Simulation of a wall jet in an enclosure performed to predict the effect of pulsation flow on improving the performance of mixing ventilation systems which are routine practices in industry. Comparing two flows with equal amount for constant and pulsation modes, it was found out that the same global airflow pattern exists for both of the cases but with generation of more eddies and local periodically velocity variations for pulsation mode. This periodic generation of turbulence at pulsatile ventilation flows happen despite the relatively low Reynolds numbers of such flows.Bigger size of boundary layer and higher turbulent kinetic energy for pulsation mode in comparisonwith the same flow rate in constant velocity mode could result in more ventilation capacity with no need to increase the use of energy. It was seen that while a higher constant velocity rate could produce the same acceptable results in terms of higher efficiency in ventilation, a lower pulsated flow could yields it without the risk of draught. Regarding the thesis procedure, the computational solution started with a grid independency study. 2-Dimensional simulation failed to simulate the results similar to the experimental data. No URANS model was able to yield good outcome in 2D mode. The study was continued with 3D SST-kω which yielded good prediction of velocity profiles near the wall regions. For predicting turbulence parameters in the center of the domain SST-URANS was not helpful so, simulation switched to SAS which was successful to some extent to get close to reality.

The basis of mixing ventilation is the airflow supply to the room by means of jets initiatedfrom the ventilation diffusers. To avoid the draught problem, the design of mixing ventilationmakes uses the throw term, which is defined as the distance to the supply air terminal inwhich the jet centreline mean velocity is decreased to a given value. Traditionally, the throw ismeasured by the supply air device manufacturer. The throw is applied by designers to estimatethe velocity levels in the occupied zone. A standard for determining the throw is the CENstandard CEN/TC156/WG4 N86 "Draft Standard. Air terminal Devices. AerodynamicsTesting And Rating For Mixed Flow Application".The measurement of the throw is very time consuming even with the free jets and theinfluence of the room (the effect of confinement) is not considered. The objective of thepresent study is to give a basis for modifying the existing design and testing method used topredict the velocities in the occupied zone during the design process. A new method whichmay probably be more easier than the existing methods and at the same time give a betterprecision by including the confinement effect.In this thesis two methodological systems of experiment and numerical simulations have beenused. The numerical predictions are used in comparison with the measurements. Thereasonable agreement of the above mentioned methods is implemented to numerical study ofthe other room configurations which are not experimentally studied. This examining methodallows the possibility of studying a lot of configurations and in this manner generalising of theresults. Although the experimental part was made for both model-scale and full-scale testrooms, a large amount of data was obtained for a new test room whose dimension aresystematically varied. All of studies have been made for the isothermal case and themeasurements of velocities and pressures conducted along the room perimeters. The effect ofshort and deep rooms on the properties of the jet ( velocities, pressure, integral scale, jetmomentum, the rate of spreading of jet and turbulence intensities) have been carried out.Some old and recent investigations have been examined. Specially the concept of correlationsfrom open to closed rooms is criticised. It is also shown that the flow field in a confined roomis affected by many other factors than the Reynolds number. The surface pressure on theperimeters was used to calculate the reaction forces at the corners which causes recirculatingbubbles at corners. A study of the turbulent axisymmetric jet which is the basic element inturbulent shear flows and some restrictions of the traditional measurement techniques at theregion of interest in ventilation applications are discussed. The jet momentum is measured byweighing on a balance. Also a study of jets which collide with a wall , that is impinging jet,the effect of walls and confinement on the jet momentum have experimentally andnumerically been carried out. A new momentum balance model was developed for both thefree jet and confined one. An empirical relation has been found for estimation of the room’srotation centre which is used for validation of CFD results.Finally, it is found that the jets in a ventilated room which are a combination of free jet, walljet and impinging jet differ from the traditional wall jets. The rate of spreading of the jet andthe maximum velocity decay in a ventilated room are also different depending on the roomsize and its confinement.

