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1
Zhao, Jiyun Ph D. Massachusetts Institute of Technology. "Stability analysis of supercritical water cooled reactors." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34651.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2005.Includes bibliographical references (p. 269-277).
The Supercritical Water-Cooled Reactor (SCWR) is a concept for an advanced reactor that will operate at high pressure (25MPa) and high temperature (500°C average core exit). The high coolant temperature as it leaves the reactor core gives the SCWR the potential for high thermal efficiency (45%). However, near the supercritical thermodynamic point, coolant density is very sensitive to temperature which raises concerns about instabilities in the supercritical water-cooled nuclear reactors. To ensure a proper design of SCWR without instability problems, the U.S. reference SCWR design was investigated. The objectives of this work are: (1) to develop a methodology for stability assessment of both thermal-hydraulic and nuclear-coupled stabilities under supercritical pressure conditions, (2) to compare the stability of the proposed SCWR to that of the BWR, and (3) to develop guidance for SCWR designers to avoid instabilities with large margins. Two kinds of instabilities, namely Ledinegg-type flow excursion and Density Wave Oscillations (DWO), have been studied. The DWO analysis was conducted for three oscillation modes: Single channel thermal-hydraulic stability, Coupled-nuclear Out-of-Phase stability and Coupled-nuclear In-Phase stability.
(cont.) Although the supercritical water does not experience phase change, the thermodynamic properties exhibit boiling-like drastic changes around some pseudo-saturation temperature. A three-region model consisting of a heavy fluid region, a heavy-light fluid mixture region and a light fluid region has been used to simulate the supercritical coolant flowing through the core. New non-dimensional governing parameters, namely, the Expansion Number (Nexp) and the Pseudo-Subcooling Number (Npsub) have been identified. A stability map that defines the onset of DWO instabilities has been constructed in the Nexp-Npsu,b plane based on a frequency domain method. It has been found that the U.S. reference SCWR will be stable at full power operating condition with large margin once the proper inlet orifices are chosen. Although the SCWR operates in the supercritical pressure region at steady state, operation at subcritical pressure will occur during a sliding pressure startup process. At subcritical pressure, the stability maps have been developed based on the traditional Subcooling Number and Phase Change Number (also called as Zuber Number). The sensitivity of stability boundaries to different two phase flow models has been studied.
(cont.) It has been found that the Homogcnouls-Nonequilibrium model (HNEM) yields more conservative results at high subcooling numbers while the Homogenous Equilibrium (HEM) model is more conservative at low subcooling numbers. Based on the stability map, a stable sliding pressure startup procedure has been suggested for the U.S. reference SCWR design. To evaluate the stability performance of the U.S. reference SCWR design, comparisons with a typical BWR (Peach Bottom ) have been conducted. Models for BWR stability analysis (Single channel, Coupled-nuclear In-Phase and Out-of-Phase) have been constructed. It is found that, although the SCWR can be stable by proper inlet orificing, it is more sensitive to operating parameters. such as power and flow rate, than a typical BWR. To validate the models developed for both the SCWR and BWR stability analysis, the analytical results were compared with experimental data. The Peach Bottom 2 stability tests were chosen to evaluate the coupled-nuclear stability analysis model. It was found that the analytical model matched the experiment reasonably well for both the oscillation decay ratios and frequencies. Also, the analytical model predicts the same stability trends as the experiment results.
(cont.) Although there arc plenty of tests available for model evaluations at subcritical pressure, the tests at supercritical pressure are very limited. The only test publicly found was for the single channel stability mode. It was found that the three-region model predicts reasonable results compared with the limited test data.
by Jiyun Zhao.
Ph.D.
2
Ellis, Colleen Laverna, and Allan D. Kraus. "Preliminary design of a water cooled avionics rack." Thesis, Monterey, California: Naval Postgraduate School, 1993. http://hdl.handle.net/10945/24217.
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Johnson, Kyle D. "High Performance Fuels for Water-Cooled Reactor Systems." Doctoral thesis, KTH, Reaktorfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-201604.
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Investigation of nitride fuels and their properties has, for decades, been propelled on the basis of their desirable high metal densities and high thermal conductivities, both of which oer intrinsic advantages to performance, economy, and safety in fast and light water reactor systems. In this time several key obstacles have been identied as impeding the implementation of these fuels for commercial applications; namely chemical interactions with air and steam, the noted diculty in sintering of the material, and the high costs associated with the enrichment of 15N. The combination of these limitations, historically, led to the well founded conclusion that the most appropriate use of nitride fuels was in the fast reactor fuel cycle, where the cost burdens associated with them is substantially less. Indeed, it is within this context that the vast majority of work on nitrides has been and continues to be done. Nevertheless, following the 2011 Fukushima-Daiichi nuclear accident, a concerted governmental-industrial eort was embarked upon to explore the alternatives of so-called \accident tolerant" and \high performance" fuels. These fuels would, at the same time, improve the response of the fuel-clad system to severe accidents and improve the economy of operation for light water reactor systems. Among the various candidates proposed are uranium nitride, uranium silicide, and a third \uranium nitride-silicide" composite featuring a mixture of the former. In this thesis a method has been established for the synthesis, fabrication, and characterization of high purity uranium nitride, and uranium nitride-silicide composites, prepared by the spark plasma sintering (SPS) technique. A specic result has been to isolate the impact of the processing parameters on the microstructure of representative fuel pellets, essentially permitting any conceivable microstructure of interest to be fabricated. This has enabled the development of a highly reproducible technique for the production of pellets with microstructures tailored towards any desired porosity between 88-99.9%TD, any grain size between 6-24 μm, and, in the case of the uranium nitride-silicide composite, a silicide-coated UN matrix. This has permitted the evaluation of these microstructural characteristics on the performance of these materials, specically with respect to their role as accident tolerant fuels. This has generated results which have tightly coupled nitride performance with pellet microstructure, with important implications for the use of nitrides in water-cooled reactors.Under artionden har forskning om nitridbranseln och dess egenskaper bedrivits pa grundval av nitridbransletsatravarda egenskaper avseende dess hoga metall tathet och hog varmeledningsformaga. Dessa egenskaper besitter vasentliga fordelar avseende prestanda, ekonomi och sakerhet for metallkylda som lattvatten reaktorer. Genom forskning har aven centrala begr ansningar identierats for implementering av nitridbranslen for kommersiellt bruk. Begransningar avser den kemiska interaktionen med luft och vattenanga, en uppmarksammad svarighet att sintring av materialet samt hoga kostnader forknippade med den nodvandiga anrikningen av 15-N. Kombinationen av dessa begransningar resulterade, tidigare, i en valgrundad slutsats att nitridbranslet mest andamalsenliga anvandningsomrade var i karnbranslecykeln for snabba reaktorer. Detta da kostnaderna forenade med implementeringen av branslet ar avsevart lagre. Inom detta sammanhang har majoriteten av forskning avseende nitrider bedrivits och fortskrider an idag. Dock, efter karnkraftsolyckan i Fukushima-Daiichi 2011, inleddes en samlad industriell och statlig anstrangning for att undersoka alternativ till sa kallade \olyckstoleranta" och \hogpresterande" branslen. Dessa branslen skulle samtidigt forbattra reaktionstiden for bransleinkapsling systemet mot allvarliga olyckor samt forbattra driftsekonomin av lattvattenreaktorer. Foreslagna kandidater ar urannitrid, uransilicid och en tredje \uran nitrid-silicid", komposit bestaende av en blandning av de foregaende. Genom denna avhandling har en metod faststallts for syntes, tillverkning och karaktarisering av uran nitrid av hog renhet samt uran nitrid-silicid kompositer, forberedda med tekniken SPS (Spark Plasma Sintering). Ett specikt resultat har varit att isolera eekten av processparametrar pa mikrostrukturen pa representativa branslekutsar. Detta mojliggor, i princip, framstallningen av alla tankbara mikrostrukturer utav intresse for tillverkning. Vidare har detta mojliggjort utvecklingen av en hogeligen reproducerbar teknik for framstallningen av branslekutsar med mikrostrukturer skraddarsydda for onskad porositet mellan 88 och 99.9 % TD, och kornstorlek mellan 6 och 24 μm. Dartill har en metod for att belagga en matris av uran nitrid-silicid framarbetats. Detta har mojliggjort utvarderingen av dessa mikrostrukturella parametrars paverkan pa materialens prestanda, sarskilt avseende dess roll som olyckstoleranta branslen. Detta har genererat resultat som ar tatt sammanlankat nitridbranslets prestanda till kutsens mikrostruktur, med viktiga konsekvenser for den potentiella anvandningen av nitrider i lattvatten reaktorer.
