Particle Image Velocimetry (PIV) application in the measurement of indoor air distribution by an active chilled beam (original) (raw)
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Particle Tracking Velocimetry for indoor airflow field: A review
Building and Environment, 2015
Airflow field measurement plays a significant role in creating a thermally comfortable indoor environment, by providing adequate quantitative information of indoor air distribution and local air velocity. In recent years, the Particle Tracking Velocimetry (PTV) technique has gradually become a promising and powerful tool for indoor airflow field measurement. This paper firstly gives an overview of the equipments and methods involved in typical PTV applications to indoor environments, and then introduces related applications of PTV for measuring indoor airflow fields. The Particle Streak Velocimetry (PSV) technique for indoor airflow measurement is also introduced. This paper shows how the quantitative and detailed turbulent flow information obtained by PTV measurement is critical for analyzing turbulent properties and developing numerical simulations. The limitations and future developments of PTV and PSV techniques are also discussed.
A Particle Image Velocimetry (PIV) system for room airflow study has been developed to quantitatively measure airflow patterns and air distribution in ventilated airspaces. Two-dimensional isothermal airflows were measured in a full-scale room (5.5×3.7×2.4 m). Measurements taken include the flow pattern of the room air, velocity vector maps and interpolated airflow pattern at two cross-sections of the test room with one typical ventilation system. This measurement method is part of a larger study of aerosol spatial distribution, ventilation effectiveness and aerial contaminant control strategies.
Building and Environment, 2010
Large-scale circulations in room air flows have been investigated with three-dimensional particle tracking velocimetry (3D PTV). This technique has been refined for large scales, enabling us to determine flow patterns, trajectories, and velocity vectors within a large cylindrical enclosure used as a model room for thermal convection. This test enclosure is called Rayleigh-Bé nard (RB) cell and addresses the limiting case of room air with very high internal loads. The flow patterns are only created by buoyancy forces. The 3D PTV system consists of four CMOS cameras, two flash lamps, and an image recording and data processing system. Helium-filled latex balloons were used as tracer particles. The spatial resolution and accuracy were investigated in a test cell with the dimensions of 4 Â 3 Â 4 m 3 by means of a given trajectory of a small glass sphere. First applications of the developed 3D PTV system in the large RB cell with a diameter of 7.15 m and a height of 3.58 m showed different characteristic flow patterns of largescale circulation outside the boundary layers. From the recorded and analyzed long-term particle trajectories further important data of room air flows like velocity time series, probability density functions (PDF) of the velocity, and acceleration fluctuations were calculated. The proposed technique has a wide range of potential applications for the three-dimensional and time-dependent analysis of indoor air flows.
Improving the measurement accuracy of PIV in a synthetic jet flow
Impinging synthetic jets have been identified as a promising technique for obtaining high convective heat transfer rates in applications with confined geometries such as electronics cooling. Using a partially enclosed cavity with orifice, alternating fluid suction and ejection generate a periodic vortex train. This flow creates stronger entrainment of surrounding air and more vigorous mixing near the heat transfer surface compared to continuous impinging jets of comparable Reynolds number. A better understanding of the flow field is needed to identify the governing convective heat transfer mechanisms and optimise the heat transfer to a synthetic jet. Particle image velocimetry is the preferred technique to quantify the whole flow field. However, a synthetic jet flow is characterised by large velocity gradients. For round jets in particular, the maximum velocity in the free jet region differs significantly from the velocity in the wall jet region. A multi-double- frame (MDF) PIV tech...
Modelling of Air Flow Analysis for Residential Homes Using Particle Image Velocimetry
IFIP advances in information and communication technology, 2015
The purpose of this paper is to simulate the designed physical Particle Image Velocimetry (PIV) system, as a simulation platform to physically build and implement a system for residential building and housing research. The focus is on the angle filter; the filter used to process the images of a laser progressively scanning through a space by adjusting its angle. An indicator of heat escape and ventilation in buildings is the airflow itself. Conventional airflow measurement techniques are typically intrusive, interfering with the data or the environment. For small flows such as that in residential housing, the error introduced can sometimes be large relative to the measured data. In contrast, PIV is a relatively a non-intrusive measurement tool that measures flows. However, there are a few problems with standard PIV techniques, for implementation in an attic space. The proposed solution is to use dust particles, already present in the air, as tracers for the PIV system. In conclusion, our PIV system with a non-diverging laser beam produces a velocity field of similar quality to a velocity field of a standard PIV system.
Visualizing the Flow Induced by an Air Curtain Using Stereo Particle Image Velocimetry
2008
A stereo particle image velocimetry technique was developed to study the flow of a commercial, off-the-shelf air curtain. Surveys were performed along lengthwise planes only. The flow leaving the air curtain was highly turbulent with turbulent intensities as high as 20 percent based on the maximum jet velocity. The jet from the air curtain did not show much spreading in the lengthwise planes. The turbulence level decreased as the flow progressed toward the floor. Upon reaching the floor vents, the turbulence level rose again.
Improved particle image velocimetry measurements in gas particle flows with a dense wall layer
Measurement Science and Technology, 2003
This work concerns particle image velocimetry (PIV) measurements with a high-speed camera in a circulating fluidized bed (CFB). Because of the nature of the gas-particle flow in the riser of the CFB a dense wall layer of particles is observed when the superficial gas velocity is increased beyond a certain limit. This dense wall layer reduced the quality of the measurements. A mask is developed which improves the quality of the PIV measurements. Furthermore, it increases the range of superficial gas velocities for which the measurements can be obtained in the CFB system. The improved PIV measurement is verified via laser Doppler anemometry measurements. The results are of interest for measurements of dense wall-layer flows.
Analysis of Particle Image Velocimetry (PIV) Data for Application to Subsonic Jet Noise Studies
1997
Global velocimetry measurements were taken using Particle Image Velocimetry (PIV) in the subsonic flow exiting a 1 inch circular nozzle in an attempt to better understand the turbulence characteristics of its shear layer region. This report presents the results of the PIV analysis and data reduction portions of the test and details the processing that was done. Custom data analysis and data validation algorithms were developed and applied to a data ensemble consisting of over 750 PIV 70 mm photographs taken in the 0.85 mach flow facility. Results are presented detailing spatial characteristics of the flow including ensemble mean and standard deviation, turbulence intensities and Reynold's stress levels, and 2-point spatial correlations.
A new method employing instantaneous 3D coupled measurements of planar laser-induced fluorescence and particle Image velocimetry is developed to compute 3D fluid fluxes. The three-dimensional fields of concentration and velocity are used for identifying the vortex structures and for the evaluation of the fluxes at the interface between a jet mixiting in a crossflow. This approach is helpful for the 3D estimation of the momentum and scalar transport at the turbulent/non-turbulent interface and will help understanding the mixing process.