This study compares indoor climate, cooling efficiency and energy consumption of an underfloor air distribution system and a ceiling-based system in a test chamber. Floor-based system appears to provide better thermal conditions with lower electricity consumption.
CFD calculations were used to compare temperature and air velocities in an environmental chamber equipped either with a conventional comfort overhead air supply system or with an underfloor supply system. Results show the advantages of underfloor system to provide adequate temperature, velocities and turbulence in the seated zone.
Thermal comfort (PMV and PPD indices) of a floor return underfloor ventilation system was evaluated through experiments with different supply air temperatures and internal heat loads. Results are shown and analysed.
Aims to study the behaviour of airflow generated by multiple jets and introduced into a room. A finite volumes mathematical model was used in the study, in which the equations were linearised in implicit form and the domain was presented in its discrete elements using the finite volume method. The numerical simulation was performed by creating unstructured computational grids. Findings were compared to experimental data including an extensive series of measurement taken in a model environment setup in a laboratory.
The paper shows detailed measurement of the air distribution in a room ventilated by mixing ventilation according to the specifications given by the International Energy Agency work. (Energy Conservation in Buildings and Community Systems programme, Annex 20). It describes a number of flow elements and how they are used as design tools. The flow elements are the throw of an isothermal jet and the change in jet velocity when the jet moves from the upper to the lower part of the room. A third flow element is the penetration length of a non-isothermal wall jet.
A field study was carried out to establish the performance of five thermal distribution systems in four large commercial buildings. They were standard single-duct or dual-duct constant air volume (CAV) system and variable air volume (VAV) systems, serving buildings with floor area greater the 2000 m2. Reports the duct air leakage. The ELAs ranged from 0.7 to 12.9 cm2/m3 of duct surface area, and from 0.1 to 7.7 cm2/m2 of floor area.
States that there are problems involved with the use of traditional instruments such as vane anemometers and pitot tubes when measuring airflow rates in HVAC systems in order to balance air distribution. Suggests that the simple and useful tracer gas techniques that are commonly used for ventilation measurements in buildings can be a suitable alternative. Describes a preliminary study intended to determine the viability and accuracy of the tracer gas technique. A good correlation between the airflow rates measured by using a pitot tube and tracer technique was found.
Computational fluid dynamics has a wide range of application in the study of room air distribution. The application is providing valuable guidance for those interested in such areas as comfort, productivity and sick building syndrome. This paper gives a comparative review of some of the work undertaken in the field and highlights some of the modelling assumptions noted within the literature.
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