QC 20170210
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Tan, Yuk Wei. "Development of a small-scale absorption cooled water chiller." Thesis, Nottingham Trent University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324572.
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Hwang, Jyh-Tzong. "Experimental evaluation of a passive water cooled containment concept." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/28127.
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Fly, Ashley. "Thermal and water management of evaporatively cooled fuel cell vehicles." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/19484.
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Proton Exchange Membrane Fuel Cells (PEMFCs) present a promising alternative to the conventional internal combustion engine for automotive applications because of zero harmful exhaust emissions, fast refuelling times and possibility to be powered by hydrogen generated through renewable energy. However, several issues need to be addressed before the widespread adoption of PEMFCs, one such problem is the removal of waste heat from the fuel cell electrochemical reaction at high ambient temperatures. Automotive scale fuel cells are most commonly liquid cooled, evaporative cooling is an alternative cooling method where liquid water is added directly into the fuel cell flow channels. The liquid water evaporates within the flow channel, both cooling and humidifying the cell. The evaporated water, along with some of the product water, is then condensed from the fuel cell exhaust, stored, and re-used in cooling the fuel cell. This work produces a system level model of an evaporatively cooled fuel cell vehicle suitable for the study of water balance and heat exchanger requirements across steady state operation and transient drive cycles. Modelling results demonstrate the ability of evaporatively cooled fuel cells to self regulate temperature within a narrow region (±2°C) across a wide operating range, provided humidity is maintained within the flow channels through sufficient liquid water addition. The heat exchanger requirements to maintain a self sufficient water supply are investigated, demonstrating that overall heat exchange area can be reduced up to 40% compared to a liquid cooled system due to the presence of phase change within the vehicle radiator improving heat transfer coefficients. For evaporative cooling to remain beneficial in terms of heat exchange area, over 90% of the condensed liquid water needs to be extracted from the exhaust stream. Experimental tests are conducted to investigate the condensation of water vapour from a saturated air stream in a compact plate heat exchanger with chevron flow enhancements. Thermocouples placed within the condensing flow allow the local heat transfer coefficient to be determined and an empirical correlation obtained. The corresponding correlation is used to produce a heat exchanger model and study the influence different heat exchanger layouts have on the overall required heat transfer area for an evaporatively cooled fuel cell vehicle. A one-dimensional, non-isothermal model is also developed to study the distribution of species, current density and temperature along the flow channel of an evaporatively cooled fuel cell using different methods of liquid water addition. Results show that good performance can be achieved with cathode inlet humidities as low as 20%, although some anode liquid water addition may be required at high current densities due to increased electro-osmotic drag. It is also demonstrated that both good membrane hydration and temperature regulation can be managed by uniform addition of liquid water across the cell to maintain a target exhaust relative humidity.
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Chan, Ping-lam. "Development of a simulation model for PWR reactor coolant system /." [Hong Kong] : University of Hong Kong, 1989. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1273617X.
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Fischer, Kai. "Design of a supercritical water cooled reactor pressure vessel and internals /." Karlsruhe : Forschungszentrum Karlsruhe, 2008. http://d-nb.info/991370759/34.
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Gelbart, W., R. R. Johnson, B. Abeysekera, L. Matei, and D. Niculae. "All-Metal water target with spherical window." Helmholtz-Zentrum Dresden - Rossendorf, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-165885.
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Introduction
The use of a prefabricated target window assembly greatly simplifies the window installation. The window module is sealed by metal knife-edges, thus eliminating any elestomers in the target construction.
Spherical Havar window offers high strength at reduced thickness and does not require helium cooling.
The target body is of platinum-plated silver.
The target assembly includes an integral beam collimator and a four-sector mask.
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Xiao, Ruiyang. "The freezing of highly sub-cooled H₂O/D₂O droplets." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1211567463.
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Mowrey, James A. "Control system modeling for a boiling water reactor." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/17083.
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Simon, M. J. "The thermal performance of water cooled panels in electric arc steelmaking furnaces." Thesis, Sheffield Hallam University, 1989. http://shura.shu.ac.uk/20363/.
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The initial stage of the work was a study of an 80 tonne industrial furnace, taking observations, panel water temperature data and samples of slag layers from the sidewalls. This resulted in a simple model of layer formation which explained the observed structures, and also the effect of slag layer thickness on heat losses was examined. However, the complexity and variety of structures found were such that a full series of direct thermal conductivity measurements was deemed impractical, and so a theoretical model to calculate the thermal conductivity of complex structures from the thermal conductivities of it s components was developed. Other aspects of heat transfer both within the furnace and from the furnace interior to the water cooling were also explored. In order to obtain a reliable value of thermal conductivity for the slag component of layer structures, a technique was developed to measure the thermal conductivity of the slag. This consisted of firstly determining a viable route for the production of homogenous samples, followed by the design, construction and refinement of an experimental measuring rig. After a large number of preliminary measurements, a series of thermal conductivity values at temperatures between 300 and 800 °C were measured using operating conditions calibrated against a heat storage brick sample of known thermal conductivity. These results were used to provide the data for the theoretical thermal conductivity model, which was then applied to real structures for which thermal data was available. Comparison of the results showed good correlation. Finally, in the appended case study, the heat loss calculation was applied for various furnace situations to identify the potential heat loss savings that could be achieved by controlling the slag layer thickness and structure, and the financial implications.
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Mtunzi, Busiso. "Design, implementation and evaluation of a directly water cooled photovoltaic- thermal system." Thesis, University of Fort Hare, 2013. http://hdl.handle.net/10353/d1016198.
