No description available.

Since the CO 2-emissions and electricity prices are ever increasing many companies have tried to reduce their energy consumption in order to reduce both CO2-emissions and the cost of using energy. Therefore, in this article an office building situated in Sweden have been investigated with its current ventilation flow and what saving poten-tials can be made from heat recovery and a different ventilation flow in regards to health, energy and cost. Empirical data have been collected to be able to calculate ener-gy savings made by heat recovery and new ventilation flow. A ventilation flow of 25 l/s per office were chosen and that the conference room should have at least 3 l/s per m² the dining room and locker was not investigated thoroughly and therefore a ventilation flow from the recommendations of Sweden was followed. The total flows became, 530 l/s respectively 630 l/s for the top and bottom floor. A rotating heat exchanger with an es-timated efficiency of 80% was used for heat recovery and through the two methods combined an energy reduction up to 96,4 % for heating and 83,4 % from the electricity could be reduced.

As a result of the rising electrical energy costs in South Africa, a method was sought to reduce the overall electrical consumption of typical shaft systems. A typical shaft configuration was analysed and the primary energy consumers were identified. The ventilation fans for this system were found to consume a total of 15% of the total energy of the shaft system. It was calculated that more than 50% of this energy is consumed by the shaft itself, more specifically by the pressure losses that occur in the shaft as the ventilation air passes through it. It was recognised that there was therefore an opportunity to achieve an energy savings and therefore a costs savings in the total cost of operating a shaft system by reducing the overall resistance of the equipped downcast shaft. However, before any work could continue in this regard, the results noted above required validation. This was achieved though the comprehensive evaluation of the Impala #14 Shaft system. This system was tested and the pressure losses noted in the calculations were verified. In order to ensure that the theory being used was accurate, the next step was to evaluate a number of shafts both from a theoretical perspective by measuring the real shaft pressure losses against time. This was done and a total of five shafts were instrumented and the actual pressure losses over the shaft plotted against time. These shafts were then subjected to a theoretical evaluation using the theory as described by McPherson in 1987. Finally, in order to ensure a thorough understanding of the behaviour of the ventilation air in shaft systems, the systems were simulated using computational fluid dynamic (CFD) techniques. On the whole there was not a good correlation between the tests and either the theoretical calculations or the CFD simulations. This was attributed to the general imperfections in the shaft and the difficulty in obtaining exact values for the drag coefficients of the buntons. These differences highlight the difficulty in modeling the non-homogenous physical environment and providing a factor that can be used to ensure that the theoretical designs are aligned with the physical reality. This factor is approximately 30%. There were also significant discrepancies between the theoretical analysis and the CFD simulation during the initial comparisons. This discrepancy reduced as the complexity of the CFD models increased, until, when the complete shaft was modeled using the full buntons sets, the pipes and the flanges, the difference between the theoretical evaluation and the CFD simulation was small. The result demonstrates that the theory is insufficient and that the inter-related effect of the buntons and fittings has not been fully appreciated. The current theory however has been developed using drag coefficients and interference factors for the buntons sets which have been taken from measurements of similar configurations. This does account for the relative accuracy of the current theory in that there is little difference between the CFD result and that of the theory. However, as the shaft parameters are changed to reflect new layouts and scenarios, it is unlikely that theory will continue to prove accurate. The final phase of the work presented here was to evaluate the cost-effectiveness of using different bunton shapes and shaft configurations. It is shown that: <ul><li> The increase in the pressure losses and therefore the direct operating costs of the shaft can vary by as much as 80%, depending on the bunton configuration chosen.</li><li> The placement of the piping in the shaft can increase the pressure losses and therefore the direct operating costs of the shaft by as much as 12%, depending on the placement of the piping in the shaft; this effect includes the use of flanges. </li><li> The use of fairings on a large cage can reduce the resistance that the cage offers to the ventilation flow by as much as 30%. This, however, does not translate into a direct saving because as the cage moves through the shaft, the overall effect is transitory. </li> </ul> The savings discussed above can be significant when the items highlighted in this work are applied correctly. / Thesis (PhD(Eng))--University of Pretoria, 2012. / Mining Engineering / unrestricted

A comprehensive experimental study has been conducted using Particle Image Velocimetry (PIV) for a wide array of ventilation schemes and mining configurations for the purpose of examining ventilation characteristics in dead end mine headings. Flow behaviors in two basic mining sequences of box and slab cuts for 30 ft and 60 ft deep cuts were studied. The present thesis discusses the effect for various geometric and flow parameters including the variation of inlet flow velocities, entry heights, face zone widths and curtain widths on the flow behavior. The Reynolds number Re considered for this study ranges from 1 105 to 3 106 based on curtain width and exit velocity. The variation of the face zone and the curtain widths considerably affected the flow behavior, resulting in recirculation regions in the face area for critical combinations. Jet spreading angles and virtual origins have been calculated for the different geometries showing that an optimum range of face and curtain widths exists. A detailed discussion employing various scenarios for exhaust ventilation systems has also been made. Full-size measurements and comparison of the experimental data with numerical simulations is presented. Implementation of machine-mounted scrubbers in the blowing system are discussed for different values of the ventilation ratios (Qs/Qin) ranging from 14% to 53%. The scrubber system, typically introduced for dust collection, is also shown to be a useful tool in providing adequate ventilation to the immediate face area.

