Download or read book Modeling and Evaluation of Personal Displacement Ventilation System for Improving Indoor Air Quality written by Yue Xu and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This research aims at evaluating a new ventilation concept: personal displacement ventilation (PDV) for improving indoor air quality. The new ventilation method combines room displacement ventilation with task ventilation, the latter being directed at controlling air quality and comfort in the microenvironment where the building occupant is working, with the premise that such directed ventilation will maintain air quality where it matters. This approach could lead to improved ventilation system design that could even provide individual control of indoor microclimate. The effectiveness of PDV was studied by using computational fluid dynamics (CFD) modeling and rigorous validation experiments. First, a small office setup was built in a controlled environmental chamber. Three PDV cases with different locations of contaminant source and one general displacement ventilation (DV) case were investigated. Spatial distributions of airflow, temperature, and hypothetical pollutant distributions were measured. The measured data were then used to evaluate the performance of PDV against defined indoor air quality and thermal comfort criteria, and to validate the CFD model. The validated CFD program was further used to study PDV under various conditions. This study found that basic equipped PDV acts no different from DV from airflow pattern2s point of view. Due to the lack of heat generation around occupant2s legs, local buoyancy effect is not strong enough to attract supply air, which is generated from diffuser nearby, to join in the plume around occupant. However, auxiliary activities adjusting the direction of supply air and adding high panels around person can improve the fraction of supply air to join the plume around person or decrease the average contaminant concentration in breathing zone.

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 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 Personal Comfort Systems for Improving Indoor Thermal Comfort and Air Quality written by Faming Wang and published by Springer Nature. This book was released on 2023-05-31 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book first describes fundamental knowledge on human thermal comfort, adaptive thermal comfort, thermal comfort in sleeping environments, modeling of human thermal comfort, and thermal comfort assessment using human trials. Next, it presents an in-depth review of concept progress and evaluation of various personal comfort system, summarizes important findings and feasible applications, current gaps as well as future research needs. The seven chapters included in this section are task/ambient conditioning systems, personalized ventilation systems, electric fans, personal comfort systems, thermoelectric systems, personal thermal management systems, and wearable personal thermal comfort systems. This book provides valuable guidance for personal comfort system design and further improvement on the personal comfort performance. It will be a valuable resource for academic researchers, engineers in industry, and government regulators in the field of sustainable buildings and built environment.

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 Measurement Analysis and Modeling of Non Isothermal Low Velocity Displacement Ventilation Jets written by Laurent Magnier-Bergeron and published by . This book was released on 2016 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: Displacement Ventilation (DV) is an air distribution method recognized to enhance indoor air quality, while having a great potential for energy savings, due to stratification, higher supply air temperature and opportunity of free cooling. A frequent complaint associated with displacement ventilation is however the draft discomfort caused by the colder air movement at foot level, and the local discomfort due to an excessive temperature difference between head and ankle. Insufficient information is currently available regarding the variations of temperature and velocity inside a DV jet. Correlation models also need to be developed to report the variation of air speed in the jet. In this thesis, the DV jet is analyzed in depth through, first, experimental measurements and, then, the development of correlation models. Measurements are performed in an environmental chamber to study the DV jet coming from two different wall-mounted DV diffusers, for different supply conditions. The variations of air speed and temperature in the longitudinal, transversal, and horizontal planes are measured and analyzed. The thermal characteristics are discussed in terms of local thermal comfort. In the second part of the thesis, the experimental data are analyzed towards developing new models for the distribution of air speed and temperature in the air jets. A new mathematical model is proposed for the variation of air speed in the secondary zone of the jet, as well as a new model is suggested for the vertical air speed profile. The variation of the thickness of the DV jet is also studied. A new mathematical is model is proposed to account for the variation of minimal air temperature in the jet. The variations of air speed and temperature in the transversal direction are also discussed. Finally, the contributions are summarized and future work is proposed.

Download or read book Progress in Applied Mathematical Modeling written by Fengshan Yang and published by Nova Publishers. This book was released on 2008 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents new research related to the mathematical modelling of engineering and environmental processes, manufacturing, and industrial systems. It includes heat transfer, fluid mechanics, CFD, and transport phenomena; solid mechanics and mechanics of metals; electromagnets and MHD; reliability modelling and system optimisation; finite volume, finite element, and boundary element procedures; decision sciences in an industrial and manufacturing context; civil engineering systems and structures; mineral and energy resources; relevant software engineering issues associated with CAD and CAE; and materials and metallurgical engineering.