Cette thèse porte sur la ventilation par mélange à haute induction pour le bâtiment au moyen de diffuseurs d’air innovants munis de promoteurs de tourbillons. Il s’agit d’inserts lobés, introduits au sein de diffuseurs d’air commerciaux, sans en modifier le processus de fabrication. L’innovation est née de travaux antérieurs et a fait récemment l’objet d’un brevet européen. Sa mise en situation à l’échelle 1 en conditions typiques de chauffage et de climatisation, constitue l’objectif premier des présents travaux. Par une démarche expérimentale, l’impact des inserts lobés sur la topologie de l’écoulement moteur, sur le confort thermique induit en zone d’occupation d’une cellule climatique thermiquement gardée, et sur les pertes de charges et le bruit générés, sont évalués. Les écoulements moteurs sont analysés par PIV 2D2C grand champ, et le confort thermique est évalué en zone d’occupation à l'aide d’un ensemble de capteurs ponctuels de vitesse et de température et du modèle PMV/PPD de Fanger. Les résultats montrent que les inserts lobés introduits dans le diffuseur, favorisent le mélange du jet qui en est issu avec l’air ambiant à traiter. Le confort thermique en zone d’occupation est amélioré de façon significative, par rapport au cas de référence du même diffuseur sans inserts. L’impact des inserts sur l’acoustique et les pertes de charges n’est pas significatif, ce qui valide l’innovation pour son application immédiate dans le bâtiment. En dernière partie, nous avons comparé la performance des diffuseurs innovants munis d’inserts lobés au diffuseur vortex, présenté sur le marché de la diffusion de l’air comme étant doté d’une grande capacité de mélange, suite à la mise en rotation du jet à l’aide d’ailettes profilées. Les résultats ont montré que l’encastrement au plafond du diffuseur vortex préconisé par le fabricant, dont il résulte l’adhérence immédiate du jet par effet Coanda, inhibe le mouvement de rotation escomptée, et sa performance dans ces conditions est inférieure à celle du diffuseur à inserts lobés. Il résulte de ce constat, la nécessité d’une installation du diffuseur vortex sur conduite apparente pour que sa performance soit réelle ; cela est envisageable pour des locaux commerciaux ou industriels de grande hauteur sous plafond. Les diffuseurs lobés encastrés au plafond, dont on a ainsi démontré la performance, sont parfaitement adaptés aux espaces de bureaux ou d’habitations de faibles hauteurs sous-plafond, et répondent par conséquent au réel besoin de la haute induction dans ce type de locaux. / This thesis deals with high-induction mixing ventilation for buildings using innovative air diffusers equipped with vortex promoters. These are lobed inserts, introduced into commercial air diffusers, without modifying the manufacturing process. The innovation was born from previous work and has recently been the subject of an European patent. The first objective of the present work is to conduct full scale experiments under typical heating and air conditioning conditions. By an experimental approach, the impact of the lobed inserts on the airflow and jet pattern, on the thermal comfort induced in the occupied zone of a thermally guarded climate chamber, and on the pressure drop and the noise generation. Airflow pattern is analyzed by large scale PIV 2D2C, and thermal comfort is evaluated in the occupied zone using a set of temperature and speed sensors and Fanger's PMV / PPD model. The results show that the lobed inserts introduced into the diffusers enhance the mixing between the jet and ambient air whose to be treated. The thermal comfort in the occupied zone is significantly improved, compared to the reference case of the same diffuser without inserts. The impact of the inserts on the acoustics and the pressure drop is not significant, which validates the innovation for its immediate application in buildings. Finally, we compared the performance of innovative diffusers with lobed inserts to the vortex diffuser, presented in the air diffusion market as a high mixing diffuser, because of the rotation generated by profiled fins. The results showed that when the diffuser is flush mounted to the ceiling, which is recommended by the manufacturer, the immediate attachment of the jet due to the Coanda effect inhibits the expected rotational movement. Its performance under these conditions is lower to that of the diffuser with lobed inserts. It follows from this finding that the installation of the vortex diffuser on a free pipe is necessary for its best performance ; this can be performed for high ceiling commercial buildings or industrial buildings. Ceiling flush mounted diffusers with lobed inserts, which we have demonstrated their performance, are perfectly suited for office spaces or homes with low ceiling heights, and therefore meet the real need for high induction in this type of buildings.

