Download or read book Numerical Simulation of Room Airflow Using Different Types of Ventilation Methods written by Chi Leung and published by . This book was released on 2011 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Natural Ventilation for Infection Control in Health care Settings written by Y. Chartier and published by World Health Organization. This book was released on 2009 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: This guideline defines ventilation and then natural ventilation. It explores the design requirements for natural ventilation in the context of infection control, describing the basic principles of design, construction, operation and maintenance for an effective natural ventilation system to control infection in health-care settings.

Download or read book Air Distribution in Rooms written by H.B. Awbi and published by Elsevier. This book was released on 2000 with total page 746 pages. Available in PDF, EPUB and Kindle. Book excerpt: The air distribution in occupied spaces is a major issue of public concern. It is widely recognized that the quality of air and the nature of airflow can affect the health of occupants and the energy consumed in buildings and transport vehicles. ROOMVENT is the principal international conference in the field of air distribution. It was first initiated in 1987 by SCANVAC, the Scandinavian Federation of Heating, Ventilating and Sanitary Engineering Associations in Denmark, Finland, Iceland, Norway and Sweden. The aim of the Conference is to bring together researchers from universities and research institutes, engineers from industry and government officials and policy makers, with the goal of experiencing the latest techniques for measuring and analyzing indoor air flow, the visualization of indoor air flow patterns, the evaluation of ventilation parameters and the most recent developments in computer simulation techniques of room airflow. It is hoped that the theme of ROOMVENT 2000 "Ventilation for Health and Sustainable Environment" will set the scene for room air distribution research and development for the new millennium.