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This research project was based on the Design, Implementation and Evaluation of a Photovoltaic Water heating system in South Africa, Eastern Cape Province. The purpose of the study was to design and investigate the scientific and economic contribution of direct water cooling on the photovoltaic module. The method involved performance comparison of two photovoltaic modules, one naturally cooled (M1) and the other, direct water cooled module (M2). Module M2 was used to produce warm water and electricity, hence, a hybrid system. The study focused on comparing the modules’ efficiency, power output and their performance. The temperatures attained by water through cooling the module were monitored as well as the electrical energy generated. A data logger and a low cost I/V characteristic system were used for data collection for a full year. The data were then used for performance analysis of the modules. The results of the study revealed that the directly water cooled module could operate at a higher electrical efficiency for 87% of the day and initially produced 3.63% more electrical energy each day. This was found to be true for the first three months after installation. In the remaining months to the end of the year M2 was found to have more losses as compared to M1 as evidenced by the modules’ performance ratios. The directly water cooled module also showed an energy saving efficiency of 61%. A solar utilization of 47.93% was found for M2 while 8.77% was found for M1. Economically, the project was found to be viable and the payback period of the directly cooled module (M2) system was found to be 9.8 years. Energy economics showed that the system was more sensitive to the price changes and to the energy output as compared to other inputs such as operation and maintenance and years of operation. A generation cost of R0.84/kWh from the system was found and when compared to the potential revenue of R1.18 per kWh, the system was found to enable households to make a profit of 40.5 %. Use of such a system was also found to be able to contribute 9.55% towards carbon emission reduction each year. From these results, it was concluded that a directly cooled photovoltaic/thermal heating (PV/T) system is possible and that it can be of much help in terms of warm water and electricity provision.
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Scholey, Kenneth Erwin. "Heat tranfser and crack formation in water-cooled zinc fuming furnace jackets." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30078.
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In the zinc slag fuming process, zinc is extracted from lead blast furnace slag by reduction with a coal/air mixture injected into the slag through submerged tuyeres. The furnace is constructed of water-cooled jackets to contain the molten bath and freeze a protective slag layer. The slag layer greatly reduces vessel wear caused by the corrosive and violently agitated bath. However, the jackets are known to develop cracks in the working face panel that initiate on the slag face and propagate towards the water cavity. If the cracks reach the water cavity explosions may result should the molten slag come into contact with the water.
In this study an analysis of heat transfer in the jacket has been carried out using in-plant measurements and mathematical modelling. The working face of a water jacket was instrumented with thermocouples and positioned in a fuming furnace at the Trail smelter of Cominco Ltd. Measurements revealed the presence of large thermal transients or temperature "spikes" in the panel approximately 20 cm above the tuyeres. The transients were observed during charging and tapping of the furnace and are likely associated with slag fall-off due to surface wave action and gas injection effects when the bath level is low. Temperatures at the mid-thickness were seen to rise by as much as 180 °C above the steady-state level. Under these conditions large compressive stresses are produced in the panel that are sufficient to cause yielding. Over time, the transients lead to low-cycle fatigue of the working face panel with crack formation initiating at pre-existing surface flaws.
A mathematical modelling analysis of the transient freezing phenomena has been carried out using the finite element method. The results indicate that the temperature spikes are associated with the sudden removal of patches of slag and molten slag
coming into direct contact with the jacket. The temperature spikes are large enough to generate compressive stresses that cause yielding of the material in the exposed area. In order to reduce the damage caused by the removal of the slag shell an increased number of anchoring studs should be used in critical areas and a higher water circulation velocity should be employed to increase the size of the frozen slag layer and its strength.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Fischer, Kai [Verfasser]. "Design of a supercritical water-cooled reactor : pressure vessel and internals / Kai Fischer." Karlsruhe : FZKA, 2008. http://d-nb.info/996911936/34.
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胡少堅 and Siu-kin Wu. "Corrosion and fouling in heat exchangers cooled by sea water from HongKong harbour." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1987. http://hub.hku.hk/bib/B31208010.
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Wang, Zhe Ph D. Massachusetts Institute of Technology. "Neutron scattering investigations on the liquid-liquid transition in deeply cooled confined water." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/103720.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 93-102).
Water is ubiquitous but mysterious. It exhibits anomalous thermodynamic behaviors at low temperatures. In addition, the glassy water, also called amorphous ice, exhibits polyamorphism. These phenomena could be understood if one accepts that a first-order low-density liquid (LDL) to high-density liquid (HDL) phase transition exists in the deeply cooled region (below 230 K) of water. However, the experimental test on the LDL and HDL in bulk water is practically difficult due to the crystallization below the homogeneous nucleation temperature (~232 K at atm). It is found that, by confining water in a hydrophilic nanoporous material, MCM-41, the homogeneous nucleation process can be avoided, which allows us to keep water in liquid state at least down to 130 K. Therefore, the confined water provides us an opportunity to detect the hypothetical HDL and LDL in the deeply cooled region of water. This thesis is devoted to the detection of the first-order LDL-to-HDL transition in the water confined in MCM-41. In this thesis, the phase behaviors of the deeply cooled water confined in MCM-41 are investigated. With elastic neutron scattering, we measure the average density of the confined water at low temperatures and high pressures. The results show the existence of a first-order LDL-to-HDL transition in such system. The phase separation starts from 1.12 0.17 kbar and 215 1 K and extends to higher pressures and lower temperatures in the phase diagram. This starting point could be the liquid-liquid critical point of the confined water. The locus of the Widom line in the phase diagram is also determined. Parallel to the density measurement, the dynamic properties, including the so-called "boson peak", the librational motion, and the relaxation process of the confined water, are also studied with dynamic neutron scattering. The time scales of these motions cover a broad range from 10-2 picosecond to hundreds of nanoseconds. The results confirm the phase diagram obtained with the density measurement and show that the HDL and LDL differ in the hydrogen-bond strength and the configuration of the local hydrogen-bond network. Combining all the experimental results, we provide a clear evidence for the existence of the LDL and HDL in the confined water. Water is crucial to protein dynamics. We investigate the role water plays in sub-picosecond collective vibration of protein with inelastic X-ray scattering and find that the hydration water makes the intraprotein longitudinal phonons "softer". We also study the slow dynamics of the protein hydration water with quasi-elastic neutron scattering. A hydration-dependent dynamic crossover phenomenon is found. The observation of the liquid-liquid transition in the confined water has potential to explain the mysterious behaviors of water at low temperatures. In addition, it may also have impact on other disciplines, because the confined water system represents many biological and geological systems where water resides in nanoscopic pores or in the vicinity of hydrophilic or hydrophobic surfaces.
by Zhe Wang.
Ph. D.
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Fischer, Kai [Verfasser]. "Design of a supercritical water cooled reactor : pressure vessel and internals / Kai Fischer." Karlsruhe : Forschungszentrum Karlsruhe, 2008. http://nbn-resolving.de/urn:nbn:de:0005-074298.
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Wu, Siu-kin. "Corrosion and fouling in heat exchangers cooled by sea water from Hong Kong harbour /." Hong Kong : University of Hong Kong, 1987. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12335472.
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陳炳林 and Ping-lam Chan. "Development of a simulation model for PWR reactor coolant system." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1989. http://hub.hku.hk/bib/B31209130.
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Arebi, Bashir H. "The formation and detachment of steam bubbles formed at submerged orifices in sub-cooled water." Thesis, University of Strathclyde, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287524.
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Zahlan, Hussam Ali Mustafa. "Derivation of a Look-Up Table for Trans-Critical Heat Transfer in Water-Cooled Tubes." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32433.
