Call number: LD2668 .T4 1951 R55 / Master of Science

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

Indoor air quality has become a challenge together with the global aim &lsquo / decreasing energy consumption&rsquo / . Increasing insulation levels of building envelopes but implementing inaccurate building system details has caused excessive heat, accumulation of pollutants, etc. in spaces. In terms of educational spaces, the increase in complaints and illnesses due to unfavorable indoor air conditions leads to a decrease in concentration and so academic performance of students and staff. In the context, the aim of the study was indicating the poor indoor air quality conditions caused by inadequate fresh air supply in crowded educational spaces and making recommendations for the improvement. In the study, a classroom and a design studio in the METU Faculty of Architecture building were investigated. In order to examine the existing situation, at two locations of each room the temperature, relative humidity and CO2 were continuously recorded between 13 September 2011 and 24 February 2012 and air speed for ten-day periods between 26 November 2011 and 5 January 2012. The evaluation of the collected data indicated that both of the rooms had temperature, so relative humidity and CO2 accumulation problems mainly due to insufficient fresh air supply in the winter period. In order to eliminate the poor conditions in the rooms, the needed outdoor air can be provided through the inlet openings coupled with fan coils, which are in existence but not in use.

Människor spenderar idag över 90% av sin tid inomhus och inomhusklimatet spelar därför en viktig roll i personers hälsa och välbefinnande, större ju yngre personerna är. Syftet med den här rapporten har varit att undersöka och jämföra inomhusklimatet på två förskolor i Hallsbergs kommun, förskolan Äppellunden och Kompassen, med följande frågeställningar: - Hur upplevs förskolan Kompassens inomhusklimat i förhållande till mätningar av inomhusklimatet? - Hur upplevs förskolan Äppellundens inomhusklimat i förhållande till mätningar av inomhusklimatet? - Hur förhåller sig de två förskolornas upplevda inomhusklimat och mätningar av inomhusklimatet, vad gäller operativ temperatur, luftkvalitet, lufthastighet och fukt? Studien har pågått under en begränsad tid och har endast studerat rummen i förskolorna som barnen vistas i kontinuerligt. Studien tar inte i beaktning faktorer såsom ljud, ljus och lukt. Inomhusklimatet har studerats genom en enkät som skickats ut till alla pedagoger på de två förskolorna samt kompletterats med egna mätningar på luftkvalité och temperatur. De två förskolorna är i grunden väldigt olika. Äppellunden är en nybyggd förskola från 2019, medan Kompassen är en industrilokal från 1981 som år 2014 byggdes om till förskola. Inomhusklimatet påverkas av många olika faktorer som alla måste samverka. Här innefattas bland annat ventilationen, vars huvudsakliga funktion är att föra bort förorenad luft och tillföra ny luft. Inomhusklimatet ska även ha en behaglig temperatur, där kraven ställs utifrån den operativa temperaturen. Det ska heller inte vara varken för fuktig eller för torr luft inomhus och människan ska inte uppleva drag. För samtliga faktorer finns krav eller rekommendationer som bör följas för att upprätta ett bra inomhusklimat. Tidigare har bland annat projektet BETSI samt undersökningen ELIB utfört landsomfattande studier på inomhusklimatet. För att undersöka hur inomhusklimatet upplevs på förskolorna skickades en enkät om inomhusklimatet ut till pedagogerna. På samma förskolor mättes medelstrålningstemperaturen, lufttemperaturen, den relativa fuktigheten samt koldioxidhalten. Detta skedde i ett rum per avdelning och på fyra punkter i vardera rum. Även den operativa temperaturen beräknades. Över lag visade mätningarna att förskolorna har ett bra inomhusklimat, dock har de en torr inomhusluft. Tidigare undersökningar har visat att torr luft oftare blir ett större problem i stora hus. Detta gällde dock en studie om flerbostadshus, men vissa paralleller till förskolorna kan fortfarande dras. Från enkäten utlästes att pedagogerna främst hade problem med en varierande rumstemperatur på Äppellunden. Detta kan bero på att Äppellunden har ett ventilationssystem med ett varierande luftflöde. Kompassen besvärades främst av torr luft, en varierande rumstemperatur samt känslan av en instängd luft. Samtliga mätningar som utförts uppfyllde kraven och rekommendationerna som finns från myndigheter med undantag från en mätning på Kompassen. / People today spend more than 90% of their time indoors, making the indoor climate an important and significant part of their health and well-being, especially for younger people. The purpose of this report is to investigate and compare the indoor climate of two preschools in Hallsbergs Municipality, Äppellunden and Kompassen, with the following questions: - How is the indoor climate of Preschool Kompassen perceived in relation to measurements of the indoor climate? - How is the indoor climate of Preschool Äppellunden perceived in relation to measurements of the indoor climate? - How do the perceived indoor climate and measurements of indoor climate compare between the two preschools regarding operative temperature, air quality, air velocity and humidity? The study was conducted over a limited period and only examined the rooms in the preschool where the children are continuously present. The study does not consider factors such as noise, light, and smell. The indoor climate was studied through a survey sent to all educators at the two preschools and complemented by independent measurements of air quality and temperature. The two preschools are fundamentally very different Äppellunden is a newly built preschool from 2019, while Kompassen is an industrial building from 1981 that was converted to a preschool in 2014. Indoor climate is influenced by many different factors that all need to work together. This includes ventilation, whose main function is to remove polluted air and bring in fresh air. The indoor climate should also have a comfortable temperature, with requirements based on the operative temperature. The indoor air should not be too humid or too dry indoors, and people should not feel drafts. For all factors, there are requirements or guidelines that should be followed to establish a good indoor climate. Projects like BETSI and the ELIB survey have previously conducted nationwide studies on indoor climate. To investigate how the indoor climate is perceived at the preschools, a survey about the indoor climate was sent to the educators. In the same preschools, measurements of mean radiant temperature, air temperature, relative humidity, and carbon dioxide levels were taken, and the operative temperature calculated. This was done in one room per department and at four points in each room. Overall, the measurements showed that the preschools have a good indoor climate; however, they both have dry indoor air. Previous studies have shown that dry air often becomes a larger problem in big buildings. This was a study on multi-family houses, but some parallels to the preschools can still be drawn. From the survey, it was found that the educators mainly had problems with a varying room temperature at Äppellunden. This may be due to Äppellunden having a ventilation system with varying air flow. Kompassen mainly suffered from dry air, varying room temperature, and a feeling of stale air. All measurements performed met the requirements and recommendations from authorities, except for one measurement at Kompassen.

