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 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 Energy Performance and Indoor Climate Analysis in Buildings written by Jarek Kurnitski and published by MDPI. This book was released on 2019-11-21 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: HVAC systems, load shifting, indoor climate, and energy and ventilation performance analyses are the key topics when improving energy performance in new and renovated buildings. This development has been boosted by the recently established nearly zero energy building requirements that will soon be in use in all EU Member States, as well as similar long-term zero energy building targets in Japan, the US, and other countries. The research covered in this Special Issue provides evidence of how new technical solutions have worked, in practice, in new or renovated buildings, and also discusses problems and how solutions should be further developed. Another focus is on the more detailed calculation methods needed for the correct design and sizing of dedicated systems, and for accurate quantification of energy savings. Occupant behavior and building operation is also examined, in order to avoid common performance gaps between calculated and measured performance. These topics demonstrate the challenge of high performance buildings as, in the end, comfortable buildings with good indoor climate which are easy and cheap to operate and maintain are expected by end customers. Ventilation performance, heating and cooling, sizing, energy predictions and optimization, load shifting, and field studies are some of the key topics in this Special Issue, contributing to the future of high performance buildings with reliable operation.

Download or read book System Performance Evaluation and Design Guidelines for Displacement Ventilation written by Qingyan Chen and published by American Society of Heating Refrigerating and Air-Conditioning Engineers. This book was released on 2003 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents system performance evaluation, and includes a 10-step design guideline for displacement ventilation systems for U.S. buildings. These design guidelines present two important models: 1) to calculate the temperature difference between the head and the foot level of an occupant; and 2) one to determine the ventilation effectiveness at the breathing level.The book notes that: A displacement ventilation system can provide a thermally comfortable indoor environment at a high cooling load through careful design. The indoor air quality in a space with displacement ventilation is better if the contaminant sources are associates with the heat sources. The displacement ventilation system can also save energy but requires a separate heating system if it is applied to building perimeter zones. 6 x 9, soft cover.

Download or read book Scale Model Studies of Displacement Ventilation written by Galip Mehmet Okutan and published by . This book was released on 1995 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt: Displacement ventilation is an air conditioning method that provides conditioned air to indoor environments with the goal to improve air quality while reducing energy consumption. This study investigates the performance of displacement ventilation systems in open plan office environments, focusing on vertical temperature stratification. It explores the possibility of improving the performance of these systems by reducing the temperature stratification at lower levels and allowing them to operate with high cooling loads without exceeding thermal comfort limits. An experimental setup consisting of a scale model of an open plan office room and equipment necessary to provide the experimental conditions was designed and constructed. Steady state experiments on displacement ventilation were conducted. The experiments simulated a variety of cases in terms of heat gain per area, air supply flow rate and slow mixing at lower levels. Temperature distributions in the model and fluid flow rates were measured. Flow visualization was performed to investigate the flow patterns in the office room. The vertical temperature profiles for the considered cases were not linear. The vertical temperature stratification increased when the heat gain in the office increased. It was within the comfort limits for all simulated cases, except the case with the maximum heat gain (38W/m2). The introduction of slow mixing at lower levels decreased the temperature differential in all experiments. This effect of slow mixing was more pronounced at lower heights. This suggested that displacement ventilation may accommodate higher cooling loads if slow mixing at the lower levels is provided. Flow visualization results indicated that the height of the stratification was about 1m above the floor. The plumes over the heat sources had different characteristics, implying the possible importance of the size, shape and spatial distribution of the heat sources.

Download or read book AIR DISTRUBUTION IN ROOMS Ventilation for Health and Sustainable Enviorment Volume II written by Marco Maroni and published by Elsevier. This book was released on with total page 562 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Thermal Science and Energy written by Fazia Ali-Toudert and published by Springer Nature. This book was released on 2023-11-30 with total page 563 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers advanced theories and methods in the field of heat and mass transfer, which are expected to improve thermal systems performance and energy efficiency. It reports on novel findings relating to a wide range of topics in industry, building, transportation and agriculture. Offering a good balance of fundamental and applied research, this book provides scientists, engineers and other professionals with a timely snapshot on advances in thermal science, renewable energies and sustainable energy technologies. It also offers a source of inspiration for future research and collaborations.

