Dissertations / Theses on the topic 'Cooling solutions'
To see the other types of publications on this topic, follow the link: Cooling solutions.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 34 dissertations / theses for your research on the topic 'Cooling solutions.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Khachaturian, Mark Haig 1979. "Solutions to various problems in reversible cooling fMRI studies." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/17030.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2003.Includes bibliographical references (p. 40).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Functional magnetic resonance imaging (fMRI) has been very useful in helping neuroscientists map the brain. One tool to investigate the interactions between brain regions is to disable a small region in the brain, and look at the functional consequences of this (reversible) inactivation upon regions anatomically connected to the inactivated site. A number of issues need to be resolved before the reversible cooling technique can be used in fMRI studies. The solutions to a number of problems directly related to using reversible inactivation by cooling in conjunction with fMRI experiments on monkey brains are presented in this thesis. Specifically, these include (1) designing a cooling system and cooling probe capable of reversibly cooling the surface cortex of the monkey's brain, (2) develop or use an existing method to measure the temperature distribution with the MR-scanner, and (3) design and construct a coil (phase array) that will be used to obtain temperature and fMRI data at the highest resolution possible. A cooling system and coolant probe were designed capable of changing the temperature of the surface cortex from 37 oC to 20 oC. The Proton Resonance Frequency Shift method, which calculates the temperature based on the phase change between two images, was used to measure the temperature distribution inside an object using an fMRI sequence similar to the one that will be used in the actual experiment. The method was tested and showed an accuracy of ± 0.6 oC as compared with concurrent thermocouple measurements when adjusted for phase drift. A precision of ± 0.15 oC was found at a resolution of 2.1 x 2.1 x 1.0 mm3. A phase array head coil was designed with superior imaging qualities to the current single coil. An increase of SNR from 40 to 52 was observed in the image (30% increase) as compared with the theoretical calculated increase of 70%.
by Mark Haig Khachaturian.
S.M.
2
Chou, Lu-chien. "Drag reducing cationic surfactant solutions for district heating and cooling systems /." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487758178238587.
Full text
3
Lambert, Océane. "Solutions architecturées par fabrication additive pour refroidissement de parois de chambres de combustion." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI048/document.
Full textAbstract:
En vue de leur refroidissement, les parois de chambres de combustion aéronautiques sont perforées de trous à travers lesquels de l’air plus froid est injecté. La paroi est ainsi refroidie par convection et un film isolant est créé en surface chaude (film cooling). Cette thèse a pour objectif d’utiliser les possibilités de la fabrication additive pour proposer de nouvelles solutions architecturées qui permettraient d’augmenter les échanges de chaleur internes et d’obtenir ainsi de meilleures efficacités de refroidissement.La première approche consiste à élaborer de nouveaux designs de plaques multiperforées par Electron Beam Melting (EBM) et Selective Laser Melting (SLM) aux limites de résolution des procédés. Les architectures sont caractérisées en microscopie, en tomographie X et en perméabilité. Des simulations aérothermiques permettent de mettre en évidence l’effet de ces nouveaux designs sur l’écoulement et les échanges de chaleur, et de proposer des voies d’amélioration de la géométrie.La deuxième approche consiste à élaborer de façon simultanée une pièce architecturée par EBM, avec des zones denses et poreuses. A partir d’analyse d’images associée à une cartographie EBSD grand champ, il est possible de remonter aux mécanismes de formation du matériau poreux et de relier la perméabilité et la porosité aux paramètres procédé. Afin de favoriser le film cooling, il pourrait être avantageux que les zones microporeuses soient orientées dans le sens de l’écoulement. Pour ce faire, un nouveau procédé dénommé Magnetic Freezing, où des poudres métalliques forment une structure orientée par un champ magnétique, est mis au point.Les diverses solutions développées durant cette thèse sont testées sur un banc aérothermique. Les essais montrent qu’elles offrent un refroidissement plus efficace et plus homogène que la référence industrielle. Enfin, de premiers tests en combustion sur l’une des structures retenues, plus légère et plus perméable que la référence, montrent qu’il s’agit d’une solution aussi efficace à un débit traversant donné, et donc a priori plus efficace à une surpression donnéeCombustion chamber walls are perforated with holes so that a cooling air flow can be injected through them. The wall is cooled by convection and an insulating film is created on the hot surface (film cooling). This PhD thesis aims to use the possibilities of additive manufacturing to provide new architectured solutions that could enhance the internal heat exchanges, and lead to a higher cooling effectiveness.The first approach is to develop new designs of multiperforated walls by Electron Beam Melting (EBM) and Selective Laser Melting (SLM) used at the resolution limits of the processes. They are characterized by microscopy, X-ray tomography and permeability tests. Some aerothermal simulations help understanding the effects of these new designs on the flow and on heat exchanges. These results lead to a geometry adaptation.The second approach is to simultaneously manufacture an architectured part with dense and porous zones by EBM. Thanks to image analysis combined with large field EBSD, it is possible to investigate the mechanisms leading to the porous zones and to link them to permeability and porosity. The film cooling effect could be favoured by the orientation of pores towards the cooling flow. Therefore, a new powder-based manufacturing process named Magnetic Freezing, where metallic powders organize into an oriented structure thanks to a magnetic field, is developed.The various solutions studied during this thesis are tested on an aerothermal bench. They all show a more efficient and homogeneous cooling than the industrial reference. Some first tests on one of the selected solutions are performed on a combustion bench. This lighter and more permeable structure proves to be a solution as efficient as the industrial reference at a given flow rate. It should therefore be a more efficient solution for a given overpressure
4
Zhou, Jian Ming. "A multi-grid method for computation of film cooling." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29414.
Full textAbstract:
This thesis presents a multi-grid scheme applied to the solution of transport equations in turbulent flow associated with heat transfer. The multi-grid scheme is then applied to flow which occurs in the film cooling of turbine blades. The governing equations are discretized on a staggered grid with the hybrid differencing scheme. The momentum and continuity equations are solved by a nonlinear full multi-grid scheme with the SIMPLE algorithm as a relaxation smoother. The turbulence k — Є equations and the thermal energy equation are solved on each grid without multi-grid correction.
Observation shows that the multi-grid scheme has a faster convergence rate in solving the Navier-Stokes equations and that the rate is not sensitive to the number of mesh points or the Reynolds number. A significant acceleration of convergence is also produced for the k — Є and the thermal energy equations, even though the multi-grid correction is not applied to these equations. The multi-grid method provides a stable and efficient means for local mesh refinement with only little additional computational and.memory costs.
Driven cavity flows at high Reynolds numbers are computed on a number of fine meshes for both the multi-grid scheme and the local mesh-refinement scheme. Two-dimensional film cooling flow is studied using multi-grid processing and significant improvements
in the results are obtained. The non-uniformity of the flow at the slot exit and its influence on the film cooling are investigated with the fine grid resolution. A near-wall turbulence model is used. Film cooling results are presented for slot injection with different mass flow ratios.Science, Faculty of
Mathematics, Department of
Graduate
5
Vattøy, Bjørnar. "Techno-economic evaluation of heat-driven cooling solutions for utilization of district heat in Aalesund, Norway." Thesis, KTH, Energiteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-245232.
