One basic goal of the commissioning process is to make sure that the HVA C system is functioning as intended. In particular, it is intended that the HVAC system not only provide adequate ventilation for the building occupants but also achieve adequate pressurization of the occupied spaces to prevent the infiltration of unconditioned air. One technique for evaluating the performance of the HVAC system in these areas is to use continual, multipoint monitoring of carbon dioxide, carbon monoxide, and dew point at selected locations in the building and the HVAC system.
This paper presents results of a project initiated by ASHRAE and the National Research Council of Canada. The project applies both physical and numerical modeling to atrium smoke exhaust systems to investigate the effectiveness of such systems and to develop guidelines for their design. In this paper, results were obtained from a series of tests conducted using a large-scale physical model.
Residential air infiltration rates predicted by a detailed multizone computational model are compared with those predicted by a single-zone model. The multizone model is created using the public domain program CONTAM96, which allows the user to break the house into a number of Zones connected to one another and the outdoors by leakage paths with user-defined characteristics. Actual floor plans for a ranch-style house and typical published leakage characteristics of residential building components are used to construct a very detailed model with roughly 2,000 zones and 7,000 leakage paths.
The use of raised access flooring systems for office environments has become much more frequent in recent years. Power and data cables housed in the floor cavity can easily be accessed and modified to accommodate changes in the occupancy and use of the space. This cavity can also be used as a supply air plenum, which allows introduction of conditioned air through the floor.
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.
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