Download or read book Reclaiming The Underground Space Volume 1 written by International Tunnelling Association and published by Routledge. This book was released on 2022-02-14 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains papers, presented at the ITA World Tunnelling Congress 2003 held in Amsterdam, which reflects the state of the art with regard to research, analysis, design and practical experience in almost all fields of tunnelling and underground space construction.

Download or read book Handbook Of Flow Visualization written by Wen Jei Yang and published by Routledge. This book was released on 2018-12-19 with total page 723 pages. Available in PDF, EPUB and Kindle. Book excerpt: With contributions from some of the world's leading experts, the second edition of this classic reference compiles all major techniques of flow visualization and demonstrates their applications in all fields of science and technology. A new chapter has been added that covers flow visualization applications in large wide tunnels for airplane and automobile testing. Several important examples of applications are included. A second new chapter details the use of infrared (IR) cameras for detecting and observing the boundary layer transition in industrial wind tunnels and flight testing of commercial transport airplanes. A final new chapter has been added on multiphase flow and pulsed-light velocimetry.

Download or read book Information Circular written by and published by . This book was released on 1987 with total page 758 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Building Ventilation written by Mat Santamouris and published by Routledge. This book was released on 2006-06-01 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ensuring optimum ventilation performance is a vital part of building design. Prepared by recognized experts from Europe and the US, and published in association with the International Energy Agency's Air Infiltration and Ventilation Centre (AIVC), this authoritative work provides organized, classified and evaluated information on advances in the key areas of building ventilation, relevant to all building types. Complexities in airflow behaviour, climatic influences, occupancy patterns and pollutant emission characteristics make selecting the most appropriate ventilation strategy especially difficult. Recognizing such complexities, the editors bring together expertise on each key issue. From components to computer tools, this book offers detailed coverage on design, analysis and performance, and is an important and comprehensive publication in this field. Building Ventilation will be an invaluable reference for professionals in the building services industry, architects, researchers (including postgraduate students) studying building service engineering and HVAC, and anyone with a role in energy-efficient building design.

Download or read book Thermal Energy written by Yatish T. Shah and published by CRC Press. This book was released on 2018-01-12 with total page 854 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book details sources of thermal energy, methods of capture, and applications. It describes the basics of thermal energy, including measuring thermal energy, laws of thermodynamics that govern its use and transformation, modes of thermal energy, conventional processes, devices and materials, and the methods by which it is transferred. It covers 8 sources of thermal energy: combustion, fusion (solar) fission (nuclear), geothermal, microwave, plasma, waste heat, and thermal energy storage. In each case, the methods of production and capture and its uses are described in detail. It also discusses novel processes and devices used to improve transfer and transformation processes.

Download or read book Diesels in Underground Mines written by and published by . This book was released on 1987 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Bulletin de L Institut International Du Froid written by and published by . This book was released on 2010 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 Industrial Ventilation Design Guidebook written by Howard D. Goodfellow and published by Elsevier. This book was released on 2001-05-19 with total page 1556 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Industrial Ventilation Design Guidebook addresses the design of air technology systems for the control of contaminants in industrial workplaces such as factories and manufacturing plants. It covers the basic theories and science behind the technical solutions for industrial air technology and includes publication of new fundamental research and design equations contributed by more than 40 engineers and scientists from over 18 countries.Readers are presented with scientific research and data for improving the indoor air quality in the workplace and reducing emissions to the outside environment.The Guidebook represents, for the first time, a single source of all current scientific information available on the subject of industrial ventilation and the more general area of industrial air technology. New Russian data is included that fills several gaps in the scientific literature. * Presents technology for energy optimization and environmental benefits* A collaborated effort from more than 60 ventilation experts throughout 18 countries* Based on more than 50 million dollars of research and development focused on industrial ventilation* Includes significant scientific contributions from leading ventilation experts in Russia* Presents new innovations including a rigorous design methodology and target levels* Contains extensive sections on design with modeling techniques* Content is well organized and easily adaptable to computer applications