of jet velocity and channel flow determine the combined thermal performance. The fluid compressibility is seen to have insignificant effect on the synthetic jet behaviour within the examined range of parameters. As for geometrical parameters, reduced orifice width increases jet velocity improving heat transfer rates while the optima is identified for the heater -to- orifice distance within 6 to 10 times the orifice width.Results conclusively show that in a stagnant fluid medium, the proposed synthetic jet mechanism delivers 40 percent higher heat transfer rates than an equivalent continuous jet. It also thermally outperforms pure natural convection at the heated channel wall by up to 120 times within the parametric range. Under cross-flow conditions, the synthetic jet can provide 2-fold improvement in heat transfer compared to an equivalent continuous jet. By adding this synthetic jet mechanism to a flow channel, the overall thermal performance of the hybrid system is enhanced up to about 18 times the pure forced convection heat transfer rates in a channel without this jet mechanism.The observed outstanding thermal performance of the pulsed jet-cross flow hybrid mechanism surpasses the heat removal potential of current conventional techniques for electronic component cooling. It operates with a unique ability of not causing flow pressure drop increases and not requiring additional fluid circuits, which are recognised as key advantages that set this method apart from other techniques. Thus, the proposed synthetic jet-cross flow hybrid mechanism is envisaged to be potentially regarded as an outstanding thermal enhancement strategy in the development of heat sinks for future high-capacity electronic cooling needs.

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Grant, Ian A. "Development and modelling of weld cooling time equations." Thesis, Robert Gordon University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290759.

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Sundberg, Jenny. "Heat Transfer Correlations for Gas Turbine Cooling." Thesis, Linköping University, Department of Mechanical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5446.

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A first part of a ”Heat Transfer Handbook” about correlations for internal cooling of gas turbine vanes and blades has been created. The work is based on the cooling of vanes and blades 1 and 2 on different Siemens Gas Turbines. The cooling methods increase the heat transfer in the cooling channels by increasing the heat transfer coefficient and/or increasing the heat transfer surface area. The penalty paid for the increased heat transfer is higher pressure losses.

Three cooling methods, called rib turbulated cooling, matrix cooling and impingement cooling were investigated. Rib turbulated cooling and impingement cooling are typically used in the leading edge or mid region of the airfoil and matrix cooling is mostly applied in the trailing edge region.

Literature studies for each cooling method, covering both open literature and internal reports, were carried out in order to find correlations developed from tests. The correlations were compared and analyzed with focus on suitability for use in turbine conditions. The analysis resulted in recommendations about what correlations to use for each cooling method.

For rib turbulated cooling in square or rectangular ducts, four correlations developed by Han and his co-workers [3.5], [3.8], [3.9] and [3.6] are recommended, each valid for different channel and rib geometries. For U-shaped channels, correlations of Nagoga [3.4] are recommended.

Matrix cooling is relatively unknown in west, but has been used for many years in the former Soviet Union. Therefore available information in open literature is limited. Only one source of correlations was found. The correlations were developed by Nagoga [4.2] and are valid for closed matrixes. Siemens Gas Turbines are cooled with open matrixes, why further work with developing correlations is needed.

For impingement cooling on a flat target plate, a correlation of Florschuetz et al. [5.7] is recommended for inline impingement arrays. For staggered arrays, both the correlations of Florschuetz et al. [5.7] and Höglund [5.8] are suitable. The correlations for impingement on curved target plate gave very different results. The correlation of Nagoga is recommended, but it is also advised to consult the other correlations when calculating heat transfer for a specific case.

Another part of the work has been to investigate the codes of two heat transfer programs named Q3D and Multipass, used in the Siemens offices in Finspång and Lincoln, respectively. Certain changes in the code are recommended.

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Morland, Lawrence Christopher. "Mathematical models for a fluid flow arising in turbine blade cooling passages." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330029.

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Tsai, Wern Tung. "A study of the inhibition of cooling water corrosion." Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240030.

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Wang, Wen Bo. "Cryopreservation of Nereis virens sars and Arenicola marina L. larvae : mechanisms and applications in aquaculture." Thesis, University of Newcastle upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245712.

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Omer, Muhammad. "Impingement Cooling: Heat Transfer Measurement by Liquid Crystal Thermography." Thesis, Linköping University, Applied Thermodynamics and Fluid Mechanics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-52859.

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In modern gas turbines parts of combustion chamber and turbine section are under heavy heat load, for example, the rotor inlet temperature is far higher than the melting point of the rotor blade material. These high temperatures causes thermal stresses in the material, therefore it is very important to cool the components for safe operation and to achieve desired component life. But on the other hand the cooling reduces the turbine efficiency, for that reason it is vital to understand and optimize the cooling technique.

In this project Thermochromic Liquid Crystals (TLCs) are used to measure distribution of heat transfer coefficient over a scaled up combustor liner section. TLCs change their color with the variation of temperature in a particular temperature range. The color-temperature change relation of a TLC is sharp and precise; therefore TLCs are used to measure surface temperature by painting the TLC over a test surface. This method is called Liquid Crystal Thermography (LCT). LCT is getting popular in industry due to its high-resolution results, repeatability and ease of use.

Test model in present study consists of two plates, target plate and impingement plate. Cooling of the target plate is achieved by impingement of air coming through holes in the impingement plate. The downstream surface of the impingement plate is then cooled by cross flow and re-impingement of the coolant air.

Heat transfer on the target plate is not uniform; areas under the jet which are called stagnation points have high heat transfer as compare to the areas away from the center of jet. It is almost the same situation for the impingement plate but the location of stagnation point is different. A transient technique is used to measure this non-uniform heat transfer distribution. It is assumed that the plates are semi-infinitely thick and there is no lateral heat transfer in the plates. To fulfill the assumptions a calculated time limit is followed and the test plates are made of Plexiglas which has very low thermal conductivity.

The transient technique requires a step-change in the mainstream temperature of the test section. However, in practical a delayed increase in mainstream temperature is attained. This issue is dealt by applying Duhamel’s theorem on the step-change heat transfer equation. MATLAB is used to get the Hue data of the recorded video frames and calculate the time taken for each pixel to reach a predefined surface temperature. Having all temperatures and time values the heat transfer equation is iteratively solved to get the value of heat transfer coefficient of each and every pixel of the test surface.

In total fifteen tests are conducted with different Reynolds number and different jet-to-target plate distances. It is concluded that for both the target and impingement plates, a high Reynolds number provides better overall heat transfer and increase in jet-to-target distance

decreases the overall heat transfer.

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Maletzke, Fabian. "Investigation Of The Influence Of Geometrical Parameters On Heat Transfer In Matrix Cooling : A Computational Fluid Dynamics Approach." Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-177185.

