This paper deals with the convective flow through a horizontal aperture connecting two superimposed large enclosures which are kept at different temperatures. The lower room is warmer than the upper room and this unstable thermal configuration generates a natural them1osyphon flow, between both volumes. This type of flow can occur inside buildings: stairwell flows or natural ventilation flows through horizontal openings. In the literature, very little information is available concerning this domain of applications.
This paper compares two well-known modelling approaches for natural ventilation in a multi-zone building with thermal stratification and large openings. The zonal approach in this paper assumes a fully mixed condition in each zone, and considers the bi-directional flows through all large openings. The zonal model is integrated into a thermal analysis code to provide simultaneous prediction of both ventilation flow rates and air temperatures in each zone. The CFD approach uses a finite-volume method for turbulent flows.
In a hot climate, a large amount of solar heat irradiates on a roof and it is transmitted to an occupied space beneath it through an attic. To interrupt this heat to attain a comfortable condition in the occupied space, ventilation of the attic is an important and effective measure. There are two ways of the ventilation, one is natural and the other is forces ventilation. The former measure should be considered prior to the latter from such reasons as simplicity in practice and power saving.
Recent research suggests that fine-particulate air pollution increases the incidence of lung disease and pre-mature death. Single fibre filter theory is used to predict the theoretical particulate collection efficiency of air permeable walls (dynamic insulation). The relationship between particle diameter and filtration efficiency for dynamic insulation, as a function of flow rate, is examined and compared to that for a conventional filter.
The light well located in the center of high-rise apartment building in Japan is called "Void". Gas water-heaters settled in Void discharge the exhaust gas into Void so that the enough opening area has to be designed at the bottom of Void to keep the IAQ in Void. In order to secure the IAQ in Void, a simple zonal model to calculate the ventilation rate induced by the wind force and the thermal buoyancy through openings at the bottom of Void with heat sources like water heaters is presented. And the accuracy of this calculation method is examined by wind tunnel test.
Until now, there is no widely accepted way to express any index for this purpose and taking into account the large variety of possible pollutants. Things can be simplified if the aim is to compare different systems and strategies rather than to give an absolute value of quality. For the study of a pollutant source, the main important point for comparison is the pattern of its production, whatever this pollutant is. The detailed data for each inhabitant is the curve of the number of hours above a pollutant level concentration Ci: Nh (Ci).
A series of CFD and model experiments were carried out in order to find the most effective ventilation system in a separated refuse disposal facility. The ventilation system needed in the facility protects the working space from dust and odors generated by handling refuse. The desired ventilation system is to introduce the outdoor air from the one side of the working area and to exhausts the contaminated air through the opposite side of the refuse stock yard, so-called the unidirectional airflow ventilation.
A set of formulae for natural ventilation by thermal buoyancy is derived for a room with two opening and with a linear temperature stratification. The formulae are based on the fundamental flow equations, and they cover air velocities, temperature differences and ventilation rates in relation to opening areas, opening position, net heat input, building geometry, and temperature stratification. The temperature stratification can simply be taken into account by introducing a stratification factor E and by using the mean difference between indoor and outdoor temperatures.
OFFICE is a research project partly funded by the CEC dealing with the passive retrofitting of office buildings to improve their energy performance and indoor working conditions. The project is coordinated by the University of Athens with the participation of organizations and research institutes from eight European countries. The aim of the project is to develop global retrofitting strategies, tools and design guidelines in order to promote successful and cost effective implementation of passive solar and energy efficient retrofitting measures to office buildings.
This paper presents results belonging to a larger investigation on low velocity indoor air jets. The experiment is undertaken in a climate room where an isothermal air jet is issued from the centre of one lateral wall. Measurements are performed with a single fiber film probe, and with Particle Streak Velocimetry system. With Particle, Streak Velocimetry has been developed a three dimensional analysis of the instantaneous velocity field. With the use of fiber filmprobe, the fluid-dynamics of the jet flow is explored in terms of mean longitudinal velocity, and relative turbulence intensity.
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