Full textAbstract:
This study is aimed to evaluate the techno-economic feasibility of implementing heat driven cooling technologies in buildings connected to Tafjord Kraftvarme’s district heating network in Aalesund, Norway. Heating and cooling demands were found by projecting two 4000 𝑚2 office buildings according to Passive House and Low Energy Building criteria, within the frame of the energy requirements in the TEK17 building regulations (Standard Norge, 2012) (Norwegian Building Authority, 2017). Suitable cooling and heating equipment, both electrical and heat driven, were dimensioned based on the peak cooling load of the projected buildings, and technical and economic information obtained from the distributors of the equipment. LCOE analysis shows that the heat driven cooling solutions could be able to compete economically, in variable extent, with the electrically driven solutions given relatively low heating demand or by applying investment subsidies or price reduction on district heat for cooling purpose. The desiccant cooling solution could even compete with the electrical driven solution even without subsidies or price reduction on DH for cooling. This is mainly because of its enhanced heat recovery reducing the heating demand. The absorption cooler on the other hand, has both a higher consumption and higher power input of district heat while running, and is therefore less competitive without subsidy or price reduction on DH for cooling. In the building cases explored, the absorption cooling solution requires either subsidy or price reduction on DH for cooling to compete with the electric chiller and district heat solution, while it require both to come close to compete economically with the heat pump solutions. With increasing heating demand the heat driven solutions, which use district heat as their heat source, become less competitive compared to the heat pump solutions. This is because, with the mild winters in Aalesund, the heat pumps can run with a COP of 2-3 while the COP of district heat it is considered to be 1. Other important factors that is not covered by the LCOE analysis is the reliability and environmental aspect. None of the heat driven cooling solutions use any environmentally unfriendly refrigerants, and the maintenance of the cooling machines are minor. The lifetimes of the machines are estimated to be 20 years for the desiccant and 40 years for the absorption cooler, compared to 15 years for the heat pumps and electric chiller. The heat driven cooling solutions can therefore be considered more reliable both in terms of regulations on refrigerants and on maintenance and lifetime. An additional important factor is that compared to the heat pump solutions, the heat driven cooling solutions with district heat to cover the heating demand can replace large quantities of electricity consumption with low-grade thermal energy. Considering both the economic, environmental and reliability factors, the heat driven cooling solutions could be a viable option and should be considered when implementing heating and cooling equipment in buildings connected to the district heating network in Aalesund or other locations with similar climate.Studiens syfte är att utvärdera den tekno-ekonomiska genomförbarheten av att implementera värmedrivna kylelösningar i byggnader knytna till Tafjord Kraftvarme’s fjärrvärmenetvärk i Aalesund, Norge. Uppvärmnings- och nerkylningskrav hittades vid at projictera två 4000 𝑚2 kontorsbyggnader enligt “Passive House and Low Energy Building” kriterier, inom ramen av energikrav i TEK 17 byggnadsförordningar (Standard Norge, 2012) (Norwegian Building Authority, 2017). Passande nerkylnings- och uppvärmingsutrustning, både elektrisk och värmedriven, blev dimensionerande baserad på toppbelastning till de projicerade byggnader, och den tekniska och ekonomiska information tagen från utrustningsdistributörerna. LCOE-analysen visar att den värmedrivna nerkylningslösningen kan vara konkurrenskraftig ekonomisk sett, i variabel utstreckning, med de elektriska drivna lösningarna om varmebehovet är lågt eller vid at använda subventioner eller prisnedsättning på fjärrvarme som används för kylning. Nerkylningslösningen med torkmedel kan även vara konkurrenskraftig med den elektrisk drivna även utan subventioner eller prisnedsättning på fjärrvarme. Det är huvudsakligen på grund av dens förbättrade värmeåterhämtning som reducerar uppvärmningskraven. Absorptionskylaren å andra sidan, har både högre ströminmatning av fjärrvarme medan den är i gång och är därför mindre konkurrenskraftig utan subventioner eller prisnedsättning på fjärrvarme som används för kylning. I de utforskade byggnadsfallen kräver absorptionskylaren antigen subventioner eller prisnedsättning på fjärvarme för att kunna konkurrera med den elektriska kylmaren, medan det krävs både för att kunna konkurrera med värmepumpelösningen. Med ökande uppvärmingskrav blir de värmedrivna lösningarna som använder fjärrvarme som värmekälla mindre konkurrenskraftiga jämfört med värmepumpelösningarna. Detta på grund av de milda vintrar i Aalesund som leder till att värmepumparna kan köra med en COP på 2-3 medan den anses vara 1 for lösningarna som brukar fjärrvarme. Andra viktiga faktorer som inte ingår i LCOE-analysen är pålitlighet och miljöaspekten. Ingen av de värmedrivna nerkylningslösningarna andvänder något miljöovänligt köldmedium och underhållet av nerkyningsmaskiner är minimalt. Maskinernas livsläng är beräknad till 20 år för torkmedelkylaren och 40 år för absorptionskylaren, jämfört med 15 år för värmepumparna och den elektriska kylaren. De värmedrivna nerkylningslösningarna kan därför anses vara mer pålitliga både beträffande reglering av köldmedium och underhåll samt livslängd. Ytterligare en viktig faktor är att de värmedrivna nerkylningslösningarna, jämfört med värmepumplösningarna, kan vara et livskraftig alternativ, både med hänsyn til den ekonomiska faktoren, miljöfaktoren och pålitligheten och borde därför tas hänsyn till vid implementering av uppvärmings- og nerkylningsutrustning i byggnader knytna till fjärrvärmenätet.
6
Narvaez, Javier Artemio. "Evaluation of Alumina Nanofluids and Surfactant Drag Reducing Solutions to Improve Heat Transfer for Aircraft Cooling Systems." University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton154479500350447.
Full text
7
Rabhi, Achref. "Numerical Modelling of Subcooled Nucleate Boiling for Thermal Management Solutions Using OpenFOAM." Licentiate thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-53307.
Full textAbstract:
Two-phase cooling solutions employing subcooled nucleate boiling flows e.g. thermosyphons, have gained a special interest during the last few decades. This interest stems from their enhanced ability to remove extremely high heat fluxes, while keeping a uniform surface temperature. Consequently, modelling and predicting boiling flows is very important, in order to optimise the two-phase cooling operation and to increase the involved heat transfer coefficients. In this work, a subcooled boiling model is implemented in the open-source code OpenFOAM to improve and extend its existing solver reactingTwoPhaseEulerFoam dedicated to model boiling flows. These flows are modelled using Computational Fluid Dynamics (CFD) following the Eulerian two-fluid approach. The simulations are used to evaluate and analyse the existing Active Nucleation Site Density (ANSD) models in the literature. Based on this evaluation, the accuracy of the CFD simulations using existing boiling sub-models is determined, and features leading to improve this accuracy are highlighted. In addition, the CFD simulations are used to perform a sensitivity analysis of the interfacial forces acting on bubbles during boiling flows. Finally, CFD simulation data is employed to study the Onset of Nucleate Boiling (ONB) and to propose a new model for this boiling sub-model, with an improved prediction accuracy and extended validity range. It is shown in this work that predictions associated with existing boiling sub-models are not accurate, and such sub-models need to take into account several convective boiling quantities to improve their accuracy. These quantities are the thermophysical properties of the involved materials, liquid and vapour thermodynamic properties and the heated surface micro-structure properties. Regarding the interfacial momentum transfer, it is shown that all the interfacial forces have considerable effects on boiling, except the lift force, which can be neglected without influencing the simulations' output. The new proposed ONB model takes into account convective boiling features, and it able to predict the ONB with a very good accuracy with a standard deviation of 2.7% or 0.1 K. This new ONB model is valid for a wide range of inlet Reynolds numbers, covering both regimes, laminar and turbulent, and a wide range of inlet subcoolings and applied heat fluxes.
8
Davin, Tanguy. "Refroidissement des moteurs électriques : exploration des solutions à huile de lubrification." Thesis, Valenciennes, 2014. http://www.theses.fr/2014VALE0003/document.
