Describes the process of designing a supervisory control to provide thermal comfort and adequate air distribution inside a single-sided naturally ventilated test room. The controller is based on fuzzy logic reasoning. Inputs are the outside wind velocity, direction, outside and inside temperatures. Output is the opening position. The strategy is then validated using experimental data from a naturally ventilated test room. Presents the initial results of the study, which show that the controller is capable of providing better thermal comfort inside the room.
Describes a system designed to maintain good ventilation consisting of special window ventilators that permit a trickle air flow rate to pass and to maintain a background ventilation. The apparatus for measuring the characteristics of window grilles are described and the results obtained from some commercial window grilles discussed.
Thermal comfort field studies were conducted in three different sessions (morning, afternoon and night) of the day to evaluate the actual thermal comfort perception of the occupants. Direct and indirect assessment of the thermal acceptability were performed to investigate whether the naturally ventilated indoor environment meet the ASHRAE Standard-55's 80% acceptability criteria. Comparison of thermal sensation and thermal comfort votes revealed that a high proportion of people experiencing sensations of +2, +3 still found the conditions to be comfortable.
This paper analyses buoyancy-driven natural ventilation assisted or opposed by winds in a building with thermal stratification. Theoretical analysis shows that the ventilation flow is mainly characterised by two air change parameters, namely a buoyancy air change parameter and a wind change parameter, as well as the ventilation openings. It also shows how the clean zone height is affected by ventilation openings. Our new analysis also reveals that the hysteresis behaviour found when uniform temperature distribution is assumed also exists in buildings with thermal stratification.
This paper derives some new analytical solutions for buoyancy-driven natural ventilation in buildings with three openings. The new solutions are used to analyse the effect of the middle opening height and area on the natural ventilation performance. The criteria for flow direction switching for the middle opening is established. It is also proved that the neutral plane level in the three-opening buildings depends only on geometrical parameters. Natural ventilation of buildings with two openings affecting by supply- or exhaust-only mechanical systems are also investigated analytically.
Since no literature on design calculations for natural ventilation could be found, the author developed an original design method in the early nineties. He is still using the method to design areas that have to be ventilated naturally. An example of a very common application, is designing the ventilation of a transformer room and the outside air grid area necessary. A surprising result of the design of a practical situation is that it can be demonstrated on the basis of the calculations that wind speed has relatively little effect on the natural ventilation.
During the last two decades the significance of indoor environmental quality in buildings has been appreciated, not only in relation to thermal comfort, but also to indoor air quality. Ventilation is an important tool for securing both a good indoor climate and air quality. However, in buildings without mechanical ventilation and air conditioning systems (which comprise the majority in most European countries) natural ventilation presents the only means to satisfy indoor air quality needs.
Results of a CFD simulation of the wind-assisted stack ventilation of a single-storey enclosure with high and low-level ventilation openings are presented and compared with both the laboratory measurements and the analytical model of the flow and thermal stratification developed by Hunt and Linden (2001). Comparisons show that close quantitative agreement is obtained between the thermal stratification predicted by the CFD and the analytical model and experimental measurements.
Explains how natural ventilation can improve the environment for workers in industrial buildings as well as those in offices. States that in industrial buildings, the primary reason for installing ventilation has always been to avoid excessive internal temperatures, particularly in summer, and to provide fresh air to breath and remove odours. Waste heat from plant, processes, lighting and people is often the main problem today. Claims that natural ventilation is still an option today for cost and environmental reasons.
Increased global warming and deterioration of the ozone layer have stimulated interest in the use of renewable energy systems. Natural ventilation is increasingly being employed in modern buildings to minimize energy consumption and the release of harmful emissions to the environment. Innovative natural ventilation techniques such as the windcatcher and solar chimney have facilitated the effective use of natural ventilation in a wide range of buildings for increasing the ventilation rate.
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