Air Exchange Effectiveness Research Articles

Behaviours of near two-dimensional ventilation configurations

Performances of eight configurations of a ventilated room are predicted. The flows exhibit increasingly three-dimensional tendencies as the proportion of wall occupied by the supply and extract vents is reduced. For all of the cases studied, short-circuiting of the air-flow is predicted. Using the concept of the air-exchange effectiveness alone, as a comparative indicator of ventilation performance, is questionable.

Ventilation characteristics of an air-conditioned office building in Singapore

The primary functions of mechanical ventilation systems include the delivery of outdoor air to the occupants, the removal of indoor contaminants and the maintenance of thermal comfort conditions in the occupied zones. Air exchange effectiveness can be employed to characterise the ventilation air mixing within a room. This paper presents our findings pertaining to air exchange effectiveness values in a seven-storey office building. Tracer gas analysis, based on concentration decay method, is employed to determine these values. The results indicate air flow patterns in the occupied zones which approximate “perfect mixing”. The measured concentration levels of indoor air pollutants are also found to be within reasonable limits.

Indoor air quality comparison of two air-conditioned zones served by the same air-handling unit

Most indoor air quality (IAQ) investigations take an air handling unit (AHU) - based zone as the basic unit for investigation from the logical viewpoint that the AHU constitutes the mechanism for mixing and (cross-) transportation of pollutants within the zone. If there is very good air-mixing, as indicated by a high air exchange effectiveness, the single zone approach may be sufficient. However, when there is large discrepancy in pollutant generation between spaces within the spaces served by the AHU, or when the ventilation is impeded due to inappropriate partitioning, the zonal characteristics are likely to differ from space to space. This paper reports a comparison of the zonal characterisation of an office space whose ventilation and thermal comfort parameters are different. In this study an integrated approach to IAQ auditing which includes measurements of chemical, biological, particulate, thermal comfort and ventilation parameters was adopted. Significant differences in the values and time profiles of the various pollutant dimensions have been observed between the two zones. These differences are attributable to the dominant influences of interior layout and partitioning, degree of exposure to the exterior, occupant activities, occupant intervention of the ventilation system by operating the operable windows, and the materials deployed for interior partitions.

オフィスビルを対象とした換気効率に関する実測調査 : オフィスビルを対象とした換気効率に関する研究 その1

In order to evaluate indoor air quality and ventilation effectiveness, it is necessary to comprehend properties of various ventilation systems. In this paper we describe the results of field measurement of ventilation effectiveness for four office rooms using age of air and air exchange effectiveness. The results are as follows. (1) In the case of air conditioning system and ventilation system using ceiling chamber for return air, the local air exchange effectiveness in the room is ranged from 0.8-1.2. (2) In the case of raised floor air supply system, the local air exchange effectiveness is ranged from 0.9-1.1, however in the case of ceiling supply chamber system is ranged from 0.8-1.0. (3) The room which is ventilated by duct system, local air exchange effectiveness becomes about 0.7-1.1. When supply outlets are closed to make bad ventilated area, local air exchange effectiveness of bad ventilated area becomes 0.8-1.0, in the other hand the release area of supply outlets becomes 1.0-1.1. (4) It is possible to evaluate ventilation characteristics of office space by local age of air and local air exchange effectiveness.

B101 水槽模型に画像計測を適用した成層換気試験

Displacement Ventilation offers improved air quality and high ventilation effectiveness, and reduces air-conditioning costs relative to conventional Diffusion Ventilation. However, it is difficult for traditional techniques to measure flow velocity, temperature and tracer concentration to evaluate the characteristics of displacement ventilation since it is influenced by natural convection and has a complex flow field In this study, a series of experiments to measure flow velocity, temperature and tracer concentration distribution was performed for geometrically similar scale water tank model of room space equipped with displacement ventilation by applying image processing techniques. The distribution of local air exchange effectiveness was calculated from temporal change of tracer concentration distribution by the step-down method. It was confirmed that PTV for velocity measurement and tracer concentration measurement for local air exchange effectiveness calculation were useful to evaluate the characteristics of DV The dynamic range of liquid crystal thermometry should be expanded.