Full textAbstract:
Le moteur électrique est l’un des organes principaux d’un véhicule électrique. Sa température, notamment celle des bobines, doit être réduite pour éviter toute dégradation. Le refroidissement par l’extérieur, comme avec une chemise d’eau dans le carter, apparait limité car les pertes générées dans les bobines doivent traverser des zones où la conduction thermique est très mauvaise. L’extraction des calories au cœur de la machine est préférable, mais les échanges thermiques avec l’air sont modérés. En application automobile, le moteur électrique est situé à proximité d’un circuit d’huile de lubrification. Le refroidissement par l'huile en contact direct avec les bobines est étudié.La thèse s’est d’abord attachée à la recherche bibliographique étendue sur les différentes solutions de refroidissement de moteur. Ensuite, les transferts thermiques à l’intérieur du moteur ont été modélisés par méthode nodale. A travers une étude de sensibilité, les principales améliorations thermiques passives ont été dégagées, puis les systèmes de refroidissement eux-mêmes ont été modélisés. Enfin, des essais ont été réalisés sur un banc spécialement conçu. Pour cette partie expérimentale, le refroidissement direct des bobines par circulation d’huile a été étudié en détail. Différents types d’injecteurs d’huile sur les têtes de bobine ont été testés dans diverses conditions de vitesse du rotor, température et débit d’huile.L’objectif de cette thèse est d’analyser l’ensemble des problématiques thermiques liées aux solutions de refroidissement à huile. Il s’agit d’une étude comparative de la performance des solutions à huile entre elles et avec celle d’un refroidissement à eau plus conventionnelElectric motor is one of the most important elements of an electric vehicle. Some elements, particularly the windings, can be affected by rising heat. External cooling, as water jacket in the case, appears to be limited because the losses generated in windings must pass through zones where conduction is very poor. Cooling in the core of the machine is preferable, but heat transfer with air is poor. Due to the presence of lubricating oil in the vicinity of the motor and the heat transfer enhancement that such a liquid provides, oil circulation on the windings has been considered.The research was first dedicated to an extensive bibliography on the different solutions of motor cooling. Then heat transfer within the motor was modelled by using the lumped system analysis. Thanks to a sensitivity analysis, the main parameters affecting temperature have been identified before cooling systems were modelled. Finally, tests were performed on a specially designed bench. Oil was introduced at each side of the machine to directly cool the stator coil end-windings. Several oil injection patterns were tested. The influence of the oil flow rate, rotation speed and oil temperature has been investigated.The objective of this PHD study is to analyse all the thermal issues related to the oil cooling systems. This is a comparative study of the performance of the oil cooling solutions. Comparison is also done with conventional water cooling
9
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.
Full textAbstract:
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.
10
Smith, Bryan C. "Flow birefringence, nuclear magnetic resonance and corrosion measurements on drag reducing cationic surfactant solutions for district heating and cooling systems /." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487780865409286.
Full text
11
Мандибура, В., and Ратушняк Г. С. "Шляхи зниження енергоспоживання при виробництві штучного холоду." Thesis, ВНТУ, 2018. http://ir.lib.vntu.edu.ua//handle/123456789/20971.
Full textAbstract:
Проведено огляд інженерних рішень холодильних систем, які найчастіше використовуються при проектуванні систем холодопостачання промислових об’єктів. Розглянуто переваги та недоліки а також шляхи підвищення ефективності систем холодопостачання.A review of the engineering solutions of refrigeration systems, which are most often used in the design of cooling systems for industrial objects. The advantages and disadvantages as well as ways to improve the efficiency of cooling systems are considered.
12
ARRAGATTU, PRAVEEN KUMAR. "OPTIMAL SOLUTIONS FOR PRESSURE LOSS AND TEMPERATURE DROP THROUGH THE TOP CAP OF THE EVAPORATOR OF THE MICRO LOOP HEAT PIPE." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1152120112.
Full text
13
Messias, Francisco Egidio. "Análise da influência da concentração e temperatura nas características de resfriamento das soluções do sal AWS-20 usados na têmpera." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-15092016-121557/.
Full textAbstract:
A determinação das curvas de resfriamento como alternativa para análise do meio de resfriamento usado nos tratamentos térmicos de têmpera, mostra-se como um dos métodos mais poderosos e eficientes para avaliar e/ou quantificar a severidade de têmpera do meio refrigerante. Assim as soluções de sal AWS-20 testadas como meio de têmpera, tiveram o seu desempenho avaliado pelos métodos tradicionais como perfil da distribuição de dureza em corpos de prova e análise metalográfica e também através das suas curvas de resfriamento. Os resultados obtidos permitiram a sugestão de uma faixa de trabalho para temperatura e concentração com excelente rendimento e sendo confirmado pelo método de análise das curvas de resfriamento.The determination of the cooling curves as alternative for analysis of the quenching media used in the heat treatments of hardening, is shown as one of the most powerful and efficient methods to evaluate and/or to quantify the quench severity of the quenchant.. Thus, the solutions of salt AWS-20 tested as quenching media, had its, acting evaluated by the traditional methods as profile of the distribution of hardness in test bodies and analysis metallographic and also through its cooling curves. The obtained results allowed the suggestion of a work strip for temperature and concentration with excellent revenue and being confirmed by the method of analysis of the cooling curves.
14
Costanzo, Matteo. "Adapting building design to climate change for an office building in Stockholm through solar control techniques." Thesis, KTH, Hållbara byggnader, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-287452.
Full textAbstract:
Climate change will affect many human activities and sectors. Among those, the built environment will face several challenges with respect to the varying climate conditions. The present study investigated the global warming impacts on energy demand and indoor climate comfort for an office building in Stockholm. Considering a service life of 50 years, the future climate conditions were investigated for the only air temperature increase in 2070, in accordance with the medium forecasted greenhouse gas emissions scenario provided by the International Panel on Climate Change (IPCC). Another climate morphing approach was adopted to develop the climate file for the year 2080 considering the variation of all the weather parameters. Three different passive cooling solutions, such as external roller shade, electrochromic glazing, and internally ventilated shading, have been implemented in the case study building to decrease the cooling demand. The characteristics of the strategies were preliminarily assessed and then implemented into the building energy simulation software IDA-ICE to evaluate the energy performances with respect to the different climates. The results indicated that an increment of the cooling demand and a reduction of the heating usage will be experienced in the future. The different morphing approaches displayed the inherent uncertainties when future evaluations are performed, although similar weather patterns were found. The improvement of the solar and optical properties, such as the introduction of the exhaust air extraction and the electrochromic technology, implied a lower cooling and ventilation usage. The EC technology reported the lowest cooling demand, while the internally ventilated shading option outperformed the others in terms of annual energy consumption.Klimatförändringar kommer att påverka många mänskliga aktiviteter och sektorer. Bland dem kommer den byggda miljön att möta flera utmaningar med avseende på de olika klimatförhållandena. Denna studie undersökte effekterna av den globala uppvärmningen på energibehovet och inomhusklimatkomforten för en kontorsbyggnad i Stockholm. Med hänsyn till en livslängd på 50 år undersöktes de framtida klimatförhållandena för ökningen av lufttemperaturen utomhus till 2070, i enlighet med det medelprognoserade växthusgasutsläppsscenariot som tillhandahålls av International Panel on Climate Change (IPCC). En annan klimatförändringsmetod antogs för att utveckla klimatfilen för år 2080 med tanke på variationen i alla väderparametrar. Tre olika passiva kyllösningar, såsom utvändigt solskydd (vertikalmarkis med screenväv), elektrokromt glas och invändigt ventilerat solskydd, har implementerats i fallstudiebyggnaden för att minska kylbehovet. Karaktären av strategierna utvärderades preliminärt och implementerades sedan i programvaran för byggenergisimulering IDA-ICE för att utvärdera energiprestanda med avseende på de olika klimaten. Resultaten indikerade att en ökning av kylbehovet och en minskning av värmeanvändningen kommer att ske i framtiden. De olika klimatförändringsmetoderna visade de inneboende/medföljande osäkerheterna när framtida utvärderingar utförs, även om liknande vädermönster hittades. De passiva kyllösningarnas reducering av total solenergitransmission, såsom införandet av frånluftsutsug och den elektrokroma tekniken, innebar en lägre kyl- och ventilationsanvändning. EC-tekniken rapporterade det lägsta kylbehovet, medan det invändiga ventilerade solskyddet överträffade de andra när det gäller årlig energiförbrukning.
