scholarly journals Numerical Study of the Transmission of Exhaled Droplets between the Instructor and Students in a Typical Classroom

2021 ◽  
Vol 11 (20) ◽  
pp. 9767
Author(s):  
Mohamed Ismail Farouk ◽  
Ahmed Fayez Nassar ◽  
Mohamed Hassan Elgamal
Keyword(s):  
Rate Ratio ◽  
Numerical Study ◽  
Ventilation Rate ◽  
Average Concentration ◽  
Critical Parameters ◽  
Exam Room ◽  
Entrance Door ◽  
Entrainment Process ◽  
Risk Of Exposure ◽  
Exposure Ratio

Conducting physical attendance exams during pandemics is a challenge facing many educational institutes and universities. Our study’s main objective is to numerically simulate the expected transmission of the harmful exhaled droplets of aerosols from an infected instructor to students in an exam room ventilated by a number of spiral diffusers. Several critical parameters, including the droplet size, the ventilation rate, and status of the entrance door were considered in the analysis. Two dimensionless indices, i.e., the specific normalized average concentration (SNAC) and the exceedance in exposure ratio (EER), were introduced to examine the effect of the said parameters on student exposure to the harmful droplets. The study revealed that the 5 mm droplets were less hazardous as they resulted in an 87% reduction in exposure when compared with the small 1 mm size droplets. We also found that when the ventilation rate ratio (VRR) increased above unity, an upward entrainment process, due to the swirl diffuser, of the aerosol droplets took place, and consequently the risk of student exposure was reduced. The results also demonstrated that increasing VRR from zero to 1 and then to 2 decreased the exceedance in the student exposure from 3.5 to 2.15 and then to less than zero, respectively. The study also showed that keeping the lecture room’s main door open is recommended as this reduced the risk of exposure by 26% in the case of a VRR equal to 2.

scholarly journals The impact of channel effect on Asian dust transport dynamics: a case in southeastern Asia

2012 ◽  
Vol 12 (1) ◽  
pp. 271-285 ◽  
Author(s):  
C.-Y. Lin ◽  
Y.-F. Sheng ◽  
W.-N. Chen ◽  
Z. Wang ◽  
C.-H. Kuo ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
High Resolution ◽  
Coupling Effect ◽  
Numerical Study ◽  
Average Concentration ◽  
Asian Dust ◽  
Dust Transport ◽  
Transport Dynamics ◽  
Channel Effect ◽  
The Impact

Abstract. A super heavy dust event was identified with unprecedented PM10 in terms of speed and concentration in the southeastern Asia. The average concentration was observed exceeding the value of 1000 μg m−3 for the duration lasting more than 10 h, with the highest value reached 1724 μg m−3 in northern Taiwan on 21 March 2010. We found that this case exhibited an uneven and intriguing spatial distribution of PM10 concentration and transport speed between eastern and western Taiwan. Higher values were observed in the western and northern areas. The peak concentrations can vary up to 5-fold between western and eastern Taiwan, and ten-fold between the northern tip and southern tip of Taiwan, only about 400 km apart. A high resolution, 10 km, numerical study by Weather Research Forecast (WRF) and WRF-chem models revealed that this intriguing spatial distribution of the Asian dust transport was resulting from a strong coupling effect of the geographic channel effect and blocking of the easterly from the Pacific Ocean. We are confident that this coupling effect can be revealed only by applying a high resolution numerical study in other similar regions.

scholarly journals Experimental and numerical study of mean zonal flows generated by librations of a rotating spherical cavity

2010 ◽  
Vol 662 ◽  
pp. 260-268 ◽  
Author(s):  
A. SAURET ◽  
D. CÉBRON ◽  
C. MORIZE ◽  
M. LE BARS
Keyword(s):  
Rate Ratio ◽  
Particle Image ◽  
Numerical Study ◽  
Zonal Flow ◽  
Outer Wall ◽  
Weakly Nonlinear ◽  
Zonal Flows ◽  
Solid Body Rotation ◽  
Weakly Nonlinear Analysis ◽  
Image Velocimetry

We study both experimentally and numerically the steady zonal flow generated by longitudinal librations of a spherical rotating container. This study follows the recent weakly nonlinear analysis of Busse (J. Fluid Mech., vol. 650, 2010, pp. 505–512), developed in the limit of small libration frequency–rotation rate ratio and large libration frequency–spin-up time product. Using particle image velocimetry measurements as well as results from axisymmetric numerical simulations, we confirm quantitatively the main features of Busse's analytical solution: the zonal flow takes the form of a retrograde solid-body rotation in the fluid interior, which does not depend on the libration frequency nor on the Ekman number, and which varies as the square of the amplitude of excitation. We also report the presence of an unpredicted prograde flow at the equator near the outer wall.