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Modern gas turbine blades and vanes are operated at temperatures above their material’s melting point. Active external and internal cooling are therefore necessary to reach acceptable lifetimes. One possible internal cooling method is called matrix cooling, where a matrix of intersecting cooling air channels is integrated into a blade or vane. To further increase the efficiency of gas turbines, the amount of cooling air must be reduced. Therefore it is necessary that heat transfer inside a cooling matrix is well understood. In the first part of the thesis, a methodology for estimating heat transfer in the flow of matrix cooling channels was established using Computational Fluid Dynamics. Two four-equation RANS turbulence models based on the k-ε turbulence model showed a good correlation with experimental results, while the k-ω SST model underpredicted the heat transfer significantly. For all turbulence models, the heat transfer showed high sensitivity towards changes in the numerical setup. For the k-ω SST turbulence model, the mesh requirements were deemed too computationally expensive and it was excluded from further investigations. As the second part of the thesis, a parameter study was conducted investigating the influence of several geometric parameters on the heat transfer in a cooling matrix. The matrix was simplified as a channel flow interacting with multiple crossing flows. The highest enhancement in heat transfer was seen with changes in taper ratio, aspect ratio and matrix angle. Compared to smooth pipe flow, an increase in heat transfer of up to 60% was observed. Rounded edges of the cooling channels showed a significant influence on the heat transfer as well. In contrast, no influence of the wall thickness on the heat transfer was observed. While no direct validation is possible, the base case and the parameter sweeps show a good correlation with similar cases found in the literature.

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Massa, Helena Maria PocÌ§as Carreiro. "Urban aerodynamics : the potential of convective mechanisms in the cooling and ventilation of urban microclimates." Thesis, Open University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252353.

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Winter, Matthias [Verfasser], Peter [Akademischer Betreuer] Stephan, and Cameron [Akademischer Betreuer] Tropea. "Heat Transfer Mechanisms During Spray Cooling of Electronic Devices / Matthias Winter. Betreuer: Peter Stephan ; Cameron Tropea." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2015. http://d-nb.info/1111111995/34.

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Johansson, Adam, and Jonas Gunnarsson. "Predicting Flow Dynamics of an Entire Engine Cooling System Using 3D CFD." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-62763.

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A combustion engine generates a lot of heat which need to be cooled to prevent damages to the engine and the surrounding parts. If the cooling system can not provide enough cooling to keep the engine in a well defined range of temperatures performance and durability will decrease and emissions increase. It is also important that the cooling system do not over-cool the engine, since this may result in rough running, increased engine friction and an overall negative performance. The aim of this thesis work is to create a complete 3D digital model of the cooling system for the first generation VED4 HP with CFD in STAR-CCM+. The simulated results are compared to available experimental data for validation. Today the entire system is being modeled with 1D CFD. One of the selected components in the cooling system being model in 3D at Volvo Cars is the water jacket. The 3D CFD model depends on the 1D CFD model for the boundary conditions which is an ineffective and time consuming process, sending data back and forth between the models when making changes. A 3D CFD model is not only more accurate than the 1D CFD model, since it capture the 3D flow phenomenas but it also allows parts or areas to be studied in detail. A study of four different turbulence models is conducted on the water jacket and on an arbitrary pipe in the cooling system. A mesh study is carried on the water jacket, the same arbitrary pipe and on the thermostat, both for the opened and closed thermostat. These studies are done with regard to pressure drop only. The study yields a low Reynolds model with the k-ε v2f turbulence model gave the best results. There is a discrepancy between the simulated results and the experiments. Main reasons to this may be the difference in the geometry used in this thesis for the digital model and the geometry used for the experiments together with the inaccuracies in the experimental data. The overall deviation is larger for a case with closed thermostat than for a case with an open thermostat. With the correct geometry and more accurate experimental data the simulations should be a close representation of reality.

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Turk, Rodney Eric. "The hydrodynamics of countercurrent two-phase flow in inclined channels." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/33444.

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Abdel-Fattah, Yahia. "The mechanics of valve cooling in internal-combustion engines : investigation into the effect of VSI on the heat flow from valves towards the cooling jacket." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4333.

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Controlling the temperature of the exhaust valves is paramount for proper functioning of engines and for the long lifespan of valve train components. The majority of the heat outflow from the valve takes place along the valve-seat-cylinder head-coolant thermal path which is significantly influenced by the thermal contact resistance (TCR) present at the valve/seat and seat/head interfaces. A test rig facility and experimental procedure were successfully developed to assess the effect of the valve/seat and seat/head interfaces on heat outflow from the valve, in particular the effects of the valve/seat interface geometry, seat insert assembly method, i.e. press or shrink fit, and seat insert metallic coating on the operating temperature of the valve. The results of tests have shown that the degree of the valve-seat geometric conformity is more significant than the thermal conductivity of the insert: for low conforming assemblies, the mean valve head temperature recorded during tests on copper-infiltrated insert seats was higher than that recorded during tests on noninfiltrated seats of higher conformance. The effect of the insert-cylinder head assembly method, i.e. shrink-fitted versus press-fitted inserts, has proved negligible: results have shown insignificant valve head temperature variations, for both tin-coated and uncoated inserts. On the other hand, coating the seat inserts with a layer of tin (20-22μm) reduced the mean valve head temperature by approximately 15°C as measured during tests on uncoated seats. The analysis of the valve/seat and seat/head interfaces has indicated that the surface asperities of the softer metal in contact would undergo plastic deformation. Suitable thermal contact conductance (TCC) models, available in the public domain, were used to evaluate the conductance for the valve/seat and seat/cylinder head interfaces. Finally, a FE thermal model of the test rig has been developed with a view to assess the quality of the calculated TCC values for the valve/seat and seat/head interfaces. The results of the thermal analysis have shown that predicted temperatures at chosen control points agree with those measured during tests on thermometric seats with an acceptable level of accuracy, proving the effectiveness of the used TCC models.

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Zhou, Zhongqing. "Flatness control of hot rolled steel strip during cooling on the run-out table." Monash University, School of Physics and Materials Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/9489.

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Amanatidou, Rebeka. "CFD Measurements of the Cooling Air in a DC-Motor." Thesis, Mälardalen University, School of Sustainable Development of Society and Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-4606.

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The cooling system of a DC-motor is examined in this thesis. A change of direction of the cooling air is desired to prevent the generated coal dust from entering into the windings of the machine. Ultimately this will have a negative effect on the cooling in the machine and the loss of cooling needs to be compensated through other ways. The purpose of this thesis is to work for an improved operational safety and performance of the DC-motor and to make it more competitive in the market. By modelling the interior geometry of the machine and defining the boundaries in the software programs Gambit and FLUENT respectively, the motion and the heat transfer of the airflow could be simulated. The simulation results would give us an understanding of the flow pattern which later could be used to develop design modifications on the cooling system of a DC-motor. In this thesis the main focus lies on creating a simulation model with a sufficiently fine mesh size.