15
Sinha, Ashish. "An adsorption based cooling solution for electronics used in thermally harsh environments." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37077.
Full textAbstract:
Growing need for application of electronics at temperatures beyond their rated limit, (usually > 150 °C) and the non availability of high temperature compatible electronics necessitates thermal management solutions that should be compact, scalable, reliable and be able to work in environments characterized by high temperature (150 -250 °C), mechanical shock and vibrations. In this backdrop the proposed research aims at realization of an adsorption cooling system for evaporator temperatures in the range of 140 °C-150 °C, and condenser temperature in the range of 160 °C-200 °C. Adsorption cooling systems have few moving parts (hence less maintenance issues), and the use of Thermo-Electric (TE) devices to regenerate heat of adsorption in between adsorbent beds enhances the compactness and efficiency of the overall 'ThermoElectric-Adsorption' (TEA) system. The work presented identifies the challenges involved and respective solutions for high temperature application. An experimental set up was fabricated to demonstrate system operation and mathematical models developed to benchmark experimental results. Also, it should be noted that TEA system comprises TE and adsorption chillers. A TE device can be a compact cooler in its own right. Hence a comparison of the performance of TEA and TE cooling systems has also been presented.
16
Wilson, Scott E. "Investigation of Copper Foam Coldplates as a High Heat Flux Electronics Cooling Solution." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6944.
Full textAbstract:
Compact heat exchangers such as porous foam coldplates have great potential as a high heat flux cooling solution for electronics due to their large surface area to volume ratio and tortuous coolant path. The focus of this work was the development of unit cell modeling techniques for predicting the performance of coldplates with porous foam in the coolant path.
Multiple computational fluid dynamics (CFD) models which predict porous foam coldplate pressure drop and heat transfer performance were constructed and compared to gain insight into how to best translate the foam microstructure into unit cell model geometry. Unit cell modeling in this study was realized by applying periodic boundary conditions to the coolant entrance and exit faces of a representative unit cell. A parametric study was also undertaken which evaluated dissimilar geometry translation recommendations from the literature. The use of an effective thermal conductivity for a representative orthogonal lattice of rectangular ligaments was compared to a porosity-matching technique of a similar lattice. Model accuracy was evaluated using experimental test data collected from a porous copper foam coldplate using deionized water as coolant. The compact heat exchanger testing facility which was designed and constructed for this investigation was shown to be capable of performing tests with coolant flow rates up to 300 mL/min and heat fluxes up to 290 W/cm2. The greatest technical challenge of the testing facility design proved to be the method of applying the heat flux across a 1 cm2 contact area. Based on the computational modeling results and experimental test data, porous foam modeling recommendations and porous foam coldplate design suggestions were generated.
17
Tseitlin, Musii, and Valentina Raiko. "Ratio between heat and mass transfer when concentrating the solution in a cooling tower." Thesis, Lviv Polytechnic National University, 2019. http://repository.kpi.kharkov.ua/handle/KhPI-Press/42106.
Full textAbstract:
The ratio between the intensity of the mass transfer in gas and the heat transfer in liquid during the evaporative solution concentration has been studied. It was determined that the share of liquid resistance in the total resistance to enthalpy transfer increases in the temperature range from 30 to 50°C by almost 2 times, and reaches 40 %. The technique has been developed for the separate determination of the mass transfer coefficients in gas and heat transfer in liquid.Досліджено співвідношення між інтенсивністю масопереносу в газі та передачею тепла в рідині під час концентрації випарного розчину. Встановлено, що частка опору рідини в загальному опорі переносу ентальпії зростає в діапазоні температур від 30 до 50 ° С майже в 2 рази, досягає 40%. Розроблена методика для окремого визначення коефіцієнтів масопереносу в газі і теплопередачі в рідині.
18
Al-Marri, Mohd Jaber F. A. "Modelling the solution crystallisation of L-gluatmic acid as prepared via reactive and cooling crystallisation." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545682.
Full text
19
Yalcin, Fidan Seza. "Cfd Analysis Of A Notebook Computer Thermal Management Solution." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609483/index.pdf.
Full textAbstract:
In this study, the thermal management system of a notebook computer is investigated by using a commercial finite volume Computational Fluid Dynamics (CFD) software. After taking the computer apart, all dimensions are measured and all major components are modeled as accurately as possible. Heat dissipation values and necessary characteristics of the components are obtained from the manufacturer's specifications. The different heat dissipation paths that are utilized in the design are investigated. Two active fans and aluminum heat dissipation plates as well as the heat pipe system are modeled according to their specifications. The first and second order discretization schemes as well as two different mesh densities are investigated as modeling choices. Under different operating powers, adequacy of the existing thermal management system is observed. Average and maximum temperatures of the internal components are reported in the form of tables. Thermal resistance networks for five different operating conditions are obtained from the analysis of the CFD simulation results. Temperature distributions on the top surface of the chassis where the keyboard and touchpad are located are investigated considering the user comfort.
20
Strömqvist, Bodil. "Fjärrvärmedriven Absorptionskyla : En ekonomisk undersökning av olika spetslösningar." Thesis, Mittuniversitetet, Institutionen för elektronikkonstruktion, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-42412.
Full textAbstract:
This independent degree project has been implemented on behalf of FVB Sverige AB in collaboration Sundsvall Energi AB with the initial purpose of mapping manufacturers of hot water driven absorption chillers. After that, several technical solutions are examined to manage the peak load of a theoretical object which cannot produce the cooling power required with only an absorptions chiller, due to limitations in the district heating supply. The market study has shown that the supply of absorption chillers with drive temperatures of 70–90˚C is limited to a few manufacturers. World Energy offers a unit with drive temperatures of 70 ˚C and efficiency (COP) of 0,4. Due to limitations of district heating flow, a unit with drive temperature of 85 ˚C and efficiency of 0,77 is chosen. The technical solutions are dimensioned for a building with a peak power of 264 kilowatt, where the required peak load ranges from 31 to 39 kilowatt. The technical solutions examined are a solar collector system, tap water heat exchanger, and a conventional compressor driven chiller. The solar collectors are dependent on location but use no refrigerants that are affected by the F-gas regulation. The tap water solution consumes large flows of tap water, but the installation is simple. The conventional chiller is not location dependent but uses ozone degrading refrigerants and has a high cost of operation. From an economic perspective the technical solutions are equally profitable with a present net value of approximately 500 000 SEK and pay-back of 13 years. The examination has also shown that the present value is one million crowns in sales of heat and building after a ten-year period. In conclusion the conventional chiller has the biggest prerequisites to be used as a standardised solution for buildings with a bigger cooling load. Based on the technical and economical conditions.
