Wind chill chart 20193/28/2024 Image Credit: “Thermal Plume from human hand” by Gary Settles via Wikimedia Commons Forced convection is the reduction of this boundary layer by fluid due to factors other than the warming of the fluid itself, such as wind. (In the next chapter we will learn how thermal images like this one are created.) Thermal image showing air (green) warmed by conduction from the skin then rising within the surrounding cooler and more dense air due to natural convection, which is discussed in the following section. The thermal image below color-codes warm and cool air so that we can visualize the formation of the warm boundary layer. In the absence of wind, a layer of warm air will form next to your skin, which effectively provides an additional layer of insulation known as a boundary layer. Both of these combinations were entirely possible in Bethel, Alaska and growing up we usually had one or two wind chill cancellation days per year. According to the windchill chart, school could be cancelled on a -30 ☏ day with 55 mph wind or on a -45 ☏ day with 15 mph wind. School was cancelled on days when the wind chill was less than -75 ☏. The author grew up in a small remote town on the tundra in Western Alaska. For example, a day with 10 ☏ air temperature and 10 mph wind would feel as cold as a -7 ☏ day without wind. The chart also shows the exposure time which is likely to result in frostbite. The chart is makes this calculation specifically for the skin on a human face. The wind chill chart above shows what calm air temperature would be necessary to produce the same heat loss rate as the actual air temperature plus wind combination. Wind chill is a significant factor in thermal injuries such as hypothermia and frost bite, which is tissue damage caused by the formation of ice crystals within the tissue. This phenomenon is known as the wind chill effect or just wind chill. Image Credit: “Wind Chill Chart” by National Weather Service, NOAAĪs stiff breeze can feel refreshing on a hot day and make a cool day feel quite cold. 93 Wind-Chill Factor The wind chill chart displays the theoretical calm air temperature which would produce the same cooling rate as the actual air temperature + wind combination.
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