Download or read book On the performance of stratified ventilation written by Ulf Larsson and published by Linköping University Electronic Press. This book was released on 2018-08-20 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: People nowadays spend most of their time indoors, for example in their homes, cars, in trains, at work, etc. In Sweden, the energy demand in the built environment is a growing issue. The building sector accounts for 40% of total energy use and 15% of total CO2 emissions, and around one-third of the energy use in the world is related to providing a healthy and good comfort indoors. To achieve acceptable indoor climates new designs for the ventilation systems have been proposed in recent decades, among them stratified ventilation systems. Stratified ventilation is a concept that often allows good performance for both indoor air quality and thermal comfort. Stratified ventilation systems are effective in reducing cross contamination, since there is virtually no mixing in the space; the temperature and the pollutant concentration increase linearly from the heat source with the height of the occupied zone. There are many different ventilation supply devices using the stratified principle, such as displacement supply device (DSD), impinging jet supply device (IJSD) and wall confluent jet supply device (WCJSD). The main aim of this thesis is to analyze and compare different supply devices based on stratified ventilation, with different setups, related to thermal indoor climate, energy efficiency and ventilation efficiency. The ultimate goal is to contribute to an increased understanding of how ventilation systems with stratified supply devices perform. Two scientific methods have mainly been used in this thesis, i.e., experimental and numerical investigations. For numerical experiments the CFD (Computational Fluid Dynamics) code ANSYS and FIDAP have been used. Experimental studies have been performed with thermocouples, Hot-Wire Anemometry (HWA) and Hot-Sphere Anemometry, thermal comfort measurement equipment and tracer gas measurement equipment. This thesis mainly focuses on three research questions: Interaction between a supply device based on stratified ventilation and downdraft from windows; Flow behavior, energy performance and air change effectiveness for different supply devices based on stratified ventilation; and Thermal comfort for different supply devices based on stratified ventilation. Research question one showed that the arrangement of displacement supply device and window in cold climate has significant effect on the flow pattern below the window. Different supply airflow rates have an effect on both the velocity and the temperature of the downdraft. In this case the velocity decreased by approximately 9.5% and the temperature in the downdraft decreased 0.5°C when the flowrate from the supply device increased from 10 to 15 l/s. Research question two showed that airflow patterns between different air supply systems were essentially related to characteristics of air supply devices, such as the type, configuration and position, as well as air supply velocities and momentum. For WCJSD, IJSD and DSD, positions of heat sources (such as occupant, computers, lights and external heat sources) played an important role in formation of the room airflow pattern. One interesting observation is that the temperature in the occupied zone is lower and a more stratified temperature field implies a more efficient heat removal by a stratified air supply device. The results revealed that the lowest temperature in the occupied zone was achieved for DSD, but with IJSD and WCJSD slightly warmer, while the system with a mixing supply device (MSD) showed a much higher temperature. The results confirm that air change effectiveness (ACE) for the DSD, WCJSD and IJSD is close to each other. However, MSD shows lower ACE in all the present papers than IJSD, WCJSD and DSD. Research question three showed that ventilation systems with stratified supply devices in almost all of the studied cases showed an acceptable level for predicted percentage dissatisfied (PPD), predicted mean vote (PMV) and percentage dissatisfied due to draft (DR). If comparing ventilation systems, using IJSD, WCJSD or DSD with MSD always showed thermal comfort better or at the same level. Människor spenderar en stor del av sin tid inomhus, exempelvis i sina bostäder och bilar, på tåg och på arbetet. Sveriges energibehov i den byggda miljön har en växande trend. Byggnadssektorn står för 40 % av det totala energibehovet och för 15 % av CO2 utsläppet och för cirka en tredjedel av energianvändningen i världen för att tillhandahålla en hälsosam och bra inomhusmiljö. För att skapa en bra inomhusmiljö har nya sätt att ventilera inomhusmiljön utvecklats under de senaste årtiondena. De olika principer som används för att ventilera en byggnad kan indelas i: kolvströmning, omblandande strömning och deplacerande strömning. De genererar rumsförhållanden som ger olika fördelning av hastighet, temperatur och föroreningar i det ventilerade utrymmet. Stratifierad ventilation är ett koncept som ofta ger ett bra utfall av både inomhusluftkvalitet och termisk komfort. Stratifierade system är effektiva för att minska korskontaminering, eftersom det nästan inte finns någon omblandning i rummet, temperaturen och föroreningskoncentration ökar linjärt från värmekällan med höjden i vistelsezonen. Det finns många olika ventilationsdon som använder den stratifierade principen, såsom deplacerande ventilationsdon (DSD), impinging jet-ventilationsdon (IJSD) och väggbaserad confluent jet-ventilationsdon (WCJSD). Huvudsyftet med denna avhandling är att analysera och jämföra olika tilluftsdon baserat på stratifierad princip i olika rumskonfigurationer med avseende på termiskt inomhusklimat, energieffektivitet och ventilationseffektivitet. Det yttersta målet är att bidra till ökad förståelse för hur ventilationssystem med olika stratifierade tilluftsdon fungerar. Två vetenskapliga metoder har huvudsakligen använts i denna avhandling: experimentella och numeriska analyser. För numeriska analyser har CFD (Computational Fluid Dynamics) använts. De simuleringsprogram som utnyttjats för detta ändamål är ANSYS och FIDAP. Experimenten har utförts med hjälp av termoelement, varmtråds- och varmsfärsteknik, mätutrustning för termisk komfort och mätutrustning för spårgas. Denna avhandling fokuserar framför allt på tre forskningsfrågor: interaktion mellan ett tilluftsflöde från ett deplacerande don och kallraset från ett fönster; strömningsbilden, energiprestandan och luftbyteseffektiviteten för olika tilluftsdon baserat på stratifierad ventilation; och termisk komfort för olika tilluftsdon baserade på stratifierad ventilation. Forskningsfråga ett visade att kombinationen av tilluftsflöde genom ett deplacerande don och fönster i kallt klimat har tydlig effekt på strömningsbilden för kallraset under fönstret. Olika tilluftsflöden har en effekt på både hastigheten och temperaturen i kallraset. I detta fall minskade hastigheten med ca 9,5% och temperaturen i kallraset minskade med 0,5°C när flödeshastigheten från tilluftsdonet ökade från 10 till 15 l/s. Forskningsfråga två visade att luftflödesmönstren mellan olika luftförsörjningssystem väsentligen var relaterade till egenskaper hos tilluftsdonen, såsom typ, konfiguration och position samt lufttillförselhastigheter och impulskraft. För WCJSD, IJSD och DSD spelade värmekällans placering, d.v.s. människor, datorer, belysning och externa värmekällor, en viktig roll vid utformningen av rummets luftflödesmönster. En intressant observation är att temperaturen i vistelsezonen är lägre och rummet har ett mer stratifierat temperaturfält, vilket innebär en effektivare ventilering av den zonen. Resultaten visade att den lägsta temperaturen i vistelsezonen uppnåddes för DSD medan IJSD och WCJSD visade en något högre temperatur, systemet med ett omblandande don (MSD) visade en påtagligt högre temperatur. Resultaten bekräftar också att luftförändringseffektiviteten (ACE) för DSD, WCJSD och IJSD ligger nära varandra. MSD visar dock i alla ingående artiklar lägre ACE än IJSD, WCJSD och DSD. Forskningsfråga tre visade att ventilationssystem med stratifierade tilluftsdon i nästan samtliga studerade fallen haren acceptabel nivå för predicted mean vote (PPD), predicted mean vote (PMV) och percentage dissatisfied due to draft (DR). Om man jämförde ventilationssystem IJSD, WCJSD eller DSD med MSD visade det sig alltid att den termiska komforten var bättre eller på samma nivå som för MSD.