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This thesis describes the development and validation of a look-up table capable of predicting heat transfer to water flowing vertically upward in a circular tube in the trans-critical pressure range from 19 to 30 MPa. The table was based on an extensive and screened experimental database and its trends were smoothened to remove unrealistic scatter and physically implausible discontinuities. When compared to other prediction methods, the present look-up table approximated the experimental data closer in values and trends. Moreover, unlike existing prediction methods, the table applies not only to normal heat transfer conditions but also to conditions with heat transfer deterioration and enhancement. A separate multi-fluid look-up table for trans-critical heat transfer was also developed, which besides the existing water database incorporated new measurements in carbon dioxide; the latter were collected at the University of Ottawa supercritical flow loop under conditions of interest for the current Super-Critical Water-Cooled Reactor designs, for which few water data were available in the literature. Existing fluid-to-fluid scaling laws were tested and two additional sets of scaling laws were proposed, which are applicable not only to the supercritical pressure region, but also to the high pressure subcritical region. The multi-fluid table is applicable to water at conditions of normal and abnormal heat transfer, but its applicability to model fluids is restricted to the normal heat transfer mode.
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CARATIN, REINALDO L. "Estudo da imobilização de rejeitos radioativos em matrizes asfálticas e resíduos elastoméricos utilizando a técnica de microondas." reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11574.
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Made available in DSpace on 2014-10-09T12:53:25Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:09:32Z (GMT). No. of bitstreams: 1 12213.pdf: 5005382 bytes, checksum: c4bde457760b3a6d6f53b64c21e33010 (MD5)
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Charry, León Carlos Humberto. "Numerical simulation of water-cooled sample holders for high-heat flux testing of low-level irradiated materials." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53100.
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The promise of a vast source of energy to power the world and protect our planet using fusion technology has been the driving force for scientists and engineers around the globe for more than sixty years. Although the materialization of this ideal still in the distance, multiple scientific and technological advances have been accomplished, which have brought commercial fusion power closer to a reality than it has ever been. As part of the collaborative effort in the pursuit of realizable fusion energy, the International Thermonuclear Experimental Reactor (ITER) is being developed by a coalition of nations of which the United States is a part of. One critical technological challenge for ITER is the development of adequate plasma facing materials (PFMs) that can withstand the strenuous conditions of operation. To date, high heat flux (HHF) testing has been conducted mainly on non-irradiated specimens due to the difficulty of working with radioactive specimens, such as instrument contamination. In this thesis, the new Irradiated Material Target Station (IMTS) facility for fusion materials at Oak Ridge National Laboratory (ORNL), in which the HHFs are provided by water-wall plasma-arc lamps (PALs), is considered for neutron-irradiated specimens, especially tungsten. The facility is being used to test irradiated plasma-facing components materials for magnetic fusion reactors as part of the US-Japan plasma facing components evaluation by tritium plasma, heat and neutron irradiation experiments (PHENIX). In order to conduct HHF testing on the PFMs various sample holders designs were developed to accommodate radioactive specimens during HHF testing.
As part of the effort to design sample holders that are compatible with the IMTS facility, numerical simulations were performed for different water-cooled sample holder designs with the commercial computational fluid dynamics (CFD) software package, ANSYS™ FLUENT®. The numerical models are validated against experimental temperature measurements obtained from the IMTS facility. These experimentally validated numerical models are used to assess the thermal performance of two sample holder designs and establish safe limits for HHF testing under various operating conditions. The limiting parameter for the current configuration was determined for each sample holder design. For the Gen 1 sample holder, the maximum temperature reached within the Copper rod limits the allowable incident heat flux to about 6 MW/m². In the case of the Gen 2 sample holder, the maximum temperature reached within the Molybdenum clamping disk limits the allowable incident heat flux to about 5 MW/m².
In addition, the numerical model are used to parametrically investigate the effect of the operating pressure, mass flow rate, and incident heat flux on the local heat flux distributions and peak surface temperatures. Finally, a comparative analysis is conducted to evaluate the advantages and disadvantages associated with the main design modifications between the two sample holder models as to evaluate their impact in the overall thermal performance of each sample holder in order to provide conclusive recommendations for future sample holder designs.
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Khamis, Ibrahim Ahmad. "Simulation of nuclear power plant pressurizers with application to an inherently safe reactor." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184378.
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Pressurizer modeling for predicting the dynamic pressure of the PIUS system is presented. The transient behavior of this model for the PIUS system was investigated. The validity of this model for the PIUS system is limited to transients that are neither too large nor too long in duration. For example, the model is not capable of describing events following a complete loss of liquid for the pressurizer. However, the model can be used for qualitative prediction of the PIUS system behavior for a wide variety of severe transients. A review of pressurizer modeling indicates that the neglecting of the change in the internal energy of the subcooled water during transients is an acceptable assumption. The inherently safe feature of the PIUS system was confirmed through the self-shutdown of the reactor or, in some cases, through reactor power reduction as a result of the ingress of the pool boric acid solution into the primary system. This dynamic model was constructed of three major components: (1) The primary loop, (2) The secondary loop, and (3) The natural convection loop through the pool. A lumped parameter model, uniform heat transfer, and point kinetics have been the main approximations in this model. Other approximations are mentioned during the modeling of each component of the model. The dynamic model was simulated using the DARE-P continuous system simulation language which was developed in the Electrical Engineering Department at the University of Arizona.
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Khoza, Samukelisiwe Nozipho Purity. "Characteristic behaviour of pebble bed high temperature gas-cooled reactors during water ingress events / Samukelisiwe Nozipho Purity Khoza." Thesis, North-West University, 2012. http://hdl.handle.net/10394/8706.
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The effect of water ingress in two pebble bed high temperature gas-cooled reactors
i.e. the PBMR-200 MWthermal and the PBMR-400 MWthermal were simulated and
compared using the VSOP 99/05 suite of codes.
To investigate the effect of this event on reactivity, power profiles and thermal
neutron flux profiles, the addition of partial steam vapour pressures in stages up to
400 bar into the primary circuit for the PBMR-400 and up to 300 bar for the PBMR-
200 was simulated for both reactors. During the simulation, three scenarios were
simulated, i.e. water ingress into the core only, water ingress into the reflectors only
and water ingress into both the core and reflectors. The induced reactivity change
effects were compared for these reactors.
An in-depth analysis was also carried out to study the mechanisms that drive the
reactivity changes for each reactor caused by water ingress into the fuel core only,
the riser tubes in the reflectors only and ingress into both the fuel core and the riser
tubes in the reflectors.
The knowledge gained of these mechanisms and effects was used in order to
propose design changes aimed at mitigating the reactivity increases, caused by
realistic water ingress scenarios. Past results from simulations of water ingress into
Pebble Bed Reactors were used to validate and verify the present simulation
approach and results. The reactivity increase results for both reactors were in
agreement with the German HTR-Modul calculations.Thesis (MSc (Engineering Sciences in Nuclear Engineering))--North-West University, Potchefstroom Campus, 2013
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Alaktiwi, Abdulsalam A. "An experimental and theoretical examination of the operating characteristics of an air-cooled lithium bromide-water absorption refrigeration machine." Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394559.
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Chester, Noel Leslie. "A study of boiling heat transfer on a hot steel plate cooled by an inclined circular bottom water jet." Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/32109.
