air flow

The calculation of airflows is of great importance for detailed building thermal simulation computer codes, these airflows most frequently constituting an important thermal coupling between the building and the outside on one hand, and the different thermal zones on the other. The driving effects of air movement, which are the wind and the thermal buoyancy, are briefly outlined and we look closely at their coupling in the case of buildings, by exploring the difficulties associated with large openings.

A three-dimensional drift-flux model for particle movements in turbulent airflows in buildings is presented. The interaction between the carrier air and the particles has been treated as a one-way coupling, assuming the effect of particles on air turbulence is negligible due to low solid loadings and comparatively small particle settling velocities. Turbulence effects are modelled with a standard K-E model. Wall functions are applied at near-wall grid points. Aerosol measurements carried out under turbulent room flow conditions are used to validate the numerical calculations.

Determination of the distribution of contaminant particles within zones becomes of great interest, with the increasing concern for indoor air quality. In order to improve the indoor air quality in a realistic building, the air movement and contaminant transport in a partitioned enclosure with ventilation have been studied numerically and experimentally. A three-dimensional analysis of air movement, temperature distribution and contaminant particle transport is made to investigate airflow patterns and deposition of contaminant particle in a partitioned enclosure.

Several studies have shown that the lowest concentrations of contamination in operating theatres are achieved by using fabric covered laminar airflow systems. These systems are distinguished due to the low turbulence intensities in the protective areas. An examination in a special designed test facility was done to get further information about the relation between the turbulence intensity and airborne contaminations. In a first stage the dispersion of airborne contaminations was examined.

Task-ambient air conditioning system is one of the systems developed to achieve quality indoor thermal environment and energy conservation simultaneously. The purpose of this study is to find the optimum supply air conditions of floor air outlet required to make thermally comfortable environment in the task area without cold draft. To achieve the purpose were carried out the experiments with subjects, who were allowed to control the supply air volume and the direction of inclined jet according to their tastes.

Improvement in methods of air flow pattern scale modelling in large enclosure requires above all, précising the conditions necessary in the model in order to maintain Reynolds number independence of the mean flow, as well as defining ways in which the flow turbulent structure could be simulated. The paper presents the results of experimental analyses of air velocity fields in scale models in the range of Reynolds number 1850 to 98000. The field maps of air velocity mean value were tested.

Similar to supply air jets in mixing ventilation this paper describes a comprehensive flow model for displacement ventilation derived from the integrated Navier-Stokes differential equations for boundary layers. A new test method for low velocity diffusers in displacement ventilation is developed based on this new flow model. Contrary to jet flow, it is shown that the only independent variable in the new model is the buoyancy flux.

This paper presents a set of detailed experimental data of room airflow with displacement ventilation. These data were obtained from a new environmental test facility at the Massachusetts Institute of Technology (MIT). The measurements were conducted for three typical room configurations: a small office, a large office with partition, and a classroom. The experiment measured the distributions of air velocity, air velocity fluctuation, and air temperature by omnidirectional hot-sphere anemometers and contaminant concentrations by tracer gas at 54 points in the room.