scholarly journals Ventilation and the SARS-CoV-2 Coronavirus Analysis of outbreaks in a restaurant and on a bus in China,and at a Call Center in South Korea

2020 ◽  
Author(s):  
Bjorn Birnir
Keyword(s):  
Call Center ◽  
Air Conditioning ◽  
Air Flow ◽  
Second Step ◽  
Infected Person ◽  
Confined Space ◽  
Air Conditioning System ◽  
Turbulent Air Flow ◽  
Lay Buddhists ◽  
Respiratory Droplets

In a previous paper [10] a model of the distribution of respiratory droplets and aerosols by Lagrangian turbulent air-flow was developed. It is used to show how the SARS-CoV-2 Coronavirus can be spread by the breathing of single infected person. The model shows that the concentration of viruses in the cloud, exhaled by one person, can increase to infectious levels within a certain amount of time, in a confined space where the air re-circulates. In [10] the model was used to analyze the air-flow and SARS-CoV-2 Coronavirus build-up in a restaurant in Guangzhou, China [19,18]. In this paper, we add the analysis of two more cases, an outbreak among lay-Buddhists, on a bus [26], traveling to a ceremony in Zhejiang province, China, and an outbreak in a Call Center in Seoul, Korea [20]. The analysis and comparison of these three cases, leads to the conclusion that the SARS-CoV-2 Coronavirus attacks in two steps: The first step is a linear spread between individuals with a couple of days delay. The second step is an exponential spread effected by the air-conditioning system affecting a much larger number of people. Thus in the second step, the ventilation becomes the super-spreader.

scholarly journals The Build-Up of Aerosols Carrying the SARS-CoV-2 Coronavirus, in Poorly Ventilated, Confined Spaces

2020 ◽  
Author(s):  
Bjorn Birnir ◽  
Luiza Angheluta
Keyword(s):  
Decay Time ◽  
Air Flow ◽  
Time Frame ◽  
Aerosol Concentration ◽  
Confined Space ◽  
Confined Spaces ◽  
Turbulent Air Flow ◽  
Short Time ◽  
Respiratory Droplets ◽  
Standard Ventilation

Abstract A model of the distribution of respiratory droplets and aerosols by Lagrangian turbulent air-flow is developed and used to show how the SARS-CoV-2 Coronavirus can be dispersed by the breathing of an infected person. It is shown that the concentration of viruses in the exhaled cloud can increase to infectious levels with time (grow linearly), in a confined space where the air re-circulates. The model is used to analyze the air-flow and SARS-CoV-2 Coronavirus build-up in a restaurant in Guangzhou, China [23, 21]. It is concluded that the outbreak of Covid-19 pandemic in the restaurant in January 2020, is due to the build-up of the airborne droplets and aerosols carrying the SARS-CoV-2 Coronavirus and would not have been pre- vented by standard ventilation. A comparison with standard models for aerosol concentration shows that, in the absence of ventilation, the decay of the aerosol concentration is also con- trolled by the decay time of the virions in aerosols. This decay time is very long and a steady state is not achieved in the time-frame of the contagion. Instead the concentration exhibits a polynomial increase and reaches infectious levels in a relatively short time, explaining the outbreak in the restaurant in Guangzhou.

scholarly journals The Build-Up of Aerosols Carrying the SARS-CoV-2 Coronavirus, in Poorly Ventilated, Confined Spaces

2021 ◽  
Author(s):  
Björn Birnir
Keyword(s):  
Decay Time ◽  
Air Flow ◽  
Time Frame ◽  
Aerosol Concentration ◽  
Confined Space ◽  
Confined Spaces ◽  
Turbulent Air Flow ◽  
Short Time ◽  
Respiratory Droplets ◽  
Standard Ventilation

Abstract A model of the distribution of respiratory droplets and aerosols by Lagrangian turbulent air-flow is developed and used to show how the SARS-CoV-2 Coronavirus can be dispersed by the breathing of an infected person. It is shown that the concentration of viruses in the exhaled cloud can increase to infectious levels with time (grow linearly), in a confined space where the air re-circulates. The model is used to analyze the air-flow and SARS-CoV-2 Coronavirus build-up in a restaurant in Guangzhou, China [32, 30]. It is concluded that the outbreak of Covid-19 pandemic in the restaurant in January 2020, is due to the build-up of the airborne droplets and aerosols carrying the SARS-CoV-2 Coronavirus and would not have been prevented by standard ventilation. A comparison with standard models for aerosol concentration shows that, in the absence of ventilation, the decay of the aerosol concentration is also controlled by the decay time of the virions in aerosols. This decay time is very long, with low relative humidity, and a steady state is not achieved in the time-frame of the contagion. Instead the concentration exhibits a polynomial increase and reaches infectious levels in a relatively short time, explaining the outbreak in the restaurant in Guangzhou.

scholarly journals The Build-Up of Aerosols Carrying the SARS-CoV-2 Coronavirus, in Poorly Ventilated, Confined Spaces

