This thesis focuses on design of device to generate hot air. This generator is supposed to be used to perform thermal tests for a company. Introduction summarizes general knowledge about ventilators, heat transport in air flow, and pressure losses. Main part of the thesis describes development of the generator. Initial design was followed by selection of suitable solution variants, design of major parts of the generator supported by calculations and overall conception of the generator. Final part summarizes the achievements and economic analysis.

Most heat transfer tubes are designed for either fully uniform wall temperature or fully uniform wall heat flux boundary conditions under forced convection. Several applications, including but not limited to the solar collectors of renewable energy systems, do however operate with non-uniform boundary conditions. Limited research has been conducted on non-uniform wall heat flux heat transfer coefficients in circular tubes, especially for mixed convection conditions. Such works are normally numerical in nature and little experimental work is available. In this experimental investigation the effects of the circumferential heat flux distribution and heat flux intensity on the single phase (liquid) internal heat transfer coefficient were considered for a horizontal circular tube. Focus was placed on the laminar flow regime of water within a stainless steel tube with an inner diameter of 27.8 mm and a length to diameter ratio of 72. Different outer wall heat flux conditions, including fully uniform and partially uniform heat fluxes were studied for Reynolds numbers ranging from 650 to 2 600 and a Prandtl number range of 4 to 7. The heat flux conditions included 360˚ (uniform) heating, lower 180˚ heating, upper 180˚ heating, 180˚ left and right hemispherical heating, lower 90˚ heating, upper 90˚ heating and slanted 180˚ heating. Depending on the angle span of the heating, local heat fluxes of 6 631 W/m2 , 4 421 W/m2 , 3 316 W/m2 , 2 210 W/m2 and 1 658 W/m2 were applied. Results indicate that the local and average steady state Nusselt numbers are greatly influenced by the applied heat flux position and intensity. Highest average heat transfer coefficients were achieved for case where the applied heat flux was positioned on the lower half (in terms of gravity) of the tubes circumference, while the lowest heat transfer coefficients were achieved when the heating was applied to the upper half of the tube. Variations in the heat transfer coefficient were found to be due to the secondary buoyancy induced flow effect. The relative thermal performance of the different heating scenarios where characterised and described by means of newly developed heat transfer coefficient correlations for fully uniform heating, lower 180° heating, and upper 180° heating. / Dissertation (MEng)--University of Pretoria, 2018. / Mechanical and Aeronautical Engineering / MEng / Unrestricted

Considering the hypothetical core melt down scenario for a light water reactor (LWR) a possible failure mode of the reactor pressure vessel (RPV) and its failure time has to be investigated for a determination of the loadings on the containment. Numerous experiments have been performed accompanied with material properties evaluation, theoretical, and numerical work /REM 1993/, /THF 1997/, /CHU 1999/. For pre- and post-test calculations of Lower Head Failure experiments like OLHF or FOREVER it is necessary to model creep and plasticity processes. Therefore a Fi-nite Element Model is developed at the FZR using a numerical approach which avoids the use of a single creep law employing constants derived from the data for a limited stress and temperature range. Instead of this a numerical creep data base (CDB) is developed where the creep strain rate is evaluated in dependence on the current total strain, temperature and equivalent stress. A main task for this approach is the generation and validation of the CDB. Additionally the implementation of all relevant temperature dependent material properties has been performed. For an evaluation of the failure times a damage model according to an approach of Lemaitre is applied. The validation of the numerical model is performed by the simulation of and com-parison with experiments. This is done in 3 levels: starting with the simulation of sin-gle uniaxial creep tests, which is considered as a 1D-problem. In the next level so called "tube-failure-experiments" are modeled: the RUPTHER-14 and the "MPA-Meppen"-experiment. These experiments are considered as 2D-problems. Finally the numerical model is applied to scaled 3D-experiments, where the lower head of a PWR is represented in its hemispherical shape, like in the FOREVER-experiments. This report deals with the 1D- and 2D-simulations. An interesting question to be solved in this frame is the comparability of the French 16MND5 and the German 20MnMoNi55 RPV-steels, which are chemically nearly identical. Since these 2 steels show a similar behavior, it should be allowed on a lim-ited scale to transfer experimental and numerical data from one to the other.

