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Chambers, Iain Robert. "Studies in human head injury." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262899.
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Ali, A. A. A.-W. "The modelling, simulation and real time control of intercranial pressure." Thesis, University of Bradford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233661.
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Morgan, Lesley C. "Pediatric head trauma cerebral perfusion pressure as an indicator of outcome /." [Gainesville, Fla.]: University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0000750.
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Tørklep, Anders Mathias. "Pressure oscillations during start and stop of a high head Francis turbine." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19323.
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Start and stop procedures affect pressure oscillations throughout a hydropower plant. A desire to study how pressure oscillations behave during these dynamic conditions was the basis of this report. Instrumentation, experimentation and measurement analysis was conducted on a Francis model turbine in the Waterpower Laboratory at NTNU. Eight pressure transducers were calibrated and used during the experiments. Two transducers were installed in the draft tube below the turbine. One was placed in the vaneless space between the guide vanes and the impeller vanes. Three pressure transducers on an impeller vane and two transducers located at the inlet were also included in the experiments. Frequency analysis (PSD) was carried out for all the measurements to explore various pressure oscillations. Except for the low frequent oscillations (< 30 Hz), definite frequencies repeatedly dominated the frequency domain during start/stop as well as for steady state operation. The impeller vane oscillation showed an increase in pressure amplitude during guide vane closing. A bigger amplitude increase was registered for BEP than for part load and full load operation. The guide vane frequency was located in and only in the runner. The amplitude of the guide vane frequency was significant and was located for all studied operational points. The power of this oscillation decreased during guide vane closing. One specific frequency arose the question of an overtone phenomenon for the water hammer oscillation, a phenomenon, were the fundamental frequency is three times higher than the customary water hammer frequency.
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Senior, James Alexander. "Hydrostatic pressure converters for the exploitation of very low head hydropower potential." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/73702/.
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Much of the world's available hydropower potential has been exploited, and within the western world attention is increasingly being focussed on hydropower sites with very low head dierences. These are sites where the vertical distance through which water falls is less than ve metres, and remain unexploited as there is a recognised lack of hydropower technology avaiable to exploit these low-power sites economically. The aim of this work was therefore to develop a novel hydropower machine which could be used to viably exploit very low head dierences in river environments. A review of the hydropower technologies determined that the established machinery is primarily driven by the operational principles of impulse, reaction, or potential. It was however noticed that some less well established designs appear to be driven directly by the hydrostatic pressure which could be generated by a depth of owing water. This observation had not been previously acknowledged. It was also recognised that investigation into this operational principle could potentially result in machines that were both relatively simple, and have high ow and power capacities when compared to the established technologies. It was identied that there could be two approaches to exploiting hydrostatic pressure, and ideal theories were developed to describe both approaches. The resulting physical concepts were called Hy- drostatic Pressure Converters. Scale models of these concepts were hydraulically tested, veriying the proposed theories, and providing data from which estimates of full scale performance were made. These predicted that the two proposed designs of Hydrostatic Pressure Converter were suitable for head dif- ferences below 2.5m, normally the domain of the traditional waterwheel. They would operate with high hydraulic eciency, at around 80%, but have a signicantly greater ow capacity and power output per unit width of machine, at 500% that possible using a traditional waterwheel. In conclusion this work has identied, analysed and prototyped a novel approach to exploiting very low head hydropower potential. The resulting Hydrostatic Pressure Converters are a signicant and promising development in the eld of very low head hydropower.
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Shaw, Martin Fraser. "Modelling the time-series of cerebrovascular pressure transmission variation in head injured patients." Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3287/.
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Cerebral autoregulation is the process by which blood ow is maintained over a changing cerebral perfusion pressure. Clinically autoregulation is an important topic because it directly effects overall patient management strategy. However accurately predicting autoregulatory state or even modelling the underlying general physiological processes is a complex task. There are a number of models published within the literature but there has been no active attempt to compare and classify these models. Starting with the hypothesis that a physiologically based model would be a better predictor of autoregulatory state than a purely statistically based one has led us to investigate approaches to model comparison. Using three different models: a new mathematical arrangement of a physiological model by Ursino, the Highest Model Frequency (HMF) model by Daley and the Pressure reactivity index (PRx) statistical model by Czosnyka, a general comparison was carried out using the Matthews correlation coecient against a known autoregulatory state. This showed that the Ursino model was approximately three times as predictive as both the HMF model and the PRx model. However, in general, all of the models predictive accuracies were relatively poor so a number of optimisation strategies were then assessed. These optimisation strategies ultimately were formed into a generalised modelling framework. This framework draws on the ideas of mathematical topology to underpin and explain any change or optimisation to a model. Within the framework different optimisations can be grouped into four categories, each of which are explored in the text of this thesis: 1) Model Comparison. This is the simplest technique to apply where the number of models under examination are reduced based on the predictive accuracy. 2) Parameter restriction. A classical form of optimisation by constraining a model parameter to cause a better predictive accuracy. In the case of both the HMF and PRx we showed between a two hundred and six hundred percent increase in predictive accuracy over the initial assessment. 3) Parameter alteration. This change allows for related parameters to be substituted into a model. Four different alterations are explored as a surrogate measure for arterial-arteriolar blood volume the most clinically applicable of which is a transcranial impedance technique. This latter technique has the potential to be a non invasive measure correlated with both mean ICP and ICP pulse amplitude. 4) Model alteration. Allows for larger changes to the underlying structure of the model. Two examples are presented: firstly a new asymmetric sigmoid curve to overcome computational issues in the Ursino model and secondly a novel use of fractal characterisation which is applied in a wavelet noise reduction technique. The framework also gives an overview of the autoregulatory research domain as a whole as a result of its abstract nature. This helps to highlight some general issues in the domain including a more standardised way to record autoregulatory status. Finally concluding with research addressing the requirement for easier access to data and the need for the research community to cohesively start to address these issues.
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Harju, Mika. "Exfoliation glaucoma : studies on intraocular pressure, optic nerve head morphometry, and ocular blood flow." Helsinki : University of Helsinki, 2001. http://ethesis.helsinki.fi/julkaisut/laa/kliin/vk/harju/.
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Brucia, Josephine Jacobs. "The effect of suction catheter insertion on head-injured adults." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1060867440.
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Tran, Chi Thanh. "The Effective Convectivity Model for Simulation and Analysis of Melt Pool Heat Transfer in a Light Water Reactor Pressure Vessel Lower Head." Doctoral thesis, Stockholm : Division of Nuclear Power Safety, Royal Institute of Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10671.
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Kostas, Vladimir Ilyich. "EFFECT OF LOWER BODY POSITIVE PRESSURE ON CARDIOVASCULAR RESPONSE AT VARIOUS DEGREES OF HEAD UP TILT." UKnowledge, 2012. http://uknowledge.uky.edu/khp_etds/3.