Full textAbstract:
Controlled cooling on the runout table is a crucial component in the production of
advanced high strength steels since there is a direct correlation between the cooling path
experienced by the steel and its final mechanical properties. Recent trends are towards
enhanced cooling of the steel so that complex dual phase microstructures can be obtained.
Cooling of the steel on the runout table is usually achieved via impinging water jets on both
the top and bottom of the strip, which can lead to significant heat transfer enhancement.
The purpose of this study is to develop a fundamental understanding of bottom jet
impingement cooling of hot steel plates. Specifically, this research has focused on the role
bottom jet nozzle inclination angle and water flow rate have on the effectiveness of heat
extraction on a hot steel plate. The methodology undertaken for this research involved
carrying out experiments using a pilot scale runout table with both stationary and moving
plates. Volumetric flow rates, strip speeds, and inclination angles were in the range of 35-
55 l/min, 0-1 m/s, and 10-30°, respectively.
Experimentally, each plate was instrumented with numerous sub-surface
thermocouples installed approximately 1 mm from the impingement surface. Temperature
measurements were taken at the impingement point and several streamwise distances from
the impingement point in all directions. Using the above measurements in conjunction with
an Inverse Heat Conduction (IHC) model allowed the calculation of boiling curves or heat
fluxes as a function of plate surface temperature and time. From the above measurements,
transient cooling data on the hot steel plate by bottom jet impingement has been analysed.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Chen, Yanhui. "Optimization of the Fin Configuration of Air-cooled Condensing Wet Electrostatic Precipitator for Water Recovery from Power Plant Flue Gas." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1384334785.
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Kahokola, K. V. "The effect of copper, arsenic and chromium on plants and the use of the water cooled atom trap as a preconcentration technique." Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384436.
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Blackburn, Brandon William. "Characterization of a high-current tandem accelerator and the associated development of a water-cooled beryllium target for the production of intense neutron beams." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/44487.
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Juráš, Filip. "Kondenzátor páry." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-319685.
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The Master´s thesis is dealing with water-cooled condensers and is splitted into three main parts. The first section provides general knowledge about condensers and heat exchangers, including the basic information of hydrophobic surfaces. These surfaces were used during verifying the impact of hydrophobicity on the heat exchange in water steam. The second section describes an experimental testing. It shows the difference between hydrophobic and nonhydrophobic surfaces and their impact on the heat exchange. The third and the last part of this thesis is design and calculation of water-cooled condenser. The design of the condenser is supported by drawings placed in attachement.
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Farhang, Mehr Farzaneh. "An investigation of the efficacy of a water-cooled chill in improving the as-cast structure of the main bearing bulkhead in A319 engine blocks." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63809.
Full textAbstract:
In recent years, the automotive industry has been increasing the production of small, high-power gas engines as part of several strategies to achieve the new “Corporate Average Fuel Economy” (CAFE) standards, while at the same time meeting consumer demand for increased performance. This trend requires an improvement in the thermal and mechanical fatigue durability of the aluminium alloys used in the production of the cylinder heads and engine blocks in these engines. In the absence of modifying alloy chemistry, which potentially has significant implications for downstream operations such as heat treating and machining, one viable way to improve fatigue performance is to reduce the length-scales of the microstructural features arising from solidification that limit fatigue life. This, in turn, may be achieved by increasing the cooling rate during solidification (reducing the solidification time). Conventionally, solid chills are employed in industry to achieve this. A potential means of improving the efficacy of these chills is to incorporate water cooling. To assess the effectiveness of this method, a water-cooled chill was designed at UBC and installed in a bonded-sand engine block mould package (1/4 section). Twelve experiments were conducted with both a conventional solid chill and with a water-cooled chill (with and without a delay in water cooling). The moulds were instrumented with thermocouples to measure the evolution of temperature at key locations in the casting, and “Linear Variable Displacement Transducers” (LVDTs) to measure the gap size at the interface between the chill and the casting. A coupled thermal-stress mathematical model was developed in “ABAQUS 2016” to reproduce the experimental conditions and provide insight into interfacial heat transport and gap dynamics. Overall, the experimental and modelling results show the gap dynamics are complex and play a critical role in governing heat transport. If implemented carefully, the adoption of water-cooled chill technology has the potential to improve the cast microstructure, hence, increase the fatigue durability of the engine blocks.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Mohr, Thomas Campion. "A study of the microstructural basis for the strength and toughness properties of water-quenched and air-cooled HSLA-100, HSLA-100 with increased copper, and a ULCB steel." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/26797.
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Krutil, Vojtěch. "Kryogenní cela pro studium vodního ledu v mikroskopu ESEM." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417097.
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The presented thesis focuses on designing a cryogenic cell for the study of water ice in an environmental scanning electron microscope (ESEM). This cell allows the study ice in the temperature range 80 K – 300 K in a nitrogen gas environment with a pressure of up to 400 Pa. The cell is cooled by a flow cooling system, where liquid or gaseous nitrogen is used as a refrigerant. The cell consists of a double-walled vessel with vacuum insulation, a flow-through heat exchanger, a sample well, and a cooled cell lid. The heat exchanger was designed to be able to dissipate the heat load at the level of 1 W. The exchanger is equipped with an electric resistance heater with an output of approximately 60 W, enabling heating of the sample at speeds of up to 100 K·min-1. The design also includes an LN2 gateway located on the door of the vacuum chamber of the microscope, to which the capillaries of the heat exchanger for the intake and outlet of refrigerant are connected. During the experimental verification of the cryogenic cell in the test vacuum chamber with a pressure of GN2 ~ 400 Pa, the limit temperature of 77.5 K on the sample well was reached.
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Olivier, J. A. (Jonathan Albert). "Single -phase heat transfer and pressure drop of water cooled at a constant wall temperature inside horizontal circular smooth and enhanced tubes with different inlet configuration in the transitional flow regime." Thesis, University of Pretoria, 2010. http://hdl.handle.net/2263/23327.
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It is common practice to design water chiller units and heat exchangers in such a way that they do not operate within the transition region. This is mainly due to the perceived chaotic behaviour as well as the paucity of information in this region. Due to design constraints or change of operating conditions, however, exchangers are often forced to operate in this region. This is even worse for enhanced tubes as much less information within this region is available. It is also well known that the entrance has an influence on where transition occurs, adding to the woes of available information. The purpose of this study is thus to obtain heat transfer and friction factor data in the transition region of fully developed and developing flows inside smooth and enhanced tubes, using water as the working fluid, and to develop correlations from these results. The use of different inlets, tube diameters and enhanced tubes was also investigated with regards to the commencement of transition. Heat transfer and pressure drop data were obtained from six different types of tubes with diameters of 15.88 mm (5/8′′) and 19.02 mm (3/4′′). Low fin enhanced tubes with a fin height to diameter ratio of 0.4 and helix angles of 18◦ and 27◦ were investigated. Heat transfer was obtained by means of an in-tube heat exchanger with the cooling of water being used as the test fluid. Reynolds numbers ranged between 1 000 and 20 000 while Prandtl numbers were in the order of 4 to 6. Uncertainties in heat transfer coefficient and friction factors were on average below 2.5% and 10% respectively. Adiabatic friction factor results showed that the use of different inlets influenced the commencement of transition. The smoother the inlet profile the more transition was delayed, confirming previous work done. The effect of increasing tube diameters had a slight delay in transition. Enhanced tubes caused transition to occur at lower Reynolds numbers which was accounted for by the fin height and not the helix angle. Heat transfer results showed that transition occurred at approximately the same Reynolds number for all the different inlets and enhanced tubes. This was attributed to the secondary flow forces influencing the growing hydrodynamic boundary layer. These secondary flow forces also influenced the laminar heat transfer and diabatic friction factors with both these parameters being higher. Turbulent enhanced tube heat transfer results were higher than those of the smooth tube, with the tube with the greatest helix angle showing the greatest increase. Correlations were developed for all the tubes and their inlets and predicted all the data on average to within 3%.Thesis (PhD)--University of Pretoria, 2010.