21
Castillo, Garcia Lorenzo. "Développement d’un outil de simulation dynamique pour la conception d’une solution de climatisation solaire réversible." Thesis, Pau, 2016. http://www.theses.fr/2016PAUU3003/document.
Full textAbstract:
Cette thèse s’inscrit dans le cadre du projet SCRIB (“dispositif Solaire de Climatisation Réversible Intégré au Bâti”) porté par la société Helioclim. Ce projet est financé par l’état français dans le cadre des « Investissements d’avenir » pilotés par l’ADEME (Agence de l’Environnement et de la Maîtrise de l’Energie). Le but de ce projet est de développer une solution de climatisation solaire réversible capable de répondre à l’ensemble des besoins thermiques des bâtiments industriels et tertiaires (climatisation, chauffage, production de froid industriel, eau chaude sanitaire). Le système est constitué d’une machine à absorption réversible, alimentée par un système de capteurs solaires innovants. Le cycle de la machine à absorption est en configuration GAX (Generator-Absorber heat eXchange – échange de chaleur entre le générateur et l’absorbeur).Ce travail de thèse s’est intéressé au développement d’un outil logiciel aidant à la conception et au contrôle d’une telle machine. Un modèle de connaissance prenant en compte les paramètres de fonctionnement et de dimensionnement a été ainsi mis en œuvre. L’originalité de ce travail repose sur les points suivants :- L’outil logiciel propose plusieurs modules qui permettent de simuler différentes configurations de machine à absorption (mono ou multi-étagée).- Les propriétés thermodynamiques des mélanges ont été modélisées à l’aide de modèles basés sur l’utilisation d’une équation d’état ou d’un modèle d’enthalpie libre d’excès. Ainsi, le couple fluide pourra être facilement changé.- Un modèle de « Flash Positif » permet de prédire l’état de chaque courant (liquide sous-refroidi, liquide-vapeur ou vapeur surchauffée) sans poser d’hypothèses a priori. Chaque courant est considéré multiconstituant.- Les bilans matière et d’énergie sont écrits pour les différents appareils (évaporateur, absorbeur, détenteur,…).- Le générateur est modélisé par un empilement d’étages théoriques. Les équations MESH (Mass balance, Equilibrium, Summation, Heat balance) ont été écrites pour chaque étage.- Les inerties thermiques et de matière sont prises en compte.Les résultats de simulation obtenus à l’aide de cet outil logiciel ont été comparés avec succès à une étude publiée qui concernait un cycle GAX fonctionnant avec le couple ammoniac/eau. A l’aide de cet outil, le régime permanent et le comportement dynamique du système soumis à une perturbation peuvent être simulés, ce qui peut constituer une aide importante dans le développement de la politique de contrôle du systèmeThis PhD thesis was carried on in the framework of the SCRIB project (“dispositif Solaire de Climatisation Réversible Intégré au Bâti”) led by the Helioclim company. This project is funded by the French government (“Investissements d’Avenir” operated by the French Agency for Energy and Environment, ADEME). The goal of this project is to develop a reversible solar cooling system which can respond to a set of thermal requirements in industrial and tertiary building sector (cooling system, heating system, industrial cooling system and domestic hot water). Thus an ammonia/water absorption chiller prototype, powered by innovative thermal solar concentrators, has been built. This absorption chiller has a GAX (Generator-Absorber heat eXchange) configuration.This PhD work focused on the development of a support tool for the conception and the control of such device. A software tool has been developed implementing knowledge-based model, which took into account the operating and design parameters of the absorption chiller. The key originalities of the proposed work are as follows:- The software has been designed in a modular way allowing the simulation of various absorption chiller configurations (single or multi-stage).- The thermodynamic properties of the mixture have been modeled by equation of state or excess Gibb’s energy model. The working fluids can then be changed easily.- A “Positive Flash” model allows the description of all the possible states (sub-cooled, super-heated, biphasic…) of the various streams which are all considered as multicomponent mixtures, without a priori assumptions.- The various devices (evaporator, absorber, valves, etc.) are modeled from balance equations (mass, energy). - The generator is modeled using the concept of theoretical plates. MESH equations (Mass balance, Equilibrium, Summation, Heat balance) have been written for each stage.- Both thermal and material inertia are considered.Simulation results obtained with this software have been successfully compared to an earlier published experimental study for a GAX configuration absorption chiller which used ammonia/water as working fluids. Thanks to this tool, the steady state and the transient behavior of the system submitted to a perturbation can be simulated, which can be helpful for the development of the control policy of the absorption chiller
22
He, Bo. "High-Capacity Cool Thermal Energy Storage for Peak Shaving - a Solution for Energy Challenges in the 21st century." Doctoral thesis, KTH, Chemical Engineering and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3781.
Full textAbstract:
Due to climatic change, increasing thermal loads inbuildings and rising living standards, comfort cooling inbuildings is becoming increasingly important and the demand forcomfort cooling is expanding very quickly around the world. Theincreased cooling demand results in a peak in electrical powerdemand during the hottest summer hours. This peak presents newchallenges and uncertainties to electricity utilities and theircustomers.
Cool thermal storage systems have not only the potential tobecome one of the primary solutions to the electrical powerimbalance between production and demand, but also shift coolingenergy use to off-peak periods and avoid peak demand charges.It increases the possibilities of utilizing renewable energysources and waste heat for cooling generation. In addition, acool storage can actually increase the efficiency of combinedheat and power (CHP) generation provided that heat drivencooling is coupled to CHP. Then, the cool storage may avoidpeaks in the heat demand for cooling generation, and this meansthat the CHP can operate at design conditions in most oftime.
Phase Change Materials (PCMs) used for cool storage hasobtained considerable attention, since they can be designed tomelt and freeze at a selected temperature and have shown apromising ability to reduce the size of storage systemscompared with a sensible heat storage system because they usethe latent heat of the storage medium for thermal energystorage.
The goal of this thesis is to define suitable PCM candidatesfor comfort cooling storage. The thesis work combines differentmethods to determine the thermophysical properties oftetradecane, hexadecane and their binary mixtures, anddemonstrates the potential of using these materials as PCM forcomfort cooling storage. The phase equilibrium of the binarysystem has been studied theoretically as well asexperimentally, resulting in the derivation of the phasediagram. With knowledge of the liquid-solid phase equilibriumcharacteristics and the phase diagram, an improvedunderstanding is provided for the interrelationships involvedin the phase change of the studied materials. It has beenindicated that except for the minimum-melting point mixture,all mixtures melt and freeze within a temperature range and notat a constant temperature, which is so far often assumed in PCMstorage design. In addition, the enthalpy change during thephase transition (heat of fusion) corresponds to the phasechange temperature range; thus, the storage density obtaineddepends on how large a part of the phase change temperaturerange is valid for a given application.
Differential Scanning Calorimetery (DSC) is one frequentlyused method in the development of PCMs. In this thesis, it hasbeen found that varying results are obtained depending on theDSC settings throughout the measurements. When the DSC runs ata high heating/cooling rate it will lead to erroneousinformation. Also, the correct phase transition temperaturerange cannot be obtained simply from DSC measurement. Combiningphase equilibrium considerations with DSC measurements gives areliable design method that incorporates both the heat offusion and the phase change temperature range.
The potential of PCM storage for peak shaving in differentcooling systems has been demonstrated. A Computer model hasbeen developed for rapid phase equilibrium calculation. The useof phase equilibrium data in the design of a cool storagesystem is presented as a general methodology.