Nanofluids are homogeneous mixture of dispersed solid particles in base fluids. These solid particles are usually smaller than 100nm. Suspended nanoparticles modify the properties of based fluids. It is claimed, in some literature, for nanofluids to have greater than expected heat transfer performance. Due to this, nanofluids have gained great attention from both research and development and industries active in cooling systems. This thesis reports several measurements of convective heat transfer coefficient in a horizontal open micro-tube test section under laminar flow regime. The test section has an inner diameter of 0.5mm made of stainless steel and it has a length of 30cm. Two different test sections have been built. The first one has 13 thermocouples attached on the wall and the second one has 10. These thermocouples are used to measure the wall temperature distribution along the tube. In addition, two more thermocouples are used inside the micro-tube, at the inlet and outlet, to measure the bulk temperature of the nanofluids. A syringe pump is used for injecting the nanofluids through the micro-tube. A DC power supply provides constant heat flux along the test section and a differential pressure transducer measures the pressure drop of the test section. Aqueous based Al2O3 (9 wt %), ZrO2 (9 wt %), TiO2(9 wt %), CeO2 (9wt %), CNT (0.15 wt %), and diamond (1 wt %) have been tested in this thesis. Local Shah’s correlation predicts very well the behaviour of these nanofluids. The results are compared with water in six different ways: heat transfer forconstant Reynolds numbers, volume and mass flow rates, pressure drops andpumping powers. Enhancement in heat transfer is recognisable only in thegraphs of Nu numbers for constant Reynolds numbers. This can be attributed to the higher viscosity for nanofluids. Moreover, friction factor for constant Reynolds numbers has been compared. All the nanofluids with the exception of Al2O3 and diamond suit quite well with Darcy-Weisbach correlation.

Due to constraints and changes in operating conditions, heat exchangers are often forced to operate under conditions of transitional flow. However, the heat transfer and flow behaviour in this regime is relatively unknown. By describing the transitional characteristics it would be possible to design heat exchangers to operate under these conditions and improve the efficiency of the system. The purpose of this study was to experimentally measure the heat transfer and pressure drop characteristics of smooth tubes at a constant heat flux in the transitional flow regime. The measurements were used to describe the flow behaviour of this regime and attempt to develop a correlation that can be used in the design of a heat exchanger. An experimental set-up was developed, consisting of an overall set-up, a removable test section as well as a controller, which ensured a uniform heat flux boundary. The test section allowed for the measurement of the temperature along the length of the test section, the pressure drop across the test section, the heat flux input and the flow rate. The measurements were used to determine the heat transfer coefficients and friction factor of the system. Three test sections were developed with outer diameters of 6, 8 and 10 mm in order to investigate the influence of heat exchanger size. Each test section was subject to four different heat flux cases of approximately 1 500, 3 000, 4 500 and 6 000 W/m2. The experiments covered a Reynolds number range of 450 to 10 300, a Prandtl number range of 4 to 7, a Nusselt number range of 2.3 to 67, and a Grashoff number range of 60 to 23 000. Good comparison was found between the measurements of this experiment and currently available literature. The experiments showed a smooth transition from laminar to turbulent flow with the onset of transition dependent on the heat flux of the system and with further data capturing, a correlation can be found to describe the Nusselt number in the transitional flow regime. / Dissertation (MEng)--University of Pretoria, 2011. / Mechanical and Aeronautical Engineering / unrestricted

Preignition is an ignition event that happens before it is expected to happen and, many times, where it is not expected to happen. Understanding this phenomenon is of great importance as it influences the design and operation of modern downsized boosted internal combustion engines. To gain a fundamental understanding of preignition, homogeneous reactors like shock tubes and rapid compression machines may be used to decipher the influence of fuel chemical structure, temperature, pressure, equivalence ratio and bath gas on preignition. In this thesis, a comprehensive study of the preignition tendency of various chemical systems is presented. Firstly, renewable fuels like ethanol, methanol and a surrogate of conventional fuels, n-hexane, are characterized by traditional shock tube techniques, such as the measurements of ignition delay times and pressure-time histories, to identify thermodynamic conditions which promote non-ideal ignition behavior. Preignition pressure rise and the expedition of measured ignition delay times are identified as the indicators of non-homogeneous combustion. It is shown that preignition effects are more likely to be observed in mixtures containing higher fuel concentration and that preignition energy release is more pronounced at lower temperatures. High-speed imaging was implemented to visualize the combustion process taking place inside the shock tube. End-wall imaging showed that low-temperature ignition may be initiated from an individual hot spot that grows gradually, while high-temperatures ignition starts from many spots simultaneously which consume the reactive mixture almost homogeneously. Simultaneous lateral and endwall imaging was implemented in both low- and high-pressure shock tube facilities. All tested fuels exhibited localized ignition at low temperatures, and methanol showed a higher propensity than ethanol to ignite far from the endwall. Imaging experiments were also performed in a rapid compression machine to understand preignition at lower temperatures. Herein, ethanol showed non-homogeneous ignition while iso-octane and diethyl ether exhibited homogeneous ignition at the low-temperature conditions. Various criteria for the onset of preignition were tested against experimental observations to propose an adequate predictor of non-ideal ignition phenomena in practical applications. A non-dimensional number, relating the ignition delay sensitivity and laminar flame speed of the mixtures, was found to be the best criterion to elucidate ignition regimes.

