This study investigates horizontal water turbine. Firstly, blade element momentum theory is exploited to design blade profiles. Then, CFD software, Fluent, is used to obtain such simulation results as torque, power and efficiency. A shroud outside the water turbine is tested to show the influence on the output power. Detailed parameters, shroud geometry and blade number, are considered too. Additionally, the maximal power generated by the turbine is analyzed under periodic sea current flow in this research. Our studies show that installed shroud can increase the output power more effectively and surely. Various kinds of shroud geometry have influence on the water turbine capability. As for the shroud types, nozzle type is better to achieve the best power. But as the inclined angle increases, the power also rises. The blade number boosts up the output power. Compared with other parameters, shroud length is of minor significance. On condition of periodic current flow, NACA63415 outperforms NACA0009, NACA0011 and Elliptical 10 in terms of airfoil, with its best efficiency and power.

The main objective of the inquiry is to deduce the methods and techniques that were employed in the manufacture of the historically unique Shroud of Turin. By taking a more or less phenomenologically based stance, it is argued that this image could only have been produced by employing a photographically related technique. To this end, an examination is made of both the nature of the image, as well as all relevant documented evidence which supports the above stated hypothesis. In addition, practical experiments are conducted which employ the kinds of technology and apparatus known to have existed c 1250-1357 AD. The results of this investigation strongly support the notion that persons living c 1250- 1357 AD did in fact have the necessary technology to manufacture what could be termed a negative solargraphic image of a human subject. / Thesis (Ph.D.)-University of Durban-Westville, 1993.

The use of renewable energy is promoted worldwide to be less dependent on fossil fuels and nuclear energy. Therefore research in the field is driven to increase efficiency of renewable energy systems. This study aimed to develop a wind turbine for low wind speeds in South Africa. Although there is a greater tendency to use solar panels because of the local weather conditions, there are some practical implications that have put the use of solar panels in certain areas to an end. The biggest problem is panel theft. Also, in some parts of the country the weather is more suitable to apply wind turbines. Thus, this study focused on the design of a new concept to improve wind turbines to be appropriate for the low wind speeds in South Africa. The concept involves the implementation of a concentrator and diffuser to a wind turbine, to increase the power coefficient. Although the wind turbine was not tested for starting speeds, the implementation of the shroud should contribute to improved starting of the wind turbine at lower wind speeds. The configuration were not manufactured, but simulated with the use of a program to obtain the power production of the wind turbine over a range of wind speeds. These values were compared to measured results of a open wind turbine developed for South Africa. The most important matter at hand when dealing with a shrouded wind turbine is to determine if the overall diameter or the blade diameter of the turbine should be the point of reference. As the wind turbine is situated in a shroud that has a larger diameter than the turbine blades, some researchers believe that the overall diameter should be used to calculate the efficiency. Theory was revised to determine the available energy in the shroud after initial calculations showed that the power coefficients should have been higher than the open wind turbine with the same total diameter. A new equation was derived to predict the available energy in a shroud. The benefits of shrouded wind turbines are fully discussed in the dissertation content. / MSc (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

The use of renewable energy is promoted worldwide to be less dependent on fossil fuels and nuclear energy. Therefore research in the field is driven to increase efficiency of renewable energy systems. This study aimed to develop a wind turbine for low wind speeds in South Africa. Although there is a greater tendency to use solar panels because of the local weather conditions, there are some practical implications that have put the use of solar panels in certain areas to an end. The biggest problem is panel theft. Also, in some parts of the country the weather is more suitable to apply wind turbines. Thus, this study focused on the design of a new concept to improve wind turbines to be appropriate for the low wind speeds in South Africa. The concept involves the implementation of a concentrator and diffuser to a wind turbine, to increase the power coefficient. Although the wind turbine was not tested for starting speeds, the implementation of the shroud should contribute to improved starting of the wind turbine at lower wind speeds. The configuration were not manufactured, but simulated with the use of a program to obtain the power production of the wind turbine over a range of wind speeds. These values were compared to measured results of a open wind turbine developed for South Africa. The most important matter at hand when dealing with a shrouded wind turbine is to determine if the overall diameter or the blade diameter of the turbine should be the point of reference. As the wind turbine is situated in a shroud that has a larger diameter than the turbine blades, some researchers believe that the overall diameter should be used to calculate the efficiency. Theory was revised to determine the available energy in the shroud after initial calculations showed that the power coefficients should have been higher than the open wind turbine with the same total diameter. A new equation was derived to predict the available energy in a shroud. The benefits of shrouded wind turbines are fully discussed in the dissertation content. / MSc (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

