Single-sided natural ventilation : design analysis and general guidelines
Author(s)Allocca, Camille, 1977-
Single-sided ventilation computer tool
Massachusetts Institute of Technology. Dept. of Mechanical Engineering.
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Natural ventilation is an effective measure to save energy consumed in buildings and to improve indoor air quality. This study focuses specifically on the principles of single-sided natural ventilation design. Single-sided ventilation is very common in building designs and has been shown to produce very complicated, fluctuating airflow patterns at the openings of buildings. An ongoing challenge in natural ventilation design is therefore the ability to control the mechanisms of wind and temperature for desirable indoor environment conditions. Understanding these effects is important in determining the feasibility of natural ventilation designs. The current research approach used mainly (CFD) tools, together with analytical solutions, empirical models, and experimental results. CFD models were created and analyzed to determine the validity of using this tool for single-sided ventilation analysis and design. The impact of using computational modeling tools for the development of natural ventilation design is great to the building industry field. The focus of this CFD study was on a single room within a residential building in Cambridge, MA. Simulations were performed under varying conditions of temperature, wind speed, wind direction, opening layout and size, and internal heat load, in order to evaluate parameter trends. Airflow rates, velocity fields, and temperature distributions were derived from analytical equations and empirical models as well as from experimental measurements, in order to validate and perform further research in this area. Consequently, this investigation found CFD tools to be valid for studying single-sided natural ventilation strategies with respect to indoor, outdoor, and combined indoor and outdoor flow. From this validation, CFD was applied further to determine the effects of buoyancy, wind, and combined flow on natural ventilation rates and overall indoor conditions. For buoyancy driven flow, CFD performed well when modeling both the indoor and outdoor environment in the calculation, resulting in a 10% difference between semi-analytical and CFD results. However, for wind-driven flow, CFD was found to under predict empirical model results by approximately 25%. This under prediction was attributed to mean or time-averaged, rather than instantaneous calculations of the CFD technique applied to this study. In addition to evaluating the effects of buoyancy and wind on ventilationrates, this study also focused on the effects of wind direction, opposing buoyancy and wind forces, and mixed-mode ventilation. The results from these studies provided further insight into the field of single-sided ventilation and revealed the need for further research in this valuable area. To fully understand and utilize this natural ventilation strategy, the results from the complete single-sided ventilation study were compiled and developed into a computer design tool and a set of general design guidelines. These tools were created in such a way so that designers can use them to evaluate ventilation performance and see immediate results for an indoor environment that they propose to design. The level of analysis that is desired by designers in this area calls for a tool such as this one. This total investigation has been essential in evaluating and analyzing the important areas of the single-sided ventilation field and in providing a strong foundation for further research in improving natural ventilation design as well as in improving CFD and turbulence modeling.
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.Includes bibliographical references (p. 102-104).
DepartmentMassachusetts Institute of Technology. Dept. of Mechanical Engineering.
Massachusetts Institute of Technology