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Various models of simulated weightlessness and resulting cardiovascular effects have been researched in the last 50 years of space exploration. Examples of such models are the Alter-G (Alt-G) treadmill used for body unweighting and head-up-tilt (HUT) model each providing similar cardiovascular effects, but differing in their stimulation of vestibular centers . Advantages of using the Alt-G include: use of lower body positive pressure (LBPP) to simulate hypogravity, it acts as a countermeasure to alleviate negative cardiovascular effects of standing and provides a constant vestibular stimulus. In addition, the Alt-G shorts themselves may be providing a certain degree of LBPP, acting as a compression garment. Therefore the purpose of this study was to determine the cardiovascular effects of Alt-G shorts and how effective they are as countermeasure to deconditioning effects of space flight.
This study tested cardiovascular changes in 12 men and women at 0 and 80 degrees head-up-tilt (HUT0 / HUT80) with and without Alt-G shorts using 5-lead ECG, 10-lead impedance, heart rate, systolic and diastolic blood pressure measurements at finger and arm. The tilt-induced increase in mean heart rate (HR) was significantly smaller when subjects wore the Alt-G shorts. Shorts ended up reducing HR by 2.3 bpm in supine control and by 6.7 bpm at HUT80 (p0.05. Other cardiovascular variables did not show any significant effect from shorts.
In conclusion, this study was in line with results from other studies that used compression garments to determine cardiovascular effects of LBPP.
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Xing, Mian. "Validation of TRACE Code against ROSA/LSTF Test for SBLOCA of Pressure Vessel Upper-Head Small Break." Thesis, KTH, Kärnkraftsäkerhet, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95745.
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OECD/NEA ROSA/LSTF project tests are performed on the Large Scale Test Facility (LSTF). LSTF is a full-height, full-pressure and 1/48 volumetrically-scaled two-loop system which aims to simulate Japanese Tsuruga-2 Westinghouse-type 4-loop PWR. ROSA-V Test 6-1 simulates a pressure vessel (PV) upper-head small break loss-of-coolant accident (SBLOCA) with a break size equivalent to 1.9% of the volumetrically scaled cross-sectional area of the reference PWR cold leg.The main objective of present thesis is to build a TRACE calculation model for simulating thermal hydraulic behaviors in LSTF and PV upper-head SBLOCA, so as to assess different modeling options and parameters of TRACE code. The results show that TRACE code well reproduce the complex physical phenomena involved in this type of SBLOCA scenarios. Almost all the events in the experiment are well predicted by the model based on TRACE code. In addition, the sensitivity of different models and parameters are investigated. For example, the code slightly overestimates the break mass flow from upper head which affects the accuracy of the results significantly. The rising of core exit temperature (CET) is significantly influenced by the flow area of leakage between downcomer and hot leg. Besides, the effect of the break location, low pressure injection system (LPIS) and accumulator setup are also studied.
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Hauxwell, Cynthia M. "Variations in Lingual Pressure during Saliva Swallows between a Healthy Adult Female and an Adult Female with Head and Neck Cancer." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1243364890.
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Stockman, A. "Signal analysis of physiological control : An investigation of blood pressure control and intercranial pressure in man with clinical applications for hypertensive skin burns and head injured patients." Thesis, University of Bradford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379868.
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Ramsey, Michael Wiechmann. "Effects of head-up tilt on mean arterial pressure, heart rate, and regional cardiac output distribution in aging rats." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3094.
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Many senescent individuals demonstrate an inability to regulate mean arterial
pressure (MAP) in response to standing or head-up tilt; however, whether this aging
effect is the result of depressed cardiac function or an inability to reduce peripheral
vascular conductance remains unknown. Therefore, the purpose of this research was to
investigate the effects of aging on MAP, heart rate (HR), regional blood flow (via
radioactive-microspheres), and vascular conductance during head-up tilt in conscious
young (4 mo; n=12) and old (24 mo; n=10) male Fischer-344 rats. Heart rate and MAP
were measured continuously during normal posture and during 10 minutes of head-up
tilt. Blood flow was determined during normal posture and at the end of 10 minutes of
head-up tilt. Young rats increased MAP significantly at the onset of head-up tilt and
generally maintained the increase in MAP for the duration of head-up tilt, while aged
rats showed a significant reduction in MAP after 10 minutes of head-up tilt. In the
normal posture, aged rats demonstrated lower blood flow to splanchnic, bone, renal, and
skin tissues versus young rats. With tilt there were decreases in blood flow to skin, bone, and hind-limb in both age groups and in fat, splanchnic, reproductive, and renal
tissues in the young. Bone blood flow was attenuated with age across both conditions in
hind foot, distal femur, femur marrow, and proximal and distal tibia. Head-up tilt caused
a decrease in blood flow across both age groups in all bones sampled with the exception
of the hind foot. These results provide evidence that the initial maintenance of MAP in
aged rats during head-up tilt occurs through decreased regional blood flow and vascular
conductance, and that the fall in pressure is not attributable to an increase in tissue blood
flow and vascular conductance. Therefore, reductions in arterial pressure during headup
tilt are likely a result of an old age-induced reduction in cardiac performance. In
addition, this is the first study to demonstrate a decreased bone vascular conductance in
both young and old rats during head-up tilt.
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van, Quang Pham. "Soil formation and soil moisture dynamics in agriculture fields in the Mekong Delta, Vietnam conceptual and numerical models." Licentiate thesis, KTH, Land and Water Resources Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10508.
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Previous studies of agricultural conditions in the Mekong Delta (MD) have identified soil compaction as an obstacle to sustainable production. A conceptual model for soil formation was presented to demonstrate the link between soil hydrology and plant response. Detailed studies of soil moisture dynamics in agricultural fields were conducted using a dynamic process-orientated model. Pressure head and water flow were simulated for three selected sites during a year for which empirical data were available. Daily meteorological data were used as dynamic input and measured pressure head was used to estimate parameter values that satisfied various acceptance criteria. The Generalised Likelihood Uncertainty Estimation (GLUE) approach was applied for calibration procedures with 10,000 runs, each run using random values within the chosen range of parameter values. To evaluate model performance and uncertainty estimation, re-sampling was carried out using coefficient of determination (R2) and mean error (ME) as the criteria. Correlations between parameters and R2 (and ME) and among parameters were also considered to analyse the relationship of the selected parameter set in response to increases/decreases in the acceptable simulations. The method was successful for two of the three sites, with many accepted simulations. For these sites, the uncertainty was reduced and it was possible to quantify the importance of the different parameters.
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Madokoro, Hiroshi [Verfasser], and T. [Akademischer Betreuer] Schulenberg. "Thermo-structural analysis of a reactor pressure vessel lower head during core-melt severe accidents / Hiroshi Madokoro ; Betreuer: T. Schulenberg." Karlsruhe : KIT-Bibliothek, 2018. http://d-nb.info/1172351775/34.
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Fukuzawa, Kenji, 健二 福澤, Takuro Muramatsu, Hiroaki Amakawa, Shintaro Itoh, and Hedong Zhang. "Nonuniform Distribution of Molecularly Thin Lubricant Caused by Inhomogeneous Buried Layers of Discrete Track Media." IEEE, 2008. http://hdl.handle.net/2237/11180.
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Horník, Jan. "Návrh komory výměníku tepla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-241229.