The implementation of a ported shroud casing treatment is often used to extend the operating range of a centrifugal compressor. This work utilizes the STAR-CCM+ CFD package to analyze steady-state, single-passage simulations of a centrifugal compressor with and without a ported shroud to better understand how a ported shroud affects compressor flow physics. Verification and validation of simulations were conducted by comparison of results with a time-accurate full-annulus simulation and experimental data. Four different ported shroud revisions were considered and modeled along the full range of their stable operation, with emphasis placed on the flow limits of choke and stall. A ported shroud is found to improve the choked mass flow limit by increasing the aerodynamic area of the compressor. Near-stall operation is improved through flow recirculation through the ported shroud. This flow, which is induced with a large component of tangential velocity from having passed the impeller blades' leading edge once, reduces the impeller incidence. The influence of a strut is found to restrict both limits of operation by reducing the aerodynamic area and obstruction of tangential velocity. The revisions considered demonstrate that facilitation of flow entering the ported shroud under either near-stall or choked conditions causes a noteworthy improvement in performance. Such alterations, in this application, demonstrate a 3.3% improvement in choked mass flow rate under choked conditions and an 1.3 degree reduction in impeller incidence under near-stall conditions, as compared to the initial ported shroud design. Understanding the effect that a ported shroud casing treatment has on compressor flow physics, especially near its limits of operation, suggests methods for improving centrifugal compressor design to increase its stable operating range.

Technological developments in the area of high power LED light sources have enabled their utilization in general illumination applications. Along with this advancement comes the need for progressive thermal management strategies in order to ensure device performance and reliability. Minimizing an LED's junction temperature is done by minimizing the total system's thermal resistance. For actively cooled systems, this may essentially be achieved by simultaneously engineering the conduction through the heat sink and creating a well-designed flow pattern over suitable convective surface area. While such systems are routinely used in cooling microelectronics, their use in LED lighting systems encounter additional constraints which must be accounted for in the design of the cooling system. These are typically driven by the size, shape, and building codes involved with the lighting industry, and thus influence the design of drop-in replacement LED fixtures. Employing LED systems for customary down-lighting applications may require shrouded radial fin heat sinks to increase the heat transfer while reducing the space requirement for active cooling. Most lighting is already in some form of housing, and the ability to concurrently optimize these housings for thermal and optical performance could accelerate the widespread implementation of cost-efficient, environmentally-friendly solid-state lighting. In response, this research investigated the use of conical, cylindrical, square, and pyramidal shrouds with pin/radial fin heat sink designs for the thermal management of high power LED sources. Numerical simulations using FLUENT were executed in order to account for details of the air flow, pressure drop, and pumping power, as well as the heat transfer and temperature distributions throughout the system. The LEDs were modeled as a distributed heat source of 25 - 75 W on a central portion of the various heat sinks. Combinations of device junction temperature and pumping power were used to assess the performance of shrouded heat sink designs for their use in air-cooled, down-lighting LED fixtures.

No description available.