Download or read book Ventilation of Buildings written by H.B. Awbi and published by Routledge. This book was released on 2004-06-02 with total page 537 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hazim Awbi's Ventilation of Buildings has become established as the definitive text on the subject. This new, thoroughly revised, edition builds on the basic principles of the original text drawing in the results of considerable new research in the field. A new chapter on natural ventilation is also added and recent developments in ventilation concepts and room air distribution are also considered. The text is intended for the practitioner in the building services industry, the architect, the postgraduate student undertaking courses or research in HVAC, building services engineering, or building environmental engineering, and the undergraduate studying building services as a major subject. Readers are assumed to be familiar with the basic principles of fluid flow and heat transfer and some of the material requires more advanced knowledge of partial differential equations which describe the turbulent flow and heat transfer processes of fluids. The book is both a presentation of the practical issues that are needed for modern ventilation system design and a survey of recent developments in the subject

Download or read book Computational Fluid Dynamics CFD Modeling of Mixed Convection Flows in Building Enclosures written by Alexander Kayne and published by . This book was released on 2012 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years Computational Fluid Dynamics (CFD) simulations are increasingly used to model the air circulation and temperature environment inside the rooms of residential and office buildings to gain insight into the relative energy consumptions of various HVAC systems for cooling/heating for climate control and thermal comfort. This requires accurate simulation of turbulent flow and heat transfer for various types of ventilation systems using the Reynolds-Averaged Navier-Stokes (RANS) equations of fluid dynamics. Large Eddy Simulation (LES) or Direct Numerical Simulation (DNS) of Navier-Stokes equations is computationally intensive and expensive for simulations of this kind. As a result, vast majority of CFD simulations employ RANS equations in conjunction with a turbulence model. In order to assess the modeling requirements (mesh, numerical algorithm, turbulence model etc.) for accurate simulations, it is critical to validate the calculations against the experimental data. For this purpose, we use three well known benchmark validation cases, one for natural convection in 2-D closed vertical cavity, second for forced convection in a 2-D rectangular cavity and the third for mixed convection in a 2-D square cavity. The simulations are performed on a number of meshes of different density using a number of turbulence models. It is found that k-[epsilon] two-equation turbulence model with a second-order algorithm on a reasonable mesh gives the best results. This information is then used to determine the modeling requirements (mesh, numerical algorithm, turbulence model etc.) for flows in 3D enclosures with different ventilation systems. In particular two cases are considered for which the experimental data is available. These cases are (1) air flow and heat transfer in a naturally ventilated room and (2) airflow and temperature distribution in an atrium. Good agreement with the experimental data and computations of other investigators is obtained.

Download or read book Multiphase Flows with Droplets and Particles written by Clayton T. Crowe and published by CRC Press. This book was released on 2011-08-26 with total page 509 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the publication of the first edition of Multiphase Flow with Droplets and Particles, there have been significant advances in science and engineering applications of multiphase fluid flow. Maintaining the pedagogical approach that made the first edition so popular, this second edition provides a background in this important area of fluid mecha

Download or read book Simulation of Room Flows with Small Ventilation Openings by a Local Grid refinement Technique written by Yuguo Li and published by . This book was released on 1993 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Small ventilation openings in large rooms constitute a numerical resolution difficulty in indoor air flow simulation. A local grid-refinement technique is Introduced to add local grid points in the small-opening regions. The method requires a relatively small increase in computer storage. A multi-grid algorithm, which turns out to be an efficient and accurate solver. is used to solve the discrete system of equations on both global and local grids. A method for implementing the wall function in the solution procedure is described. Solutions of a three-dimensional isothermal mixing ventilation problem at Reynolds number of 5000 are compared with the experimental results in the literature. The method is then applied in a three-dimensional scaled model room ventilated by a plaque diffuser. The calculations show good agreement with the smoke visualisations of the flow pattern close to the diffuser. The method can be used to predict air flows with more realistic ventilation openings and more applications in large enclosures are expected in the future.

