A three-dimensional mathematical model to solve the mixing, displacement and vortex ventilation systems in the removal of pollutants with a thermal source is described. The study carried out to investigate the effectiveness of each of the individual ventilation systems showed that the vortex ventilation system performed better than the other two systems in providing moderate occupancy thermal comfort but very effective in purging pollutants away from a typical office room environment
The purpose of this study is to identify the ventilation effectiveness of a displacement ventilation system in a concert hall with 501 seats, where a large amount of outside air is required for ventilation. Displacement ventilation was considered appropriate to reduce the amount of outside air. Light bulbs were placed on all the seats to simulate the heat source from the audience. From the measured concentrations, the local mean age of air at the breathing point with the displacement ventilation system was found around one third of that of the fully mixed condition.
This paper presents a way of ventilating a large room so that the room can be divided into different zones by temporary vertical walls (canvas, plastic sheets etc) and with no physical ceiling. Different activities, like welding, painting or mechanical assembly, can go on inside each of these zones, unaffected by each other, as long as pollutants are extracted through designated extract openings in the outer walls. These inner, temporary walls need only reach from say 3 - 4 metres above the floor and up to some metres above the pollutants' height of equilibrium.
We examine transient displacement flows in naturally ventilated spaces that are subject to an increase in internal heat gains as in, for example, an empty lecture theatre which is then occupied by an audience. Heat gains create a layer of warm air at the ceiling which initially increases in depth and temperature, and descends towards the occupied regions. A theoretical model is developed to predict the time-dependent movement of the interface that separates the warm upper and cool lower layers of air, and comparisons are made with the results of laboratory experiments.
At Hermann-Rietschel-Institute systematic tests of the limits for the ventilation with openable windows are under way. The parameters temperature distribution and air velocity are the most attended values. Window ventilation in office buildings has limits in application. An open window can remove cooling loads out of the room. With one window and a room with a depth of 5 m, the maximum cooling load is about 20 to 30 W/m2. These limits are determined by air velocities within thermal comfort.
The heat sources in a room with upward air supply, can be ideally decomposed into some basic models. Based on searching of the solution of the basic models, then solving the varieties of practical problems, a simplified method for predicting vertical temperature distribution of room air is submitted in this paper. Calculated values of some practical examples agree satisfactorily with experiment results.
This study is a part of a research project named 'Convective Flows and Vertical Temperature Gradient within Active Displacement Air Distribution'. The project was started in 1996 in order to determine guidelines for air flow rate dimensioning of the system. Aim of this study was to determine the characteristics of the thermal plumes of the heat sources used in the project. The characteristics were determined in order to apply the results to different kinds of plumes, which may occur with active displacement air distribution system.
The paper presents the results of the research on application of the equation describing the increase in the air volume flux in buoyant plume above a point heat source to calculate plumes in rooms with displacement ventilation.The tests carried out in test room have given information about practical defining of the distance from the origin, assuming entrainment coefficient values and possibilities of assuming equal widths of temperature and velocity profiles in order to determine the origin distance.
Health effects caused by aerosol air pollutants in the breathing air is a main target for occupational health investigations. The effects of aerosol particles on health usually depend on the dose of particulate matter (PM:) retained at various locations of the respiratory tract. Displacement ventilation has been proved to be an effective ventilation system for the removal of passive pollutants in many buildings. The question is often asked about the performance of non-passive particle removal in a room ventilated by displacement ventilation.
Information on thermal plume characteristics is essential for designing ventilation systems with displacement air supply. Empirical, analytical and computational fluid dynamics are the commonly used approaches to evaluate air temperatures, velocities and airflow rates in thermal plumes above different heat sources. However, only limited information is available on the behavior of thermal plumes in rooms with a temperature gradient along the room height.
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