ABSTRACT Einleitung: In einer retrospektiven Analyse untersuchten wir die Anwendung der Proteinführungssonde nach Ermisch bei Ileuspatienten. Methoden: Insgesamt 288 klinikinterne Fälle aus dem Zeitraum 2000 bis 2010 wurden zum Thema „Ileusoperation mit versus ohne Ermischsonde“ analysiert. Alle Patienten mit erfolgreicher Sondenplatzierung wurden der Gruppe 1 zugeordnet (n=102). Fälle ohne Sondentherapie bildeten die Gruppe 2. Ergebnisse: Im Patientenkollektiv (n=288) lag das Durchschnittsalter bei 66,8 (±17,7) Jahren. 51,7% waren weiblich. Eine Ileusvoroperation betraf in Gruppe 1 12,7%, in Gruppe 2 6,5% (p=0,081,n.s.). Die Dünndarmeröffnung erfolgte in Gruppe 1 bei 27,3%, in Gruppe 2 bei 72,7% (p=0,001). Ein paralytischer Ileus lag in Gruppe 1 bei 15,7% und in Gruppe 2 bei 5,4% vor (p=0,001). Als postoperativ paralytischen Ileus wurden in Gruppe 1 5,9%(6/102), in Gruppe 2 3,8%(7/186) identifiziert (n.s.). In 5% der Fälle aus Gruppe 1 handelte es sich um ein Ileusfrührezidiv (vs. 1,1% in Gruppe 2; n.s.). 28 (80%) der 34 Reileus-Fälle traten in Gruppe 2 auf (Gr. 1: n=7, 20%; p=0,022). Die Letalität aufgrund postoperativer Sepsis (S) und Peritonitis (P) lag bei 24,1% (S) und 28,6% (P) in Gruppe 1 versus 65,4%(S) und 47,6%(P) in Gruppe 2 ( p(S)=0,003=s.; p(P)=0,31=n.s.). Postoperatives Multiorganversagen (ngesamt=20/288) betraf 5 Patienten (4,9%) der Gruppe 1 versus 15 Patienten (8,1%) in Gruppe 2 (n.s.). In 5,9% der 102 untersuchten Fälle kam es zu sondenspezifischen Majorkomplikationen. Die postoperative Letalität lag hingegen in Gruppe 1 bei 16,7% und in Gruppe 2 bei 18,3% (n.s.). Schlussfolgerung: Die Ermischsonde stellt vor allem beim postoperativ paralytischen Ileus (insbes. Ileusfrührezidiv), aber auch bei fortgeschrittenen mechanischen Ileusformen ein effektives Instrument zur geschlossenen Sekretausleitung und postoperativen Dünndarmschienung dar. Bei rein vaskulären Ileusformen bzw. im akuten Schub einer chronisch entzündlichen Darmerkrankung ist das Verfahren häufiger mit Risiken verbunden.:ABKÜRZUNGEN VI ABBILDUNGSVERZEICHNIS VIII TABELLENVERZEICHNIS IX 1 EINLEITUNG 12 1.1 Fragestellung 12 1.2 Definition des Krankheitsbildes Ileus 13 1.2.1 Einteilung des Ileus nach ätiologischen Gesichtspunkten 16 1.2.2 Einteilung in Primärileus und Formen des postoperativen Ileus 16 1.3 Intestinalsonden in der Ileuschirurgie 17 1.4 Alternative Dekompressionsverfahren 21 2 MATERIAL UND METHODEN 23 2.1 Methode 23 2.2 Krankengut 25 2.3 Aufbau und Funktionsweise der Ileusdekompressionssonde nach J. Ermisch 26 2.3.1 Aufbau und chemische Eigenschaften 26 2.3.2 Sondierungstechnik 29 2.3.3 Statistik 29 3 ERGEBNISSE 31 3.1 Soziodemografische Betrachtungen 31 3.1.1 Alter und Geschlecht 31 3.1.2 Gesundheitszustand 34 3.2 Charakteristik der beiden Patientengruppen 37 3.2.1 Voroperationen 37 3.2.2 Strahlentherapie und Chemotherapie 42 3.2.3 Chronisch entzündliche Darmerkrankung 42 3.2.4 Ileusform 42 3.2.5 Ileusgenese 49 3.2.6 Lokalisation der Passagestörung 51 3.2.7 Intraoperative Daten 54 3.2.8 Stationärer Aufenthalt und Exitus letalis 57 3.2.9 Komplikationen 64 3.2.10 Relaparotomie und Wundrevision 74 3.2.11 Daten zur Anwendung der Ermischsonde 77 4 DISKUSSION 81 4.1 Diskussion der Methodik unter Berücksichtigung möglicher Fehlerquellen 82 4.2 Problematik des retrospektiven Vorgehens im Rahmen der vorgelegten Untersuchung 86 4.2.1 Dauer des präoperativen Ileuszustandes 86 4.3 Diskussion der Ergebnisse 87 4.3.1 Soziodemographische Charakteristik 87 4.3.2 Indikationen für den Gebrauch der Ermischsonde 87 4.3.3 Technik der Darmsondierung 90 4.3.4 Effektivität 91 4.3.5 Perioperative Morbidität 94 4.3.6 Letalität 97 4.3.7 Ausblick 102 5 ZUSAMMENFASSUNG 103 6 LITERATUR 107 7 ANLAGEN 114 7.1 Reileus-Fälle (5 von 102) nach einer Operation mit PFS 114 8 SELBSTÄNDIGKEITSERKLÄRUNG 116 9 DANKSAGUNG 117 10 TABELLARISCHER LEBENSLAUF 118