Mechanical and Aeronautical Engineering
unrestricted
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Karpiscak, Martin, and Mary H. Marion. "Evaporative Cooler Water Use." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 1994. http://hdl.handle.net/10150/146414.
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SANTOS, DIOGO F. dos. "Caracterização dos campos neutrônicos obtidos por meio de armadilhas de nêutrons a partir da utilização de água pesada (D2O) no interior do núcleo do reator nuclear IPEN/MB-01." reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23825.
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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Dvořák, Josef. "Zvýšení průtoku chladící vody pro absorpční chladící agregáty ve stanici zdroje chladu na JE Dukovany." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231828.
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The thesis focuses on comparison of the original and the new solutions of cooling water circuit of the York cooling units for the purpose of cooling water flow increase for the absorption units in the Dukovany Nuclear Power Plant. The individual parts of the cooling units that were changed and modified within a reconstruction are described here. The aim of the work is also to process and compare the original and the new solutions of the cooling units and the cold source station from the available measured data. The data are processed into illustrative graphs and tables. Based on the obtained data we can observe the changes achieved by the reconstruction that have affected the effectiveness of the cooling units.
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Alsaiari, Abdulmohsen Omar. "Augmentation of Jet Impingement Heat Transfer on a Grooved Surface Under Wet and Dry Conditions." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/98502.
Full textAbstract:
Array jet impingement cooling experiments were performed on flat and grooved surfaces with the surface at a constant temperature. For the flat surface, power and temperature measurements were performed to obtain convection coefficients under a wide range of operating conditions such as jet speed, orifice to surface stand-of distance, and open area percentage. Cooling performance (CP) was calculated as the ratio between heat transfer and fan power. An empirical model was developed to predict jet impingement heat transfer taking into account the entrainment effects. Experimental results showed that jet impingement can provide high transfer rates with lower rates of cooling cost in comparison to contemporary conventional techniques in the industry. CP values over 279 were measured which are significantly higher than the standard values of 70 to 95 in current technology. The model enhanced prediction accuracy by taking into account the entrainment effects; an effect that is rarely considered in the literature. Experiments on the grooved surfaces were performed at dry and wet surface conditions. Under dry conditions, results showed 10%~55% improvement in heat transfer when compared to the flat surface. Improvement percentage tends to be higher at wider gaps between the array of orifices and the grooved surface. An improvement of 30%~40% was observed when increasing Re either by increasing orifice diameter or jet speed. Similar improvement was observed at higher flow open area percentages. No significant improvement in heat transfer resulted from decreasing the size of the grooves from 3.56mm to 2.54mm. Similarly, no noticeable change in heat transfer resulted from changing the relative position of the jets striking the surface at the top of the grooves to the bottom of the grooves. Deeper grooves with twice the depth gave statistically similar average heat transfer coefficients as shallower grooves. Under wet conditions, a hybrid cooling technique approach was proposed by using air jets impinging on a grooved surface with the grooves containing water. The approached is proposed and evaluated experimentally for its feasibility as an alternative for cooling towers of thermoelectric power plants. Convection heat and mass transfer coefficients were measured experimentally using the heat mass transfer analogy. Results showed that hybrid jet impingement provided high magnitudes of heat flux at low jet speeds and flow rates. High coefficients of performance CP > 3000, and heat fluxes > 8,000W/m2 were observed. Hybrid jet impingement showed 500% improvement as compared to jet impingement on a dry flat surface. CP values of hybrid jet impingement is 600% to 1,500% more as compared to performance of air-cooled condensers and wet cooling towers. Water use for hybrid jet impingement cooling is efficient since evaporation energy is absorbed from the surface directly instead of cooling air to near wet-bulb temperature.PHD
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Hanna, Rani. "Étude d'une compression refroidie par injection d'huile dans un compresseur scroll : application au remplacement du R-410A dans les groupes refroidisseurs d'eau." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM035.
Full textAbstract:
Le problème du réchauffement climatique actuel conduit au renforcement des règlementations environnementales. Ainsi, le domaine du génie climatique est affecté par ces évolutions réglementaires, ce qui impose le passage à une nouvelle génération de réfrigérants à plus bas impact environnemental. Dans cette thèse, ce sujet est étudié dans le cas des groupes refroidisseurs d’eau utilisant le R-410A qui est visé par la réglementation. Mais, résoudre ce problème ne s’arrête pas au simple changement du réfrigérant par un autre à plus bas GWP ; il faut que la transition soit accompagnée par une amélioration ou un maintien de la puissance frigorifique et de la performance énergétique du système par crainte d’avoir un effet environnemental inverse parce que la consommation énergétique représente un plus grand effet sur l’impact environnemental que celui du GWP du réfrigérant.Une revue de la littérature et des tests expérimentaux réalisés en remplaçant le R-410A montrent que les réfrigérants présents sur le marché et proposés par les fabricants pour remplacer le R-410A ne permettent pas d’avoir les améliorations souhaitées. Parmi ces substituants le R-32 est le plus utilisé et semble être prometteur mais avec une réduction du COP et des températures de refoulement du compresseur très élevées. Ainsi, la solution de la compression refroidie par injection d’huile de lubrification au niveau du compresseur est étudiée et modélisée. Le modèle théorique montre qu’elle permet de refroidir la compression et de réduire la consommation du compresseur à condition d’avoir des gouttes d’huile très fines avec un débit et une température de l’huile injectée contrôlables.Pour appliquer cette solution, un système d’atomisation de l’huile est conçu et testé ; les résultats montrent qu’il estpossible de créer un spray de gouttes très fines pour des pressions d’injection de l’ordre de la différence entre la haute et labasse pression du groupe refroidisseur d’eau. La compression refroidie est testée en connectant le système d’atomisationde l’huile au groupe refroidisseur d’eau. Une réduction de la température de refoulement du compresseur et de lapuissance consommée par le compresseur est mesurée, mais elle est plus faible que la réduction prévue théoriquement. Enintégrant une augmentation du diamètre des gouttes durant la compression dans le modèle théorique, les résultats de la simulation sont proches des résultats expérimentauxCurrent global warming problem leads to more stringent environmental standards. Thus the HVAC field is affected by these standard changes, which requires the transition to a new generation of refrigerants with lower environmental impact. In this thesis, this aspect is studied in the case of water chillers using R-410A that is subject to substitution due to new standards. But solving this problem doesn’t stop at mere refrigerant change by another with lower GWP. It is necessary that improvement or maintain of cooling capacity and energy efficiency of the system accompanies this transition by fear of having a reverse effect because global energy consumption represents a greater effect on the environmental impact than refrigerant GWP.A review of literature and experimental tests carried out by replacing R-410A show that refrigerants used in the market and offered by manufacturers to replace R-410A don’t allow the desired improvements. Among these substituents, R-32 is the most used and seems promising, but it causes a decrease of COP and very high compressor discharge temperatures. Thus, the solution of cooled compression by injection of lubricating oil in the compressor is studied and modeled. The theoretical model shows that this solution helps cooling the compression and reduces compressor power consumption provided that injection is characterized by very fine drops of oil with controllable flowrate and oil temperature.To implement this solution, an oil atomization system is designed and tested, the results show that it is possible to create a spray of very fine droplets for injection pressures of the order of the difference between the high and low pressures of the water chiller. Cooled compression is then tested by connecting the oil atomization system to the water chiller. Reductions of compressor discharge temperature and of compressor power consumption are measured, but measured reductions are lower than the theoretical expected reductions. By integrating an increased droplet
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Nghiem, Anna. ""Eat cooked, drink boiled" - A study on Vietnamese household usage behaviour." Thesis, Malmö universitet, Fakulteten för kultur och samhälle (KS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-24031.