La compréhension de la distribution de l'air intérieur accompagné du transfert couplé "chaleur-air-humidité" est essentielle à la conception des systèmes de ventilation des bâtiments. Parmi les méthodes de distribution d'air intérieur, la ventilation par mélange est l'une des plus couramment utilisées, dont la performance est déterminée par celle du jet d'air injecté. Au cours des dernières décennies, bien que de nombreuses recherches aient été menées sur les études des jets d'air, la majorité de ces études se sont concentrées sur une disposition symétrique des bouches de soufflage et d’extraction par rapport à la géométrie du local. En outre, les études traitant du transfert couplé "chaleur-air-humidité", qui inclut le phénomène de condensation sur la surface interne du local, sont encore limités dans la littérature. Ainsi, ce travail se concentre sur la problématique suivante : Quel est le comportement d'un jet d'air réaliste sous des effets d'interaction et comment caractériser de tels jets d'air ? Dans des conditions d'intérieur réalistes favorisant la condensation sur une surface froide, serait-il possible de quantifier le débit massique de condensation ? Les deux études sont expérimentées dans la cellule d’essais MINIBAT à l’échelle 1. La première partie consiste à caractériser un jet d'air turbulent au plafond dans une configuration d’écoulement intérieur réaliste. Les résultats expérimentaux montrent les effets d'interaction visibles des éléments architecturaux de la pièce sur le comportement du jet d'air tels que la déviation de la trajectoire du jet ainsi que la déformation des profils du jet. Les principales caractéristiques du jet, telles que le taux d’expansion, la décroissance de vitesse et de température, sont quantifiées. Une méthode graphique basée sur un indicateur de déformation est proposée pour quantifier la déformation des profils transversaux du jet.La deuxième partie de ce travail traite le phénomène de condensation sur une surface vitrée en reproduisant les conditions hivernales dans la cellule d’essais. L’apparition de la condensation et son mécanisme de croissance sont observés à l'aide d'une technique de macrophotographie. Le post-traitement de l'image permet d'estimer le débit de condensation. Les comparaisons entre les résultats expérimentaux et théoriques montrent un certain accord, ce qui pourrait valider la faisabilité des techniques d'imagerie dans les études de condensation à l’échelle 1. Des données expérimentales détaillées accompagnées de conditions aux limites bien connues issues de ce travail pourraient servir de test de benchmark pour la validation des modèles CFD, en particulier pour les configurations d’écoulement asymétrique, avec la présence de la condensation. / Understanding room air distribution with coupled heat-air-moisture transport is essential to the design of building ventilation systems. In the past decades, although numerous research have been undertaken on air jet studies, there are still some issues that deserve a consideration. In fact, the majority of these studies focused on a symmetric arrangement of supply and exhaust air outlets with respect the room geometry. Besides, studies dealing with room coupled heat-air-moisture transport, which includes the condensation phenomenon on the room inner surface, are generally lacking in the literature. Hence, this work focuses on the following problematic: What is the behavior of a realistic air jet under interaction effects and how to characterize such air jets? In realistic indoor conditions promoting condensation on cold surface, would we be able to quantify the condensate mass flow rate? The two studies are experimentally investigated in the full-scale MINIBAT controlled test cell. The first part consists in characterizing a ceiling turbulent air jet in a realistic indoor airflow configuration. The experimental results show visible interaction effects of the room architectural elements on the air jet behavior: they have deviated the jet trajectory as well as deformed the jet cross-sectional shape. The jet main characteristics such as the spread rate, the velocity and temperature decay are quantified. A graphical-based method is proposed to quantify the jet shape deformation using a so-called deformation indicator. The second part of this work treats the phenomenon of moisture condensation on a glazing surface by reproducing a winter condition within the test cell. The condensation appearance and its growth mechanism are observed using a macro-photography technique. The image post-processing enabled to estimate the condensation rate. Comparisons between experimental and theoretical results show some agreement, which could validate the feasibility of imaging techniques in full-scale condensation studies.Detailed experimental data accompanied by well-known boundary conditions from this work could serve as a benchmark test for CFD models validation, in particular for asymmetric airflow configurations, with the presence of the condensation phenomenon.

