Modeling And Characterizing Bi Directional Airflow In Natural Ventilation
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Author | : Qin Zhang (S.M.) |
Publisher | : |
Total Pages | : 105 |
Release | : 2016 |
Genre | : |
ISBN | : |
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.
Author | : Francis Allard |
Publisher | : Earthscan |
Total Pages | : 378 |
Release | : 1998 |
Genre | : Architecture |
ISBN | : 9781873936726 |
AIOLOS is a computational tool for the calculation of the airflow rates in naturally ventilated buildings.
Author | : Y. Chartier |
Publisher | : World Health Organization |
Total Pages | : 132 |
Release | : 2009 |
Genre | : Medical |
ISBN | : 9241547855 |
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.
Author | : J. W. Drysdale |
Publisher | : |
Total Pages | : 3 |
Release | : 1949 |
Genre | : |
ISBN | : |
Author | : Melissa Cain |
Publisher | : |
Total Pages | : 58 |
Release | : 2004 |
Genre | : |
ISBN | : |
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.
Author | : Panagiota Karava |
Publisher | : |
Total Pages | : 0 |
Release | : 2008 |
Genre | : |
ISBN | : |
Natural/hybrid ventilation systems with motorized operable windows, designed and controlled to utilize the potential for cross-ventilation, represent an area of significant interest in sustainable building design as they can substantially reduce energy consumption for cooling and ventilation. Presently, there is a need for accurate prediction models that can contribute to the improvement of indoor environmental quality and energy performance of buildings, and the increased use of low energy, naturally driven cooling systems. In this regard, the present research aims to enhance airflow prediction accuracy for natural ventilation design of buildings considering advanced experimental and simulation methods. The study considers a Boundary Layer Wind Tunnel (BLWT) approach to investigate the wind-induced driving forces and ventilation flow rates in various building models subject to cross-ventilation. The Particle Image Velocimetry (PIV) technique was used for the first time to evaluate accurately the air velocity field for various cross-ventilation configurations. Detailed measurements were performed to determine mean and fluctuating internal pressures since they affect airflow prediction, occupants' thermal comfort, as well as cladding and structural wind load design of buildings with operable windows. PIV data for the inflow velocity were compared with those by using conventional techniques (e.g., hot-film anemometry) and results show differences, between the two methods, up to a factor of 2.7. This clearly indicates that accuracy can be enhanced with carefully conducted PIV experiments. The study provides guidelines for implementation of cross-ventilation in design practice. These guidelines were developed on the basis of parametric experimental investigations, which quantify the impact of relative inlet-to-outlet size and location on ventilation airflow rates and thermal comfort of building occupants. The study develops a novel simulation methodology combined with a sensitivity analysis focused on modelling issues, such as the impact of zoning assumptions, to predict the envelope pressures and related air-exchange rates in buildings due to wind, stack, and mechanical system effects. An integrated simulation tool (ESP-r) was used to model the airflow/energy interactions in an existing high-rise residential building, and simulation results agree well with monitoring data.
Author | : |
Publisher | : |
Total Pages | : 1472 |
Release | : 1988 |
Genre | : Power resources |
ISBN | : |
Author | : H.B. Awbi |
Publisher | : Routledge |
Total Pages | : 537 |
Release | : 2004-06-02 |
Genre | : Architecture |
ISBN | : 1134489625 |
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
Author | : Christoph Gengnagel |
Publisher | : Springer Nature |
Total Pages | : 793 |
Release | : 2019-08-28 |
Genre | : Technology & Engineering |
ISBN | : 3030298299 |
This book reflects and expands on the current trend in the building industry to understand, simulate and ultimately design buildings by taking into consideration the interlinked elements and forces that act on them. Shifting away from the traditional focus, which was exclusively on building tasks, this approach presents new challenges in all areas of the industry, from material and structural to the urban scale. The book presents contributions including research papers and case studies, providing a comprehensive overview of the field as well as perspectives from related disciplines, such as computer science. The chapter authors were invited speakers at the 7th Symposium “Impact: Design With All Senses”, which took place at the University of the Arts in Berlin in September 2019.
Author | : M. Santamouris |
Publisher | : Routledge |
Total Pages | : 627 |
Release | : 2013-06-17 |
Genre | : Architecture |
ISBN | : 113425797X |
Both the number and percentage of people living in urban areas is growing rapidly. Up to half of the world's population is expected to be living in a city by the end of the century and there are over 170 cities in the world with populations over a million. Cities have a huge impact on the local climate and require vast quantities of energy to keep them functioning. The urban environment in turn has a big impact on the performance and needs of buildings. The size, scale and mechanism of these interactions is poorly understood and strategies to mitigate them are rarely implemented. This is the first comprehensive book to address these questions. It arises out of a programme of work (POLISTUDIES) carried out for the Save programme of the European Commission. Chapters describe not only the main problems encountered such as the heat island and canyon effects, but also a range of design solutions that can be adopted both to improve the energy performance and indoor air quality of individual buildings and to look at aspects of urban design that can reduce these climatic effects. The book concludes with some examples of innovative urban bioclimatic buildings. The project was co-ordinated by Professor Mat Santamouris from the University of Athens who is also the editor of the book. Other contributions are from the University of Thessaloniki, Greece, ENTPE, Lyons, France and the University of Stuttgart, Germany.