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Nadalina, Jafabadi Hossein. "Investigation of Film Cooling Strategies CFD versus Experiments -Potential for Using Reduced Models." Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-61263.

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The ability and efficiency of today’s gas turbine engines are highly dependent on development of cooling technologies, among which film cooling is one of the most important. Investigations have been conducted towards discovering different aspects of film cooling, utilizing both experiments and performing CFD simulations. Although, investigation by using CFD analysis is less expensive in general, the results obtained from CFD calculations should be validated by means of experimental results. In addition to validation, in cases like simulating a turbine vane, performing CFD simulations can be time consuming. Therefore, it is essential to find approaches that can reduce the computational cost while results are validated by experiments. This study has shown the potential for reduced models to be utilized for investigation of different aspects of film cooling by means of CFD at low turn-around time. This has been accomplished by first carrying out CFD simulations and experiments for an engine-like setting for a full vane. Then the computational domain is reduced in two steps where all results are compared with experiments including aerodynamic validation, heat transfer coefficient and film effectiveness. While the aerodynamic results are in close agreement with experiments, the heat transfer coefficient and film effectiveness results have also shown similarities within the expected range. Thus this study has shown that this approach can be very useful for e.g. early vane and film cooling design.

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Wilde, Daniel G. "Validation of a CFD Approach for Gas Turbine Internal Cooling Passage Heat Transfer Prediction." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1384.

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This report describes the development and application of a validated Computational Fluid Dynamics (CFD) modelling approach for internal cooling passages in rotating turbomachinery. A CFD Modelling approach and accompanying assumptions are tuned and validated against academically available experimental results for various serpentine passages. Criteria of the CFD modelling approach selected for investigation into advanced internal cooling flows include accuracy, robustness, industry familiarity, and computational cost. Experimental data from NASA HOST (HOt Section Technology), Texas A&M, and University of Manchester tests are compared to RANS CFD results generated using Fluent v14.5 in order to benchmark a CFD modelling approach. Capability of various turbulence models in the representation of cooling physics is evaluated against experimental data. Model sensitivity to boundary conditions and mesh density is also evaluated. The development of a validated computational model of internal turbine cooling channels with bounded error allows for the identification of particular shortcomings of heat transfer correlations and provides a baseline for future CFD based exploration of internal turbine cooling concepts.

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26

Bohner, John David. "The effect of countercurrent flow limitation in small passages." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/19003.

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Pervaiz, Salman. "Numerical and Experimental Investigations of the Machinability of Ti6AI4V : Energy Efficiency and Sustainable Cooling/ Lubrication Strategies." Doctoral thesis, KTH, Industriell produktion, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173594.

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Titanium alloys are widely utilized in the aerospace, biomedical,marine, petro-chemical and other demanding industries due to theirdurability, high fatigue resistance and ability to sustain elevateoperating temperature. As titanium alloys are difficult to machine, dueto which machining of these alloys ends up with higher environmentalburden. The industry is now embracing the sustainable philosophy inorder to reduce their carbon footprint. This means that the bestsustainable practices have to be used in machining of titanium alloys aswell as in an effort to reduce the carbon footprint and greenhouse gas(GHG) emissions.In this thesis, a better understanding towards the feasibility of shiftingfrom conventional (dry and flood) cooling techniques to the vegetableoil based minimum quantity cooling lubrication (MQCL) wasestablished. Machining performance of MQCL cooling strategies wasencouraging as in most cases the tool life was found close to floodstrategy or sometimes even better. The study revealed that theinfluence of the MQCL (Internal) application method on overallmachining performance was more evident at higher cutting speeds. Inaddition to the experimental machinability investigations, FiniteElement Modeling (FEM) and Computational Fluid Dynamic (CFD)Modeling was also employed to prediction of energy consumed inmachining and cutting temperature distribution on the cutting tool. Allnumerical results were found in close agreement to the experimentaldata. The contribution of the thesis should be of interest to those whowork in the areas of sustainable machining.

QC 20150915

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Pender, G. A. "Dual laser driven cavity cooling of a levitated nanosphere to test quantum mechanics, and other research." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10049699/.

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The first two chapters of the thesis are primarily a review of the work in the field. Chapter 1 focusses on optomechanics broadly and chapter 2 on levitated systems, which are of particular interest due to their thermal isolation from the surroundings. Chapters 3, 4 and 5 consist of my own research, much of which was presented in papers published in 2012* and 2013**. * Pender, G. A. T., Barker, P.F., Marquardt, F., Millen, J. and Monteiro, T. S. Phys. Rev. A 85 021802 (2012) ** Monteiro, T. S., Millen, J, Pender, G. A. T., Marquardt, F., Chang, D. and Barker, P. F., New J. Phys. 15, 015001 (2013) Chapter 3 is primarily concerned with determining the conditions for trapping and cooling a dielectric sphere in an optical cavity, with two laser modes. It is found that, by using two symmetric cooling and trapping beams (as opposed to the one-field-trapping-one-field-cooling of Chang et. al.) we predict around twenty times greater level of cooling than previously predicted. Typical experimental parameters are presented in section 3.7. Chapter 4 deals with additional complications and considerations including: beads with a diameter which is a significant proportion of the diving wavelength, the effect of damping, heating and radiometric forces from the background gas, heating by black body radiation and other more realistic assumption. From this I am able to conclude that the dominant source of heating is the background gas and that, despite this heating, ground state cooling would still be possible at realistically low pressure (of less than 10-7 mbar). Chapter 5 discusses how we might observe quantum behaviour in this system. In this chapter I am able to determine that quantum behaviour is observable via a heterodyne detection which allows an asymmetry to be observed in the positional power spectrum of the bead (a classically impossible result).

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Lu, Yu-Yu. "Experimental Study of Installation Effects on Cooling Fan Noise." Thesis, KTH, Marcus Wallenberg Laboratoriet MWL, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302269.