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The master thesis is focused on the field of heat exchangers. Theoretical part makes the reader familiar with heat exchangers. Practical part is focused on design of chamber, which is part of heat exchanger. Practical part consists of strength calculation by standard ČSN EN 13445. Dimensions of tube sheet are gained in program Visual vessel design. Those parameters are used for creating of 3D model with accurate dimensions which is analyzed in ANSYS Workbench. Output of this analysis is evaluation by stress classification. Practical part is supplemented by drawing of heat exchanger.
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Carlson, Kjirste Lynn. "Human hip joint mechanics : an investigation into the effects of femoral head endoprosthetic replacements using in vivo and in vitro pressure data." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/31043.
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McCafferty, Sean, Jason Levine, Jim Schwiegerling, and Eniko T. Enikov. "Goldmann and error correcting tonometry prisms compared to intracameral pressure." BIOMED CENTRAL LTD, 2018. http://hdl.handle.net/10150/626542.
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Background: Compare Goldmann applanation tonometer (GAT) prism and correcting applanation tonometry surface (CATS) prism to intracameral intraocular pressure (IOP), in vivo and in vitro. Methods: Pressure transducer intracameral IOP was measured on fifty-eight (58) eyes undergoing cataract surgery and the IOP was modulated manometrically to 10, 20, and 40 mmHg. Simultaneously, IOP was measured using a Perkins tonometer with a standard GAT prism and a CATS prism at each of the intracameral pressures. Statistical comparison was made between true intracameral pressures and the two prism measurements. Differences between the two prism measurements were correlated to central corneal thickness (CCT) and corneal resistance factor (CRF). Human cadaver eyes were used to assess measurement repeatability. Results: The CATS tonometer prism measured closer to true intracameral IOP than the GAT prism by 1.7+/-2.7 mmHg across all pressures and corneal properties. The difference in CATS and GAT measurements was greater in thin CCT corneas (2.7+/-1.9 mmHg) and low resistance (CRF) corneas (2.8+/-2.1 mmHg). The difference in prisms was negligible at high CCT and CRF values. No difference was seen in measurement repeatability between the two prisms. Conclusion: A CATS prism in Goldmann tonometer armatures significantly improve the accuracy of IOP measurement compared to true intracameral pressure across a physiologic range of IOP values. The CATS prism is significantly more accurate compared to the GAT prism in thin and less rigid corneas. The in vivo intracameral study validates mathematical models and clinical findings in IOP measurement between the GAT and CATS prisms.
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Pearce, Christopher William. "On the dynamic pressure response of the brain during blunt head injury : modelling and analysis of the human injury potential of short duration impact." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/14185.
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Impact induced injury to the human head is a major cause of death and disability; this has driven considerable research in this field. Despite this, the methods by which the brain is damaged following non-penetrative (blunt) impact, where the skull remains intact, are not well understood. The mechanisms which give rise to brain trauma as a result of blunt head impact are frequently explored using indirect methods, such as finite element simulation. Finite element models are often created manually, but the complex anatomy of the head and its internal structures makes the manual creation of a model with a high level of geometric accuracy intractable. Generally, approximate models are created, thereby introducing large simplifications and user subjectivity. Previous work purports that blunt head impacts of short duration give rise to large dynamic transients of both positive and negative pressure in the brain. Here, three finite element models of the human head, of increasing biofidelity, were employed to investigate this phenomenon. A novel approach to generating finite element models of arbitrary complexity directly from three-dimensional image data was exploited in the development of these models, and eventually a highly realistic model of the whole head and neck was constructed and validated against a widely used experimental benchmark. The head models were subjected to a variety of simulated impacts, ranging from comparatively long duration to very short duration collisions. The dynamic intracranial pressure response, characterised by large transients of both positive and negative pressure in the brain, was observed following short duration impacts in all three of the models used in this study. The dynamic intracranial response was also recorded following short duration impacts of high energy, involving large impact forces, which were deemed to be realistic representations of actual impact scenarios. With the aid of an approximate analytical solution, analysis of the simulations revealed that the dynamic response is caused by localised skull deflection, which induces flexural waves in the skull. The implications of these magnified pressures are discussed, with particular regard to the potential for intracranial cavitation.
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Antonucci, Marta. "Uterine function in labour : an investigation of the relationship between intrauterine pressure, head-to-cervix force and cervical dilatation, and their correlation with mode of delivery." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394277.
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McCafferty, Sean, Jason Levine, Jim Schwiegerling, and Eniko T. Enikov. "Goldmann applanation tonometry error relative to true intracameral intraocular pressure in vitro and in vivo." BIOMED CENTRAL LTD, 2017. http://hdl.handle.net/10150/626266.
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Background: Goldmann applanation tonometry (GAT) error relative to intracameral intraocular pressure (IOP) has not been examined comparatively in both human cadaver eyes and in live human eyes. Futhermore, correlations to biomechanical corneal properties and positional changes have not been examined directly to intracameral IOP and GAT IOP. Methods: Intracameral IOP was measured via pressure transducer on fifty-eight (58) eyes undergoing cataract surgery and the IOP was modulated manometrically on each patient alternately to 10, 20, and 40 mmHg. IOP was measured using a Perkins tonometer in the supine position on 58 eyes and upright on a subset of 8 eyes. Twenty one (21) fresh human cadaver globes were Intracamerally IOP adjusted and measured via pressure transducer. Intracameral IOP ranged between 5 and 60 mmHg. IOP was measured in the upright position with a Goldmann Applanation Tonometer (GAT) and supine position with a Perkins tonometer. Central corneal thickness (CCT) was also measured. Results: The Goldmann-type tonometer error measured on live human eyes was 5.2 +/- 1.6 mmHg lower than intracameral IOP in the upright position and 7.9 +/- 2.3 mmHg lower in the supine position (p <.05). CCT also indicated a sloped correlation to error (correlation coeff. = 0.18). Cadaver eye IOP measurements were 3.1+/-2. 5 mmHg lower than intracameral IOP in the upright position and 5.4+/- 3.1 mmHg in the supine position (p <.05). Conclusion: Goldmann IOP measures significantly lower than true intracameral IOP by approximately 3 mmHg in vitro and 5 mmHg in vivo. The Goldmann IOP error is increased an additional 2.8 mmHg lower in the supine position. CCT appears to significantly affect the error by up to 4 mmHg over the sample size.
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Hasnain, Shahid. "Steady Periodic Water Waves Solutions Using Asymptotic Approach." Thesis, Linköpings universitet, Tillämpad matematik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-69421.
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The aim of this work is to study the relation between two invariants of water flow in a channel of finite depth. The first invariant is the height of the water wave and the second one is the flow force. We restrict ourselves to water waves of small amplitude. Using asymptotic technique together with the method of separation of variables, we construct all water waves of small amplitude which are parameterized by a small parameter. Then we demonstrate numerically that the flow force depends monotonically on the height.
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Liporaci, Rogério Ferreira. "Respostas cardiovasculares e biomecânicas aos efeitos do tilt test ativo e passivo em indivíduos saudáveis." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/17/17138/tde-10012017-112630/.
