Download or read book Analysis of Buoyancy Driven Airflow Patterns in a Model of a Naturally Ventilated Building written by Melissa Cain and published by . This book was released on 2004 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: Models can help us understand the climate conditions inside naturally ventilated buildings in order to improve the efficiency of the design. Naturally ventilated buildings use temperature gradients to create buoyancy forces in the space and drive the airflow pathways in the space. One architectural design feature that facilitates natural ventilation is the presence of stack ventilation in the roof of the building, which facilitates the expulsion of heated air from the space. An architectural feature that changes the airflow pathways is the presence of railing on the upper floors where there is a danger of falling into the atrium. Using the model of a naturally ventilated building located in the Building Technology Department at MIT airflow visualization studies were carried out using incense to view the airflow patterns in the model. The variables of temperature, size of stack ventilation opening, and whether there were railings in the building or not were varied to determine their effects on the airflow. Temperature had the effect of increasing the velocity of the airflow, but did not significantly change the overall airflow profile. The size of the stack vent opening changed the airflow pathways significantly as did adding railings into the model. Comparing the results with a computational fluid dynamics model shows that there are some discrepancies.
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 Modeling and Characterizing Bi directional Airflow in Natural Ventilation written by Qin Zhang (S.M.) and published by . This book was released on 2016 with total page 105 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bi-directional airflow in natural ventilation is an essential but not-well-understood scenario due to the complexity of airflow patterns as well as the strong coupling effect between temperature and ventilation. Neglecting bi-directional natural ventilation will result in problematic solutions and inaccuracy in estimation of ventilation performance. This work is focused on filling the knowledge gap by understanding the bi-directional airflow using computational fluid dynamics (CFD). Two important scenarios are simulated and analyzed: 1. Two-zone model with pure buoyancy forces, 2. Multi-zone model with combined wind and buoyancy forces. In the 1st model, a new concept of "local discharge coefficient" is proposed for its consistency under different boundary conditions. The influence of radiative heat transfer on simulation accuracy and ventilation performance is also investigated. In the 2nd model, the transient behaviors of airflow and the dynamics of wind and buoyant forces are analyzed and characterized. A new physical model is proposed based on simplified assumptions and nondimensionalization. This model is able to predicting the transient behavior of multi-zonal ventilation that involves bidirectional airflow patterns. The result of this study is to be integrated in CoolVent, the software designed by Building Technology Lab.
Download or read book Modeling Buoyancy driven Airflow in Ventilation Shafts written by Stephen Douglas Ray and published by . This book was released on 2012 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: Naturally ventilated buildings can significantly reduce the required energy for cooling and ventilating buildings by drawing in outdoor air using non-mechanical forces. Buoyancy-driven systems are common in naturally ventilated commercial buildings because of their reliable performance in multi-story buildings. Such systems rely on atria or ventilation shafts to provide a pathway for air to rise through the building. Although numerous modeling techniques are used to simulate naturally ventilated buildings, airflow network tools (AFNs) are most commonly used for annual simulations. These AFNs, however, assume minimal momentum within each zone, which is a reasonable approximation in large atria, but is inappropriate in smaller ventilation shafts. This thesis improves AFNs by accounting for momentum effects within ventilation shafts. These improvements are validated by Computation Fluid Dynamics (CFD) models that haven been validated by small scale and full scale experiments. The full scale experiment provides a detailed data set of an actual atrium that can be used in further validations and demonstrates the first use of a neutrally buoyant bubble generator for flow visualization and particle image velocimetry within a buoyancy driven naturally ventilated space. Small scale experiments and CFD simulations indicate an "ejector effect" within the shaft that uses momentum from lower floors to induce flow through upper floors. In some configurations, upper floors achieve higher flow rates than lower floors. Existing AFNs do not predict this "ejector effect" and are shown to significantly under predict flow rates through ventilation shafts by 30-40%. Momentum effects are accounted for in AFNs using empirical relationships for discharge coefficients. This approach maintains the current structure of AFNs while enhancing their ability to simulate airflow through ventilation shafts. These improvements are shown to account for the "ejector effect" and predict airflow rates that agree with CFD simulations to within 1-25%.
Download or read book Single sided Natural Ventilation written by Camille Allocca and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Natural Ventilation in Buildings written by Francis Allard and published by Earthscan. This book was released on 1998 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: AIOLOS is a computational tool for the calculation of the airflow rates in naturally ventilated buildings.