Numerous studies have indicated that the microgravity environment of space has harmful effects on several tissues throughout the body. Although this phenomenon is well documented, research in this area is still in its relative infancy. This study investigates the effects of space flight on mucin production of the uterine tubes of mice. This study examined the epithelium of the uterine tubes from female mice that were flown on the space shuttle Endeavour for 13 days in August, 2007 and their concomitant controls. The tissue was qualitatively analyzed for the type of mucin produced, i.e.; acidic, neutral, acidic/neutral mixture. Further, the tissue was quantitatively analyzed for the amounts of mucins produced by measuring the thickness of the mucin layer for each region of the uterine tube: isthmus, ampulla, and infundibulum. One way ANOVA tests were used to compare mucin thickness between all three sets of animals. Results indicate similar but not identical results between the three regions of the uterine tube. The Baseline tissue had the thickest mucin layer regardless of treatment group. In the ampulla the mucin layer was the thinnest in the Flight tissue, followed by the Ground Control, with the Baseline being the thickest. Analysis of the mucin layer of the infundibulum of the three treatment groups indicated no difference in its thickness between the three regions of the uterine tube. These results indicate a trend toward thinning of the mucin layer of the uterine tube in space flight, but also indicate an influence by the housing environment.

Numerous studies have indicated that the microgravity environment of space has harmful effects on several tissues throughout the body. Although this phenomenon is well documented, research in this area is still in its relative infancy. This study investigates the effects of space flight on mucin production of the uterine tubes of mice. This study examined the epithelium of the uterine tubes from female mice that were flown on the space shuttle Endeavour for 13 days in August, 2007 and their concomitant controls. The tissue was qualitatively analyzed for the type of mucin produced, i.e.; acidic, neutral, acidic/neutral mixture. Further, the tissue was quantitatively analyzed for the amounts of mucins produced by measuring the thickness of the mucin layer for each region of the uterine tube: isthmus, ampulla, and infundibulum. One way ANOVA tests were used to compare mucin thickness between all three sets of animals. Results indicate similar but not identical results between the three regions of the uterine tube. The Baseline tissue had the thickest mucin layer regardless of treatment group. In the ampulla the mucin layer was the thinnest in the Flight tissue, followed by the Ground Control, with the Baseline being the thickest. Analysis of the mucin layer of the infundibulum of the three treatment groups indicated no difference in its thickness between the three regions of the uterine tube. These results indicate a trend toward thinning of the mucin layer of the uterine tube in space flight, but also indicate an influence by the housing environment.

Background: Laryngospasm is a common and often serious adverse respiratory event encountered during anesthetic care of children. We examined, in a case control design, the risk factors for laryngospasm in children. Material and Methods: The records of 130 children identified as having experienced laryngospasm under general anesthesia were examined. Cases were identified from those prospectively entered into the Mayo Clinic performance improvement database between January 1, 1996 and December 31, 2005. Potential demographic, patient, surgical and anesthetic related risk factors were determined in a 1 : 2 case-control study. Results: No individual demographic factors were found to be significantly associated with risk for laryngospasm. However, multivariate analysis demonstrated significant associations between laryngospasm and intercurrent upper respiratory infection (OR 2.03 P = 0.022) and the presence of an airway anomaly (OR = 3.35, P = 0.030). Among those experiencing laryngospasm during maintenance or emergence, the use of a laryngeal mask airway was strongly associated even when adjusted for the presence of upper respiratory infection and airway anomaly (P = 0.019). Ten patients experienced postoperatively one or more complications whereas only three complications were observed among controls (P = 0.008). No child required cardiopulmonary resuscitation and there were no deaths in either study cohort. Conclusions: In our pediatric population, the risk of laryngospasm was increased in children with upper respiratory tract infection or an airway anomaly. The use of laryngeal mask airway was found to be associated with laryngospasm even when adjusted for the presence of upper respiratory tract infection and airway anomaly.