Basically title, you always hear “windchill only affects humans” but we use fans to cool things all the time?
In: Physics
The wind affects at what rate heat is transferred from an object, it does not affect what temperature an object that does not produce its own heat ends up at. So the time for temperature to change, not the final temperature.
If an object activity tries to keep a specific temperature like a human does wind has an effect of the rate heat has to be generated. Enough can be generated it determine what temperature the object ends up at.
For something that generates heat at a constant rate like for example a computer CPU at a constant load, a car’s engine at a constant load the wind will determine what temperature it reaches.
Let’s first look at an object that does not produce any heat.
If the wind cools something down it has to be cooler the the object. Cold is not a thing it is just less hot. It is the object that heats up the air, it will reduce the temperature of the object and increase the temperature of the air. The result is both end up at a temperature in between what they started at. Air is not still but moves and transfers heat to other cooler air, the result is the temperature of the object will after some time be the same as the air temperature.
What wind does is move away the air that has been heated up and replace it with cooler air. The rate at which energy is transferred depends on the temperature diffrence. The result is wind results in the time it takes for the object to reach the same temperature as the air is shorter, but it does not affect what temperature the object ends up at.
A human on the other hand needs to be in a quite small temperature range to function. The extremities can handle larger temperature diffrence than our internal organs. We can cool ourselves down by sweating or wake ourselves up by using the calories in our food. Moving around gets lots of heat and is an efficient what to stay warm.
Wind will just like other objects result in heat being transferred faster from our bodies. We need to replace that hat to keep the body temperature. We need to generate more heat if there is a wind. This is why windchill matters for humans, we try to keep a constant temperature.
Windchill that is measured/calculated for humans in some specific clothes. The face is bar and the person walks into the wind. It shows how much cooler the air would be if there is no wind to remove heat at the same rate as the air with wind. If you were naked the effect would be larger. It is a tool to help you determine the amount of clothes you need when the effect of wind it included.
It will be relevant for another object that tries to keep a constant temperature like a house we heat up. Bot to what degree differs. If you are out you likely have the face exposed that is warm, and the clothes are not airtight. A house on the other hand is covered all over, no part hat is at room temperature is on the outside. The outer shell is hopefully airtight, but that is not always the case for our clothes. So wind will increase the heating required for a house a small bit.
For something that generates a constant amount of heat like the CPU or a car engine wind will once again change the rate heat is removed. If the heat generated in constant but the amount that is removed changes with the wind the result is the object’s temperature depends on the amount of wind. There will be an equilibrium temperature where heat is removed and heat added is the same.
There are models for heating too,m it is called heat index. They will include air humidity because the rate of heat is removed when we sweat depends on the air humidity. We increase the humidity of the air around us and replace it will dryer air resulting in we bring able to cold down faster.
When the air is warmer your body wind will heat you up faster. When the air heats you it gets cooler and the wind replaces it will air that you have not cold down and you get warm faster.
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