2020 ◽  
Author(s):  
Björn Birnir
Keyword(s):  
Decay Time ◽  
Air Flow ◽  
Time Frame ◽  
Aerosol Concentration ◽  
Confined Space ◽  
Confined Spaces ◽  
Turbulent Air Flow ◽  
Short Time ◽  
Respiratory Droplets ◽  
Standard Ventilation

AbstractA model of the distribution of respiratory droplets and aerosols by Lagrangian turbulent air-flow is developed and used to show how the SARS-CoV-2 Coronavirus can be dispersed by the breathing of an infected person. It is shown that the concentration of viruses in the exhaled cloud can increase to infectious levels with time (grow linearly), in a confined space where the air re-circulates. The model is used to analyze the air-flow and SARS-CoV-2 Coronavirus build-up in a restaurant in Guangzhou, China [30, 28]. It is concluded that the outbreak of Covid-19 pandemic in the restaurant in January 2020, is due to the build-up of the airborne droplets and aerosols carrying the SARS-CoV-2 Coronavirus and would not have been prevented by standard ventilation. A comparison with standard models for aerosol concentration shows that, in the absence of ventilation, the decay of the aerosol concentration is also controlled by the decay time of the virions in aerosols. This decay time is very long and a steady state is not achieved in the time-frame of the contagion. Instead the concentration exhibits a polynomial increase and reaches infectious levels in a relatively short time, explaining the outbreak in the restaurant in Guangzhou.

Research on Constant Pressure of Air Supplying and Energy Saving for the Air Conditioning System

2012 ◽  
Vol 164 ◽  
pp. 362-365
Author(s):  
Guang Zhen Cheng ◽  
Zuo Qing Liu ◽  
Hong Fei Lin
Keyword(s):  
Air Conditioning ◽  
Frequency Conversion ◽  
Constant Pressure ◽  
Frequency Control ◽  
Air Flow ◽  
Air Conditioning System ◽  
Velocity Modulation ◽  
Speed Regulation ◽  
Soft Start ◽  
Energy Conservation Principle

This paper provides a method of supply constant pressure air for air conditioning system. It analysis the energy consumption betwwen the damper adjuste air flow with variable frequency speed regulation adjuste air flow. The paper Introduce the Energy conservation principle of the frequency control blower. The supplying air Pipeline subject to a uniform force, the equipments mechanical properties was improved.The results show that Uses the frequency conversion velocity modulation to carry on supply constant pressure air, obviously reduces the energy consumption.The electrical motor starting characteristic is improved, realizes the electrical motor soft start.

Using a Fan Air Flow Station to Control Building Static Pressure in a Variable Volume Air Conditioning System

Solar Energy ◽  
2005 ◽  
Author(s):  
B. Zheng ◽  
X. Pang ◽  
M. Liu ◽  
I. Joo
Keyword(s):  
Air Conditioning ◽  
Static Pressure ◽  
Air Flow ◽  
Pressure Control ◽  
Speed Profile ◽  
Air Conditioning System ◽  
Variable Volume ◽  
Fan Speed ◽  
Sensor Locations

A fan airflow station measures airflow through a fan using fan speed, fan head, and the field-calibrated fan curve. This paper presents the theory and techniques of using fan airflow station in a variable volume system for building pressure control. These techniques include fan curve calibration, determination of the volumetric flow difference of the supply and return airflows, and sensor locations. The return fan speed profiles were plotted, and data was collected on building pressure after implementing the fan air flow station. The Implementation of a fan air flow station demonstrates that the return fan speed can track the supply fan speed profile as building loads change, such that building pressure is maintained within a satisfactory range.

scholarly journals The Examination of Air Blowing Method and Thermal Comfort of Variable Air Conditioning System using Coanda Effect

2019 ◽  
Vol 111 ◽  
pp. 01079
Author(s):  
Hikari Sakakibara ◽  
Takashi Akimoto ◽  
Hitomi Igarashi ◽  
Shunsuke Nakamura ◽  
Madoka Kimura
Keyword(s):  
Thermal Comfort ◽  
Air Conditioning ◽  
Air Flow ◽  
Building Design ◽  
Upper Body ◽  
Coanda Effect ◽  
Subjective Perception ◽  
Air Conditioning System ◽  
Air Blowing ◽  
Coandǎ Effect

The “Strategic Energy Plan” implemented by the Cabinet of Japan in 2014 strives for zero energy building design for typical new construction by 2030. The present study focuses on a ductless and variable air conditioning system, using the Coanda effect, with the aim of reducing fan power, and saving of resources by reducing the space between the ceiling. In this study, we examined the air blowing method and evaluated thermal comfort using computational fluid dynamics as well as subjective perception of coolness in a midsize office. A draft zone was reduced by extending the interval between conditioned air outlets. However, if the extension of throw length was excessive, hot space would be formed near the air outlets, and there would be a risk of impacting thermal comfort. Moreover, we confirmed that the thermal comfort was generally favourable. In particular, perceived thermal comfort was better at the position in the office where the air flow landed on the upper body of the subjects. On the other hand, it decreased when the influence of the air flow was small, and at the point where air flow landed on the lower body of the subjects.

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