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Para avaliação da sincope neurocardiogênica, testes ativos e passivos de mudança postural são utilizados, e verificar o comportamento da musculatura e da oscilação do corpo pode auxiliar no melhor entendimento das respostas cardiovasculares e biomecânicas. O objetivo do presente estudo foi comparar protocolos ativo e passivo de mudança postural, padronizado de 15 minutos, associado a três manobras de Valsalva intervaladas, para os testes de mudança postural ativa, Acive Standing test (AS) e passiva, Head-Up Tilt test (HUT), utilizados no diagnóstico da síncope neurocardiogênica (SNC), em relação às mudanças nos valores de frequência cardíaca, pressão arterial sistólica e diastólica, atividade eletromiográfica dos músculos reto abdominal (RA), eretores da espinha (EE), tibial anterior (TA) e gastrocnêmio porção medial (GM) bilateral, em 23 mulheres saudáveis, além de analisar o deslocamento e velocidade média do centro de pressão do corpo sobre uma plataforma de força. Verificamos alterações com relevância estatística para todas variáveis ao longo dos testes, principalmente durante o período onde as manobras de Valsalva eram realizadas, sendo estas alterações maiores durante o teste ativo, além do centro de pressão do corpo demonstrar um maior deslocamento e velocidade de movimento durante o mesmo período. Concluímos que este protocolo proposto para os dois testes causa mudanças tanto cardiovasculares quanto biomecânicas, mas que foram mais evidentes no teste de mudança postural ativa.To evaluate the neurocardiogenic syncope (NCS), active and passive postural change tests are used and verify the muscles and body oscilation behavior´s can be helpful to better understand the cardiovascular and biomechanics responses. The aim of the present study was compare a standard 15 minute tilt test protocol associated with three Valsalva maneuver during both Active Standing (AS) and passive Head-Up tilt test (HUT). These tests are used to diagnosis of neurocardiogenic syncope (NCS). We analysed the effects of orthostatic position in relation to changes in the values of heart rate, systolic and diastolic blood pressure, electromyographic activity of the rectus abdominis (RA), erector of spinae (ES), tibialis anterior (TA) and medial gastrocnemius (MG) bilateral in 23 healthy women, and analyze the displacement and average velocity of the body\'s center of pressure on a force platform. We found changes with statistical significance for all variables during the tests, especially around the period where the Valsalva maneuvers were performed, and these major changes occurred during the active test, beyond the center of body pressure what indicates a greater movement and speed of movement during the same period. We conclude that the proposed protocol for the two tests produce both cardiovascular and biomechanical changes and these alterations were more evident in active postural test.
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Coelho, Welington Ricardo [UNESP]. "Análise do fenômeno de cavitação em bomba centrífuga." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/88879.
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Cavitação em bombas centrífugas é a formação de bolhas de vapor do fluido bombeado na região de sucção do equipamento. As bolhas de vapor formadas em algum local do escoamento, em geral na região de sucção da bomba, entrarão posteriormente em colapso. Este fenômeno é importante cientificamente, tecnicamente e economicamente. Cientificamente é interessante, pois envolve o escoamento de um fluido em estado líquido, simultaneamente ocorre a formação de bolhas de vapor, que também escoam juntamente ao fluido líquido. O processo de vaporização e condensação de um fluido é complexo, pois envolve mudança de fase, um fenômeno térmico não linear. Tecnicamente, é importante porque quando o escoamento se dá com cavitação os parâmetros hidrodinâmicos do escoamento bem como da bomba, em geral, são fortemente alterados na direção termodinâmica de maior produção de irreversibilidades. Economicamente, é custoso porque a cavitação, em geral, leva a perda de eficiência termodinâmica dos processos e em conseqüência haverá maior custo na produção de um dado bem, diminuindo a eficiência econômica e a competitividade da empresa. O escoamento com cavitação na sucção de bombas apresenta três aspectos danosos principais: cavitação pulsante com baixa vazão; cavitação não pulsante com baixa altura útil; e erosão cavitacional. A cavitação pulsante é caracterizada por grande formação de bolhas de forma transitória com baixa freqüência e grande amplitude, gerando forças vibratórias importantes no sistema de bombeamento. A cavitação pulsante também causa colapso do fluxo de massa do fluido bombeado com valores que vão do fluxo normal da instalação até valores quase nulos, transitoriamente. Na cavitação pulsante a erosão cavitacional e a queda na altura útil são pequenas...
Cavitation in centrifugal pumps is the development of vapor bubbles from the pumped liquid into equipment suction region. Vapor bubbles developed somewhere in the flow, generally in the pump suction, will afterwards along the flow to collapse. This phenomenon is scientifically, technically and economically important. Scientifically, it is interesting because involves the flow of a fluid on liquid state, and simultaneously happens vapor bubbles development that also flow together the liquid fluid. Fluid vaporization and condensation processes are complex because involves phase change, a non-linear thermal phenomenon. Technically, it is important because when the flow happens with cavitation the flow and pump hydrodynamic parameters, generally, are strongly modified toward bigger thermodynamic irreversibility production. Economically, it is expensive because cavitation, generally, leads to thermodynamic process efficiency loss, and consequently it will have bigger costs for production of a given good, then decreasing economic efficiency and company competitiveness. Flow with cavitation in the pump suction presents three main devastating aspects: surging cavitation with low flow rate; steady cavitation with low total head; and cavitational erosion. Surging cavitation is characterized by unsteady, low frequency and high amplitude, intense bubbles development, producing strong vibration forces into the pumping system. Surging cavitation also causes the collapse of pumped fluid mass flow rate with values that goes from the normal flow to values that almost reach the zero flow, unsteadily. In surging cavitation, the cavitational erosion and the breakdown in total head are small. In steady cavitation the mass flow rate, and even the flow rate... (Complete abstract click electronic access below)
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Gomes, Pedro Miguel Bule. "Traumatismo craniano : contribuição da craniectomia descompressiva para a sobrevivência de pacientes caninos com hipertensão intracraniana traumática refractária ao tratamento médico : estudo retrospectivo." Bachelor's thesis, Universidade Técnica de Lisboa. Faculdade de Medicina Veterinária, 2011. http://hdl.handle.net/10400.5/3051.
