The present thesis aims to study the effect of human movements on local exhaust ventilation. In its simplest terms, local exhaust ventilation is a system which has the function of extracting contaminated air situated close to the contaminant source, protecting a working person from exposure to hazardous substances by containing or capturing them locally, at the emission point. As an important security measure referred to terms of health, it is crucial for the healthiness of workers to control and prevent them from the exposure to vapour, mist, dust or other airborne contaminants. Additionally, to a lesser degree of significance, it can be stressed an expected increase in worker performance due to an improvement of the working conditions. There is an existing necessity for well-defined and appropriate methods to test the performance of local exhaust devices in order to reach standard efficiency values. The lack of an international standardization led to the realization of this study, which, ultimately, has the purpose of obtaining relevant results that can be utilized for future normalized test procedures. The study entails full scale experimental measurements that include air velocity measurements in 3 dimensions, a local exhaust ventilation device with circular hood and a flat flanged plate and a controlled generation of air turbulence through physical movements of a human-sized cylinder, simulating a walking person. The present study extends previous similar studies at the University of Gävle, where the controlled air turbulence was generated by a moving plate. After meaningful results obtained in that study, one of the considerations was to better simulate a walking person, by replacing the plate for a movable cylinder. The present study points at a larger similarity occurring with a cylinder than with a plate, as regards the air flow pattern produced by a real walking person. As in the previous study, the Percentage of Negative Velocities, PNV, has been used as the main measure of turbulence induced risk of contaminant spread. The PNV represents the fraction of the time when the flow is directed opposite to the suction air stream in front of the local exhaust hood. The obtained results conclude that the use of the cylinder as a moving object has been an improvement to simulate the effect of the movement of a human being on a relaxed walking pace. The present study was carried out in parallel with the thesis work by Leyre Catalán Ros, which complements this study by analyzing the effect of an added heated dummy, simulating a person seated in front of the local exhaust device.

Local exhaust (LE) ventilation is a ventilation technique where contaminated air is locally extracted close to the contaminant source usually with the purpose to reduce the exposure of workers to dust, fumes or vapour, which can be hazardous to their health. The performance of a LE installation depends however on many influential factors, and there is not yet an international standardized way to test LE constructions. The present study is the natural continuation of some previous studies at the University of Gävle that aimed at contributing to the establishment of such tests. The study entails full scale experimental measurements that include 3-D air velocity measurements and tracer gas tests in a controlled air turbulence environment generated through physical movements of a vertical, human-sized cylinder. These measurements were focused on human exposure, which was analysed by means of a seated human simulator for different configurations in which the exhaust flow rate, turbulence level, the exhaust hood arrangement and the measuring/injecting distance varied. The use of a sonic 3-D anemometer, that yielded both magnitude and direction of the air movement, proved very useful in analysing the generated air turbulence. As a measure of the LE performance, PNV value (Percentage of Negative Velocities) was used. This measure represents the percentage of time when the air flow at the measuring point in front of the exhaust hood is directed away from the nozzle, i.e. when the velocity component in the direction towards the exhaust hood opening is negative. Regarding the results obtained, in an otherwise undisturbed environment, measurement data showed that the natural convection from the human simulator sitting in front of the LE introduces some disturbances of the air flow in the suction region, proportional to the exhaust flow rate. However, when additional turbulence was generated through the controlled movements of the human-sized cylinder, thus creating a controlled turbulence setting, natural human convection leaded to a lower percentage of negative velocities (PNV) in comparison with the case in which human simulator was not present, especially for low exhaust air flow rates and when the exhaust hood was raised from the table. The tracer gas tests implied injection of a neutrally buoyant tracer gas through a perforated sphere placed in front of the exhaust hood. The amount of tracer gas that escaped from the suction flow was measured both in the room air and in the breathing zone. The first measurements yielded a sensitive method for measuring the capture efficiency (CE) of the exhaust hood. The CE is the percentage of injected tracer gas that is directly captured by the exhaust hood. This parameter showed that although the  convection flow generated by the human simulator leads to low PNV values, it seems that the tracer gas is not actually being captured, but trapped in that convection flow. As a consequence, PNV and CE get a strong correlation, which is even more intense when injection and capture point are closer together. Hence, PNV represents a good alternative to tracer gas measurements only if the relationship between the correlation of PNV and CE with respect to the distance from the injection to the capture point is known. Finally, measurements of tracer gas in the breathing zone showed random, short and high exposures when turbulence was generated and those exposures got worse by natural human convection.

