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Overview of the Most Significant Standards on Thermal Comfort
Published in Ivana Špelić, Alka Mihelić-Bogdanić, Anica Hursa Šajatović, Standard Methods for Thermal Comfort Assessment of Clothing, 2019
Ivana Špelić, Alka Mihelić-Bogdanić, Anica Hursa Šajatović
Anemometers are divided into deflecting vane anemometers, propeller or revolving vane anemometers, cup anemometers and thermal or hot-wire anemometers. Low and highly directional air velocities in rooms are measured by a smoke puff or solid airborne tracer. Directional moderate air velocities in rooms can also be measured by the deflecting vane anemometer or revolving vane anemometer, while the low and high air velocities can be measured by the hot-wire anemometer. Pitot tubes are used to measure duct standard and transient velocity with turbulence. The pitot-static tube, in conjunction with a suitable manometer or differential pressure transducer, provides a simple method of determining air velocity at a point in a flow field (usually velocities above 7.5 m/s). Other high-velocity measurements include the impact tube. Meteorological measurements are done by the cup anemometer, which has poor accuracy at low air velocity below 2.5 m/s.
Protecting the Worker II: Providing Clean Air
Published in Ronald Scott, of Industrial Hygiene, 2018
Either a deflecting vane velometer or a rotating vane anemometer are most often used for measuring air velocity at large hood openings. In the deflecting vane velometer, air strikes a vane, which deflects in proportion to the air velocity, and the angle of deflection is read on a scale directly in feet per minute. It can be adapted to different velocity ranges by changing probes, the low end of the low-velocity probe reading 30 fpm. A rotating vane anemometer has a multivaned fan blade that is spun by the moving air, and the speed of rotation is read directly in feet per minute. A hand-held unit reads down to about 100 fpm. With either of these instruments error is introduced if air velocity at small hood openings is measured, because the blockage of the hood opening by the instrument distorts the value obtained.
Concentrations and deposition
Published in Abhishek Tiwary, Jeremy Colls, Air Pollution, 2017
The gas flux can be measured by a variety of methods. The most straightforward is to measure the concentration gradient between one point close to the surface and another point at a reference height such as 2 m. Then by using Fick’s law and a measured value for the turbulent diffusivity, the flux can be calculated. Usually the measurement is averaged over a 30-minute period to smooth out short-term fluctuations. A more sophisticated technique, known as conditional sampling, is shown in Figure 5.13. The principle of the device is to measure directly the upward-going and downward-going fluxes, and subtract them to give the net flux. An ultrasonic anemometer measures the wind speed and direction with very high time resolution. When the vertical component of the wind vector is upward, the air is switched by high-speed solenoid valve into one sample line. When the wind is downward, the sample air is switched into a second line. Either the samples can be accumulated in bags for later analysis, or the difference measured real-time by an in-line gas analyser (for CO2 in this example, but in principle any gas can be measured this way). A sample of the results from this system is shown in Figure 5.14. The CO2 flux is small and upwards (respiration) during the night, large and downwards (photosynthesis) by day.
Reducing COVID-19 airborne transmission risks on public transportation buses: an empirical study on aerosol dispersion and control
Published in Aerosol Science and Technology, 2021
Nathan J. Edwards, Rebecca Widrick, Justin Wilmes, Ben Breisch, Mike Gerschefske, Jon Sullivan, Richard Potember, Angelica Espinoza-Calvio
Airflows on the school bus were measured with only a single anemometer due to equipment acquisition delays. The anemometer was positioned in the central aisle at an approximate head height of a standing child (118 cm from the floor), 10 cm above the level of a seat back, and provided real-time data over a USB2.0 cable interface (SI Figure S2). Twelve anemometers were used on the low floor transit bus positioned at various locations throughout the bus: forward seat areas, rear seat areas, central aisle, rear roof hatch, and the HVAC return air grille (SI Figure S3). These sensors connected to a laptop computer using their 900 MHz ISM band radio communications, an USB radio receiver (Omega UWTC-REC1), and the provided Omega data recording software. All anemometers were of a hotwire type sensor to monitor single direction airflows and temperature, had measurement accuracy of 1.5% with ranges of 0 to 25.4 m/s, and were also configured to provide 1 s sampling rates.
Maximum Power Extraction from a Wind Turbine Using Terminal Synergetic Control
Published in IETE Journal of Research, 2023
K. K. Prabhakaran, R. Saravanakumar
Generally, an anemometer is used for measuring the wind speed. This speed is called point wind speed, but it varies at every point in rotor swept area. So, it is necessary to estimate effective wind speed. The aerodynamic torque depends on wind speed and rotor speed. Equation (13) relates the effective wind sped through aerodynamic torque by fixing the pitch angle to its optimal value. The effective wind speed is obtained by solving (13) using the Modified Newton Raphson (MNR) method. By considering the estimated wind speed, the reference rotor speed is obtained using (12).
Studies on divergent solar chimney subjected to variable collector configurartions
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Pedasingu Likhith Raj, Pemmasani Hemanth, Nuvvula Phani Raju
Uncertainty analysis is defined as the modification of variation of the output due to the presence of variation occurred in the input. This uncertainty is present in the measuring devices used in the experiments. Hot wire anemometer used has a precision of ±3% to ±0.1% with measuring range of 0–50 m/s. the sensitivity of the thermocouple is 0.006 mV/oC at 25°C and 0.013°C is the equivalent temperature uncertainty with an accuracy of ±2.2°C or ±0.75%