Numerical Study on Indoor Air Quality of Commercial Kitchen in China

2011 ◽  
Vol 374-377 ◽  
pp. 1100-1105 ◽  
Author(s):  
Xiao Tan Hou ◽  
An Gui Li ◽  
Zhi Hua Wang ◽  
Yu Jiao Zhao
Keyword(s):  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Numerical Study ◽  
Average Concentration ◽  
Energy Utilization ◽  
Change Rate ◽  
Air Supply ◽  
Air Change Rate

Indoor air quality of commercial kitchen is investigated and analyzed through velocity, temperature, humidity, and CO2 concentration under different air change rate and supply air temperature. the best air change rate is 30 times per hour and air supply temperature is 301.15K for kitchen, the mean value of the minimum velocity and standard deviation is 0.410m/s and 0.129 respectively, the maximum of the average concentration of CO2 is 659.78ppm, which is less than the acceptance criteria (CO2<1000ppm), and the energy utilization coefficient is maximum of 1.352. Research results show that this air supply mode can optimize indoor air quality.

scholarly journals ANALISIS RISIKO PAJANAN GAS AMMONIA (NH3) PADA PEKERJA DI BAGIAN PABRIK AMMONIA I PT PETROKIMIA GRESIK

2020 ◽  
Vol 18 (1) ◽  
Author(s):  
Dinda Dwi Firmansyah ◽  
Khambali . ◽  
Koerniasari .
Keyword(s):  
At Risk ◽  
Risk Analysis ◽  
Maximum Concentration ◽  
Average Concentration ◽  
Gas Production ◽  
Respiratory Disorder ◽  
Factory Workers ◽  
Minimum Concentration ◽  
Risk Of Exposure ◽  
Level Of Risk

ABSTRACT PT Petrokimia Gresik is the Complete Fertilizer Manufacturer in Indonesia which produces various kinds of fertilizers and chemicals for agro-industrial solutions. Ammonia (NH3) is one of the results of chemical production at PT Petrokimia Gresik which poses a risk to the health of ammonia factory workers at PT Petrokimia Gresik. The purpose of this study is to analyze the risk of exposure to ammonia (NH3) gas in ammonia I factory workers of PT Petrokimia Gresik.This study is a descriptive survey using Environmental Health Risk Analysis approach. The data analysis method used was risk analysis to determine the risk characterization of PT Petrokimia Gresik ammonia (NH3) I workers. The level of risk is said to be safe if RQ ≤ 1, and the level of risk is said to be unsafe if RQ> 1.The results showed that the average concentration of ammonia (NH3) gas was 6.6 mg / m3, the highest concentration was 9.2 mg / m3, the lowest concentration was 4.3 mg / m3. The physical air environment obtained at an average air temperature of 36oC, the average air humidity was 43%, the average wind speed was 0.85 m / s and the wind direction when the measurements blew from the West and East. Agents at risk of causing health problems to workers at ammonia I factory of PT Petrokimia Gresik were ammonia (NH3) gas in the work environment air sourced from the ammonia (NH3) gas production process, and 57% of the ammonia I factory workers of PT Petrokimia Gresik had a history of respiratory disorder. The response dose of ammonia (NH3) gas was 5x10-1 mg / m3. All ammonia I factory workers at PT Petrokimia Gresik obtained a minimum concentration, average concentration and maximum concentration of RQ <1.From the results of the study it can be concluded that the level of risk of exposure to ammonia (NH3) gas in ammonia I factory workers of PT Petrokimia Gresik is safe and not at risk of developing respiratory tract disorders, because the concentration is minimal, average concentration and maximum concentration does not exceed risk (RQ). It is recommended that the ammonia I plant manager of PT Petrokimia Gresik keep monitoring and evaluating the air pollution control and prevention system regularly. Key words: Risk Analysis, Ammonia Gas (NH3), Workers

scholarly journals Improving Greenhouse Microclimate Control with the Help of Plant Temperature Measurements

1995 ◽  
Author(s):  
Marcel Fuchs ◽  
Ishaiah Segal ◽  
Ehude Dayan ◽  
K. Jordan
Keyword(s):  
Transfer Functions ◽  
Warm Season ◽  
Sweet Pepper ◽  
Ventilation Rate ◽  
Critical Parameters ◽  
Vegetable Crops ◽  
Climate Control ◽  
High Productivity ◽  
Leaf Resistance ◽  
Layer Resistance

A model of the energy balance of a transpiring crop in a greenhouse was developed in a format suitable for use in climate control algorithms aimed at dissipating excess heat during the warm periods. The model's parameters use external climatic variables as input. It incorporates radiation and convective transfer functions related to the operation of control devices like shading screens, vents, fans and enhanced evaporative cooling devices. The model identified the leaf boundary-layer resistance and the leaf stomatal and cuticular resistance as critical parameters regulating the temperature of the foliage. Special experiments evaluated these variables and established their relation to environmental factors. The research established that for heat load conditions in Mediterranean and arid climates transpiring crops maintained their foliage temperature within the range allowing high productivity. Results specify that a water supply ensuring minimum leaf resistance to remain below 100 s m-1, and a ventilation rate of 30 air exchanges per hour, are the conditions needed to achieve self cooling. Two vegetable crops, tomato and sweet pepper fulfilled maintained their leaf resistance within the prescribed range at maturity, i.e., during the critical warm season. The research evaluates the effects of additional cooling obtained from wet pad systems and spray wetting of foliage.

scholarly journals Dust emissions from a tunnel-ventilated broiler poultry shed with fresh and partially reused litter

2010 ◽  
Vol 50 (6) ◽  
pp. 552 ◽  
Author(s):  
Robin L. Modini ◽  
Victoria Agranovski ◽  
N. K. Meyer ◽  
Erin Gallagher ◽  
Mark Dunlop ◽  
...  
Keyword(s):  
Large Scale ◽  
Emission Rate ◽  
Ventilation Rate ◽  
Average Concentration ◽  
Dust Particles ◽  
Size Distributions ◽  
Dust Emissions ◽  
Production Cycles ◽  
Fresh Litter ◽  
Litter Properties

Dust emissions from large-scale, tunnel-ventilated poultry sheds could have negative health and environmental impacts. Despite this fact, the literature concerning dust emissions from tunnel-ventilated poultry sheds in Australia and overseas is relatively scarce. Dust measurements were conducted during two consecutive production cycles at a single broiler shed on a poultry farm near Ipswich, Queensland. Fresh litter was employed during the first cycle and partially reused litter was employed during the second cycle. This provided an opportunity to study the effect that partial litter reuse has on dust emissions. Dust levels were characterised by the number concentration of suspended particles having a diameter between 0.5 and 20 μm and by the mass concentration of dust particles of less than 10 μm diameter (PM10) and 2.5 μm diameter (PM2.5). In addition, we measured the number size distributions of dust particles. The average concentration and emission rate of dust was higher when partially reused litter was used in the shed than when fresh litter was used. In addition, we found that dust particles emitted from the shed with partially reused litter were finer than the particles emitted with fresh litter. Although the change in litter properties is certainly contributing to this observed variability, other factors such as ventilation rate and litter moisture content are also likely to be involved.

scholarly journals Simulation study of solar chimney assisted solarium.

2021 ◽  
Author(s):  
Afrooz Ravanfar
Keyword(s):  
Cross Section ◽  
Thermal Response ◽  
Ventilation Rate ◽  
Critical Parameters ◽  
Thermal Engineering ◽  
First Principle ◽  
Solar Chimney ◽  
Modelling Method ◽  
Simulation Results ◽  
Thermal Simulations

The objective of this study is to develop a modelling method for optimizing the design of a solar chimney integrated solarium to maximize the ventilation rate in the solarium. A thermal model is developed and implemented in SIMULINK to simulate the thermal response of the solarium combined with a solar chimney based on the first principle of thermal engineering. Thermal simulations are performed for critical summer days. The greenhouse air temperature and its ventilation rate with various geometrical configurations are calculated on the basis of solar irradiance intensity and ambient temperature. The preliminary numerical simulation results show that a solar chimney, combined with an appropriately inclined roof of a solarium, would be a better option for ventilation improvement in the solarium. The solarium height and solarium/solar chimney cross section areas are the critical parameters. The combination of a shorter solar chimney with a high solarium would be suitable for Toronto.

scholarly journals Simulation study of solar chimney assisted solarium.

2021 ◽  
Author(s):  
Afrooz Ravanfar
Keyword(s):  
Cross Section ◽  
Thermal Response ◽  
Ventilation Rate ◽  
Critical Parameters ◽  
Thermal Engineering ◽  
First Principle ◽  
Solar Chimney ◽  
Modelling Method ◽  
Simulation Results ◽  
Thermal Simulations

The objective of this study is to develop a modelling method for optimizing the design of a solar chimney integrated solarium to maximize the ventilation rate in the solarium. A thermal model is developed and implemented in SIMULINK to simulate the thermal response of the solarium combined with a solar chimney based on the first principle of thermal engineering. Thermal simulations are performed for critical summer days. The greenhouse air temperature and its ventilation rate with various geometrical configurations are calculated on the basis of solar irradiance intensity and ambient temperature. The preliminary numerical simulation results show that a solar chimney, combined with an appropriately inclined roof of a solarium, would be a better option for ventilation improvement in the solarium. The solarium height and solarium/solar chimney cross section areas are the critical parameters. The combination of a shorter solar chimney with a high solarium would be suitable for Toronto.

Numerical Study of Sand Deposition and Control by Flat Solar Panels

2012 ◽  
Author(s):  
Chuanjin Lan ◽  
Zhen Li ◽  
Yanbao Ma
Keyword(s):  
Large Scale ◽  
Numerical Study ◽  
Optimal Choice ◽  
Solar Panels ◽  
Inclination Angles ◽  
Mean Wind Speed ◽  
Entrainment Process ◽  
The Mean ◽  
And Control ◽  
Better Than

To make the best use of solar energy, most solar plants are located in deserts or dry and sandy areas, where most of the sand originate in sandstorms and desertification. For large scale solar plants, the structure of the solar panels can reduce the mean wind speed greatly, thus having a great effect on the deposition and entrainment process of the sand and dust. To study the effect of installment of solar panels on wind flow, numerical simulations are applied to get the turbulent flow field in the lee of the solar panels, with inclination angles ranging from 15° to 30° and at different spacing. The results show that 30° is the optimal choice and the performance with larger spacing at 2.5 times panel length is better than the case at 1.5 times.

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