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SammanfattningIntroduktion: Sedan år 2000 har antalet byggnader i Sverige ökat kraftigt. Enligt Statiska centralbyrån (SCB) fanns över 5 miljoner bostäder i Sverige i slutet av år 2021. Av dessa bostäder är cirka 42 % villor, 51 % flerbostadshus och resterande är lägenheter i specialbostäder. Energiförbrukningen i småhus har ökat med cirka 22% sedan 1970-talet, främst på grund av ökad användning av cirkulationspumpar, golvvärme och ventilation. Detta har resulterat i ökad miljöpåverkan från byggsektorn. Effektivisering av ventilationssystem har varit ett fokusområde under lång tid, eftersom användningsfasen av ventilationssystemen har visat sig ha hög energianvändning och stor miljöpåverkan. En studie visar att VVS-systemen påverkar miljön både vid tillverknings- och användningsfasen. Dessutom har nya lågenergihus en högre miljöpåverkan i byggfasen på grund av användningen av mer material för att minska driftanvändningen. Valet av ventilationssystem är avgörande för villor, eftersom ett effektivt ventilationssystem inte bara förbättrar inomhusluften utan också minskar risken för hälsoproblem som kan uppstå vid otillräcklig ventilation. Nyckelord: Livscykelkostnad, LCC, Ventilationssystem, Självdragssystem, FTX-system, VIP-Energy, Från- och tilluftssystem, Värmeåtervinning. Syfte: Syftet med examensarbetet är att visa att valet av ventilationssystem har betydelse för minskad klimatpåverkan vid tillverknings- och användningsfasen under 30 års tid. Mål: Målet är att ta fram vilket av självdragsventilation och från- och tilluftssystem med värmeåtervinning som är mest ekonomiskt och ger lägst klimatpåverkan baserat på ett livscykelperspektiv på ett småhus under en kalkylperiod på 30 år. Frågeställningar: Vilken av självdrag och FTX är mest effektivt med tanke på energiförbrukningen under tillverknings- och användningsfasen?Hur påverkar självdrag respektive FTX-systemet uppvärmningskostnaderna för ett småhus under förutsättning att uppvärmningen sker med fjärrvärme?Vilket av de två ventilationssystemen är mest ekonomisk lönsamt enligt en jämförande LCC, baserad på ett småhus med en kalkylperiod på 30 år?Vilket av ventilationssystemen orsakar störst klimatpåverkan? Metod: Metoden är en fallstudie där VIP-Energy används för att visa byggnadens energiförbrukning timme för timme under ett helt år. En LCC-beräkning utförs för att bestämma kostnaden för ventilationssystemet under dess livslängd, inklusive uppskattade underhållskostnader och nyinvesteringar. Slutsats: Baserat på energiförbrukningen under tillverknings- och användningsfasen är det mer effektivt att använda självdrag istället för ett FTX-system. Självdrag med vedeldning har ett lägre fjärrvärmebehov jämfört med FTX-systemet och ger därmed lägre årliga uppvärmningskostnader. Över en 30-årsperiod har självdragssystemet en lägre total livscykelkostnad än FTX-systemet. FTX-systemet har en högre elförbrukning och därmed en större påverkan på klimatet än självdragssystemet. / AbstractIntroduction: Since the year 2000, the number of buildings in Sweden has seen a significant increase. According to the Statistics Sweden (SCB), there were over 5 million dwellings in Sweden at the end of 2021. Out of these dwellings, approximately 42% are single-family houses, 51% are multi-family buildings, and the remaining is apartments in specialized housing. The energy consumption in single-family houses has increased by around 22% since the 1970’s, primarily due to the increased use of circulation pumps, underfloor heating, and ventilation. This has resulted in an increased environmental impact from the construction sector. Efficiency improvements in ventilation systems have been a longstanding focus due to the high energy consumption and significant environmental impact associated with their operational phase. A study reveals that HVAC systems impact the environment both during the manufacturing and the operational phases. Furthermore, new low-energy buildings have a higher environmental footprint during the construction phase due to the increased use of materials aimed at reducing operational energy consumption. The choice of a ventilation system is crucial for homes, as an efficient ventilation system not only improves indoor air quality but also reduces the risk of health problems that can arise from inadequate ventilation. Keywords: Life Cycle Cost, LCC, Ventilation System, Self-Exhaust Ventilation, Supply and Exhaust Ventilation, VIP-Energy, Supply and Exhaust Air System, Heat Recovery. Purpose: The purpose of the thesis is to demonstrate that the choice of ventilation system has a significant impact on reducing environmental emissions during the manufacturing and operational phases over a 30-year period. Goal: The objective is to determine which of self-exhaust ventilation and supply and exhaust ventilation with heat recovery is the most cost-effective and has the lowest climate impact based on a life-cycle perspective for a single-family building over a calculation period of 30 years.Questions: Which of self-exhaust ventilation and supply and exhaust ventilation is the most efficient in terms of energy consumption during the manufacturing and usage phases?How do self-exhaust ventilation and supply and exhaust ventilation affect the heating costs for a single-family building assuming that heating is provided through district heating?Which of the two ventilation systems is most economically viable according to a comparative Life Cycle Cost (LCC) analysis, based on a single-family building with a calculation period of 30 years?Which of the two ventilation systems causes the greatest climate impact?