Download or read book Numerical Prediction of Flow Heat Transfer Turbulence and Combustion written by D. Brian Spalding and published by Elsevier. This book was released on 2015-07-14 with total page 445 pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerical Prediction of Flow, Heat Transfer, Turbulence and Combustion: Selected Works of Professor D. Brian Spalding focuses on the many contributions of Professor Spalding on thermodynamics. This compilation of his works is done to honor the professor on the occasion of his 60th birthday. Relatively, the works contained in this book are selected to highlight the genius of Professor Spalding in this field of interest. The book presents various research on combustion, heat transfer, turbulence, and flows. His thinking on separated flows paved the way for the multi-dimensional modeling of turbulence. Arguments on the universality of the models of turbulence and the problems that are associated with combustion engineering are clarified. The text notes the importance of combustion science as well as the problems associated with it. Mathematical computations are also presented in determining turbulent flows in different environments, including on curved pipes, curved ducts, and rotating ducts. These calculations are presented to further strengthen the claims of Professor Spalding in this discipline. The book is a great find for those who are interested in studying thermodynamics.
Download or read book Research in Building Physics and Building Engineering written by Paul Fazio and published by CRC Press. This book was released on 2020-11-26 with total page 1017 pages. Available in PDF, EPUB and Kindle. Book excerpt: Buildings influence people. They account for one third of energy consumption across the globe and represent an annual capital expenditure of 7%-10% of GNP in industrialized countries. Their lifetime operation costs can exceed capital investment. Building Engineering aims to make buildings more efficient, safe and economical. One branch of this discipline, Building Physics/Science, has gained prominence, with a heightened awareness of such phenomena as sick buildings, the energy crisis and sustainability, and considering the performance of buildings in terms of climatic loads and indoor conditions. The book reflects the advanced level and high quality of research which Building Engineering, and Building Physics/Science in particular, have reached at the beginning of the twenty-first century. It will be a valuable resource to: engineers, architects, building scientists, consultants on the building envelope, researchers and graduate students.
Download or read book Buoyancy Driven Flows written by Eric P. Chassignet and published by Cambridge University Press. This book was released on 2012-03-05 with total page 445 pages. Available in PDF, EPUB and Kindle. Book excerpt: Buoyancy is one of the main forces driving flows on our planet, especially in the oceans and atmosphere. These flows range from buoyant coastal currents to dense overflows in the ocean, and from avalanches to volcanic pyroclastic flows on the Earth's surface. This book brings together contributions by leading world scientists to summarize our present theoretical, observational, experimental and modeling understanding of buoyancy-driven flows. Buoyancy-driven currents play a key role in the global ocean circulation and in climate variability through their impact on deep-water formation. Buoyancy-driven currents are also primarily responsible for the redistribution of fresh water throughout the world's oceans. This book is an invaluable resource for advanced students and researchers in oceanography, geophysical fluid dynamics, atmospheric science and the wider Earth sciences who need a state-of-the-art reference on buoyancy-driven flows.
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 Buoyancy Effects on Natural Ventilation written by Torwong Chenvidyakarn and published by Cambridge University Press. This book was released on 2013-09-02 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes in depth the fundamental effects of buoyancy, a key force in driving air and transporting heat and pollutants around the interior of a building. It is essential reading for anyone involved in the design and operation of modern sustainable, energy-efficient buildings, whether a student, researcher or practitioner. The book presents new principles in natural ventilation design and addresses surprising, little-known natural ventilation phenomena that are seldom taught in architecture or engineering schools. Despite its scientific and applied mathematics subject, the book is written in simple language and contains no demanding mathematics, while still covering both qualitative and quantitative aspects of ventilation flow analysis. It is therefore suitable for both non-expert readers who just want to develop intuition of natural ventilation design and control (such as architects and students) and for those possessing more expertise whose work involves quantifying flows (such as engineers and building scientists).