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Owing to the ever-changing developments of battery and electric powertrain, vehicle electrification is the trend in the future. Without the presence of a combustion engine, masking effect from it reduces and noises from other components become perceivable. Among all, the cooling fan is one of the major noise sources. The design of cooling fan modules is usually carried out in the early stage before building prototype vehicles. Therefore, it is essential to come up with a method for selecting optimal fan design without performing complete vehicle testing. This is a Master's degree project in collaboration with Volvo Cars, with a focus on cooling fan noise at the charging state of electric vehicles. The main objective of this thesis is to understand the effects of fan installation. Three different setups of acoustic measurement are carried out, namely free-space, wall-mounted, and in-vehicle measurement. Correlations of these measurements are investigated through comparisons of the measurement results and the installation effects are identified through spectrum difference between free-space and in-vehicle measurement. Moreover, the implementation of spectral decomposition method enables the separation of source strength and propagation effect. Analyses of sound pressure levels are studied by looking into tonal and broadband components. In addition, sound power levels are determined by following ISO standards. Finally, a subjective rating session is held to understand the human perception of cooling fan noise.
Med anledning av den pågående utvecklingen mot elektrifiering där bilarna går mot batterier och elmotorer för framdrivning så ändras ljudbilden. Utan förbränningsmotorer som tidigare maskerade mycket av ljudet från bilarna så framträder nya ljudkällor. En sådan är kylfläkten som allt mer blir en störningskälla. Vanligtvis sker designen av kylfläktsmodulen i en tidig fas innan det finns någon prototypbil att tillgå. Detta gör att det är viktigt att utveckla metoder för att i tidig fas kunna optimera designen av kylfläkten. Detta är ett examensarbete i samarbete med Volvo Cars med fokus på det ljud som uppstår vid laddning av eldrivna bilar. Uppsatsens huvudsakliga mål är att förstå fläktinstallationens påverkan på ljud genom att korrelera olika typer av mätningar. Detta genomfördes m.h.a tre separata konfigurationer, fritt-upphängd mätning, väggmonterad och installerad i bil. Korrelation undersöktes genom att jämföra mätresultat och analys av spektrumet. Analysen av ljudtrycksnivåerna genom att titta på dels de tonala komponenterna men också på bredbandsnivåerna. Utöver detta fastställs även ljudeffekten genom att följa gängse ISO standard. Slutligen så gjordes en subjektiv utvärdering för att få en förståelse av upplevelsen av ljudet från en kylfläkt.

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Al-Tameemi, Wafaa. "Studying the mechanisms of chemotherapy-induced alopecia and the effect of cooling using in vitro human keratinocyte models." Thesis, University of Huddersfield, 2017. http://eprints.hud.ac.uk/id/eprint/32611/.

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Chemotherapy-induced alopecia (CIA) is widely regarded as the most traumatic side effect associated with cancer treatment and the associated stress can be detrimental to overall outcomes. Yet there has been little research into its pathobiology and no pharmaceutical intervention is available. CIA is caused by chemotherapy-mediated damage of the rapidly dividing cells of the hair follicle and although it is normally reversible, on regrowth the hair is often different in colour and/or texture and only grows gradually. The only effective treatment for CIA currently available is scalp cooling. It has been hypothesised that scalp cooling works by a combination of vasoconstriction, a reduction in the metabolic rate and/or reduced drug uptake by cells in the hair bulb. The ability of cooling to protect from CIA has been clinically demonstrated for years yet, to date, no cell biology is available to support its cytoprotective effects. The overall aim of this work was to for the first time provide a systematic investigation of the effects of cooling on chemotherapy-induced toxicity in human cells. The work established cellular models to determine the efficacy of cooling in rescuing from toxicity, investigate the temperature conditions providing maximal rescue and understand not only the mechanisms responsible for drug-mediated cytotoxicity, but also the way in which cooling regulates such mechanisms. Various human keratinocyte models were established, including normal (epidermal, NHEK, and follicular, HHFK) cells and adapted HaCaT (HaCaTa) cells. Viability, cell cycle and apoptosis assays were used, alongside Reactive Oxygen Species (ROS) detection, mitochondrial integrity assays and Western blotting, as well as functional pharmacological inhibition experiments. A panel of chemotherapy drugs commonly used in the clinic were employed, including doxorubicin, docetaxel and active metabolite of cyclophosphamide, 4-hydroxy-cyclophosphamide (4-OH-CP) and 5-FU, whilst a series of temperature conditions were tested, including 22°C as well as more severe cooling, particularly 18°C and 14°C (and even extreme cooling at 10°C). This study showed that cooling dramatically reduces or completely prevents the cytotoxic effects of docetaxel (T), doxorubicin (A), 5-FU (F) and particularly 4-OH-CP (C); however, optimal rescue was observed in conjunction with mono-therapy treatments (and substantial rescue with dual therapies, e.g. AC), whereas combinatorial treatment (TAC) showed relatively poor response to cooling, in agreement with clinical observations. Importantly, the work demonstrated that lowering the temperature below the widely accepted 22C threshold, even by a small number of degrees (e.g. 18C), resulted in significantly improved or even complete cytoprotection, a striking observation strongly suggesting that the scalp temperature achieved clinically is of critical importance in dictating the success of head cooling in CIA prevention. The panel of chemotherapy drugs tested caused differential effects on keratinocyte cell cycle progression and drug-mediated cell cycle arrest was significantly attenuated by cooling. Notably, cooling alone appeared to decelerate cell cycle progression, providing evidence for metabolic effects. More importantly, protective pre-conditioning (PPC) achieved either by growth factor removal or pharmacological inhibition of EGFR activation enhanced the cytoprotective effects of cooling and significantly reduced the effects of the chemotherapy drugs. As the ability of PPC to enhance protection from drug cytotoxicity could be attributed to its propensity to regulate the cell cycle progression, the work provided evidence that one mechanism via which cooling cytoprotects might be due to its ability to decelerate cell cycle progression. Disruption of mitochondrial membrane potential and elevation of ROS indicated the activation of an apoptotic pathway, which was confirmed by cell death-specific assays that confirmed a mitochondrial apoptotic pathway, as evident by plasma membrane disruption, caspase activation and DNA fragmentation. Importantly, cooling at a variety of temperatures (but mainly at or below 18C) attenuated drug-mediated apoptosis. To further investigate the precise mechanisms of growth arrest and/or cytotoxicity, activation/regulation of critical intracellular signalling mediators was investigated at the protein level. The majority of the drugs used induced activation of p53 and subsequent induction of p53-inducible mediators such as p21, as well as pro-apoptotic mediators associated with the mitochondrial pathway, such as Bak, PUMA and Noxa, whilst induction of pro-apoptotic FasL and Bid cleavage was detected, suggesting possible cross-talk with the extrinsic apoptotic pathway. Strikingly, cooling attenuated or blocked in a time- and, more importantly, temperature-dependent fashion induction of these pro-apoptotic mediators (an effect that became more marked as the temperature was reduced from 37C, to 22C, 18C and 14C); these results have provided for the first time a more detailed mechanistic explanation for the cytoprotective effects of cooling. As ROS appeared to be important in cytotoxicity, the hypothesis raised was that the cytoprotective effect of cooling might be enhanced via co-treatment with an antioxidant (e.g. NAC), aimed at enhancing the cytoprotective capacity of cooling at sub-optimal temperatures (such as 26°C). The findings presented here suggested that cooling plus topical treatment with antioxidants might represent a promising approach to improve the cytoprotective effects without compromising the anticancer effects of chemotherapy. Overall, despite their reductive nature, these in vitro models have provided experimental evidence for the ability of cooling to rescue from chemotherapy drug-mediated toxicity and shown that the choice of temperature may be critical in determining the efficacy of cooling in the clinic. This, whilst generating a novel combinatorial approach that has the potential to significantly enhance the ability of scalp cooling to protect against CIA in the clinic.

