Submitted by Maria.Kapsalaki on Mon, 10/28/2013 - 13:56
Passive stack ventilation is a key feature of sustainable building design and has particular potential for use in tall, multi-storey buildings. However, natural ventilation flows through multiply connected spaces may not behave as expected. Recirculation of air through occupied parts of the building and bidirectional exchange flows at ventilation outlets may compromise the intended ventilation scheme resulting in an uncomfortable indoor environment.
The natural ventilation of a room with a source of uniformly distributed heating at the base andwith vents at multiple heights is investigated both theoretically and experimentally. It is shown that the impact of additional vents can be predicted by determining the height of neutral buoyancy. As a room is heated it heats up to a uniform state and the relative height of neutral buoyancy depends on the ratio of the upper and lower vent areas. When a simple additional intermediate level vent is introduced a unique solution can be used to predict the resulting air flow.
For static smoke exhaust systems, such as horizontal ceiling vents, buoyancy of the smoke layer is the driving force for smoke removal. However, wind effect should also be considered, as the smoke layer interface height can be raised up or pulled down, depending on the conditions. Key equations on calculating the smoke exhaust rates and the required vent area will be reviewed first in this paper. Modifications of those equations with wind effects are discussed. An atrium is taken as an
Investigates the functional connection between the ventilation rate experienced within a building and both the separation of the inlet and outlet vents and the temperature difference between the internal and external air. Identifies two regimes of operations: one where separation drives the situation and one where temperature is the main influence. States that considering these two regimes can have an impact on design philosophy.
It is possible to make high wall inducing vents with low air resistance, combined with natural ventilation or a mechanical exhaust. By means of these vents draughts may be prevented and high efficiencies in fresh air and contaminant removal may be realised, the latter being determined by the position of the outlet. Existing equations related to air flow patterns and Computational Fluid Dynamics (CFD) computer programs can be used, provided that the equations and the CFD program (Phoenics) are modified in order to get better agreement with measurements.
The following report documents the design and development of an automatic vent closure system for residential exhaust systems. The report discusses the rationale behind the perceived need for such a system and defines the objectives of the design and development work with respect to these needs. A detailed account of the development of the design and construction of successive prototypes will be given along with a thorough description of the testing procedures employed to evaluate the operational characteristics of each prototype as their design was further refined and developed.