Download or read book A Predictive Simulation Framework for Buoyancy driven Natural Ventilation in Office Buildings written by Chen Chen and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Natural ventilation and cooling can significantly reduce building energy consumption, but inherent variability in boundary and operating conditions makes optimal and robust design of natural ventilation a challenging task. The goal of this study is to enable robust design and operation of natural ventilation systems by developing an efficient simulation framework that can predict the building's thermal response under buoyancy-driven natural ventilation. A simplified building thermal model that solves for the time-evolution of the volume-averaged indoor air temperature with uncertain quantification (UQ) can provide an intuition of the likely effects of design choices under a variety of operating conditions in the early building design stage. Subsequently, computational fluid dynamics (CFD) simulations can be employed to fine-tune the building design at the design development stage, and the CFD results can be used to reduce the uncertainty in the building thermal model coefficients that determine the flow and heat transfer rates. The predictive capability of the resulting multi-fidelity framework was validated with a carefully designed full-scale experiment performed in an operational atrium building. A CFD-based experimental design ensured optimal temperature sensor placement under the full range of expected operating conditions to ensure an accurate characterization of the volume-averaged indoor air temperature, as well as of the spatial variability in the temperature field. The prediction of thermal performance matches well to the experiments with discrepancies lower than 0.38 °C for all the approaches, and the final widths of the 95% confidence interval are reduced to less than 0.18 °C, indicating promising predictive capabilities for buoyancy-driven natural ventilation at all stages of designs.
Download or read book Analysis of Natural and Hybrid Ventilation in Simple Buildings written by Hugh Leung and published by . This book was released on 2017-01-28 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Analysis of Natural and Hybrid Ventilation in Simple Buildings" by Hugh, Leung, 梁修賢, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled ANALYSIS OF NATURAL AND HYBRID VENTILATION IN SIMPLE BUILDINGS submitted by Leung Hugh for the degree of Master of Philosophy at The University of Hong Kong in February 2003 The main objective of this thesis is to study analytically the main physical parameters affecting natural ventilation flow rates in some simple building models. The ventilation air flows are driven by either natural forces such as thermal buoyancy and wind forces alone, or by combined natural and mechanical forces, i.e. mixed- mode ventilation. This analytical study is an extension of earlier studies on natural ventilation in a simple building with two vertically displaced openings. Our suggested new building models include a single-zone building with three openings, and a two-opening hybrid building with a mechanical fan. The effects of physical and geometrical parameters such as the size and location of openings and the driving forces upon ventilation flow rates are investigated. Our new analytical solutions can provide a simple analysis tool for parameter studies and give some physical insights on natural and mixed-mode ventilation. The analytical study on natural and mixed-mode ventilation also provides detailed and accurate information that can be used for validating numerical models of natural and hybrid ventilation and developing simple vent sizing methods. The effect of stratification is also considered in a single-zone building with three openings, and 2this has made some of our analyses useful for studying smoke movement in building fires, although they have neglected the effect of compressibility. Existing empirical formulae used for calculating the combined ventilation flow rate in a mixed-mode ventilation system, such as the quadratic superposition formula, are based on a simple physical assumption that the driving pressures due to natural and mechanical forces can be added linearly. This assumption is shown to be invalid in the current study when natural and mechanical forces are at similar magnitudes. The results from these simplified empirical formulae are compared with the derived analytical solutions. Our comparisons show that the errors due to the quadratic superposition formula can be quite large when both natural and mechanical forces have a similar magnitude. In the study of natural and mixed-mode ventilation, solution multiplicity behaviour was identified previously when thermal buoyancy force opposes the wind force under identical physical conditions. Our study on stratified flows in a building with three openings suggests that two smoke layers may also exist for the same set of parameters. We also show that mechanical fans can reduce and in some situations eliminate the existence of multiple solutions. This might explain why that solution multiplicity has not been a major concern in a modern building ventilation design, where mechanical fans are mostly used. __________________________ Leung Hugh Total words: 410 3 DOI: 10.5353/th_b2666310 Subjects: Ventilation - Mathematical models Ventilation - Testing