Around the world the implementation of the 5G mobile network is under way. With this latest generation of mobile data transfer comes many advantages compared to the previous generations. One tradeoff however is the reduced range of the transmitting radios due to the higher frequencies of the signal. One way to solve this is to place smaller radios closer to where the user is. This work studies one such radio and since it is cooled by fans and meant to be placed close to where people live and reside it is favorable to be able to reduce the noise transmitted to its surrounding. This work has therefor developed a proof of concept for a noise suppressing casing that accommodates three radios in order to reduce the total A-weighted sound power level that reaches its surrounding. This was done by using ducts with micro-perforated plates (MPPs) as a sound dampening element. To assist in the design process as well as to verify that placing the radios inside the casing did not raise the temperature of the radio’s component beyond acceptable levels a CFD-simulation was performed. The results of the CFD-simulations were also verified using an experiment where the radio’s temperature was recorded during different fan speeds. When measured, the casing lowered the total A-weighted sound power level of three radios by between 11.6 dB(A) and 14.2 dB(A) depending on the fan speed. The result of the thermal experiment show that the temperature was raised by between 2.8 °C and 5.9 °C depending on the fan speed, with higher fan speeds showing less difference when compared to the radio’s standalone performance. The results are deemed to show promise for the future use of casings fitted with Micro-perforated plates being used to reduce the noise transmitted by telecom radios. / Runt om i världen pågår implementeringen av 5G-mobilnätet. Med den senaste generationens mobila dataöverföring kommer många nya fördelar jämfört med tidigare generationer. En nackdel är däremot den kortare räckvidden hos signalen på grund av den högre frekvens som sänds ut av radion. Ett sätt att kringgå detta är att placera mindre radior närmare där användaren befinner sig. Detta examensarbete utgår från en sådan radio och eftersom den kyls med fläktar och ska placeras nära där människor bor och vistas är det fördelaktigt att kunna sänka ljudet som når omgivningen. Därför har ett ljudisolerande hölje utvecklats med plats för tre telekomradior med syfte att sänka den totala A-vägda ljudeffektnivån som når dess omgivning. För att åstadkomma detta användes kanaler i kombination med mikroperforerade plåtar (MPPs) tillsammans som ett ljuddämpande element. Som ett verktyg i designprocessen och för att säkerställa att radions komponenter inte blev för varma gjordes en CFD-simulering. Resultatet av simuleringen verifierades även med ett experiment där temperaturen hos radions kylflänsar mättes under olika fläktvarvtal. När den totala A-vägda ljudeffektnivån mättes för höljet tillsammans med tre radior uppstod en sänkning med mellan 11,6 dB(A) och 14,2 dB(A) beroende på aktuellt fläktvarvtal. Resultatet från experimentet visade även att temperaturen på radions kylfläns höjdes med mellan 2,8 och 5,9 °C beroende på fläktvarvtal, med mindre skillnad för högre fläktvarvtal vid jämförelse med radions temperatur vid drift utan hölje. Resultaten anses visa på den goda potentialen av att använda höljen utrustade med mikroperforerade plåtar för att minska överfört ljud från telekomradior.

As technology moves forward it has a tendency to consume more and more power that needs to be cooled by bigger and louder fans, this is especially true for the new generation of 5G radio equipment. This Master thesis is a collaboration with Ericsson and attempts to construct a shroud for containing a number of 5G radio units whilst attenuating the fan noise of the units as effectively as possible. In this project are air ducts used and at the ends silencers are created utilizing the Cremer impedance; the optimal wall impedance for damping an acoustic mode of a propagating wave. To predict the result, a simplified model in an acoustic FEM program was also explored and compared to the sound level of the constructed shroud. The finished shroud successfully reduces the noise of the radio units by 13 dB(A) while causing an increase in temperature of between 2.8°C to 5.9°C. This result was deemed to be a success and the Cremer impedance approach of reducing noise is therefore advised for future development. / Allt eftersom tekniken går framåt tenderar den att också förbruka mer och mer energi som i sin tur måste kylas av kraftigare och mer högljudda fläktar, detta fenomen är särskilt påtagligt när det kommer till den senaste generationens radioutrustning för 5G. Detta examensarbete är ett samarbete mellan KTH och Ericsson med avsikt att skapa en kåpa som är designad för att innesluta ett bestämt antal 5G radiomoduler. Denna kåpa ska i så stor utsträckning som möjligt dämpa det fläktinducerade bullret. I det här projektet nyttjas kanaler med ljuddämpare vid ändarna som dämpar ljudet med hjälp av Cremerimpedans, dvs: den väggimpedans som optimalt dämpar en akustisk mod. För att kunna förutspå resultatet skapades en förenklad akustisk modell i ett FEM program. Resultatet från denna modell jämförs sedan med ljudeffektnivån från slutmätningen av den färdiga kåpan. Resultatet från slutmätningen visar att kåpan lyckas sänka radioenheternas totala ljudeffektnivå med 13 dB(A) samtidigt som en temperaturökning på mellan 2.8°C och 5.9°C erhålls. Det här resultatet bedöms vara en framgång, vilket leder till slutsatsen att ljuddämpning med användning av Cremerimpedans rekommenderas för vidare arbete.