The objective of this study was to determine whether improvements could be made to increase the capture distance of traditional local exhaust ventilation (LEV) hoods by designing a circular slotted-hood. The criterion of success for this study was to achieve increases in capture velocity at an upstream distance equal to the diameter of the hood (11 inches). By increasing capture velocity further from the face, contaminant capture could take place at distances more convenient to the circular slotted-hood operator while maintaining adequate suction. This was to be achieved by the addition of two slots and a flange to a traditional conical hood opening. Three plates were designed to change the geometry of a plain conical hood (slot area: 0.1334, 0.0963 and 0.0694 ft2). They were tested at different airflow rates (243, 347, 467, 647, 897 cubic feet per minute) for a set number of distances from the hood face using a thermal anemometer. Three-dimensional maps of performance were created for visual comparisons, and t-tests were conducted to analyze performance by comparison of velocity at any point upstream of the hood. Velocity contours illustrated that two of the three designs had greater capture velocities compared to the standalone conical hood, and paired t-tests confirmed the significance (p<0.05). Each of the new designs failed to significantly increase capture distance further than 11 inches from the hood. However, increased velocities occurred near the hood opening (within 5 inches). These modest improvements for the largest slot design increases operating pressures by approximately 0.1" wg @ 250 cfm but 1.1" wg @ 650 cfm. Implementing these new designs would increase capture velocities close to the hood, although this advantage is offset by the cost it would require to compensate for the pressure loss incurred.

Energy consumption for heating and ventilation of buildings is still in 2011considered far too high, but there are many ways to save energy and construct lowenergy buildings that have not been fully utilised. This doctoral thesis has focused onone of these - low temperature heating systems. Particular attention has been given tothe ventilation radiator adapted for exhaust-ventilated buildings because of itspotential as a low energy consuming, easily-operated, environmentally-friendlysystem that might also ensure occupant health and well-being. Investigations were based on Computational Fluid Dynamics (CFD) simulations andanalytical calculations, with laboratory experiments used for validation. Main conclusions: Low and very low temperature heating systems, such as floor heating, in general createan indoor climate with low air speeds and low temperature differences in the room, whichis beneficial for thermal comfort. A typical disadvantage, however, was found to beweakness in counteracting cold down-flow from ventilation air supply units in exhaustventilatedbuildings. with ventilation radiators, unlike most other low temperature systems, it was found thatthe risk of cold draught could be reduced while still maintaining a high ventilation rateeven in cold northern European winters. ventilation radiators were found to be more thermally efficient than traditional radiators. design of ventilation radiators could be further modified for improved thermal efficiency. at an outdoor temperature of -15 °C the most efficient models were able to give doublethe heat output of traditional radiators. Also, by substituting the most efficient ventilationradiators for traditional radiators operating at 55 °C supply water temperature, it wasfound that supply water temperature could be reduced to 35 °C while heat outputremained the same and comfort criteria were met. lowering the supply water temperature by 20 °C (as described above) could givecombined energy savings for heating and ventilation of 14-30 % in a system utilising aheat pump. supply water temperatures as low as 35 °C could increase potential for utilising lowtemperature heat sources such as sun-, ground-, water- or waste-heat. This would beparticularly relevant to new-built “green” energy-efficient buildings, but severaladvantages may apply to retrofit applications as well. Successful application of ventilation radiators requires understanding of relevant buildingfactors, and the appropriate number, positioning and size of radiators for best effect.Evaluation studies must be made at the level of the building as a whole, not just for theheating-ventilation system. This work demonstrated that increased use of well-designed ventilation radiatorarrangements can help to meet regulations issued in 2008 by the Swedish Departmentof Housing (Boverket BBR 16) and goals set in the Energy Performance of BuildingsDirective (EPBD) in the same year. / QC 20110328 / STEM Projektnummer:30326-1 Energieffektiva lågtemperatursystem i byggnader

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