Detta examensarbete presenterar resultatet från en experimentell studie med syfte att undersöka sambandet mellan ventilation i kontor och smittspridning av luftburna virus och bakterier. Fokuset i studien har framför allt riktats mot coronaviruset och även avgränsats till att enbart studera omblandande-, och deplacerande ventilation under den experimentella delen. Studien genomfördes i ett testrum lokaliserat vid Högskolan i Gävle. Syftet för studien har varit att besvara hur exponeringen av luftburna smittämnen förändras i andningszonen när distributionen av tilluften ändras och om placering av smittkällan i sig har någon betydelse. Studien har även haft för avsikt att besvara vilken utav deplacerande eller omblandande ventilation som lämpar sig bäst vad gäller minimering av överföringssannolikheten från en smittad persons andning. För att besvara studiens frågeställningar genomfördes spårgasmätningar och parallellt med spårgasmätningarna granskades även lufthastigheter och temperaturer på flera positioner i rummet. För omblandande ventilation undersöktes två olika riktningar på tilluftsstrålen, som valdes till vertikal och horisontell. För deplacerande ventilation undersöktes två olika inblåsningstemperaturer vilka var 21,3 ˚C och 16 ˚C. Resultatet av studiens experimentella del visade att deplacerande ventilation hade en mindre överföringssannolikhet vid jämförelse med omblandande ventilation. Detta då överföringssanolikheten låg på 0,3–0,5 % för omblandande och 0,1–0,3 % för deplacerande, vilket visar att deplacerande ventilation generellt varit på en lägre nivå oavsett position av smittkällan. Att deplacerande ventilation har en mindre benägenhet att sprida infektioner vidare bland olika individer i samma rum bekräftas också av flera tidigare artiklar som studerat ämnet. Då omblandande ventilation undersöktes visade studiens experimentella del att resultatet vad gäller riktningen på tilluftstrålen hade en inverkan på överföringssannolikheten. Den vertikala tilluftstrålen påverkade forceringen mellan de termiska dockor som placerades framför varandra, vilket resulterade i en minskning på överföringssannolikheten mitt emot de två olika positionerna där de infekterade dockorna satt. För bägge ventilationssystemen - förutom vid vertikal riktning på tilluftstrålen vid omblandande ventilation - visade avståndet mellan smittkällan och frånluftsdonet ha en effekt på smittspridningen. Detta eftersom överföringssanolikheten varit lägre vid placeringen mitt emot smittkällan och diagonalt från smittkällan vilket är ett större avstånd än vad positionering bredvid smittkällan är. Vad gäller deplacerande ventilation har placeringen av smittkällan visat effekt då överföringssannolikheten varit lägre vid placering av smittkällan närmare frånluftdonet samt att det minsta avståndet från smittkällan i det fallet haft lägst överföringssannolikhet. / This thesis presents the results of an experimental study with the aim to investigate the connection between ventilation in offices and spread of airborne viruses and bacteria. The focus is on coronavirus and this thesis only investigates mixed ventilation and displacement ventilation in the experimental part. The study is done in a full scale mook up room located in Högskolan i Gävle. The aim of the study was to answer how the exposure of airborne diseases change in the breathing zone when the distribution of supply air changes and if placement of the source of infection has any affect. The study also aims to investigate if displacement or mixing ventilation is the best choice to minimize transfer probability from an infected persons breath. Tracer gas measurements was done to answer the main questions. The tracer gas measurements were studied parallel to measurements of air velocities and temperatures on several positions in the room. For mixing ventilation, the measurements were done for two different directions of supply air jet, vertical and horizontal. For displacement ventilation measurements are done for two different temperatures on the supply air which was 21,3 ˚C and 16 ˚C. The results of the experimental part of this study showed that displacement ventilation had a lower transfer probability between an infected person and a non-infected person when compared to mixing ventilation. The transfer probability was 0,3 – 0,5 % for mixing ventilation and 0,1 – 0,3 % for displacement ventilation, which shows that displacement ventilation is generally at a lower level than mixing ventilation regardless of the position of the source of infection. The result in this thesis is like results found in the literature review which also shows that displacement ventilation has a lower tendency to spread infections between persons in the same room. The result for mixing ventilation regarding the direction of the supply air jet showed an impact on the transfer probability. The vertical supply air jet was affecting the force of the breath jet between the thermal manikin placed in front of each other, which is done as part of reduction in the transfer probability at the two different positions for the same direction of the supply air jet. For both ventilation systems – except for the vertical direction of the supply air jet in the case of mixing ventilation - the distance between the source of infection and exhaust diffuser has been shown to have an impact on the transfer probability. This means the transfer probability was lower at the location opposite the source of infection and diagonally from the source of infection, which is a greater distance than the location next to the source of infection. In terms of displacement ventilation, the location of the source of infection has shown an effect as the transfer probability was lower when the source of infection was placed closer to the exhaust diffuser and that the minimum distance from the source of infection in that case was the lowest.