Operações de produção de petróleo, que utilizam sistemas de bombeamento centrífugo submerso, constantemente encontram a presença de gás livre nos poços, o que pode gerar ou agravar problemas como cavitação e falhas dinâmicas, quando o gás é succionado pela bomba. O separador gravitacional do tipo shroud invertido é uma solução possível para este problema nos casos de operação em poços direcionais de petróleo. O trabalho tem como objetivo apresentar um estudo do diâmetro das bolhas que ocorrem no interior de um separador gravitacional gás-líquido do tipo shroud invertido. A finalidade é o aprimoramento de um modelo fenomenológico do funcionamento deste tipo de separador, aplicado à indústria petrolífera, sendo que o modelo fenomenológico garante total separação de gás, fornecidas determinadas condições. O modelo prevê, através do cálculo da energia cinética turbulenta, o tamanho médio das bolhas carregadas para o seio do líquido por aeração no duto anular. Partindo de estudos anteriores, uma verificação do modelo fenomenológico foi feita utilizando um aparato experimental com misturas bifásicas ar-água e ar-óleo em três diferentes inclinações. O aparato possui dimensões radiais reais de um poço de petróleo offshore. Foi utilizado um sensor 3D ORM para a medição do tamanho médio (sauter) das bolhas arrastadas pelo líquido até a entrada do tubo de produção, em diversas combinações de vazões da mistura água-ar. Esta medição permite o ajuste das correlações que regem o modelo fenomenológico, no que diz respeito às equações dependentes do diâmetro teórico de bolhas arrastadas pela fase líquida. As descobertas provenientes deste estudo foram implementadas em um código computacional que será utilizado pela PETROBRAS, financiadora do projeto, para suas operações de bombeamento. / Oil mining operations powered by centrifugal submersible pumping systems suffer constant setbacks due to the presence of free gas in wells. Decompression in the reservoir liberates this gas in the form of bubbles that, upon reaching the suction end of the pump, cause cavitation and dynamic failures resulting in production and equipment losses. The Inverted-shroud gravitational separator is a possible solution to this problem. This work presents a study on diameters of bubbles that occur inside this separator. The goal is the improvement of the understanding of this kind of separator as well as the enhancement of a previously reported phenomenological model, which ensures total gas separation when the separator is installed in directional wells and under specific operational conditions. Empirically adjusted correlations are used to ensure that all entrained bubbles do not reach the pump. The model was tested for two-phase flows of water-air and oil-air mixtures using three different inclinations. Tests were performed with an experimental apparatus that simulates a pilot-scale well casing with an inverted-shroud separator installed. A 3D ORM particle-size sensor was employed in order to measure the average (sauter) diameter of entrained bubbles that are dragged by the liquid flow towards the end of the production tube. This investigation will be used to improve the reliability of the phenomenological model and reduce its dependency on a theoretical prediction of the bubble size. The findings were incorporated to the final version of an in-house gas separator design software developed at the request of PETROBRAS, the project funder and Inverted-shroud patent holder, for usage on its oil mining operations.