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Vietnam is a country that is characterized by a dense river network, experiencing a rapid economic growth, and still faces challenges with supplying enough water for the residents due to increased pollution levels. With water being perceived as one of the most stressed resources today, there is a need of understanding water usage behaviour. To fill in the gap in knowledge and provide a better understanding of the attitudes and the perceptions of household consumption behaviour could be a key to water savings on local and global levels. This field study was carried out in Hai Phong, the third largest city in Vietnam, as the potential of generalizing the result to other fast-growing cities and urban areas of the country was identified. In order to reach an improved understanding of water usage behaviour, the field study was of multi-design nature and was conducted by combining semi-structured interviews, water-diaries and observations. The results show that water usage behaviour is strongly determined by interpersonal trust issues which in most cases lead to an excess water consumption. The lack of trust did however also generate a cautiousness in water treatment routines, which could turn into a water savings behaviour. Other factors that affect water usage behaviour were seasonal aspects and cultural traditions perceptions. Despite the interpersonal trust issues, the institutional trust proved to be greater than expected while the role of marketing and information-based messages proved to influence behaviour. Based on this, water authorities have the potential of encouraging behaviour changes in upcoming challenges.
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Toman, Filip. "Výpočet tepelné bilance využití latentního tepla spalin pomocí kondenzátoru." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-378488.
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Thesis is focused on calculation of the condenser of flue gas, which is created by burning of natural gas. In the first part is theoretical overview of equations describing film condensation and physical properties of the flue gas. The second part deals with practical thermal calculation of the specified condenser. In third part parametric study is done in which a tempature of cooling water at inlet and the coefficient of excess air are changed. The last part of the thesis is dedicated to geometric design of the flue gas condenser whose required power is 8 MW.
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UMBEHAUN, PEDRO E. "Desenvolvimento de um elemento combustível instrumentado para o reator de pesquisa IEA-R1." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26935.
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Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2016-12-21T17:48:50Z
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Após o aumento de potência do reator IEA-R1 de 2 MW para 5 MW observou-se um aumento da taxa de corrosão nas placas laterais de alguns elementos combustíveis e algumas dúvidas surgiram com relação ao valor de vazão utilizada nas análises termo-hidráulicas. A fim de esclarecer e medir a distribuição de vazão real pelos elementos combustíveis que compõe o núcleo do reator IEA-R1, um elemento combustível protótipo, sem material nuclear, chamado DMPV-01 (Dispositivo para Medida de Pressão e Vazão), em escala real, foi projetado e construído em alumínio. A vazão no canal entre dois elementos combustíveis é muito difícil de estimar ou ser medida. Esta vazão é muito importante no processo de resfriamento das placas laterais. Este trabalho apresenta a concepção e construção de um elemento combustível instrumentado para medir a temperatura real nestas placas laterais para melhor avaliar as condições de resfriamento do combustível. Quatorze termopares foram instalados neste elemento combustível instrumentado. Quatro termopares em cada canal lateral e quatro no canal central, além de um termopar no bocal de entrada e outro no bocal de saída do elemento. Existem três termopares para medida de temperatura do revestimento e um para a temperatura do fluido em cada canal. Três séries de experimentos, para três configurações distintas, foram realizadas com o elemento combustível instrumentado. Em dois experimentos uma caixa de alumínio foi instalada ao redor do núcleo para reduzir o escoamento transverso entre os elementos combustíveis e medir o impacto na temperatura das placas externas. Dada a tamanha quantidade de informações obtidas e sua utilidade no projeto, melhoria e capacitação na construção, montagem e fabricação de elementos combustíveis instrumentados, este projeto constitui um importante marco no estudo de núcleos de reatores de pesquisa. As soluções propostas podem ser amplamente utilizadas para outros reatores de pesquisa.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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CHEN, TSUNG-SHIN, and 陳宗欣. "Air-Cooled Casing Engine Cooling Fins Installed with Water-Cooled Analysis." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/ssw4nh.
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碩士國立虎尾科技大學
動力機械工程系機械與機電工程碩士在職專班
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During the engine operates, the temperature generated in the combustion chamber is very high, the heat would be transferred to the cylinder wall of the combustion chamber, so the cylinder block must have good heat dissipation to avoid the deformation of the metal materials. The biggest difference between an air-cooled engine and a water-cooled engine is that the water-cooled engine can control the temperature in a certain range because the water-cooled engine has a thermostat to control the flow of cooling water, as well as a radiator, a water pump and a cooling fan to do the cooling work. However, the air-cooled engine only relies on the fins around the cylinder block to dissipate heat, i.e. relies on the generated airflow when the vehicle is moving, so it cannot control the temperature in a certain range as the water-cooled engine does, and cause the engine too hot or too cold. The engine temperature of the current air-cooled jet locomotive is relatively unstable. At present, most of the Scooters in the market use forced air cooling, that is, a fan is installed outside the engine generator to suck in the air and take away the heat source, and the fins in the cylinder head and the cylinder block can Increase the heat dissipation area, take away more heat after the air circulates, but it is easy to cause high temperature when the engine is at high speed and high loading. The high temperature and the frictional heat generated by the engine components will increase the temperature of the piston, cylinder block, cylinder head and other components. The high temperature will easily cause the deformation of the machine parts and accelerate the wear, especially make the valve most likely to burn out, besides it cause the oil consumption and viscosity decreased which results in poor lubrication. In this experiment, the Sym Tini 100 locomotive was used, also, we purchased and installed an additional locomotive radiator, electric fan and an electric water pump. Meanwhile, we covered the cylinder block of the original engine with an aluminum sheet. The first type was to simulate via a computer, only to wrap the first three layers of the fins. The second type was fully wrapped type, like the motorcycle shops do the refit. Both types were to let the cooling water circulate continuously in the cylinder block to test and see the results of before refit and after refit. Finally, we compared the difference between the first method and the second method. We also wanted to figure out whether the first method used can achieve the same effect in temperature control. Before the modification, we did the simulation test with computer, the result verified that to cover the first three layers of the fins of the cylinder block could achieve the required cooling effect. This way is enough to reduce the temperature of the cylinder head, it does not need to do the modification as the locomotive shops do (using the full covered method). Furthermore, the full cladding method would make the lower half of the cylinder block being too cold, and causes too much temperature difference between the upper and lower half of the cylinder block. The much temperature difference between the parts would make the material deformed. Therefore, we retain the cooling fins of the air-cooled engine and add the water-cooled engine to improve the cooling effect of the engine.