Full textAbstract:
Dissertação de Mestrado Integrado em Medicina VeterináriaO traumatismo crânio-encefálico (TCE) grave está associado a uma taxa de mortalidade muito elevada e é cada vez mais comum na clínica de pequenos animais. Isto deve-se em grande parte ao crescente número de animais domésticos e consequentemente de acidentes rodoviários envolvendo esses mesmos animais. A lesão cerebral causada pelo TCE tem duas componentes essenciais: a primária que diz respeito à lesão mecânica causada pelas forças de aceleração, desaceleração, rotação e compressão que actuam sobre o crânio e cérebro no momento do impacto e a secundária que se refere a um número de alterações metabólicas e bioquímicas que se auto-perpetuam e agravam o quadro inicial. A formação de hematomas e edema cerebral de origem vascular e citotóxica vão aumentar o volume do conteúdo intracraniano o que, devido à natureza não expansível do crânio, vai levar ao aumento da pressão intracraniana (PIC) e compromisso da perfusão e oxigenação cerebrais. Quando não controlada a hipertensão intracraniana leva à hérnia cerebral e à morte do animal. A abordagem terapêutica à vítima de TCE e hipertensão intracraniana ainda é algo controversa pois não existem evidências clínicas e experimentais suficientes para elaborar um protocolo definitivo. É no entanto inquestionável que esta deverá ser expediente e agressiva. No estudo retrospectivo aqui apresentado procura-se avaliar a eficácia de uma técnica de descompressão cirúrgica como meio de reduzir a PIC e assim contribuir para a sobrevivência de pacientes vítimas de hipertensão intracraniana traumática. Foram para isso recolhidos os dados de 86 indivíduos de espécie canina vítimas de TCE fechado grave, tendo 40 deles sido submetidos a uma craniectomia descompressiva de urgência e os restantes 46 tratados apenas de forma conservativa, com recurso à hiperventilação controlada e à terapêutica hiperosmolar. As taxas de sobrevivência acumulada às 72 horas foram de 4,3% e 15% respectivamente para os grupos de controlo e cirúrgico. Não foi no entanto encontrada relação estatisticamente significativa entre a realização da craniectomia e a probabilidade de sobrevivência dos indivíduos. Concluiu-se então que não houve relação entre a realização de craniectomia descompressiva de urgência e a sobrevivência dos pacientes sendo no entanto necessários mais estudos para que se possam fazer afirmações neste sentido.
ABSTRACT - THE CONTRIBUTION OF DECOMPRESSIVE CRANIECTOMY FOR THE SURVIVAL OF CANINE PATIENTS SUFFERING FROM REFRACTORY TRAUMATIC INTRACRANIAL HYPERTENSION - Severe traumatic brain injury (TBI) is associated with a very high mortality rate and its expression in small animal practice is becoming progressively higher. This is in great measure due to the always increasing number of both domestic animals and motor vehicles which translates into more road accidents involving those animals. Traumatic brain injury has two main components: the primary injury, which refers to the mechanical lesions caused by the acceleration, deceleration, rotation and compression forces that act on the brain and cranium at the moment of impact and the secondary injury, which refers to a number of self-perpetuating biochemical and metabolic changes that and aggravate the prognosis. The development of hematomas, citotoxic and vasogenic edema causes an increase in the intracranial volume that, due to the inexpansible nature of the cranium, will lead to an increased intracranial pressure (ICP) and compromised brain perfusion and oxygenation. If unattended, intracranial hypertension will lead to brain herniation and death. There is still a lot of debate surrounding the therapeutic approach to the TBI and intracranial hypertension mainly because there’s not enough clinical and experimental evidence to elaborate a standard protocol. However, few would argue that it should be expedient and aggressive. The present study aims to evaluate the role of a surgical decompression technique in reducing ICP and therefore contribute to an increased survival of patients suffering from traumatic intracranial hypertension. In order to achieve this, data from 86 canine patients suffering from severe TBI was collected. 40 of those 86 were submitted to an emergency decompressive craniectomy and the other 46 were treated conservatively using controlled hyperventilation and hyperosmolar therapy. The 72 hours post-admission cumulative survival rates where 4, 3% and 15% for the control group and surgical group, respectively. However, no statistical significant relation was found between the surgical procedure and the probability of survival. It was concluded that the emergency decompressive craniectomy did not contribute to the survival of the patients, thought further investigation is needed before any affirmations concerning this matter can be made.
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Brink, Lize. "An investigation into the weld integrity of the head–to–skirt junction on tall distillation columns / L. Brink." Thesis, North-West University, 2010. http://hdl.handle.net/10394/4877.
Full textAbstract:
This study addresses the fatigue life of the head–to–skirt welds of tall distillation columns.
Fatigue tests were done on two types of weld geometries which approximate the head–toskirt
configurations. From the fatigue tests it was determined that the fatigue life of the
experimental samples can be substantially improved by applying weld build–up between
the head and the skirt.
The expected fatigue life of the test samples was determined by way of calculation
employing the so called Nominal–Stress–Approach, the Effective–Notch–Stress–Approach
and the Stress–Life–Approach.
For both the Nominal–Stress–Approach and the Effective–Notch–Stress–Approach the
predicted fatigue life was found to be overly conservative compared to the experimental
results. The Stress–Life–Approach predicted the fatigue life to within a factor of 1.3 for
both the geometries under investigation when displacements due to welding are taken
into account. If displacements due to welding is omitted this factor is increased, for the
geometry without weld build–up, to 2. For the geometry with weld build–up the factor
remains 1.3.Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2011.
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Coelho, Welington Ricardo. "Análise do fenômeno de cavitação em bomba centrífuga /." Ilha Solteira : [s.n.], 2006. http://hdl.handle.net/11449/88879.
Full textAbstract:
Orientador: João Batista AparecidoBanca: Jose Luiz Gasche
Banca: Paulo Gilberto de Paula Toro
Resumo: Cavitação em bombas centrífugas é a formação de bolhas de vapor do fluido bombeado na região de sucção do equipamento. As bolhas de vapor formadas em algum local do escoamento, em geral na região de sucção da bomba, entrarão posteriormente em colapso. Este fenômeno é importante cientificamente, tecnicamente e economicamente. Cientificamente é interessante, pois envolve o escoamento de um fluido em estado líquido, simultaneamente ocorre a formação de bolhas de vapor, que também escoam juntamente ao fluido líquido. O processo de vaporização e condensação de um fluido é complexo, pois envolve mudança de fase, um fenômeno térmico não linear. Tecnicamente, é importante porque quando o escoamento se dá com cavitação os parâmetros hidrodinâmicos do escoamento bem como da bomba, em geral, são fortemente alterados na direção termodinâmica de maior produção de irreversibilidades. Economicamente, é custoso porque a cavitação, em geral, leva a perda de eficiência termodinâmica dos processos e em conseqüência haverá maior custo na produção de um dado bem, diminuindo a eficiência econômica e a competitividade da empresa. O escoamento com cavitação na sucção de bombas apresenta três aspectos danosos principais: cavitação pulsante com baixa vazão; cavitação não pulsante com baixa altura útil; e erosão cavitacional. A cavitação pulsante é caracterizada por grande formação de bolhas de forma transitória com baixa freqüência e grande amplitude, gerando forças vibratórias importantes no sistema de bombeamento. A cavitação pulsante também causa colapso do fluxo de massa do fluido bombeado com valores que vão do fluxo normal da instalação até valores quase nulos, transitoriamente. Na cavitação pulsante a erosão cavitacional e a queda na altura útil são pequenas... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Cavitation in centrifugal pumps is the development of vapor bubbles from the pumped liquid into equipment suction region. Vapor bubbles developed somewhere in the flow, generally in the pump suction, will afterwards along the flow to collapse. This phenomenon is scientifically, technically and economically important. Scientifically, it is interesting because involves the flow of a fluid on liquid state, and simultaneously happens vapor bubbles development that also flow together the liquid fluid. Fluid vaporization and condensation processes are complex because involves phase change, a non-linear thermal phenomenon. Technically, it is important because when the flow happens with cavitation the flow and pump hydrodynamic parameters, generally, are strongly modified toward bigger thermodynamic irreversibility production. Economically, it is expensive because cavitation, generally, leads to thermodynamic process efficiency loss, and consequently it will have bigger costs for production of a given good, then decreasing economic efficiency and company competitiveness. Flow with cavitation in the pump suction presents three main devastating aspects: surging cavitation with low flow rate; steady cavitation with low total head; and cavitational erosion. Surging cavitation is characterized by unsteady, low frequency and high amplitude, intense bubbles development, producing strong vibration forces into the pumping system. Surging cavitation also causes the collapse of pumped fluid mass flow rate with values that goes from the normal flow to values that almost reach the zero flow, unsteadily. In surging cavitation, the cavitational erosion and the breakdown in total head are small. In steady cavitation the mass flow rate, and even the flow rate... (Complete abstract click electronic access below)
Mestre
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Kuhmmer, Regina. "Efeitos da suplementação de sal na profilaxia da síncope vasovagal : ensaio clínico randomizado." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2007. http://hdl.handle.net/10183/17367.