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31

Fransen, Rémy. "LES based aerothermal modeling of turbine blade cooling systems." Phd thesis, Toulouse, INPT, 2013. http://oatao.univ-toulouse.fr/10012/1/fransen.pdf.

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This PhD dissertation, conducted as part of a CIFRE research project between TURBOMECA and CERFACS in partnership with the VKI, deals with improving performance of axial turbines from helicopter engines. One of the most critical design points of such engines is the control of the high pressure turbine blade lifetime which face the high temperatures from the combustor. Today, industrial numerical aerothermal predictions of the flows around the blade (in the vein and in its cooling system) are performed with the Reynolds Averaged Navier-Stokes (RANS). Thanks to the increasing computational power, Large Eddy Simulation (LES) becomes affordable to offer further flow predictions. Therefore, this thesis focuses on the capabilities of the LES to estimate the flow in turbine blade internal cooling channels. To simplify this analysis where several physical phenomenon are present, the problem is described in three parts with increasing complexity. The first part addresses simplified typical geometries of cooling channel (U-bend and ribbed channel) in a static configuration. Considering the flow regime, a wall-resolved approach using a hybrid unstructured mesh is proposed in view of the application on an industrial case. The second part extends the study of the ribbed channel in rotation using an inertial reference frame. LES provides mean and unsteady results in good agreement with the available experimental data and previous works, for the flow dynamic and the heat transfer. Finally, the third part presents the application of the method to an industrial case with conjugate heat transfer between a complex cooling channel and the blade. This last section is not present in the public manuscrit for confidential reasons. Results of the use of the wall-resolved approach in rotation in an inertial frame of reference are compared to RANS predictions and show the potential of the method with high local differences.

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Ahmedullah, Sharizal Shaik. "Integrated solar energy and absorption cooling model for HVAC (heating, ventilating, and air conditioning) applications in buildings /." Available online. Click here, 2006. http://sunshine.lib.mtu.edu/ETD/DISS/2006/MechanicalEng/ahmedullahs/diss.pdf.

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JONG, RUDOLF P. de. "Avaliacao de tubulacoes trincadas em sistemas primarios de reatores nucleares PWR." reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11228.

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Made available in DSpace on 2014-10-09T12:49:42Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T14:03:16Z (GMT). No. of bitstreams: 1 09834.pdf: 11774838 bytes, checksum: 940cf578592bd4491d6495c63535f0a7 (MD5)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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Barthe, Stephanie Cecile. "Investigation and modeling of the mechanisms involved in batch cooling crystallization and polymorphism through efficient use of the FBRM." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24752.

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Thesis (Ph.D.)--Chemical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Dr Rousseau, Ronald W; Committee Co-Chair: Dr Grover Gallivan, Martha; Committee Member: Dr Realff, Matthew; Committee Member: Dr Garmestani, Hamid; Committee Member: Dr Nenes, Athanasios.

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Ragab, Reda M. "Experimental Investigation of Mist Film Cooling and Feasibility Study of Mist Transport in Gas Turbines." ScholarWorks@UNO, 2013. http://scholarworks.uno.edu/td/1762.

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In the modern advanced gas turbines, the turbine inlet temperature may exceed 1500°C as a requirement to increase power output and thermal efficiency. Therefore, it is imperative that the blades and vanes are cooled so they can withstand these extreme temperatures. Film cooling is a cooling technique widely used in high-performance gas turbines. However, the film cooling effectiveness has almost reached plateau, resulting in a bottleneck for continuous improvement of gas turbines' efficiency. In this study, an innovative cooling scheme, mist film cooling is investigated through experiments. A small amount of tiny water droplets with an average diameter about 10-15 µm (mist) is injected into the cooling air to enhance the cooling performance. A Phase Doppler Particle Analyzer (PDPA) system is used for droplet measurements. Mist film cooling performance is evaluated and compared against air-only film cooling. This study continues the previous work by (a) adding fan-shaped holes and comparing their cooling performance with the round holes, (b) extending the length of the test section to study the performance farther downstream the injection holds, and (c) using computational simulation to investigate the feasibility of transporting mist to the film cooling holes through gas turbine inside passages. The results show that, with an appropriate blowing ratio, the fan-shaped holes performs about 200% better than round holes in cooling effectiveness and adding 10% (wt.) mist can further enhance cooling effectiveness 170% in average. Farther downstream away from the injection holes (X/D> 50), mist cooling enhancement prevails and actually increases significantly. PDPA measurements have shed lights to the fundamental physics of droplet dynamics and their interactions with thermo-flow fields. These experimental results lead to either using lower amount of cooling air or use fewer number of cooing holes rows. This means higher gas turbine power output, higher thermal efficiency, and longer components life which will reflect as a cheaper electricity bill. Computational Fluid Dynamics (CFD) showed that it is feasible to transport the water mist, with initial diameters ranging from 30 µm-50 µm and mist ratio of 10-15%, to the cooling holes on the surface of the turbine vanes and rotors to provide the desired film cooling. Key words: Gas Turbines, Heat Transfer, Film / mist Cooling, Experimental Study, Mist Transport, CFD, PDPA.

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Monleon, Jimenez Alex, and Roca David Villas. "Study of temperature raise in Gavleån river related to district cooling." Thesis, University of Gävle, Department of Building, Energy and Environmental Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-7129.

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This project is a preliminary study in order to build a small power plant, located beside to Gavleån River. It has been designed with the aim of cooling a district of Gävle city, Sweden. That big project is carried out by the international consulting engineering company SWECO. The mentioned plant contains a thermodynamic cycle that takes water from the river and afterwards, it is returned back warmer. It will attempt to study the temperature raise downstream along the river due to the spill of hot water. In addition, it will try to quantify and weight which may be the importance of the increment of temperature compared to the entire river. This work could be vital for an environmental impact study. The thermo and fluid dynamic problem is going to be solved using typical procedure for numerical simulations. To do this, it will be used Computer Aided Design (CAD) to model Gavleån River path and Computational Fluent Dynamics (CFD) to predict the distribution of temperatures. Finally the results of the simulations will be analyzed and discussed to draw conclusions about the final temperature raise in Gavleån River.

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Allred, Jacob D. "An Investigation into the Mechanisms of Formation of the Hard Zone in FSW X65." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3806.