Keywords:Comfort cooling, peak shaving, PCM, coolthermal storage system, DSC, phase change temperature range,the heat of fusion, phase equilibrium, phase diagram. Language:English
23
Wang, Shan. "Further study of the “GreenRoom” concept – an approach to sustainable datacenter cooling solution : Identification of improvement possibilities using Life Cycle Assessment (LCA) and discussion about the effect of the choice of Life Cycle Impact Assessment (LCIA) methods on the results." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-116474.
Full textAbstract:
The growing industry of Information and Communication Technology requires higher computing capacity of data centers/technical sites. The air conditioning in data centers is the key to assure a sustainable computing environment. However, the traditional cooling systems cost are responsible for large environmental footprints especially on energy consumption and greenhouse gas emissions. As a result, a green innovation of data center cooling solutions is taking place. The telecommunication company Teliasonera is developing a high density data center cooling system - the “Green Room” and has been studying the environmental performance of this system using a Life Cycle approach. As an extension of the previous study, more aspects of the project i.e. the location, life span, alternative cooling solutions, energy recovery possibilities and uncertainty analysis is explored by using Life Cycle Assessment (LCA) methodology. The comparison of the locations of the Green Room indicates that the local temperature and electricity production sources are essential factors for the environmental performance of the Green Room. The analysis of the Green Room’s life span reveals that the utilization phase may not always cause the most significant impact during the whole life cycle of the Green Room. If the life span changes, the manufacture phase may predominate the life cycle of the Green Room. The comparative result of alternative cooling technologies addresses that utilizing “natural coolant” (e.g. geo cooling) is a key for sustainable cooling innovation as it would significantly reduce the environmental footprint of the cooling system. Besides, heating a single building (partly) by the waste heat generated from the Green Room could save 30% of cumulative energy input and could reduce more than half of the total environmental impact. Additionally, results uncertainties caused by the choice of different LCIA methods are discussed in the end of the study.The Teliasonera Green Room Concept for high and mid density of ICT equipment
24
Accorinti, Flavio. "Two-Phase Power Electronics Cooling Solution Design in Air Context Answering to the Objectives of the Hybrid Aircraft 2035 High-efficiency cooling system for highly integrated power electronics for hybrid propulsion aircraft Systèmes diphasiques pour le contrôle ther- mique de l’électronique de puissance Steady-state analysis of a capillary pumped loop for terrestrial application with methanol and ethanol as working fluids Experimental and Numerical Analysis of Start-Up of a Capillary Pumped Loop for Terrestrial Applications." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0005.
Full textAbstract:
Le monde aérien est lui aussi destiné à réduire drastiquement son empreinte environnementale. Cela passe pour partie par l’innovation technologique et la réduction de l’énergie nécessaire à la propulsion. Dans cet objectif, les travaux relatés dans ce mémoire s’inscrivent dans un projet de recherche (Clean Sky 2-HASTECS) visant le développement de propulsion hybride mettant à profit les performances d’une chaîne électrique. Les puissances mises en jeu requièrent de revisiter les solutions de refroidissement pour atteindre les spécifications de puissance massique envisagées à l’horizon 2035. Nous nous intéressons ici à la gestion thermique de l’électronique de puissance qui vise une puissance massique de 25kW/kg à cet horizon.Le travail effectué, essentiellement numérique, est lié à la recherche, au dimensionnement, à l’optimisation, et à l’analyse d’une technologie de refroidissement efficace, caractérisée par une faible masse et capable de contrôler la température des composants électroniques dans les conditions opératoires les plus drastiques. Différentes technologies de refroidissement, actives mono et diphasiques et passives, à pompage capillaire, ont été analysées et comparées sur la base de données disponibles dans la littérature et d’un dimensionnement de première approximation : la solution la plus adaptée a été choisie en utilisant comme critère sa masse spécifique. La solution finalement retenue et présentant le meilleur indice de masse spécifique global est une boucle diphasique CPLIP (Capillary Pumped Loop for Integrated Power), par ailleurs pourvues des caractéristiques thermiques et hydrauliques uniques. Après son dimensionnement, la CPLIP a été optimisée pour répondre aux objectifs à deux horizons successifs, 2025 et 2035 (mentionnons un travail itératif avec les chercheurs responsables du développement de l’électronique permettant une optimisation mutuelle). L’attention a été en particulier concentrée sur le condenseur, le composant le plus lourd de la boucle. La solution 2025 est caractérisée par un condenseur classique air-méthanol, et a démontré sa capacité d’aller au-delà du seuil de 15 kW/kg demandé. La solution 2035, caractérisée par un concept de condenseur innovant : à micro-canaux et à ailettes à persiennes, a permis d’obtenir, après ce travail de co-dimensionnement thermique-électronique, des valeurs de puissance spécifique doubles par rapport à l’objectif 2035. Dans cette thèse, les caractéristiques hydrauliques et thermiques de la boucle CPLIP ont été analysées expérimentalement sur un prototype issu d’études antérieures, et numériquement à l’aide d’un modèle CFD ainsi qu’à l’aide d’un modèle 0D innovant. Les résultats démontrent l’aptitude de la CPLIP à gérer thermiquement l’électronique de puissance pour des cycles de mission d’un avion court ou moyen-courrier, caractérisés par des changements brutaux de puissance thermique, tout en assurant le contrôle de la température des modules électroniques.Enfin, une étude a été conduite portant sur le comportement transitoire de la boucle, en particulier lors des démarrages sévères à très hautes puissances, ainsi que pendant des cycles d’accélérations sévères qui caractérisent ce champ d’application. Dans le premier cas, une étude expérimentale et numérique a été menée pour démontrer la capacité de la boucle à démarrer dans les conditions thermiques et environnementales les plus difficiles (haute puissance de démarrage et haute température environnementale). Dans le deuxième cas, une étude numérique a été utilisée pour comprendre quel est le comportement de la boucle quand des champs d’accélérations, jusqu’à 10g, perturbent ses conditions opératoires. Ce travail ouvre des perspectives très intéressantes tant du point de vue de l’application que vis-à-vis de la nécessité aujourd’hui d’adopter des approches de recherche couplées pour dimensionner simultanément thermiquement et électriquement l’électronique de puissanceTechnological innovation and reduction of the energy required for propulsion is necessary to reduce aircrafts environmental impact. The present work is part of the research project Clean Sky 2 – HASTECS, which purpose is the development of a hybrid propulsion aircraft. The high powers involved make classical cooling solutions obsolete, in terms of efficiency, and not suitable for the power to mass ratio required for the target 2035. In particular, the problem related to power electronics cooling is assessed in this work with the purpose to achieve a performance coefficient of 25 kW/kg.This work, essentially numerical, is linked to the research, design, optimisation and analysis of a high efficiency cooling system, able to control power electronics components temperature, operating in pretty severe conditions (high thermal power density, >15kW; cyclic variation of cold source temperature and severe transient phases) and which has to be lightweight to ensure performance coefficient requirements. Different cooling technologies, active single and two-phase and passive capillary driven, have been analysed and compared on the basis of literature data and of a first approximation design: the most adapted solution has been chosen on the base of its specific power [kW/kg]. The solution that has been finally retained is a Capillary Pumped Loop for Integrated Power (CPLIP), which thermal characteristics are quite interesting and unique. After its design, the loop has been optimised to answer to objectives of 2025 and 2035. It is worth of attention the work carried out in collaboration with power electronics team of the same project to achieve a mutual optimisation of the systems. Concerning the thermal side, the attention was focused on the condenser, the heaviest component in the loop. The 2025’s solution is characterised by a classical flat plate air-methanol condenser which allowed to cross over the threshold of 15kW/kg for 2025. 2035’s solution, on the contrary, is characterised by an innovative condenser typology, using microchannels on methanol side and louvered fins on air side, allowing to obtain more than double of the power coefficient required! In this work, thermal and hydraulic characteristics of the CPLIP have been experimentally analysed, using a prototype deriving from previous studies, and by using CFD and a 0D model. Results show the ability of the CPLIP to control the temperature of power electronics modules during a short and medium-range aircraft mission profile, characterised by sudden changes of thermal load and cyclic variations of the cold source temperature.Finally, a study focused on the transient behaviour of the loop has been carried out. In particular, the start-up of the CPLIP and its behaviour during sudden and violent acceleration stages, characterising this application filed, have been exploited. In the first case, an experimental and a numerical study were carried out to demonstrate the ability of the loop to starts its operation in the most difficult thermal and environmental conditions (high thermal load and high environmental temperature). In the second case, a numerical study has been performed to understand the behaviour of the loop when an acceleration field up to 10g perturbs its operations.This work opens new interesting perspectives stand points concerning the application itself and the necessity to adopt a multidisciplinary approach to simultaneously thermally and electronically design new generation power electronics
25
Štaffa, Jan. "Jednofázový pulzní měnič DC/AC s digitálním řízením." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217881.
