We present a method capable of measuring the velocity field in a 7.00m x 3.50m plane of a large-scale Rayleigh-Bénard (RB) experiment using an adapted Particle Image Velocimetry (PIV) technique. The structure of the flow in RB convection is well known for
For a specific thermal anemometer with omnidirectional velocity sensor the expanded total uncertainty in measured mean velocity Û(Vmean) and the expanded total uncertainty in measured turbulence intensity Û(Tu) due to different error sources are estimated
It is difficult to evaluate the effect of cross ventilation quantitatively, because the indoor environment under cross ventilation is uneven and changes with the outside conditions. In this paper, the decay process of tracer gas is measured in uneven space under cross ventilation, and the property of spatial unevenness is examined by the concentration decay and velocity distribution.
Multiple regression analysis is used to predict the mean room velocity and determine the most influencing parameters on the velocity. More than 120 experiments for four different heat source locations were carried out in a test chamber with high level mixing ventilation. The measured parameters, such as supply air momentum, room heat load, Archimedes number and local temperature ratio, were used as independent variables. These parameters are examined by two methods: a simple regression analysis incorporated into scatter matrix plots; and multiple stepwise regression analysis.
This study examines the way of utilizing a ceiling fan for airflow control in a large air-conditionedroom. Although it seems that CFD simulation is useful in predicting the airflow around a ceiling fan, modeling of a ceiling fan as a body of rotation is very complicated. Therefore, in this study, airflow of a ceiling fan is modeled as boundary conditions of air velocity data measured near the ceiling fan.
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.
The mean velocity in rooms predicted by CFD simulations based on RANS equations differs from the mean (in time) magnitude of the velocity, i.e. the mean speed, in rooms measured by low velocity thermal anemometers with omnidirectional sensor. This discrepancy results in incorrect thermal comfort assessment by the CFD predictions as well as incorrect validation of the predicted velocity field. In this paper the discrepancies are discussed and identified, and a method for estimating the mean speed based on the CFD predictions of mean velocity and kinetic turbulence energy is suggested.
Zoning room air conditioning strategy is based on the idea of controlling the conditions of one zone by supply air and, at the same time, utilizing the stratification of temperature and contaminants in another zone. The aim of this study was to assess the ability of CFD-simulation to predict the supply air flow pattern and the overall performance of the system. The study was based on a series of laboratory experiments and corresponding CFD-simulations.
Within the last years CFD has become an essential tool to investigate and optimize concepts of train coaches during an early design stage to achieve best results without major modifications of the final design. The simulation of the current railroad double deck coach gives some special challenges because of the complex channel system and the different boundary conditions on each floor. First the air duct including the outlet vents is investigated and optimized. The results are used as boundary condition for the simulation of the passenger's compartment.
The effects of environmental factors can be important in simulating indoor levels of VOCs emitted from building materials. In this study the effort has been made to quantify the relationship between air movements and emissions of decane applied on an oak substrate.
The aim of this research is to determine the correlation between environmental factors and coefficients of mass-transfer based emission models in a mathematical form.