Zweck - Von Piloten werden u.a. die sogenannten "Manual Flying Skills" gefordert. Dabei muss der Pilot in der Lage sein (ohne Autopiloten) nach grundlegenden Instrumenten zu fliegen. Dafür sind neben Geschick auch Faustformeln erforderlich. Die Faustformeln müssen dafür verlässlich sein. Der Inhalt dieser Arbeit beschäftigt sich exemplarisch mit einer Faustformel zur Umrechnung der kalibrierten Fluggeschwindigkeit (Calibrated Airspeed, CAS) in die wahre Fluggeschwindigkeit (True Airspeed, TAS). --- Methodik - In Excel und Matlab werden die Ergebnisse aus den Berechnungen der Faustformel mit dem Ergebnis einer exakten Berechnungsweise anhand flugmechanischer Formeln verglichen. Dabei wird die Flughöhe und Fluggeschwindigkeit variiert. Es werden die Abweichungen ermittelt und in Diagrammen zwei- und dreidimensional visualisiert. --- Ergebnisse - Die zu prüfende Faustformel liefert in dem für Sie vorgesehen Anwendungsbereich hinreichend genaue Ergebnisse mit Abweichungen unter 5 %. Dabei nehmen die Abweichung zu, umso weiter die Parameter (Höhe und Geschwindigkeit) von typischen Reiseflugbedingungen entfernt sind. --- Bedeutung in der Praxis - Piloten können bedenkenlos auf die in dieser Arbeit geprüfte Faustformel zurückgreifen und kommen so mit überschaubarem Kopfrechenaufwand auf relativ genaue Ergebnisse. --- Wert - Diese Arbeit zeigt, wie mit mäßigem Zeitaufwand in Excel eine Faustformel über einen gesamten Bereich geprüft werden kann. Das Vorgehen kann auf weitere Faustformeln übertragen werden, sodass sich ein Pilot sein "Kniebrett" mit verifizierten Faustformeln füllen kann.