Download or read book Global Gidelines for the Pevention of Surgical Site Infection written by World Health Organization and published by . This book was released on 2017-01-27 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surgical site infections are caused by bacteria that get in through incisions made during surgery. They threaten the lives of millions of patients each year and contribute to the spread of antibiotic resistance. In low- and middle-income countries, 11% of patients who undergo surgery are infected in the process. In Africa, up to 20% of women who have a caesarean section contract a wound infection, compromising their own health and their ability to care for their babies. But surgical site infections are not just a problem for poor countries. In the United States, they contribute to patients spending more than 400 000 extra days in hospital at a cost of an additional US $10 billion per year. No international evidence-based guidelines had previously been available before WHO launched its global guidelines on the prevention of surgical site infection on 3 November 2016, and there are inconsistencies in the interpretation of evidence and recommendations in existing national guidelines. These new WHO guidelines are valid for any country and suitable to local adaptations, and take account of the strength of available scientific evidence, the cost and resource implications, and patient values and preferences.

Download or read book Numerical Simulations written by Lutz Angermann and published by BoD – Books on Demand. This book was released on 2010-12-30 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book will interest researchers, scientists, engineers and graduate students in many disciplines, who make use of mathematical modeling and computer simulation. Although it represents only a small sample of the research activity on numerical simulations, the book will certainly serve as a valuable tool for researchers interested in getting involved in this multidisciplinary field. It will be useful to encourage further experimental and theoretical researches in the above mentioned areas of numerical simulation.

Download or read book Technical Note AIVC written by and published by . This book was released on 1991 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Study of Mixing Under Floor Air Distribution Using Zonal Model based Simulation and Experimental Measurements written by Hong Fang and published by . This book was released on 2014 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: The major function of HVAC systems is to create comfortable and healthy indoor environment to occupants. Compared to traditional mechanical ventilation such as overhead ventilation and displacement ventilation, mixing u nder f loor a ir d istribution (UFAD) is a more effective ventilation system because it incorporates the advantages of overhead ventilation and displacement ventilation. When predicting the performance of a ventilation system, zonal model is a good method as its complexity and function are between the multi-zone model and CFD model, which are the widely used two numerical simulation methods for indoor environment. Multi-zone model is a so simplified method that it cannot provide environmental details but, as a very detailed calculation tool, CFD requires high computational cost and highly educated simulation users. Zonal model offers some level of detailed environmental information with very limited computational cost. This thesis presents the potential of using zonal model to simulate indoor airflow and temperature distributions for a lab-scale mixing UFAD system. At first, this work has re-derived the numerical algorithms for the zonal model targeting mixing UFAD application by following the direction of an established zonal model - POMA. A computer program from re-derived zonal model thus has been developed, where the numerical algorithm has been disaggregated into two separate components: natural convection and mechanical convection. The re-derived zonal model and the newly developed computer program have been validated using lab experiments under mixing UFAD ventilation. The comparison figures have validated that the re-derived zonal model can accurately predict temperature distributions and reasonably estimate airflows for mixing UFAD ventilation.

Download or read book Performance Study of Outlets and Its Impact on Airflow Characteristics written by Ramy Hamdy Abdelhady and published by LAP Lambert Academic Publishing. This book was released on 2014-10-15 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, the investigation of indoor airflow in a sub-scale ventilated room is conducted using two approaches: experimental measurements and numerical simulations. The study concerns the prediction of comfort properties in a sub-scale room. Particular interest is concentrated on the three types of ceiling diffusers namely; square, round and swirl (vortex) diffusers. Basic parameters included air temperature, relative humidity, and air velocity are measured and/or predicated at different inlet conditions to obtain thermal comfort indices such as mean age of air, ventilation effectiveness, and effective draft temperature. Experiments are carried out to find the temperature profile for a certain space at conditions in the range of those expected in daily applications. These data are then used to verify and validate the numerical prediction. The experiments are performed by varying certain parameters and studying the effect of each of these parameters on the air temperature, the velocity profile and hence the thermal comfort.