Download or read book Evaluation of Displacement Ventilation for Use in High ceiling Facilities written by Anthony Daniel Arens and published by . This book was released on 2000 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Displacement Ventilation Performance written by and published by . This book was released on 1993-03-01 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Modeling Indoor Air Pollution written by Darrell W Pepper and published by World Scientific. This book was released on 2009-03-23 with total page 361 pages. Available in PDF, EPUB and Kindle. Book excerpt: Emission of pollutants and their accumulation due to poor ventilation and air exchange are serious problems currently under investigation by many researchers. Of particular concern are issues involving air quality within buildings. Toxic fumes and airborne diseases are known to produce undesirable odors, eye and nose irritations, sickness, and occasionally death. Other products such as tobacco smoke and carbon monoxide can also have serious health effects on people exposed to a poorly ventilated environment; studies indicate that indirect or passive smoking can also lead to lung cancer.Design for prevention or remediation of indoor air pollution requires expertise in optimizing geometrical configurations; knowledge of HVAC systems, perceived or expected contaminants and source locations; and economics. Much of the design concept involves ways in which to optimize the benefits or balance the advantages and disadvantages of various configurations and equipment. The fact that a room or building will conceivably become contaminated is generally an accepted fact — to what extent indoor air pollution will become critical is not really known until it happens.A series of numerical models that run in MATLAB are described in the text and placed on the Web. These models include the finite difference method, finite volume method, finite element method, the boundary element method, particle-in-cell, meshless methods, and lagrangian particle transport. In addition, all example problems can be run using COMSOL, a commercial finite-element-based computer code with a great deal of flexibility and application. By accessing AutoCad ICES or DWG file structures, COMSOL permits a building floor plan to be captured and the interior walls discretized into elements./a

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 Floor supply Displacement Ventilation System written by Nobukazu Kobayashi and published by . This book was released on 2001 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research on indoor environments has received more attention recently because reports of symptoms and other health complaints related to indoor environments have been increasing. Heating, ventilating, and air-conditioning (HVAC) systems are used to control the indoor environment. Therefore, it is necessary to provide a good ventilation system that can provide good indoor environment. To improve indoor air quality, displacement ventilation systems can work well. The system provides fresh air directly to the occupied zone. However, the existing floor-supply displacement ventilation systems have some problems. Hence, the objective of this research was to improve the disadvantages of the current system, and to develop a new design for the floor-supply displacement ventilation system with floor diffusers. The research used numerical simulations through computational-fluid-dynamics (CFD). The experiment was carried out in a full -scale environmental chamber to obtain a reliable data on the floor-supply ventilation system. With the detailed data, the CFD program used in this research was validated. By using the validated program, we conducted numerical simulations of several different cases of the floor-supply system to evaluate the design and the performance of the system. The impacts of several parameters, such as the air change rate, number of diffusers, furniture arrangement, and cooling loads, on the indoor environment were investigated based on the thermal comfort level and indoor air quality. From the results, the parameters were ranked in the order of their impact. This result can be used for more specific case studies of each building design.

Download or read book Study of Displacement Ventilation Systems for Residential Houses with Radiant Floor Heating Systems written by Jianshun S. Zhang and published by . This book was released on 2001 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is estimated that about 1% of Canadians are environmentally hypersensitive. These people suffer partial to toal debilitation. Some of them require a home environment that is as free as possible from air-borne contaminants. Designing and constructing such houses are hampered bythe lack of practical guidelines both for selecting suitable building materials and furnishings, and for designing and installing effective ventilation systems. CMHC has recently designed and constructed a prototype house for environmentally hypersensitive individuals. It includes a range of features to help to achieve an acceptable indoor environment for these people at a minimal cost. These features include the use of commercially available low emission building materials and easily cleanable interior finishing, and a specially designed displacement ventilation system. A joint project was established between CMHC and the Institute for Research in Construction to assess the performance of the displacement ventilation system installed in this prototype house. This report presents the results of this evaluation. The results will help to develop guidelines for designing and constructing suitable and affordable housing for environmentally hypersensitive individuals. Some to the measures used in this prototype house may also be adopted in new and existing houses to improve indoor air quality.

Download or read book Study of Displacement Ventilation Systems for Residential Houses with Radiant Floor Heating Systems written by Canada Mortgage and Housing Corporation and published by . This book was released on 1998 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Air Infiltration Review written by and published by . This book was released on 1994 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Indoor Air Quality Modeling and Demand Controlled Ventilation written by Steven John Emmerich and published by . This book was released on 1993 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: