Air Speed
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2021 ◽  
Vol 11 (18) ◽  
pp. 8339
Wachara Kalasee ◽  
Panya Dangwilailux

The size distribution, total particle mass concentration (TPMC), polycyclic aromatic hydrocarbons (PAHs) value, and total Benzo[a]pyrene Toxic Equivalence (BaPTE) concentration of smoke particles from palm oil sewage sludge (POSS) bio-char combustion were studied. In this experiment, temperature data of the POSS bio-char combustion were recorded in two parts: particle temperature (Tp) by using a two-color pyrometer and temperature at 300, 500 and 800 mm, respectively, above the fire base by using K-type thermocouples. The POSS bio-char moisture content, clean air speed values, and burning period affected the change of temperature above the fire base. The mass median aerodynamic diameter (MMAD) values of the POSS bio-char combustion were found to be 0.44 to 1.05 micron at various moisture contents and burning periods. The MMAD, TPMC, and PAHs values increased with increasing moisture content and decreased the POSS bio-char combustion period. For the total BaPTE values, the results showed that the decrease in moisture content of the POSS bio-char samples had a prime influence in decreasing the total BaPTE values. Meanwhile, with decreases in the clean air speed values, the total BaPTE values were increased. Comparing the total BaPTE data between the experimental results and predicted values, the first-degree model had a better fit in predicting than the zero-degree model; this result was confirmed by the higher mean of the coefficient of determination.

2021 ◽  
pp. 073490412110432
Ping-Jung Li ◽  
Chao-Shi Chen ◽  
Cheng-Yu Weng ◽  
Hsin-Hsiu Ho

This article discusses the overpressure of a gas explosion and the performance of applying water mist for explosion suppression. According to the experimental results, the larger the opening area, the more difficult it is for pressure to accumulate, resulting in lower overpressure of a gas explosion. When the opening was opened under a high air speed environment, the amount of entrained air was greater. Consequently, the occurrence time of the explosion was shorter than at a low air speed. Despite the water mist nozzle being installed outside the enclosure, a propane gas explosion still occurred regardless of the amount of water mist used, failing to suppress the explosion. However, the water mist nozzle installed inside the enclosure supplied an adequate amount of water mist that could wash a part of the propane, resulting in the fuel concentration dropping below the lower explosion limit, hindering the occurrence of an explosion.

Sensors ◽  
2021 ◽  
Vol 21 (17) ◽  
pp. 5845
Zenon Nieckarz ◽  
Jerzy A. Zoladz

This paper presents a calibration system for low-cost suspended particulate matter (PM) sensors, consisting of reference instruments, enclosed space in a metal pipe (volume 0.145 m3), a duct fan, a controller and automated control software. The described system is capable of generating stable and repeatable concentrations of suspended PM in the air duct. In this paper, as the final result, we presented the process and effects of calibration of two low-cost air pollution stations—university measuring stations (UMS)—developed and used in the scientific project known as Storm&DustNet, implemented at the Jagiellonian University in Kraków (Poland), for the concentration range of PM from a few up to 240 µg·m–3. Finally, we postulate that a device of this type should be available for every system composed of a large number of low-cost PM sensors.

2021 ◽  
Vol 36 (3) ◽  
pp. 332-344
A. N. Md. Shahin ◽  
V. Shaayegan ◽  
P. C. Lee ◽  
C. B. Park

Abstract In situ generation of polyethylene terephthalate (PET) nanofibrils in polypropylene (PP) microfibers via fiber spinning in a spunbond process was studied in this work. The effects of polymer flow rate and air speed in the drafter on the formation of PET fibrils were investigated using a pilot scale machine. An in-situ visualization technique was applied to examine the fiber evolution events and stretch profile at die exit. A scanning electron microscope was used to analyze and investigate the morphology of the dispersed domain. The PET dispersed phase was fibrillated within the PP matrix such that a nonofibrillated composite containing fibrils with an average size around 100 nm was obtained. It was found that the final fibril size directly depends on the degree of die swell, the air speed and the polymer flow rate. It was also found that the in situ observed size of the micro-scale PP/PET fibers was well correlated to the size of the nano-scale PET fibers formed in the PP matrix. The visualization results revealed that a smaller fibril diameter was obtainable by increasing the stretching on the spin line and/or decreasing the die swell.

2021 ◽  
pp. 107979
Maohui Luo ◽  
Hui Zhang ◽  
Paul Raftery ◽  
Linxuan Zhou ◽  
Thomas Parkinson ◽  

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 366
Yang Xia ◽  
Yun Tian ◽  
Lanbin Zhang ◽  
Zhihao Ma ◽  
Huliang Dai ◽  

We present an optimized flutter-driven triboelectric nanogenerator (TENG) for wind energy harvesting. The vibration and power generation characteristics of this TENG are investigated in detail, and a low cut-in wind speed of 3.4 m/s is achieved. It is found that the air speed, the thickness and length of the membrane, and the distance between the electrode plates mainly determine the PTFE membrane’s vibration behavior and the performance of TENG. With the optimized value of the thickness and length of the membrane and the distance of the electrode plates, the peak open-circuit voltage and output power of TENG reach 297 V and 0.46 mW at a wind speed of 10 m/s. The energy generated by TENG can directly light up dozens of LEDs and keep a digital watch running continuously by charging a capacitor of 100 μF at a wind speed of 8 m/s.

В.В. Агафонова ◽  
А.П. Скибин ◽  
В.Ю. Волков

Рассмотрены вопросы улучшения качества внутренней среды помещения офисного здания при применении современного воздухораспределительного устройства – текстильного воздуховода с микроотверстиями. Преимуществом такого вида устройств является подача приточного воздуха струями с малым импульсом, что позволяет размещать их вблизи рабочей зоны помещения, исключая возможность возникновения сквозняков на рабочих местах. Цель работы – сопоставительный численный расчет эффективности организации воздухообмена в помещении офисного здания при двух схемах подачи воздуха: через приточные решетки и посредством текстильного воздуховода с микроперфорацией. Моделирование проводилось с использованием коммерческого программного комплекса STAR-CCM+. Для описания движения воздуха используется система уравнений Рейнольдса с замыканием с помощью модели турбулентности k-ω SST (Mentor). В ходе проведения исследований были получены данные о характере изменения температуры и скорости воздуха по высоте рабочей зоны помещения. Определено, что при подаче воздуха через приточные решетки температура (23,3–27,2 °С) и скорость воздуха (0,06–0,22 м/с) соответствуют допустимым параметрам микроклимата (ГОСТ 30494-2011), при организации воздухообмена с помощью микроперфорированного воздуховода – оптимальным параметрам (температура 23,1–25,4 °С, скорость воздуха 0,09–0,13 м/с), комфортным для организма человека. Таким образом, применение воздуховода с микроперфорацией повышает эффективность ассимиляции тепловых избытков по сравнению с традиционными воздухораспределительными устройствами (вентиляционными решетками). The issues of improving the quality of the internal environment of an office building using an advanced air dispersion device – a fabric air duct with micro-orifices are considered. The advantage of this device is supplying the incoming air by jets with a low impulse allowing to locate the devices near the working space in offices eliminating the risk of drafts at the working places. The purpose of the work is a comparative numerical calculation of the efficiency of arranging the air exchange in an office building with two air supply schemes: through supply grilles and through a fabric air duct with microperforation. Modeling was carried out using the commercial STAR-CCM + software package. The system of Reynolds equations with closure using the k-ωSST turbulence model (Mentor) is used to describe the air movement. As part of the study, data on the nature of the change in temperature and air speed along the height of the working area of the office were obtained. It has been determined that while air is supplied through the supply grilles, the temperature (23.3–27.2 °C) and air speed (0.06–0.22 m/s) meet the permissible microclimate standards (GOST 30494-2011); while arranging the air exchange with the use of a microperforated air duct they correspond to the optimal parameters (temperature 23.1–25.4 °С, air speed 0.09–0.13 m/s) that are comfortable for the human body. Thus, the use of a microperforated air duct enhances the efficiency of heat surplus assimilation in comparison with traditional air distribution devices (ventilation grilles).

2021 ◽  
Vol 1719 (1) ◽  
pp. 012042
J Pitakarnnop ◽  
U Chaiyapat ◽  
P Piromgraipak ◽  
K Luanghirun

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