Full textAbstract:
Introdução: Síncope e sintomas ortostáticos são comuns em pessoas saudáveis. A suplementação de sal é utilizada em pacientes com melhora na resposta pressora e aumento da tolerância ortostática. Nós testamos à hipótese de que uma suplementação de sal aumentaria a tolerância ortostática em voluntários saudáveis. Métodos e Resultados: Vinte voluntários saudáveis (13 do sexo feminino, idade 29 ± 5,6 anos), sem história de síncope, foram submetidos ao teste inclinação ortostática, em um ângulo de 70 graus, por 35 minutos ou até que sintomas de pré-síncope ou síncope fossem observados. Foram randomizados e cruzados para receber 6g de sal em um dos exames e placebo no outro, 3 horas antes, em um protocolo duplo-cego. Para avaliar para-efeitos, foram avaliados índices clínicos e laboratoriais. A ingestão de sal melhorou a tolerância ortostática em 11 de 12 voluntários (55%) que apresentaram présincope ou síncope (variação de 1 a 6 minutos). O tempo com a suplementação de sal foi de 33,35 ± 4,1 minutos e com placebo 31,95 ± 4,4 minutos (média ± DP; p = 0,009), a tolerância ortostática diferiu em 1,4 ± 2,09 minutos (IC 95%, 0,42 - 2,37 minutos). A pressão arterial sistólica, a diastólica e a freqüência cardíaca na posição supina não alteraram de forma significativa. No entanto, a pressão arterial sistólica e a diastólica (120,85 ± 30,9 e 78,75 ± 20,6 mmHg) mantiveram-se mais elevadas ao término do exame com a suplementação de sal quando comparadas com o placebo (99,2 ± 29,8 e 64 ± 21 mmHg; p = 0,006 e p = 0,007, respectivamente). Conclusão: A suplementação de sal parece melhorar a tolerância ortostática em voluntários saudáveis, sem alterar as variáveis clínicas em repouso.Background: Orthostatic symptoms and syncope are common in healthy subjects. Salt supplementation can be used in patients showing improvement in the pressor response and increase in the orthostatic tolerance. We tested the hypothesis that single salt supplementation increases the orthostatic tolerance in healthy subjects. Methods e Results: Twenty healthy volunteers (13 females, 29.05 ± 5.57 years old), without syncope history, were submitted to head-up tilt test, at an angle of 70 degrees, for 35 minutes or until presyncope or syncope were observed. They were randomized and crossover to receive 6g of salt in one of the exams and placebo in the other, 3 hours before, in a double-blind protocol. To evaluate for side effects, there were evaluate clinical and laboratorial indexes. Ingestion of salt improved orthostatic tolerance in 11 out of 12 volunteers who presented presyncope or syncope (variation from 1 to 6 minutes). The time with salt supplementation was of 33.35 ± 4.1 minutes and with placebo it was of 31.95 ± 4.4 minutes (mean ± SD; p = 0.009), orthostatic tolerance differed in 1.4 ± 2.09 minutes (95% CI, 0.42 - 2.37 minutes). Systolic and diastolic blood pressure and heart rate in the supine position did not change significantly with salt or with the placebo. However, Systolic and diastolic blood pressure with salt supplementation (120.85 ± 30.9 mmHg and 78.75 ± 20.6 mmHg) were higher at the end of the exam when compared to placebo (99.2 ± 29.8 and 64 ± 21 mmHg; p = 0.006 and p = 0.007, respectively). Conclusion: Salt supplementation seems to improve orthostatic tolerance in healthy volunteers without changing clinical variables at rest.
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Ramaswamy, Raghupathy. "Thermal behavior of food materials during high pressure processing." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1190122901.
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Ševčík, Ondřej. "Aplikace vysokotlakého palivového systému na vznětový motor." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-378502.
Full textAbstract:
This thesis focuses on the design of new high pressure injection system application on diesel engine. The design came from company Zetor’s demands. For this application was chosen system Common Rail supplied by company Bosch. Assignment was separated into several tasks. Research of suitable components for low pressure section, design of waste system and high pressure injection tubes design including injector clamping. Due to injectors used in this system was necessary to redesign cover for valves and even new system to lead wires from outside of the engine to injectors. Injector is attached by screw connection, which is composed from screw and clamping jaw. These parts are subjected to an analytic calculations. Clamping jaw of injector is even subjected to a FEM analysis, which focuses on fatigue life. Finally, the drawings were documented.
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Schaefer, Laura Atkinson. "Single presssure absorption heat pump analysis." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17924.
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Maffulli, Roberto. "Conjugate heat transfer in high pressure turbines." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:6044f198-77ae-43e2-99af-cea4960e9407.
Full textAbstract:
In the present thesis the link between aerodynamics and heat transfer in high pressure turbines is investigated through steady numerical calculations. The investigations include the effect of wall temperature on the Heat Transfer coefficient (HTC), aiming to understand whether the conventional assumption of HTC being invariant with the thermal boundary condition does hold in a typical compressible flow, where the aerodynamic and thermal fields are strongly coupled. A novel non-linear three point method is proposed to scale wall heat transfer accounting for the dependence of HTC on wall temperature and local flow history. The effect of wall boundary condition on external aerodynamics and heat transfer calls for the need of Conjugate Heat Transfer (CHT) methods as design tools. For this reason CHT capabilities have been developed and integrated in Rolls-Royce Hydra CFD solver. The implemented CHT solver is fully-coupled, allowing for simultaneous solution of the solid and fluid domains. The implemented CHT coupling has been shown to be numerically stable with a good convergence rate for all cases tested. The implemented code has been successfully validated against both experimental, analytical and numerical data. Conjugate analysis of a double-wall trailing edge cooling design has been performed under matched external Biot conditions. Aim of the investigation has been to quantify the effect of CHT on the cooling discharge characteristics and external aerodynamics in a cooling configuration where coolant and external flow are separated by a lower thermal resistance than in a traditional internal cooling configuration. Detailed CHT results for this case are presented and discussed.
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Shahi, Mohammad Hassan Panjeh. "Pressure drop consideration in process integration." Thesis, University of Manchester, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333599.
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Miller, Keith Martin. "Heat transfer and velocity measurements in a kettle reboiler." Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/1204.