Today, a significant portion of individuals’ time is spent indoors, estimated at approximately 90% of their total time. This raises concerns about the transmission of Coronavirus Disease 2019 (COVID-19) instigating Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and similar viruses and highlights the critical role of ventilation systems in indoor environments, which this study aims to investigate. Narrowing the focus to healthcare facilities, particularly hospitals in Sweden, the study includes the importance of ventilation systems in safeguarding the health safety and well-being of patients, healthcare workers in hospitals. To effectively combat the spread of the SARS-CoV-2 virus, it is crucial to have a thorough understanding of its viral characteristics, with a specific centre on airborne transmission size, virus longevity, and quantum of infection. Furthermore, it is essential to recognize the major impact of ventilation rate, thermodynamic factors such as temperature and humidity, as well as pollutants in effectively mitigating the transmission of SARS-CoV-2 and similar pathogens.  The comprehensive findings of this literature review underscore that, for hospitals in Sweden, a Heat Recovery Ventilation (HRV) system incorporating a plate heat exchanger is the most suitable ventilation system for this specific objective. Moreover, the recommended ventilation strategy is specifically tailored for implementation in wards or isolated rooms, where it is ideal for the incoming air to originate from the patient’s room floor, while the exit point is preferably located near or at the ceiling. In the context of this study, identified effective solutions involve the utilization and combination of high-efficiency filters and ultraviolet (UV) technology installed within ventilation system unit, particularly when an air recirculation system is used. Additionally, the implementation of RM3 (Rheem’s third generation products) UV-C technology for indoor use can be achieved without considerable intervention in ventilation system, depending on the type of ventilation system being utilized. In summary, this study enhances understanding of the complex relationship between ventilation systems, COVID-19 transmission and similar diseases, the optimization of thermodynamic factors, and selection of effective and practical measures. It provides valuable insights for designing effective ventilation strategies across various indoor environments, with a specific attention on healthcare facilities. / Idag spenderas en betydande del av individers tid inomhus, uppskattningsvis cirka 90% av deras totala tid. Detta väcker oro över överföringen av Coronavirussjukdom 2019 (COVID-19), som initierar Svårt Akut Respiratoriskt Syndrom Coronavirus 2 (SARS-CoV-2) och liknande virus och belyser den kritiska rollen som ventilationssystem spelar i inomhusmiljöer, som denna studie syftar till att undersöka. Genom att begränsa fokus till vårdinrättningar, särskilt sjukhus i Sverige, inkluderar studien vikten av ventilationssystem för att säkerställa hälsosäkerheten och välbefinnandet för patienter och vårdpersonal på sjukhus. För att effektivt bekämpa spridningen av SARS-CoV-2-viruset är det viktigt att ha en grundlig förståelse för dess virala egenskaper, med ett specifikt fokus på luftburen överföringsstorlek, viruslivslängd och infektionsmängd. Dessutom är det viktigt att identifiera den stora inverkan av luftomsättningstakt, termodynamiska faktorer som temperatur och fuktighet samt föroreningar för att effektivt minska överföringen av SARS-CoV-2 och liknande patogener. De omfattande resultaten av denna litteraturstudie understryker att värmeåtervinningsventilationssystem (HRV) med plattvärmeväxlare är det mest lämpliga ventilationssystemet för sjukhus i Sverige för detta specifika mål. Dessutom är den rekommenderade ventilationsstrategin speciellt anpassad för implementering på avdelningar eller isolerade rum, där den är idealisk för att inkommande luft ska komma från patientens rumsgolv, medan utgångspunkten företrädesvis är placerad nära eller i taket. I samband med denna studie involverar identifierade effektiva lösningar, användning och kombination av högeffektiva filter och ultraviolett (UV)-teknik installerad i ventilationssystemenhet, särskilt när ett luftcirkulationssystem används. Dessutom kan implementeringen av RM3 (Rheems tredje generationens produkter) UV-C-teknik för inomhusbruk uppnås utan betydande ingrepp i ventilationssystem, beroende på vilken typ av ventilationssystem som används. Sammanfattningsvis ökar denna studieförståelse för det komplexa förhållandet mellan ventilationssystem, COVID-19-överföring och liknande sjukdomar, optimering av termodynamiska faktorer och val av effektiva och praktiska åtgärder. Den ger värdefulla insikter för att utforma effektiva ventilationsstrategier i olika inomhusmiljöer, med särskild uppmärksamhet på vårdinrättningar.