Narrowing the Air Outlet of a PET Bottle
Increases Airflow Speed and Provides a Slight Cooling Effect
In China, where temperatures have been soaring above 40 degrees Celsius for consecutive days, a unique fan has emerged. It features several plastic bottles cut in half attached in front of the fan, which reportedly has the effect of slightly lowering the actual air temperature.
Recently, numerous videos explaining how to make a 'PET bottle fan' have been posted on local Chinese social networking services (SNS) such as Douyin. The PET bottle fan is a form that combines several plastic bottles cut in half with a fan. Although it looks crude, it is said to have the effect of making the breeze feel somewhat cooler.
So, what is the principle behind the PET bottle fan? A netizen who introduced the fan explained that it utilizes the properties of airflow. The speed of airflow varies depending on the diameter of the outlet. In other words, if the air hole is large, the airflow speed is slow, and if the hole is small, it becomes faster.
Plastic Bottle Fan [Image Source=Captured from Chinese SNS]
Just as the breath feels cooler when you purse your lips and blow compared to blowing with your mouth wide open saying "ha," this is due to the same property of airflow. By using PET bottles to narrow the diameter of the fan's airflow, it is said that the air temperature can be lowered by about 0.2 degrees Celsius.
Of course, the PET bottle fan is an invention with clear limitations. Unlike air conditioners that use refrigerants to cool the temperature of a space itself, it only slightly cools the air. Therefore, it is likely to be ineffective during extreme heatwaves.
Moreover, PET bottle fans have long been popular in developing countries where purchasing air conditioners is difficult. In 2019, an advertising company in Bangladesh created an 'Eco Cooler,' which narrows the air outlet as much as possible using PET bottles, and provided it to a slum area. When Eco Coolers were operated simultaneously in several households, the perceived temperature in the village reportedly dropped by about 5 degrees Celsius.
Meanwhile, from this month, Beijing, Shandong Province, Hebei Province, Henan Province, and other areas in China have been experiencing abnormal heatwaves with temperatures exceeding 40 degrees Celsius. On the 17th (local time), the China Central Meteorological Observatory issued a heatwave warning, reporting that the maximum temperature in some parts of Beijing and Inner Mongolia approached 38 degrees Celsius.
China has been observing unusual high temperatures since this spring, which has led to lowered river water levels and withering crops, causing subsequent damage.
© The Asia Business Daily(www.asiae.co.kr). All rights reserved.
