Studies have also shown how specific classroom configurations can affect air quality and reduce the spread of aerosols by using HVAC or taking extra measures outside of open windows সেই tiny, potentially covid-carrying particles that can remain suspended in the air for hours.
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“There are some conditions where we’ve clearly found that there’s a problem, and when you look at the predicted density of aerosols around other people in the house, in some cases it’s much more than what the (standard) model would say,” said Leon Glixman, an MIT architect. And Professor of Engineering. For the study, published online in the journal Building and Environment, the researchers used computational fluid dynamics – a state-of-the-art simulation of airflow – involving the ventilation conditions of 14 different classrooms, nine HVAC systems and five open windows. The research team compared their modeling with past experimental results.
A typical scenario involves fresh air entering a classroom near ground level and moving continuously until you exit the room through the ceiling vent. This process is helped by the fact that hot air rises, and the human body temperature rises naturally to the “heat plume”, which carries air towards the ceiling vent at a rate of about 0.15 meters per second.
When ceiling ventilation is provided, the goal is to create vertical upward vertical ventilation for ventilation outside the room, while limiting horizontal ventilation, which spreads the aerosol among seated students.
That’s why wearing a mask inside a home is understandable, Glixman said. The masks limit the horizontal motion of the led aerosol, placing those particles close to the heat plume so that the aerosols rise vertically, as the researchers saw in their simulations. Normal exhalation produces an aerosol speed of 1 meter per second, and the cough still produces a high speed – but the mask keeps that speed low.
But, with the use of closed windows and HVAC, airflow problems occur in a simulated classroom in winter, with cold windows on the side. In this case, because the cold air near the window naturally sinks, it disrupts the overall ward upward flow of air in the classroom despite the human heat.
In this context, if someone infected with Covid-1 is sitting by the window, his or her aerosol is likely to spread around. But there is a solution to this problem: among other things, installing heaters near cold windows limits their impact on classroom airflow, Glixman said.
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