This research evaluated the performance of four kinds of ventilation systems for dwellings under various conditions by means of numerical simulation. The total number of combinations of various parameters for the calculation was 174. Calculations were performed hourly for indoor air pollutant concentration, humidity and condensation, indoor outdoor pressure difference, airflow rate, and heat energy by ventilation, etc., through the heating season. A multizone infiltration and pollutant transport model (COMIS) was used to perform the simulation.
To remedy comfort problems in a 99,000 fi2 (9,200 m2) office building, the total airflow rate was reduced by 35%, and the total outside airflow was reduced by 86% in four multi-zone air-handling units that serve the office building. After the airflow reduction, the peak room relative humidity level was reduced from 70% to 55%, and cold and hot deck reset schedules were implemented. These improved operating practices reduced building energy consumption by 27%.
In the last decade, public awareness of the greenhouse effect has pushed the building sector toward higher energy efficiencies. This move has had consequences for roofs with a cathedral ceiling. AU-factor in the vicinity of 0.2 W/(m2·K) instead of 0. 6 W/(m2· K) became the new target value. The move toward such a low U-factor for cathedral ceilings was evaluated in an extended test house program.
This paper presents a computational fluid dynamics ( CFD) study of the indoor environment provided by a cold air distribution system using three alternative types of diffusers, i.e., a square multi--cone type, a wall-mounted nou.le type, and a ceiling nozzle type. The surface condensation risk on the diffusers is also discussed using the CFD results and a simple condensation model. An innovative proposal to prevent surface condensation and cold air dumping when using multicone circular diffusers with cold air is presented.
This paper addresses atria smoke management systems where it is intended that occupants will be in contact with smoke. While this approach is unusual, it is recognized by several authoritative publications on atrium smoke management. A tenability analysis for an atrium smoke management system needs to account for the effects of ( 1) exposure to toxic gases, (2) exposure to elevated temperatures, and (3) smoke obscuration. Much of this paper consists of adapting and presenting well-established tenability methods for application to smoke management.
Pre-assessing the reliability of ventilation systems is a dificult task and no simple methodshave existed. This paper presents a tool for estimating the reliability of domestic ventilationsystems. In general, ventilation reliability means the probability that the chosen ventilationsystem performs in an acceptable way for a certain building, in a certain climate, betweenscheduled maintenance measures.
The principles of a new tracer gas technique is described in the paper. The new technique involves pulse injection of tracer gas and has the same advantages as the previously known homogeneous emission technique. It can for example advantageously be used in large buildings and buildings with many rooms and yields information on the distribution of ventilation air within the building. However, contrary to the homogeneous emission technique, yielding the average ventilation performance during an extended time, the new technique allows measurement during short term periods.
Concentration of pollutants produced by car traffic in a street below the roof level has large spatial variations. In a street, pollutants are diluted by the turbulent air flow which is induced by the wind speed above the roof level, and also produced by car displacement. The airflow structure is in relation with street size and building shape. Particularly strong gradients of concentrations can be observed vertically and also horizontally in front and along buildings where are set up ventilation inlets and windows.
Natural ventilation in office buildings can sometimes offer other advantages than traditionalmechanical ventilation systems. Often natural ventilation systems are promoted at an earlystage by an architect, but perceived dificulties, e.g. to pre-determine the function of a naturalventilation system, can serve as a barrier and a mechanical system is often chosen instead.
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