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Keinath, Brendon Louis. "Void fraction, pressure drop, and heat transfer in high pressure condensing flows through microchannels." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45806.
Full textAbstract:
Flow mechanisms affect transport processes during condensation. Most studies on two-phase flow regimes are qualitative in nature, typically providing only information to guide the identification of the respective regimes and the transitions between them. These studies have, however, not yielded quantitative information to assist the development of pressure drop and heat transfer models. Such qualitative studies have also yielded results with considerable variability between investigators. A comprehensive investigation of flow mechanisms, void fraction, pressure drop and heat transfer during condensation of R404A in microchannels was conducted. In contrast to all prior investigations, high-speed video recordings and image analyses were used to directly measure void fraction, slug frequencies, vapor bubble velocity, vapor bubble dimensions and liquid film thicknesses in tube diameters ranging from 0.508 to 3.00 mm. Experiments were conducted at reduced pressures and mass fluxes ranging from 0.38 to 0.77 and 200 to 800 kg m-2 s-1, respectively, to document their influences on the condensation process at local vapor qualities ranging from 0 to 1. This information was used to develop a model for the void fraction in condensing flows. A complementing set of heat transfer and pressure drop measurements were conducted on the same geometries at similar conditions, and the void fraction model was used in conjunction with these measurements to develop improved heat transfer and pressure drop models. This comprehensive set of experiments and analyses yields a self-consistent and accurate treatment of high-pressure condensation in small hydraulic diameter geometries. Furthermore, the heat transfer model was found to agree well with condensing ammonia and carbon dioxide data that were obtained at significantly different conditions in different tube diameters. The added physical understanding of the condensation process and the models developed will serve as important building blocks for the design of microscale condensers and thermal systems.
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Polyzoev, Vasco. "HAND-HELD TONOMETER FOR TRANSPALPEBRAL INTRAOCULAR PRESSURE MEASUREMENT." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202517.
Full textAbstract:
This dissertation describes the development of a portable, hand-held tonometer for measurement of the intraocular pressure through the eyelid. The primary use of such device will be by people diagnosed with the eye disease glaucoma. Glaucoma is the second leading cause of blindness in the world and is asymptomatic to the patient in its early stages. This allows it to remain undiagnosed for prolonged periods, causing irreversible damage to the affected person's vision. Elevated intraocular pressure is the main risk factor associated with the development of glaucoma, and is currently the only symptom that is treatable for the slowing down or stopping of the progression to blindness caused by the disease. The effectiveness of the medications or procedures aimed at reducing the pressure to below risk levels is currently monitored through visits to the ophthalmologists' offices, which makes the frequent monitoring of the pressure inconvenient, expensive and sometimes impossible. Due to the variation of the pressure throughout the day and during different activities or food and beverage intake, the portability of the device is important in order to allow the user to carry it with them and take measurements as frequent as needed. The option to perform the measurement through the eyelid avoids direct contact with the eye, eliminating possible discomfort, the use of anesthetics, and the risk of contamination.Several designs and measuring concepts are evaluated using a custom made pressure regulation system. A series of prototypes have been built and tested and the results are reported in the respective sections of the dissertation. The final concept selected for the measurement technique was based on multiple force probe indentation and a custom MEMS-based force sensor for it was designed and tested.The main contributions of this dissertation are the design, fabrication and test of the prototype devices and the MEMS force sensors. The obtained results and experience described here can serve as a platform for further optimization and improvement of the device, and eventual development of a prototype capable of performing clinical research studies and passing FDA approval for home and clinical use.
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Jeong, Eun S. "Heat transfer with oscillating pressure in reciprocating machinery." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13259.
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Alenezi, Abdulrahman. "Heat removal in high pressure turbine seal segments." Thesis, Cranfield University, 2017. http://dspace.lib.cranfield.ac.uk/handle/1826/12318.
Full textAbstract:
An important parameter for turbomachinery designers is “clearance control”, because the clearances between interfaces must be set to optimum values to maximize power output, operational life and efficiency. Leakage of hot gas result- ing from excessive clearance, can lead to flow instabilities, components overheat- ing, lower cycle efficiency and a dramatic increase in specific fuel consumption (SFC). Seal segments are used to reduce blade tip leakage, maintain coolant air flow and the stability of rotor-dynamic systems, helping to maximize blade perfor- mance. Seal segments in the High-Pressure Turbine (HPT) stages are one of the hottest components as they face the hot gases coming from the combustion chamber with temperatures which can reach 1700 0 C and which makes them sub- ject to oxidation, erosion, and creep. Thus, seal segments need to be protected. They are currently cooled using jet impingement techniques, passing cooling air (supplied by the high-pressure stage of the compressor) through channels to di- rectly impinge on the hot surfaces. The focus of this research was to improve the jet impingement cooling of the seal segments in HPTs by investigating methods that provide more effective heat removal. The role played by configurations of ribs (surface roughness using be- spoke turbulators), custom-made seal-segments, and surface features such as contouring, both in isolation and combination, were investigated using numerical methods. A set of 174 simulations were carried including the use of uniform and non-uniform roughness elements with different shapes and heights. Firstly, three different uniform roughness elements were tested, a square cross-sectional continuous rib, a hemi-spherical pin-fin and a cubical pin-fin for three jet impingement angles of α=90°, 60° and 45°. Each roughness element was also tested for six different heights (e) between 0.25 mm and 1.5 mm in increments of 0.25 mm. Results are presented in the form of average Nusselt number within and beyond the stagnation region. Secondly, the effect of using a roughness element with a square cross section in the shape of a circle, on the average Nu was investigated for four different radial locations (R), three jet angles (α) and six rib heights (e). Finally, the roughness element used was continuous, of square cross-sec- tion, in the shape of tear drops and reversed tear drops. This meant the rib did not act as a total barrier to flow in either the uphill or downhill direction.
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Johnson, Thomas G. "Heat Transfer in Brine Solutions at Supercritical Pressure." Ohio University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1439504843.
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Papangelakis, V. G. (Vladimiros George) 1958. "Aqueous pressure oxidation of arsenopyrite." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65435.
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竹井, 理絵, Rie TAKEI, 真貴 辻村, Maki TSUJIMURA, 丈子 高木, and Takeko TAKAGI. "異なる採取法による土壌水中の溶存無機イオン濃度の違い." 名古屋大学農学部付属演習林, 1998. http://hdl.handle.net/2237/8492.
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Agarwal, Akhil. "Heat Transfer and Pressure Drop During Condensation of Refrigerants in Microchannels." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14129.
Full textAbstract:
Two-phase flow, boiling, and condensation in microchannels have received considerable
attention in the recent past due to the growing interest in the high heat
fluxes made possible by these channels. This dissertation presents a study on
the condensation of refrigerant R134a in small hydraulic diameter (100 < Dh
< 160 mm) channels. A novel technique is used for the measurement
of local condensation heat transfer coefficients in small quality increments,
which has typically been found to be difficult due to the low heat transfer
rates at the small flow rates in these microchannels. This method is used to
accurately determine pressure drop and heat transfer coefficients for mass
fluxes between 300 and 800 kg/m2-s and quality 0 < x <
1 at four different saturation temperatures between 30 and 60oC. The
results obtained from this study capture the effect of variations in mass flux,
quality, saturation temperature, hydraulic diameter, and channel aspect ratio
on the observed pressure drop and heat transfer coefficients. Based on the available
flow regime maps, it was assumed that either the intermittent or annular flow
regimes prevail in these channels for the flow conditions under consideration.