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Friction stir welding (FSW) of HSLA steel commonly produces a hard zone (HZ) on the advancing side (AS) of the weld. Despite its detrimental effects on weld toughness, the mechanisms of its formation have not been thoroughly investigated and are not well understood. This paper investigates the various mechanisms in FSW believed to affect the weld HZ, namely: strain, strain-rate, peak temperature and cooling rate. Gleeble tests indicate that strain and strain rate have negligible effects on weld HZ with cooling rate and peak temperature as dominant effects. Jominy tests resulted in cooling rate having 270% greater influence than peak temperature on the formation of lath ferrite microstructures similar to what is observed in the HZ of FSW X65. Comparing weld HZ microstructures to Jominy tests, it is estimated that cooling rates on the AS of the weld are at least 150°C/s higher than the retreating side. Reducing the cooling rate on the AS will likely lead to an improved microstructure at the weld HZ.

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Reddy, Sohail R. "Multi-Objective Analysis and Optimization of Integrated Cooling in Micro-Electronics With Hot Spots." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2205.

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With the demand of computing power from electronic chips on a constant rise, innovative methods are needed for effective and efficient thermal management. Forced convection cooling through an array of micro pin-fins acts not only as a heat sink, but also allows for the electrical interconnection between stacked layers of integrated circuits. This work performs a multi-objective optimization of three shapes of pin-fins to maximize the efficiency of this cooling system. An inverse design approach that allows for the design of cooling configurations without prior knowledge of thermal mapping was proposed and validated. The optimization study showed that pin-fin configurations are capable of containing heat flux levels of next generation electronic chips. It was also shown that even under these high heat fluxes the structural integrity is not compromised. The inverse approach showed that configurations exist that are capable of cooling heat fluxes beyond those of next generation chips. Thin film heat spreaders made of diamond and graphene nano-platelets were also investigated and showed that further reduction in maximum temperature, increase in temperature uniformity and reduction in thermal stresses are possible.

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Khatri, Ashutosh Mahesh. "INVESTIGATING TOOL WEAR MECHANISM AND MICROSTRUCTURALCHANGES FOR CONVENTIONAL AND SUSTAINABLE MACHINING OFTITANIUM ALLOY." Miami University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=miami1533287855502478.

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40

Näslin, Joel. "Utformning av en beräkningsmodell samt dimensionering av en elmotors kylvätskesystem." Thesis, Mittuniversitetet, Institutionen för naturvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-39420.

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Effektuttaget ur en elmotor grundar sig i hur mycket ström som kan överföras i elmotorns lindning, vilken i sin tur oftast begränsas av hur varm den blir genom resistiv uppvärmning. Målet med arbetet var att ta reda på vilket värme som uppstår i ledaren, vilken kyleffekt ett vätskeflöde genom ledaren har samt vilket vätsketryck som krävs för att temperaturen på kylvätskan inte ska överstiga 95℃. Genom att ställa upp en analytisk modell kring en ledare och ett vätskeflöde genom denna, vilket i sin tur betyder att hitta kopplingar mellan strömningsmekanikens teori och värmeöverföringsteorin sa erhölls ett resultat. Sedan gjordes både simuleringar och experiment med samma förutsättningar för att kunna validera den analytiska modellen. Den analytiska modellen visade sig stämma väl överens med verkligheten och det skulle visa sig att för en elmotor med 48 ledare med en strömflödestäthet på 50 𝐴/𝑚𝑚2, med en inkommande kylvätsketemperatur på 60℃ och där kylvätskan inte får överstiga 95℃ sa kommer det krävas en pump som kan ge ett flöde av 15 𝑙/𝑚𝑖𝑛 vid ett tryckfall på 1 𝑏𝑎𝑟.

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Ghahremanian, Shahriar, and Setareh Janbakhsh. "Construction and Evaluation of a Controlled Active Mass (CAM) : A new cooling system design for increased thermal comfort using low exergy sources." Thesis, University of Gävle, Department of Technology and Built Environment, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-146.

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Nowadays, office buildings often have large temperature variations during the day and building envelope acts as an energy storing mass and damp these effects and so Offices need more cooling because of internal heat sources. But we know that cooling is more expensive than heating and it uses the very good quality of energy sources (exergy). Controlled Active Mass (CAM) is new approach to absorb radiant heating and acts as a passive cooling device. It has direct cooling effect and reduces the peak load. CAM is a new cooling system design with applying the low energy sources and operates at water temperature close to room temperature and increase the efficiency of heat pumps and other systems.

In this project, we calculated the transient heat transfer analysis for CAM in a very well insulated test room with façade wall, Internal heat generators (such as Manikin, Computer simulator & lighting) and ventilation.

Then Polished (shiny) CAM constructed from Aluminum sheets with 0.003 m thickness. It is cube shape with 0.6 m length. This size of CAM is according to 2.5 times larger than human body volume and initial water temperature assumed near half of human body temperature. Then in order to more radiation damping (absorption) by CAM, it painted black (also based on color analysis in heat transfer calculation).

Some velocity and temperature measurement have been carried out on both polished CAM and black CAM, after visualization by smoke and Infrared Camera. And more cases tested to see the effect of façade wall, IHG’s and ventilation inlet temperature. Thermal comfort measurement also have been done for finding PMV, PPD and temperature equivalent for a seated person which is doing an office job with normal closing.

At the end results discussed which includes the effect of CAM in room, differences between polished CAM and black CAM and effect of main heat sources on both CAM types (Polished / Black).

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Yaser, Hussnain A. "Novel System Design For Residential Heating And Cooling Load Shift Using PCM Filled Plate Heat Exchanger And Auxiliaries For Economic Benefit And Demand Side Management." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1397234246.

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43

Nelson, Lauren May. "Rayleigh Flow of Two-Phase Nitrous Oxide as a Hybrid Rocket Nozzle Coolant." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/284.

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The Mechanical Engineering Department at California Polytechnic State University in San Luis Obispo currently maintains a lab-scale hybrid rocket motor for which nitrous oxide is utilized as the oxidizer in the combustion system. Because of its availability, the same two-phase (gas and liquid) nitrous oxide that is used in the combustion system is also routed around the throat of the hybrid rocket’s converging-diverging nozzle as a coolant. While this coolant system has proven effective empirically in previous tests, the physics behind the flow of the two-phase mixture is largely unexplained. This thesis provides a method for predicting some of its behavior by modeling it using the classic gas dynamics scenarios of Rayleigh and Fanno flows which refer to one-dimensional, compressible, inviscid flow in a constant area duct with heat addition and friction. The two-phase model produced utilizes a separated phase with interface exchange model for predicting whether or not dryout occurs. The Shah correlation is used to predict heat transfer coefficients in the nucleate boiling regime. The homogeneous flow model is utilized to predict pressure drop. It is proposed that a Dittus-Boelter based correlation much like that of Groeneveld be developed for modeling heat transfer coefficients upon the collection of sufficient data. Data was collected from a series of tests on the hybrid rocket nozzle to validate this model. The tests were first run for the simplified case of an ideal gas (helium) coolant to verify the experimental setup and promote confidence in subsequent two-phase experimental results. The results of these tests showed good agreement with a combined Rayleigh-Fanno model with a few exceptions including: (1) reduced experimental gas pressure and temperature in the annulus entrance and exit regions compared to the model and (2) reduced experimentally measured copper temperatures uniformly through the annulus. These discrepancies are likely explained by the geometry of the flowpath and location of the copper thermocouples respectively. Next, a series of two-phase cooled experiments were run. Similar trends were seen to the helium experiment with regards to entrance and exit regions. The two-phase Rayleigh homogeneous flow model underpredicted pressure drop presumably due to the inviscid assumption. Ambiguity was observed in the fluid temperature measurements but the trend seemed to suggest that mild thermal non-equilibrium existed. In both cases, the dryout model predicted that mist flow (a post-CHF regime) occurred over most of the annulus. Several modifications should be implemented in future endeavors. These include: (1) collecting more data to produce a heat transfer coefficient correlation specific to the nitrous oxide system of interest, (2) accounting for thermal non-equilibrium, (3) accounting for entrance and exit effects, and (4) developing a two-phase Fanno model.