Full textAbstract:
This work is focused on single phase inverters, which are used for the conversion of the direct current to the alternating current and are nowdays used especially in systems of back-up power supply. The specific aim of this work is implementation of design hight power circuit of inverter include calculation of control algorithm. It describes the complete solution of power circuit. Next step is a analysis of problems concerning the digital control with help of signal processor which is used for solution of regulator structure. Check of the design and checkout of control algorithm is made in the form of simulation in the MATLAB Simulink. Debugged program algorithm is subsequently implemented into the signal microprocessor. The work results rate estimation functionality of inverter and solution of control algorithm.
26
Schmid, Gerd, and 施高德. "Numerical and Experimental Analysis of Passive and Active Cooling Solutions for High-Power LED Light Sources." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/08213870682751115734.
Full textAbstract:
博士國立臺灣大學
機械工程學研究所
104
Effcient thermal management is one of the most important design considerations for LED applications. This thesis presents a systematic approach to the analysis, optimization, and comparison of two thermal solutions to support high-power LED street and flood lights. Both systems, one passive and one active design, were first experimentally investigated and then numerically improved by performing large-scale parametric studies. The passive solution consists of an oversized, free-hanging rectangular heat sink with straight fins, cooled by natural convection. The main aim was to study how the inter-fin base length influences the thermal performance. A total of 55 cases were examined experimentally, and the data were used to validate the numerical model. The results show that a shorter inter-fin base length can significantly enhance thermal performance, especially when the fins are along the longer base side. For the present case, the heat transfer coefficient was increased by up to 62.7%, and the thermal resistance was reduced by 36.7% to 0.29 K/W. It was further shown that the inter-fin base length greatly influences the optimal fin spacing. In addition, Nusselt correlations including a dimensionless geometrical parameter for the inter-fin base length, which are valid for a wide range of dimensions, were developed. The active cooling system is especially designed for high-power LED street lights. It is driven by a centrifugal fan placed inside a chamber at the lower part of the lamp post. The fan is connected to the lamp head via an internal pipe to form a closed-loop forced air cooling system, where the lamp post is used for heat dissipation. The experiments were conducted using a full-scale model with an overall height of 5 m. The design includes two different heat exchangers, which were separately modeled and analyzed. The first is a vertical double pipe single-flow heat exchanger integrated into the lamp post. A 2D-axisymmetric CFD simulation with Rayleigh numbers of over 10e10 was used to investigate the heat transfer characteristics of the lamp post for various flow conditions. The second is a horizontal counter-flow heat sink inside the lamp head, which was simulated as a 3D-model using ANSYS Icepak. The effect of geometric parameters and boundary conditions, such as the inlet position, fin thickness, and fin density, were analyzed in order to optimize the thermal performance of the cooling system. It was shown that the counter-flow heat sink with a higher fin density in the middle section can reduce thermal resistance. A direct thermal comparison of both cooling systems using a 150 W COB LED revealed that the passive system can keep the excess temperature of the LED close to 40∘C at an ambient temperature of 30∘C. Under the same conditions, the active cooling system can further lower the LED temperature by 8 to 13∘C. Based on an economical comparison of both cooling systems over a period of 24 years, it was concluded that, in its present configuration, the additional costs and increased complexity of the active system outweigh the performance improvements.
27
ZHENG, BO-JUN, and 鄭伯俊. "Solution of 3-D cooling problem in injection molding by finite element method." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/35005641466483095338.
Full text
28
Lian, Gou-Jaan, and 連國展. "The flow design and thermal solution of the liquid cooling system with swirl flow." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/80046900554878839808.
Full textAbstract:
碩士東南科技大學
機電整合研究所
98
This study investigates the flow field design and the thermal solution of the high power heating element by the vortex liquid cooling system. Heat was impacted directly by water liquid to go through the swirl fin of the cooling system and dissipated. The geometry parameter λ of the swirl fin is 0.00151 , 0.00436 , 0.00740 respectively, and the Reynolds number Re is the1.38 ×106, 1.85 ×106, 2.31 ×106, 2.77 ×106 respectively in the experiments of the heat flux in the range of 5.380 ~ 7.174 W/cm2. By the control parameters of different volume flow and height lift, the experiments show the best cooling effect at geometry parameter λ = 0.00151 under the condition of the same volume flow and at geometry parameter λ = 0.00436 under the condition of the same height lift. This investigation also uses the I-DEAS software to analysis the flow and thermal fields of the vortex liquid cooling system. The results compared with the practical experimental are not so significant.
29
Chen, Yen-lin, and 陳彥霖. "Effect of cooling rate of solution treatment on microstructure and mechanical properties of SP-700." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/58386312108010814686.
Full textAbstract:
碩士國立中央大學
材料科學與工程研究所
100
According to this research, the microstructure of solution treatment by WQ alloy of SP-700 is constructed by αp(primary α）+ α”(martensite) + βr(retained β). Stress induced martensite transformation happened during tensile process, which makes strength superior due to βr transformed into α”. WQ alloy has high strength and ductility in the meanwhile. In addition, α” and βr is going to precipitate α+β stable phase by aging treatment. Aging makes WQ alloy became much stronger but poor ductility. The microstructure of AC and FC alloys are both formed by αp+α(precipitation)+β(stable), and have better strength than WQ alloy, but there is no phase transformation during aging treatment. From the above, solution treatment and aging of WQ alloy of SP-700, which has the best strength. Good tensile properties prefer WQ alloy without aging.
30
Chen, Xin-Yu, and 陳欣榆. "Applying Heat Pump in Plant Factory for the Cooling of Nutrient Solution and Indoor Air." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/36216942653196960134.
Full textAbstract:
碩士國立臺灣大學
生物產業機電工程學研究所
99
Facing the global problems such as global warming, exploded population, reduction in cultivated land, food shortage, fresh water and energy crisis and food safety, plant factory is considered one of the promising methods to solve the problems, thus catching lots of attention recently. However, grow plants indoor takes lots of energy to provide light needed by the crop and to maintain proper temperature and humidity. The cost on artificial light plus the cost on air conditioning system is the major operating cost, thus reducing these light-heat related cost is the major task for the related research and successful business. This study aims at reducing air conditioning cost by applying heat pump system. The goal is to find a balance between reducing air temperature and nutrient temperature. Traditionally, only air temperature was controlled. This study tried to control the nutrient temperature and let the air temperature several degree higher and to compare the energy consumption throughout the entire growth period. Two types of heat pump cooling system were used. A-W type used a plate type exchanger to exchange energy between water in tank and refrigerant in evaporator. A-R type put the evaporator in water tank directly. No matter which type was used, the COP of the system is the major concern, if the COP is less than the commercially available Air conditioning system, there is making no sense to use it. In our experiment, the COP of A-W is much higher than A-R type. This study successfully set up a heat pump cooling system suitable or air cooling and nutrient solution cooling at the same time. A cooling system for multi-layer bench was established. The system consists of water cooled heat exchanger for each layer, fans attached to the heat-exchangers, submersible pump, nutrient tank and tap water tank which cooled with heat pump cooling system, and can be used to keep temperatures of the air within each layer and temperature of nutrient for the whole bench in different level, thus making it a flexible system for research.
