A Ventilation Strategy Based On Confluent Jets
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A Ventilation Strategy Based On Confluent Jets
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Author : Setareh Janbakhsh
language : en
Publisher: Linköping University Electronic Press
Release Date : 2015-04-27
A Ventilation Strategy Based On Confluent Jets written by Setareh Janbakhsh and has been published by Linköping University Electronic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-04-27 with categories.
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.
Experimental And Numerical Investigations Of A New Ventilation Supply Device Based On Confluent Jets
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Author :
language : en
Publisher:
Release Date : 2018
Experimental And Numerical Investigations Of A New Ventilation Supply Device Based On Confluent Jets written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
On The Performance Of Stratified Ventilation
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Author : Ulf Larsson
language : en
Publisher: Linköping University Electronic Press
Release Date : 2018-08-20
On The Performance Of Stratified Ventilation written by Ulf Larsson and has been published by Linköping University Electronic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-08-20 with categories.
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.
Optimization Of Confluent Jets Ventilation With Variable Airflow
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Author : Harald Andersson
language : en
Publisher:
Release Date : 2022
Optimization Of Confluent Jets Ventilation With Variable Airflow written by Harald Andersson and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with categories.
Experimental And Numerical Investigations Of A Ventilation Strategy
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Author :
language : en
Publisher:
Release Date : 2014
Experimental And Numerical Investigations Of A Ventilation Strategy written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
Proceedings Of Ecocomfort 2024
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Author : Zinoviy Blikharskyy
language : en
Publisher: Springer Nature
Release Date :
Proceedings Of Ecocomfort 2024 written by Zinoviy Blikharskyy and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on with categories.
Urban Transition
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Author : Marita Wallhagen
language : en
Publisher: BoD – Books on Demand
Release Date : 2023-12-20
Urban Transition written by Marita Wallhagen and has been published by BoD – Books on Demand this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-12-20 with categories.
Proceedings Of Cee 2019
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Author : Zinoviy Blikharskyy
language : en
Publisher: Springer
Release Date : 2019-08-08
Proceedings Of Cee 2019 written by Zinoviy Blikharskyy and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-08-08 with Technology & Engineering categories.
This book gathers the latest advances, innovations, and applications in the field of effective methods of calculation, resource-saving technologies and advanced materials in civil and environmental engineering, as presented by leading international researchers and engineers at the XVII International Scientific Conference Current Issues of Civil and Environmental Engineering “Lviv- Košice – Rzeszów”, held in Lviv, Ukraine on September 11-13, 2019. It covers highly diverse topics, including structural shaping and optimization; aspects of structural behavior and modeling; advanced analysis methods; experimental tests and numerical simulations; design codes, in particular Eurocodes and other national and regional limit state codes; and highway and bridges engineering. It also discusses modern architectural and structural solutions; innovative materials and products; durability and maintenance; fabrication and erection; sustainability in construction; renewable energy sources; heat, gas and water supply; ventilation and air-conditioning; ecological and energy-saving technologies, modern water-purification and treatment technologies; and the protection of water ecosystems. The contributions, which were selected by means of a rigorous international peer-review process, highlight numerous exciting ideas that will spur novel research directions and foster multidisciplinary collaborations.
Challenges Opportunities And Solutions In Structural Engineering And Construction
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Author : Nader Ghafoori
language : en
Publisher: CRC Press
Release Date : 2009-10-29
Challenges Opportunities And Solutions In Structural Engineering And Construction written by Nader Ghafoori and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009-10-29 with Technology & Engineering categories.
Challenges, Opportunities and Solutions in Structural Engineering and Construction addresses the latest developments in innovative and integrative technologies and solutions in structural engineering and construction, including: Concrete, masonry, steel and composite structures; Dynamic impact and earthquake engineering; Bridges and
Office Buildings
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Author : Pranab Kumar Nag
language : en
Publisher: Springer
Release Date : 2018-12-31
Office Buildings written by Pranab Kumar Nag and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-12-31 with Technology & Engineering categories.
This book brings together concepts from the building, environmental, behavioural and health sciences to provide an interdisciplinary understanding of office and workplace design. Today, with changes in the world of work and the relentless surge in technology, offices have emerged as the repositories of organizational symbolism, denoted by the spatial design of offices, physical settings and the built environment (architecture, urban locale). Drawing on Euclidian geometry that quantifies space as the distance between two or more points, a body of knowledge on office buildings, the concept of office and office space, and the interrelationships of spatial and behavioural attributes in office design are elucidated. Building and office work-related illnesses, namely sick building syndrome and ailments arising from the indoor environment, and the menace of musculoskeletal disorders are the alarming manifestations that critically affect employee satisfaction, morale and work outcomes. With a focus on office ergonomics, the book brings the discussion on the fundamentals of work design, with emphasis on computer workstation users. Strategic guidance of lighting systems and visual performance in workplaces are directed for better application of ergonomics and improvement in office indoor environment. It discusses the profiles of bioclimatic, indoor air quality, ventilation intervention, lighting and acoustic characteristics in office buildings. Emphasis has been given to the energy performance of buildings, and contemporary perspectives of building sustainability, such as green office building assessment schemes, and national and international building-related standards and codes. Intended for students and professionals from ergonomics, architecture, interior design, as well as construction engineers, health care professionals, and office planners, the book brings a unified overview of the health, safety and environment issues associated with the design of office buildings.