Personal på Högskolan i Gävle tycks periodvis uppleva dålig komfort ikontorsrummen på södersidan i skolans gamla kasernbyggnader. En undersökninggjordes därför på högskolan i april månad i tre kontor, ett med fönsterhuvudsakligen i norrläge och två med fönster huvudsakligen i söderläge. Syftet varatt kartlägga den termiska komforten och luftkvaliteten i de olika väderstrecken ochjämföra med gällande rekommendationer, bland annat genom att beräkna PMV vidolika tillfällen. Vidare undersöktes potentiella samband mellan ute- och inneklimatsamt tunna gardiners inverkan på termostat, värmeflöde och komfort. Den undersökta byggnaden är en äldre stenbyggnad med ovanligt välisoleradefönster och termostatstyrda, vätskeburna radiatorer. Byggnaden har FTX-ventilationmed ett till- och ett överluftsdon i varje kontorsrum. Mätningarna utfördes meddataloggrar som mätte lufttemperatur, relativ luftfuktighet och koldioxidhalt. I tvåav rummen mättes även globtemperatur. Utöver det mättes lufthastighet på tre olikahöjder i två av rummen samt ventilationsflödet i samtliga rum. Resultatet visade att inomhus- och utomhustemperatur har en relativt högkorrelation. Relativa luftfuktigheten var nästan alltid högst i norrläge, men i samtligarum var den låg – lägre än vad som rekommenderas i riktlinjerna. Soligt väderpåverkade temperatur och relativ luftfuktighet inomhus mest av alla vädervariabler,men personnärvaro och ventilation påverkade mer än utomhusklimatet. Kontor isöderläge hade som förväntat högre temperatur än i norrläge, och översteg deriktlinjer som finns för temperatur i kontor. Som följd av detta blev PMV högre isöderläge, tillfälligt högre än komfortgränsen 0,5, med ett högsta värde på 1,41. Kontoret i norrläge höll sig vid de undersökta tillfällena inom intervallet föraccepterat PMV med ett lägsta värde på -0,35. Detta tyder på att värme i söderlägeär ett större problem än kyla i norrläge. Lufthastigheterna blev låga i bådaväderstrecken. Ventilationsflödena visade sig vara 2/3 av det projekterade värdet,men ändå låg koldioxidhalten på en acceptabel nivå enligt riktlinjer. Gardiner påverkade komforten mer i söderläge än norrläge, men påverkade intetillräckligt mycket för att komma ner i en acceptabel komfortnivå vilket kan bero påatt de var av mycket tunt material. Det var svårt att se tydlig gardinpåverkan påtermostaten, men fråndragna gardiner kan leda till att termostaten reagerar påtemperaturökningar i ett rum snabbare. Däremot påverkades värmeflödet tydligaregenom fönstret av gardinerna. Skillnaden i värmeflödet vid för- och fråndragnagardiner blev 4,1 W. / Employees at University of Gävle seem to periodically experience suboptimalcomfort in south facing offices in the school’s old barrack buildings. Therefore, acase study was conducted in April in three offices, one facing north and two facingsouth. The aim of the study was to map the thermal comfort and air quality in thedifferent directions and compare these to the existing recommendations, includingcalculating PMV at different times. A potential correlation between out- and indoorclimate was also examined, as well as the effect of thin curtains on the thermostat, heat flux and comfort. The University of Gävle is an old brick building with unusually well insulatingwindows and thermostatically regulated, waterborne radiators. The building hasmechanical ventilation with heat recovery, and each office has one supply and oneover-air diffuser. The measurements were made with data loggers that measured airtemperature, relative humidity and carbon dioxide. The globe temperature was alsomeasured in two of the rooms. The air velocity on three heights was measured aswell in two of the offices and the ventilation flow was measured in all the rooms. The result showed that indoor- and outdoor temperature have a relatively highcorrelation. The relative humidity was almost always higher in the north facingoffice, but in all the rooms it was low – lower than the recommended guidelines.Sunny weather affected the indoor temperature and relative humidity the most of allthe weather variables, but presence of people and ventilation affected more than theoutdoor climate. South facing offices had as expected a higher temperature thannorth facing ones, and exceeded the guidelines concerning temperatures in offices.Due to that the PMV was higher in the south facing office, temporarily exceedingthe comfort limit of 0,5, with a maximum value of 1,41. The north facing office waswithin the limits during the measurements and had a minimum value of -0,35. Thisindicates that heat in the south facing office is more of a problem than coldness inthe north facing office. The air velocities were low in both directions of thebuilding. The ventilation flow turned out to be 2/3 of the intended value, but thecarbon dioxide content was still acceptable according to guidelines. Curtains influenced the comfort more in the south facing office than in the northfacing office, but they didn’t influence enough to get to an acceptable comfort level,which may be because of the very thin material. It was difficult to see a distinctinfluence from the curtains on the thermostat, but using no curtains could lead tothe thermostat responding faster to increases in temperature in a room. However,the heat flow through the window was influenced more distinctly by the curtains.The difference in heat flow when using curtains compared to no curtains was 4,1 W.

The master’s thesis deals with air flow in the interior of automobile Škoda Octavia. The attention is focused only at a side ventilating outlet. Author’s effort was to propose the appropriate criteria for evaluation and assessment of ventilating outlet quality and elaborate the methodology of measurement for these criteria. Then follows the application of the methodology and measurement of velocity field of air flow from the outlet by the method of hot wire anemometry. The thesis also contains comparison of the results with the results attained by the smoke visualization.

No description available.