31
Nieh, Jo-Kuang, and 聶若光. "Effect of cooling rate, plastic deformation and solution temperature on microstructure and mechanical properties of SP-700 titanium alloys." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/329qe2.
Full textAbstract:
博士國立中央大學
機械工程學系
104
The relationship between the microstructures and the mechanical properties of solution-treated SP-700 titanium alloys, as obtained with different cooling rates, was investigated. The results indicate that the water-quenched alloy contains the primary α (αp), α”-martensite and residual β (βr) phases. Aging heat treatment can convert both α”-martensite and the βr phases to the fine-grained α + β equilibrium phases, resulting in a significant increase in tensile strength and hardness. Both the air-cooled and furnace-cooled alloys consist of the αp, α and β phases. The air-cooled alloy containing the fine-grained α phase has relatively higher hardness. Aging heat treatment causes only a slight enhancement in tensile properties because it cannot convert the phases in both alloys. Stress-induced martensitic phase transformation occurs in the water-quenched alloy under applied stress, after which the alloy exhibits higher tensile strength, higher ductility, and lower yield strength. This study investigates the effects of cold working prior to aging on the microstructure and mechanical properties of SP-700 titanium alloy. The results indicate that the microstructure of the quenched alloy comprises blocky primary α, retained β, and acicular α” martensite distributed in the β matrix. The retained β is transformed to denser and finer brittle acicular martensite α” by stress-induced martensitic transformation and the quantity of retained β decreases with higher degrees of cold working. The quenched alloy exhibits not only low yield strength, but the stress-induced martensite leads to a distinct increase in strength with good ductility. Plastic deformation prior to the aging treatment produces a great increase in the yield strength due to refinement of the precipitate microstructure, leading to the ratio of strength increment and ductility being very low.
32
Chiou, Mau-Sheng, and 邱茂盛. "Study of Aluminum Element and Solution Heat Treatment Cooling Rate on High-Temperature Creep and Oxidation Behavior of Directionally Solidified CM-247LC Ni-based Superalloy." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/a79zc6.
Full textAbstract:
博士義守大學
材料科學與工程學系
103
In this study, CM-247LC nickel-based superalloy was selected as a base material for alloy design, by revising heat treatment process and changing element content, to explore the effects of high temperature creep behavior and high temperature oxidation properties. The results showed that adding 1 wt.% Al element in CM-247LC nickel-based superalloy could promote gamma prime phase precipitation, improve volume fraction, enhance its high temperature creep properties, increase the Al activity, stimulate Al2O3 oxide layer at high temperatures, and advance oxidation resistance. When cooling rate after solution treatment is slower, gamma prime phase becomes thicker; consequently the high temperature creep properties are reduced. In the high temperature and ultra-high temperature creep testing, gamma prime phase was transformed into rafting structure to resist dislocation movement, but diffusion behavior is the main mechanism in the ultra-high temperature. Rafting structure was not produced in intermediate temperature; however the main deformation mechanism is dislocation movement.
33
Chang, Chin-Wei, and 張晉瑋. "Using thermochromic liquid crystal slurries to investigate the effect of a slanted cooling wall on the development of double-diffusive convection during the solidification of a liquid super-eutectic binary solution." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/6rh494.
Full textAbstract:
碩士國立臺北科技大學
能源與冷凍空調工程系碩士班
100
Solidification of liquid binary alloys is found in various industrial applications, such as marine science, silicon crystal growth process, the ice storage system in HVAC, the food processing and cold storage in food industry, the metal alloys casting and low-temperature biotechnology applications. The natural convection phenomenon, also known as double-diffusive convection, which occurs during the solidification process owing to the effects of temperature and concentration gradients, is likely to cause poor quality of alloy castings. The factors contributing to the formation of double-diffusive convection and the means to eliminate or weaken such phenomenon have been the focus of research in the past. This study focused on the effect of slanted lateral cooling wall with negative slope on the formation of double-diffusive convection during the solidification of a 25 wt. % hyper-eutectic binary solution (NH4CL-H2O). Particle Image Velocimetry (PIV) techniques, thermochromic liquid crystal (TLC) and Schlieren method were employed to observe the flow development of the binary solution in the liquid. The experimental results showed that the water-rich fluid was continuously released through the mushy layer during solidification, resulting in the formation of a red color layer on the thermochromic liquid crystal. The image processing software was used for temperature field visualization. The experimental results also indicated that the lateral cooling wall with different slope has significant effects on the formation of double-diffusive convection during solidification. The growth process of double-diffusive convection varies apparently between the lateral cooling walls with higher slopes, such as in the case of 0 and 5 degrees compared to those with lower slopes, such as in the case of 10 and 15 degrees. As the slope of lateral cooling wall decreases, the filling-box process becomes faster and the time for the flow development to reach steady state becomes shorter.
34
CHANG, CHIA-HSING, and 張家馨. "(I)Synergistic Effect of Dynamic-cooling/Freeze-drying Process and Fullerene Bisadduct on the Morphology of Conjugated Polymer/PCBM Blends(II)Shear-induced Crystallization Process of pBCN/PCBM in o-xylene Solution." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/7d946x.
Full textAbstract:
碩士輔仁大學
化學系
107
P3HT/PCBM blend films have been used in the photoactive layer of polymer solar cells. In the blend film, bulk-heterojuction (BHJ) structure can enhance contact area between materials and facilitate the exciton dissociation. In addition, controlling molecular aggregation of conjugating polymer has been a critical issue for polymer solar cells. Higher crystalline of P3HT is benificial to absorption spectra and carrier mobility. Thermal annealing has been used to improve crystalline of P3HT in many references. However, thermal annealing results in phase separation due to poor compatibility. Here, the new processes are applied to improve crystalline of polymer prior to coating process and decrease probability of phase separation so that minimum/or no post-treatment .With respect to materials, in high PCE polymer solar cells, low band-gap conjugated copolymer has been widely used to enhance absorption spectra recently, however, they are not often crystallizable because of different monomers used in the polymer backbones. Therefore, this study will apply the new processes to conjugated copolymer (pBCN). Part one, synergistic effect of dynamic cooling/freeze drying process is applied to pBCN/PCBM blend to enhance aggregation of pBCN and decrease agglomeration of PCBM. The dynamic-cooling process allows pBCN molecules to aggregate in solution into a more organized structure during the cooling process; the freeze-drying process prevents severe agglomeration of PCBM during the solvent removing process. To improve stability of blend films, we add additive (bis-PCBM) to decrease agglomeration of PCBM after thermal annealing. Part two, a shear–induced-crystallization (SIC) process is applied to the polymer solution prior to coating process. Experimental results indicate that after applying SIC process to a crystallizable polymer, pBCN, aggregation of pBCN is enhanced than that from spin-coating process. Additionally, film absorption study shows that aggregation of pBCN does not affected by addition of PCBM, which makes the SIC process feasible for the fabrication of polymer solar cells.