Download or read book Advances in Building Energy Research written by Mat Santamouris and published by Routledge. This book was released on 2012-05-04 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Building Energy Research (ABER) offers state-of-the-art information on the environmental science and performance of buildings, linking new technologies and methodologies with the latest research on systems, simulations and standards. As stringently reviewed as a journal but with the breadth of a book, this annual volume brings together invited contributions from the foremost international experts on energy efficiency and environmental quality of buildings. Spanning a broad range of technical subjects, this is a 'must have' reference on global developments in the field, suitable for architects and building engineers, environmental engineers, industry professionals, students, teachers and researchers in building science, technical libraries and laboratories. Volume 3 covers: - Energy, Carbon and Cost Performance of Building Stocks - Solar Chimneys in Buildings - Optimization and Economics of Solar Cooling Systems - Artificial Neural Networks and Genetic Algorithms in Energy Applications in Buildings - Decision Support Methodologies on the Energy Efficiency and Energy Management in Buildings - Progress in Numerical Modelling for Urban Thermal Environment Studies - Post Occupancy Evaluation (POE): An Inevitable Step Toward Sustainability - Guidelines to Avoid Mould Growth in Buildings - Thermal Impact of Strategic Landscaping in Cities - Urban Heat Island and its Impact on Building Energy Consumption - Green Roofs in Buildings: Thermal and Environmental Behaviour - Building Earth-Contact Heat Transfer
Download or read book Building Ventilation written by David Etheridge and published by . This book was released on 1996-12-23 with total page 760 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book sets down the fundamentals of the theory and measurement of building ventilation and describes the various techniques for predicting and measuring ventilation. It addresses both envelope flows and internal air motion. The first part of the book is primarily concerned with physical descriptions and theoretical models: starting with an overview of the basic mechanisms and characteristics of envelope flows, it then addresses the treatment of the flow characteristics of individual openings and mathematical models for complete building envelopes. Theories for internal air motion are then discussed in detail: mechanisms of mass transport in terms of air motion and age distribution, primary air flows in isolation, resulting flows in enclosed spaces, and flows through large internal openings. The second part, concerned with measurement techniques both at full scale and at model scale, begins with techniques for determining flow characteristics of envelope openings. The use of tracer gases in the study of age distribution and ventilation efficiency is dealt with in detail. Scale modelling for investigating both envelope flows and internal motions is also addressed. The final chapter deals with Computational Fluid Dynamics, since one of its main applications is an alternative to conventional experimental techniques. Natural ventilation is re-emerging as an alternative to mechanical systems in some commercial buildings and both natural and mechanical ventilation are dealt with in detail.
Download or read book Particle Image Velocimetry for Building Thermal Airflow Analysis written by Cheng Zhang and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: It is crucial to quantify the airflow field in and around a building, as this can provide information for creating a healthy and comfortable thermal environment for people. Over the last decade, particle image velocimetry (PIV) has gradually become the most popular measurement technique for measuring building environment airflow fields. The objective of this thesis is to provide an overview of the typical two-dimensional PIV technique used in the building environment. The measurement principle and procedures are discussed based on the existing literature and previous research experiences. Four problems are investigated to show different applications of the PIV technique in measuring airflow fields, combined with other assessment models: the analytical model, the empirical model, the multizone model and the computational fluid dynamics (CFD) model. The performance of buoyancy-driven natural ventilation in a single-zone sub-scale model is studied using different experimental technologies. The behavior of single jet flow interaction with wind is investigated through experimental and numerical methods. The hybrid ventilation flow field and temperature distribution is measured by PIV and thermocouple experiments. PIV, combined with empirical models, is used to predict localized mechanical ventilation system performance in a warehouse model. The results show that the quantitative and detailed flow information obtained by PIV can be used for flow pattern visualization, flow structure analysis, numerical model validation, and empirical model correlation. The limitations of the PIV technique in sub-scale model measurements is also discussed.
Download or read book Elementary Buoyancy driven Ventilation written by Karl Terpager Andersen and published by . This book was released on 2019-01-04 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: Buoyancy-driven ventilation is a part of natural ventilation, where wind forces may participate, but only buoyancy-driven ventilation (i.e. driven by the difference between outdoor and indoor air density) is considered in this book. The buoyancy-driven part is to some extent complicated from a theoretical point of view and requires a well-founded theory based on the fundamental flow equations to ensure reliable results. In the book, a model is set up for a room with two openings to the surroundings and with a uniform indoor temperature. From this basic model, variants are developed for rooms with several openings and/or with a stratified indoor temperature. Further, for each variant, versions are set up where the difference between outdoor and indoor air density, or the difference between the indoor and outdoor temperature, or the net heat input rate is the independent thermal variable. The scope of application is determined, and the opening area ratios are analysed with the aim to obtain optimal ventilation conditions. The book is of interest for building engineers who are or want to specialise in natural ventilation, to under-graduates who wish to have natural ventilation as their special subject, and to postgraduates who work with subjects where it is relevant to involve buoyancy-driven ventilation. For undergraduates in general, especially Chapters 2 and 3 are of interest.