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Mehrtash, Mehdi. "Numerical Investigation Of Natural Convection From Plate Finned Heat Sinks." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613530/index.pdf.

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Finned heat sink use for electronics cooling via natural convection is numerically investigated. An experimental study from the literature that is for vertical surfaces is taken as the base case and the experimental setup is numerically modeled using commercial CFD software. The flow and temperature fields are resolved. A scale analysis is applied to produce an order-of-magnitude estimate for maximum convection heat transfer corresponding to the optimum fin spacing. By showing a good agreement of the results with the experimental data, the model is verified. Then the model is used for heat transfer from inclined surfaces. After a large number of simulations for various forward and backward angles between 0-90 degrees, the dependence of heat transfer to the angle and Rayleigh number is investigated. It is observed that the contributions of radiation and natural convection changes with the angle considerably. Results are also verified by comparing them with experimental results available in literature.

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Pridasawas, Wimolsiri. "Solar-driven refrigeration systems with focus on the ejector cycle." Doctoral thesis, Stockholm : Department of Energy Technology, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4151.

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Erdil, Baris. "Behavior Of Cfrp Confined Concrete Specimens Under Temperature Cycles And Sustained Loads." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614137/index.pdf.

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The application of carbon fiber reinforced polymers (CFRP) is one of the effective retrofitting and strengthening methods that is used worldwide and is starting to be used in Turkey as well because they have high strength and high modulus in the fiber direction, have very low coefficient of thermal expansion when compared to concrete and steel and are known not to corrode. Since FRPs are lightweight, their mass can be neglected when compared to concrete and steel. However, before proposing this material as an alternative for strengthening and retrofitting applications their long-term behavior should be understood because they are applied on to concrete by several layers of epoxy-based adhesives, which can be affected by change in humidity, temperature and load. Therefore, behavior of CFRP-strengthened structures in varying temperature and humidity conditions must be investigated. In this dissertation, behavior of CFRP confined cylindrical and prismatic concrete specimens having square cross-section were investigated under sustained compressive loads, dry and wet heating-cooling cycles, and outdoor exposures under direct sunlight, to determine the possible changes in their mechanical properties. Sustained loads were applied as the 40% and 50% of their confined axial load capacity. In addition to the sustained loads, specimens were subjected to 200 heating-cooling cycles between -10°
C to 50°
C. In order to understand the change in behavior of CFRP confined concrete specimens better, they were divided in six groups. A single effect was investigated in each group. After aging tests mechanical properties of the specimens were recorded via monotonic uniaxial loading. It was observed that temperature cycles had little effect on behavior but sustained loads changed the shape of the axial stress-strain diagram and resulted in a dramatic decrease in ultimate strain. Based on the test results and also using the data of similar studies available in the literature, strength and strain models considering the exposures as independent parameters were established and finally axial stress-strain curve was tried to be predicted.

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Lima, Leon Matos Ribeiro de. "Desenvolvimento de modelos 2D para simulação de escoamentos ambientais." Universidade do Estado do Rio de Janeiro, 2010. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=7695.

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Arroyo, Molina Javier. "Towards a virtual climate chamber – A physical experimental study." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-282848.

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This project focuses on experimentally characterizing one of the tools used at Ericsson AB to test product performance, the climatic chamber. By conducting experiments inside the climate chamber and post processing the data obtained, the airflow inside it can be understood and compared to outdoor experimental data. One of the main sections of this work is to prove the hypothesis: The energy potential of the wind outdoors is greater than indoors, which is shown to be true when comparing values for the integral length scales of the flow, at the same mean wind speed. The second main part of this project is to obtain valuable experimental input that will serve to construct a virtual model of the climate chamber. With the conclusions drawn from the experiments, which involve heat transfer, boundary conditions for the numerical model can be established.
Det här projektet fokuserar på att experimentellt karakterisera ett av verktygen som används i Ericsson AB för att testa produktprestanda - klimatkammaren. Genom att utföra experiment inuti klimatkammaren och efterbehandla de erhållna data, kan man få en förståelse för luftflödet inuti kammaren och jämföra resultat med experimentella data från utomhus. Ett av delmomenten i detta arbete bevisar hypotesen: 'Vindens energipotential är större än inomhus', vilket visar sig vara sant när man jämför värden för flödets integrala längdskalor, med samma medelvärde i vindhastighet. Den andra etappen av detta projekt är att erhålla en värdefull experimentell vägledning som kommer att tjäna till att konstruera en virtuell modell av klimatkammaren. Med slutsatserna från experimenten, som innefattar värmeöverföring, kan gränsvillkor för den numeriska modellen fastställas.

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Jourdan, Nicolas. "Hydrodynamique dans les circuits de refroidissement industriels : influence sur les phénomènes d’encrassement, caractérisation et modélisation." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0179.

