turbulence intensity

Carbon dioxide has already been recognized as a potential tracer gas for estimating the mean air exchange rates of a room or building. The wind direction and mean wind velocity have also been identified as critical factors that affect the air infiltration. In this paper, the indoor CO2 concentration has been logged at three specific points in an office room for seven selected measurement-periods. The decay method was used to estimate the infiltration rates (ac/h).

The main purpose of this paper is to review the effect of the dynamic aspect of natural air movement on occupants’ thermal comfort. Recent advanced investigations addressed the dynamic aspect of air movement in terms of turbulence intensity, probability distribution and power spectrum. This paper is not only about providing a thorough description and discussion on the underlying physical mechanisms of these factors, it is also about reviewing the effect of these parameters on occupants’ thermal sensation, perception and comfort under different thermal conditions.

Carbon dioxide has been already recognized as a potential tracer gas towards estimation of the mean air exchange rates (ACH) of a room or building. The wind direction and mean wind velocity have been also clarified as critical factors that affect the air infiltration. In this study, the indoor CO2 concentration is detected and logged at three specific points in an office room for seven selected measurement-periods. The decay method is used to estimate the leakage rates.

In hot climates a comfortable indoor environment is important. Mechanical fans are often introduced to cool the indoor air. However, it has been found that the airflow from such fans is not comfortable, especially compared with natural wind. Artificial airflow in an enclosure has been known to disturb hair, irritate eyes, and distract occupants. This paper presents the result of an experimental study on the characteristics of household airflow inducing appliances. The details of experiments carried out in the laboratory are described.

Equivalent temperature is a thermal index used today for assessment of the thermal comfortin vehicles. Prediction of the percentage of people dissatisfied by the thermal environment iscalculated by implementing equivalent temperature in the PMV/PPD thermal index. In this work,PMV/PPD and PD (draft rate) indices are compared for vehicle conditions, with respect to air velocity and turbulence intensity. Results indicate that turbulence intensity must be taken in consideration for higher air velocities and that PD is the predominant thermal index after a certain air velocity is reached.

Thermal comfort in ventilated spaces depends mainly on air temperature, air speed and turbulence intensity. Mean air speed is commonly measured with omnidirectional hot sphere sensors, whereas directionally sensitive measurement instruments and CFD-simulations normally give the mean velocity vector. The magnitude of the mean velocity vector in turbulent room air flows can be much lower than the mean air speed due to different time averaging processes. This paper studies the difference both experimentally and theoretically as a function of turbulence intensity.

To investigate the dispersion of aerosols in an airflow, a test facility was build at the HermannRietschel- Institute. The distribution of aerosols across the cross section of the test duct was measured at several distances from the emission source. The turbulence intensity of the airflow in the duct was varied by installing different turbulence generating grids (I% to 20%) at the top of the test duct. Far enough downstream the source, the concentration profiles have a Gaussian distribution.

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.