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Jeffery, Christopher A. "The thermodynamic behaviour of super-cooled water." Thesis, 1996. http://hdl.handle.net/2429/4593.
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A new statistical-mechanical, analytical equation of state for water is developed based on the Song and Mason equation of state and Poole et al.'s simple model of the free energy of open tetrahedral hydrogen bonds. Following Weeks et al. (1971b,a) the intermolecular potential is divided at its minimum into regions of attractive and repulsive force. Repulsive forces are modelled accurately using the algorithm of Ihm et al. (1991), and the attractive forces are modelled by (non-open tetrahedral) hydrogen bonds that contribute both energy and entropy to the free energy of water. Open tetrahedral hydrogen bonds are modeled explicitly using a simplified partition function. The resulting equation of state is 20 to 30 times more accurate than any equivalent simple cubic equation of state over a wide range of pressures (0.1 -» 3000 bar) and temperatures (—34 —> 1200 °C) including the supercooled region. A further extension of the equation of state down to virtually 0 K is possible because of its strong statistical-mechanical basis. The new equation of state predicts a second liquid-liquid critical point at pc — 101 kbar, pc> = 1.03 (g cm- 3 ) and Tc = 222.5 K. A liquid-liquid spinodal bounds a region in which a low-density (p « 0.93 g cm- 3 ), open tetrahedrally bonded liquid and a high-density (p w 1.1 —> 1.5 g cm- 3 ) liquid may exist. A detailed analysis of the physics of homogeneous nucleation using the density and entropy of water calculated from the new equation of state reveals that the homogeneous nucleation temperature above 1 kbar is determined solely by a high-density —> low-density phase transition.
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Saltanov, Eugene. "Steam-reheat option for supercritical-water-cooled reactors." Thesis, 2010. http://hdl.handle.net/10155/139.
Full textAbstract:
SuperCritical-Water-cooled Reactors (SCWRs) are being developed as one of the Generation-IV nuclear-reactor concepts. Main objectives of the development are to increase thermal efficiency of a Nuclear Power Plant (NPP) and to decrease capital and operational costs. The first objective can be achieved by introducing nuclear steam reheat inside a reactor and utilizing regenerative feedwater heaters. The second objective can be achieved by designing a steam cycle that closely matches that of the mature supercritical fossil-fuelled power plants. The feasibility of these objectives is discussed. As a part of this discussion, heat-transfer calculations have been performed and analyzed for SuperCritical-Water (SCW) and SuperHeated-Steam (SHS) channels of the proposed reactor concept. In the calculations a uniform and three non-uniform Axial Heat Flux Profiles (AHFPs) were considered for six different fuels (UO2, ThO2, MOX, UC2, UC, and UN) and at average and maximum channel power. Bulk-fluid, sheath, and fuel centerline temperatures as well as the Heat Transfer Coefficient (HTC) profiles were obtained along the fuel-channel length. The HTC values are within a range of 4.7 – 20 kW/m2⋅K and 9.7 – 10 kW/m2⋅K for the SCW and SHS channels respectively. The main conclusion is that while all the mentioned fuels may be used for the SHS channel, only UC2, UC, or UN are suitable for a SCW channel, because their fuel centerline temperatures are at least 1000°C below melting point, while that of UO2, ThO2, and MOX may reach melting point.UOIT
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Cheng, Pai Chen, and 鄭百晟. "Airflow Simulation of Air-Cooled Water Chiller Units." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/247qcx.
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
99
Air-Cooled Water Chiller Units (ACWCU) was used as a component for heat rejection by means of heat convection. Through the contact with air, the high-temperature condenser can be cooled down. Because the cooling of the condenser needs a great amount of outdoor air, the spacing between ACWCU should be large enough. Alternatively, installing stacked tower could reduce the occurrence of short recirculation and enhance the cooling of the condenser. This study adopted the CFD method to investigate several parameters, including wind speed, wind direction, atmospheric boundary layer and stacked tower, on the impact of heat rejection of ACWCU. According to the numerical results: (1) ACWCU could have better thermal efficiency under the condition of no wind t; (2) installing stacked towers could avoid short recirculation more effectively; (3) the existence of atmospheric boundary layer could suppress the growth of thermal plumes issuing from ACWCU, resulting in poorer thermal efficiency of the system; (4) wind direction played an important role on the thermal efficiency of ACWCU. The results of this study can provide the guidance for manufacturers to install ACWCU and improve their thermal efficiency.
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Guo, Heng-shen, and 郭恆伸. "Water-cooled Heat Sink in Finite Element Analysis." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/jj89h3.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
97
Abstract With the development of computer processors, the size of chip has become smaller. But the processors used in high-power needs high performance of heat dissipation. In electronic design of the thermal management, the heat sink is the most basic application. Since the natural convection can not cool down effectively, it needs to use the forced convection cooling. The purpose of this study explored water-cooled sink as the heat source for the high-power chip. The study findings show that the ATC cooling chip enhances the potency and decreased the noise. Most importantly, it dissipates heat. In the present study, the researcher used Computational Fluid Dynamics to analyze the heat flow problem. By applying three variables in terms of the flow channel, the housing size, and the heat sink size in data analyses, the researcher classified different types of water-cooled sink. From the discussion of different flow rate and the thermal resistance, it shows that the trend curve of the fin-gilled sink is different from others. It also shows that it performs better in the low flow rate. After all using each method of heat dissipation, the potency of N-type channel sink is the best. When flow rate is 2.2 L/min, the thermal resistance is 0.0971˚C/W.
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Chia-HsienKang and 康嘉顯. "Performance of kW-scale Water-cooled PEMFC Stack." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/4kqqvv.
Full textAbstract:
碩士國立成功大學
航空太空工程學系
103
In this study, a kW-scale water-cooled PEMFC stacks is designed and tested under different conditions, including fuel conditions, inlet water temperatures , inlet water flow rates, in order to understand effects of the above three parameters on the stack performance and impedance. Based on the qualitative analysis of the experimental results, the gas parameters and thermal management conditions which make the water-cooled PEMFC stack best to be uniform thermally are applied to the stack. The experimental results show that the best performance of this stack, 1431 Watts, and its power density, 694.8 mW/cm2 is exhibited at the inlet water flow rate of 5 L/min, the inlet water temperature of 55oC, the hydrogen stoichiometric ratio of 1.5, the air stoichiometric ratio of 3.0, the air dew point temperature of 65oC. And the maximum power generating efficiency is up to 40.6 %. In addition, with increasing the inlet water temperature and decreasing the inlet water flow rate will decrease the charge transfer resistance because elevated stack temperatures improve the electrochemical reaction. However, the Ohmic resistance rises due to membrane dehydration at elevated stack temperatures. It is also noticed that the stack performance changes significantly with temperature operating conditions at low inlet water flow rates owing to significantly non-uniform temperature distributions over the stack. As a result, the inlet water temperature becomes a critical operational parameter at low inlet water flow rates.