Internally consistent pressure drop and heat transfer models are proposed
taking into account the effect of mass flux, quality, saturation temperature, hydraulic
diameter, and channel aspect ratio. The proposed models predict 95% and 94% of
the pressure drop and heat transfer data within ±25%, respectively. Both
pressure drop and heat transfer coefficient increase with a decrease in
hydraulic diameter, increase in channel aspect ratio and decrease in saturation
temperature. A new non-dimensional parameter termed Annular Flow Factor is also
introduced to quantify the predominance of intermittent or annular flow in the
channels as the geometric parameters and operating conditions change. This
study leads to a comprehensive understanding of condensation in microchannels
for use in high-flux heat transfer applications.
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Kingsley-Rowe, James Robertson. "Pressure and heat transfer measurement using a luminescent paint method." Thesis, University of Bath, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248105.
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Alhajeri, Hamad. "Heat removal in axial flow high pressure gas turbine." Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/11465.
Full textAbstract:
The demand for high power in aircraft gas turbine engines as well as
industrial gas turbine prime mover promotes increasing the turbine entry
temperature, the mass flow rate and the overall pressure ratio. High
turbine entry temperature is however the most convenient way to increase
the thrust without requiring a large change in the engine size.
This research is focused on improving the internal cooling of high pressure
turbine blade by investigating a range of solutions that can contribute to
the more effective removal of heat when compared with existing
configuration. The role played by the shape of the internal blade passages
is investigated with numerical methods. In addition, the application of mist
air as a means of enhanced heat removal is studied.
The research covers three main area of investigation. The first one is
concerned with the supply of mist on to the coolant flow as a mean to
enhancing heat transfer. The second area of investigation is the
manipulation of the secondary flow through cross-section variation as a
means to augment heat transfer. Lastly a combination of a number of
geometrical features in the passage is investigated.
A promising technique to significantly improve heat transfer is to inject
liquid droplets into the coolant flow. The droplets which will evaporate after
travelling a certain distance, act as a cooling sink which consequently
promote added heat removal. Due to the promising results of mist cooling
in the literature, this research investigated its effect on a roughened
cooling passage with five levels of mist mass percentages.
In order to validate the numerical model, two stages were carried out.
First, one single-phase flow case was validated against experimental
results available in the open literature. Analysing the effect of the rotational
force, on both flow physics and heat transfer, on the ribbed channel was
the main concern of this investigation. Furthermore, the computational results using mist injection were also validated against the experimental
results available in the literature.
Injection of mist in the coolant flow helped achieve up to a 300% increase
in the average flow temperature of the stream, therefore in extracting
significantly more heat from the wall. The Nusselt number increased by
97% for the rotating leading edge at 5% mist injection.
In the case of air only, the heat transfers decrease in the second passage,
while in the mist case, the heat transfer tends to increase in the second
passage. Heat transfer increases quasi linearly with the increase of the
mist percentage when there is no rotation. However, in the presence of
rotation, the heat transfers increase with an increase in mist content up to
4%, thereafter the heat transfer whilst still rising does so more gradually.
The second part of this research studies the effect of non-uniform cross-
section on the secondary flow and heat transfer in order to identify a
preferential design for the blade cooling internal passage. Four different
cross-sections were investigated. All cases start with square cross-section
which then change all the way until it reaches the 180 degree turn before it
changes back to square cross-section at the outlet. All cases were
simulated at four different speeds. At low speeds the rectangle and
trapezoidal cross-section achieved high heat transfer. At high speed the
pentagonal and rectangular cross-sections achieved high heat transfer.
Pressure loss is accounted for while making use of the thermal
performance factor parameter which accounts for both heat transfer and
pressure loss. The pentagonal cross-section showed high potential in
terms of the thermal performance factor with a value over 0.8 and higher
by 33% when compared to the rectangular case.
In the final section multiple enhancement techniques are combined in the
sudden expansion case, such as, ribs, slots and ribbed slot. The maximum
heat enhancement is achieved once all previous techniques are used
together. Under these circumstances the Nusselt number increased by
60% in the proposed new design.
47
Venables, Robert. "Thermal behaviour of transient high pressure hydrocarbon systems." Thesis, Imperial College London, 1997. http://hdl.handle.net/10044/1/8020.
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Abuserwal, Ahmed. "Pressure drop and forced convective heat transfer in porous media." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/19512/.
Full textAbstract:
Metal foams, a new class of porous material with highly permeable structure and higher porosity (>0.60) compared with classical porous granular beds, are a viable solution to enlarge the thermal exchange area and provide a high heat capacity and high specific area. These metal foams are available in a number of solid materials with different porosities and pore size. There is a current lack of understanding regarding metal foam microstructure parameters’ effects on hydraulic and thermal parameters. This is a barrier to the design and implementation of various industrial applications. The current study aims to discover the effects of the pore shape and morphological parameters in terms of pore size and porosity at relatively low ranges of porosity on fluid flow and conductive and convective thermal transport phenomena. The manufacturing defects were tracked using the image processing technique for scanned surfaces samples. The effect of these defects on the thermal and hydraulic parameters was also studied.
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Kamalian, Amirali. "Heat transfer modelling of high pressure steam pretreatment of biomass." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-238585.
Full textAbstract:
Pretreatment of biomass plays an important role in IGCC processes. Optimized operating conditions improve overall process eciency, product diversity and producergas composition. This project focuses on the pretreatment of spruce woodbiomass using high pressure superheated steam in a packed bed reactor with heated walls. The objective is to optimize the operation for ecient energy consumption and uniform thermal treatment of wood particles along the reactor. For this purpose,two models have been developed: Single-phase superheated steam in porous media where local thermal nonequilibrium condition prevails, Multi-phase ow in porous media.The rst model investigates the essential parameters to be taken into accountto ensure a uniform thermal treatment as the pyrolytic agent i.e. steam exchanges heat with solid particles. It is found that solid matrix and steam reach thermalequilibrium at early stages of the process however, sharp decrease in uid temperatureis observed. This trend is believed to be aected mostly by uid inlet velocity and solid initial temperature. The model suggests that the initial solid temperaturedoes not play an important role compared to the uid inlet velocity.The focus of the second model is optimization of reactor heat source to avoidthe complications attributed by a two-phase ow. The model can predict the phasesaturation of uid in the porous media along with the pressure and velocity prolesfor a given inlet ow condition and reactor heating power. A reactor with heatsource localized at the inlet is recommended to satisfy the thermal requirements ofthe system.Steam treatment of biomass at elevated pressures is a novel technology whichis believed to bring about many advantages for IGCC process. However, detailed optimization is necessary to benet from these advantages.
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Keefe, Daniel Anthony. "Thermal behaviour of transient high pressure high speed flowing systems." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312028.
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