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Les circuits de refroidissement industriels à tour aéroréfrigérante humide utilisent de l’eau naturelle (rivière ou mer) pour évacuer la puissance thermique du procédé industriel. L’eau provenant de l’environnement contient des matières en suspension ainsi que des espèces chimiques et biologiques. Elle subit un échauffement dans le circuit de refroidissement et une concentration de ces espèces par évaporation d’eau. Ces circuits sont donc soumis à un encrassement chimique (e.g. tartre), biologique (e.g. biofilm) et/ou particulaire (e.g. dépôts de matières en suspension sur les surfaces). Les écoulements dans les différentes parties du circuit jouent un rôle prépondérant sur la formation des dépôts. L’objectif de ce travail est de caractériser les écoulements dans les différentes parties des circuits de refroidissement et d’en proposer une modélisation pour appréhender les phénomènes d’encrassement. Une étude bibliographique a orienté le choix vers l’approche compartimentale, permettant une modélisation hybride multi-échelle (locale et système) qui découpe un système complexe en compartiments spatialement répartis pour en représenter l’hydrodynamique. Le modèle compartimental peut être implémenté avec tout modèle phénoménologique dépendant de l’hydrodynamique. Pour le construire, il a été nécessaire de caractériser les écoulements dans les parties d’un cas d’étude de circuit de refroidissement : les tubes du condenseur, les conduites en béton de transport de l’eau, le garnissage de la tour aéroréfrigérante et le bassin froid. Un dispositif expérimental à l’échelle pilote d’une tour aéroréfrigérante a été construit pour étudier les écoulements gaz/liquide des garnissages. Des simulations de mécanique des fluides numérique mono et diphasique (Volume of Fluid avec prise en compte des angles de contact) ont été réalisées pour les garnissages et le bassin froid. Des corrélations de la littérature ont permis d’étudier les conduites et les tubes de condenseur. Pour chaque partie du circuit il a été possible de déterminer : les distributions de conditions hydrodynamiques, notamment : vitesse, cisaillement, taux de présence de phase, épaisseur d’eau. Les méthodes mises en place peuvent être étendues à l’étude de tous les types de garnissages industriels. Pour l’encrassement, un modèle de croissance de biofilm tenant compte des limitations au transfert de matière au sein et à l'extérieur du biofilm et de l'effet du cisaillement a été développé sur la base d'informations expérimentales de la littérature sur plusieurs dispositifs industriels et différentes conditions opératoires. Les données hydrodynamiques et le modèle de biofilm ont été assemblés dans le modèle compartimental, qui permet ainsi la simulation du dépôt de biofilm dans l’ensemble du circuit en fonction des conditions de fonctionnement. Le modèle compartimental est donc un outil adéquat pour la modélisation de l’influence de l’hydrodynamique sur l’encrassement des circuits industriels
Industrial cooling circuits with wet cooling towers use raw water (from rivers or sea) in order to remove residual heat from industrial processes. Raw water contains suspended matters, chemical and biological species. This water is heated in the circuit condenser and evaporation induces species concentration. That’s why different kind of fouling can be observed in cooling circuits: particulate fouling, chemical reaction fouling and biofouling. Hydrodynamics in the different parts of the circuit strongly influence fouling deposition. This report aims to provide a complete characterization of the cooling circuit hydrodynamics and to model all the fouling phenomena. The Compartmental Modelling approach has been selected doing a critical review of the modelling approaches available in Chemical Engineering. Compartmental modeling is a multi-scale (local and system) approach dividing the studied system into spatially representative hydrodynamic compartments network. Different physico-chemical models can be patched into the compartmental model. To create the compartmental model, it was necessary to characterize the flow characteristics in the different parts of the circuit: condenser tubes, concrete pipes, cooling tower packing and cold water basin. A pilot-scale cooling tower experimental setup has been built to visualize and measure water flow into packing. Mono-phase and multi-phase (Volume of Fluid with solid/liquid contact angle model) Computational Fluid Dynamics simulations have been performed to study hydrodynamics in packing and in cold water basin. All the required information about hydrodynamics in the circuit have been obtained such as velocity, shear stress, phase fraction and water film thickness. The method processed in this work can also be used to characterize different industrial packing. A biofouling growth model has been created considering transport and transfer phenomena limitations into the biofilm and into the liquid bulk. The model has been built taking into account shear stress as main hydrodynamic parameter using experimental data from literature with different geometries and different operating conditions. Finally, the compartment model has been developed using data from hydrodynamic characterization and the biofouling model. This model can simulate and predict biofilm deposition in the different parts of the cooling circuit. The created compartmental model is a suitable approach to study the influence of hydrodynamics behavior on fouling in cooling circuits

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Good, Mattias. "Structural analysis of thermal interface materials and printed circuit boards in telecom units - a methodology." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-59746.

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En struktur analys på Ericssons MINILINK-6352 har utförts för att undersöka spänningar och deformationer på enheten, främst med fokus på de termiska gränskiktsmaterialen och buktningar av kretskortet. Dessa är viktiga aspekter när man överväger om enheten är termiska lämpad ur en mekanisk synvinkel, där god ytkontakt mellan de olika kropparna är avgörande för ordentlig kylning genom värmeledning. Analysen kräver tillräcklig materialdata till gränskiktsmaterialen och kretskortet för att kunna skapa lämpliga matematiska modeller. Enaxliga kompressionstester har genomförts för att karakterisera de hyperelastiska och viskoelastiska lagar för fyllda silikongummimaterial som används som termiska gränskiktsmaterial, som ibland kallas för gappad. Böjning av ett kretskort simulerades och jämfördes med ett tre--punkts böjtest för att verifiera om befintlig materialdata i beräkningsprogrammen var tillräcklig, jämförelsen visade god överensstämmelse. Kretskortet med dess komponenter, som modellerades som styva block, med gappads ovanpå som komprimeras av en platta simulerades och ett svagt område hittades. Detta område var sedan tidigare känt och har i ett senare skede eliminerats genom att tillsätta ytterligare en stödpelare. Därav visar denna studie en metod för att hitta intressanta regioner tidigt i konstruktionsfasen som lätt kan ändras för att uppfylla nödvändiga krav och undvika brister i konstruktionen. Arbetet har visat sig användbart genom att hitta detta svaga område i exempel produkten, arbetet ger även tillräckligt med information och exempeldata för att ytterligare utreda liknande produkter. Kombinationen av erfarenhet och simulering möjliggör smartare designval.
A structural analysis on Ericssons MINILINK-6352 has been performed in order to investigate stresses and deformations of the unit, mainly focusing on the thermal interface materials and warpage of the printed circuit boards. These are important aspects when considering if the unit is thermally adequate from a mechanical point of view, where good surface contact between various bodies are critical for proper cooling through heat conductivity. The analysis requires sufficient materal data for the interface material and the circuit board in order to create suitable mathematical models. Uniaxial compression tests have been conducted to characterise the hyperelastic and viscoelastic constitutive laws of a filled silicone rubber material used as a thermal interface material, commonly referred to as a thermal pad. Bending of a printed circuit board was simulated and compared to a three-point bend test on the circuit board in order to verify material data already available in the computational software, which showed good agreement. The entire radio unit was mechanically analysed during its sealing process. The circuit board with attached components modelled as stiff blocks with thermal pads on top compressed by plates was simulated and a weak area was found. This area in question was already known and has in a later stage been eliminated by adding an additional supporting pillar. Hence this study shows a methodology to find regions of interest at an early design phase which can easily be altered to fulfil necessary requirements and eliminate design flaws. This work has proven useful in finding weak regions in the example product, it also provides enough information and example data to further investigate similar products. The combination of experience and simulation allows for smarter design choices.

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Dissertations / Theses on the topic 'Cooling mechanism'

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