Download or read book Numerical Simulation on Mechanical Ventilation Two Case Studies with Different Operation Modes written by Yiin-Kuen Fuh and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerical Simulation on Mechanical Ventilation- Two Case Studies with Different Operation Modes.

Download or read book A Ventilation Strategy Based on Confluent Jets written by Setareh Janbakhsh and published by Linköping University Electronic Press. This book was released on 2015-04-27 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study presents air distribution systems that are based on confluent jets; this system can be of interest for the establishment of indoor environments, to fulfill the goals of indoor climate and energy-efficient usage. The main objective of this study is to provide deeper understanding of the flow field development of a supply device that is designed based on wall confluent jets and to investigate the ventilation performance by experimental and numerical methods. In this study, the supply device can be described as an array of round jets on a flat surface attached to a side wall. Multiple round jets that issue from supply device apertures are combined at a certain distance downstream from the device and behave as a united jet or so-called confluent jets. Multiple round jets that are generated from the supply device move downward and are attached to the wall at the primary region, due to the Coanda effect, and then they become wall confluent jets until the floor wall is reached. A wall jet in a secondary region is formed along the floor after the stagnation region. The characteristics of the flow field and the ventilation performance of conventional wall confluent jets and modified wall confluent jets supply devices are investigated experimentally in an office test room. The study of the modified wall confluent jets is intended to improve the efficiency of the conventional one while maintaining acceptable thermal comfort in an office environment. The results show that the modified wall confluent jets supply device can provide acceptable thermal comfort for the occupant with lower airflow rate compared to the conventional wall confluent jets supply device. Numerical predictions using three turbulence models (renormalization group (RNG k– ?), realizable (Re k– ?), and shear stress transport (SST k– ?) are evaluated by measurement results. The computational box and nozzle plate models are used to model the inlet boundary conditions of the nozzle device. In the isothermal study, the wall confluent jets in the primary region and the wall jet in the secondary region, when predicted by the three turbulence models, are in good agreement with the measurements. The non-isothermal validation studies show that the SST k– ? model is slightly better at predicting the wall confluent jets than the other two models. The SST k– ? model is used to investigate the effects of the nozzle diameter, number of nozzles, nozzle array configuration, and inlet discharge height on the ventilation performance of the proposed wall confluent jets supply device. The nozzle diameter and number of nozzles play important roles in determining the airflow pattern, temperature field, and draught distribution. Increased temperature stratification and less draught distribution are achieved by increasing the nozzle diameter and number of nozzles. The supply device with smaller nozzle diameters and fewer nozzles yields rather uniform temperature distribution due to the dominant effect of mixing. The flow behavior is nearly independent of the inlet discharge height for the studied range. The proposed wall confluent jets supply device is compared with a mixing supply device, impinging supply device and displacement supply device. The results show that the proposed wall confluent jets supply device has the combined behavior of both mixing and stratification principles. The proposed wall confluent jets supply device provides better overall ventilation performance than the mixing and displacement supply devices used in this study. This study covers also another application of confluent jets that is based on impinging technology. The supply device under consideration has an array of round jets on a curve. Multiple jets issue from the supply device aperture, in which the supply device is positioned vertically and the jets are directed against a target wall. The flow behavior and ventilation performance of the impinging confluent jets supply device is studied experimentally in an industrial premise. The results show that the impinging confluent jets supply device maintains acceptable thermal comfort in the occupied zone by creating well-distributed airflow during cold and hot seasons.

Download or read book Advanced Building Simulation written by Ali Malkawi and published by Routledge. This book was released on 2004-07-29 with total page 267 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces recent advances in building simulation and outlines its historic development. Two important topics are described: uncertainty in simulation and coupled simulations, which are both closely linked to attempts to improve control and accuracy. This is followed by coverage of wind simulations and predictions, and then by an introduction to current systems and phenomenological modelling. Written by leading experts in the field both in the US and Europe, Advanced Building Simulation is an excellent graduate-level student textbook as well as a practical guide for architects, engineers and other construction professionals.

Download or read book Ventilation Systems written by Hazim B. Awbi and published by Psychology Press. This book was released on 2008 with total page 459 pages. Available in PDF, EPUB and Kindle. Book excerpt: This comprehensive account of the methods used for ventilating buildings and the type of systems currently in use for achieving the desired indoor environment will be of particular interest to graduate students, professionals and researchers.