If all the air is the same temp, such as in your explanation, air flowing would do the opposite from cooling. The kinetic energy of the flowing air would actually lose kinetic energy to heat stuff up more. Now it is very negligible, but it certainly isn't cooling anything down.

> Windchill is a human experience and does not apply to physical objects like a computer.

It does if the computer is on and is exposed to wind. It has nothing to do with being human or alive, and everything to do with having an internal source of heat. Even in things that have no source of heat, wind chill will accelerate cooling until the object reaches the dry bulb temp (assuming there's no evaporation), as you mention... which rather obviously means it is not limited to "human experience".

You can argue that the term windchill refers to something typically used to describe human/animal outdoor comfort, but the concept is in no way limited to that.

Wind chill can never reduce the temperature of an object below the dry bulb temperature of the air, unless that object is wet. In that case evaporation can occur and will result in cooler-than-dry-bulb temps until the water evaporates or until the air reaches 100% humidity.

The only time wind chill has any other effect is if the item in question is producing heat...e.g. a person or a house with the heat on inside. In this case the object will experience greater heat loss as the windspeed goes up. If the object doesn't have an internal heater, then the wind chill will speed cooling until the object reaches the dry bulb temp, and then have no impact.

[removed]

[removed]

This is how a sling psychrometer works. It has two thermometers, one which has a cloth soaked in distilled water wrapped around the bulb. This produces a "wet bulb" and "dry bulb" temperature, from which you can determine humidity, enthalpy, dew point, etc. The wet bulb will always read the same or lower than the dry bulb. If they read the same, the RH% is 100%. If they are far apart, it's closer to 0%.

[removed]

I know you were probably not trying to be completely rigorous in your answer, but I would add an important qualifier to the gist of your answer. All other things being equal (AKA ceterus paribus), heat will always flow from the hot thing to the cold thing.

Heat can and sometimes without (human) intervention does flow from a cold thing to a hot thing, but it requires some other change. That change could be doing work on the system ala refrigeration. The change could be that a chemical potential gradient is causing a certain type of particle to move preferentially from a cold region to a hot one which leaves the cold region even colder (something like this is the principle behind Helium dilution refrigerators). I'm sure there are other example, although I can't think of more off the top of my head.

So to be more general we might say that closed systems tend toward maximum entropy (or equivalently minimum grand thermodynamic potential), which usually means heat flows from hot to cold, and all else being equal guarantees that heat will flow from hot to cold.

why not? Is this metal the outer layer of the system. One side at 105 the other at some other temp, such as room temp. Conduction of the material is important especially if the question is why is one thing one temp and this other thing another temp. How thick is this metal? Why would it not act as a "heat sink?" I think it applies, it is thermodynamics but the last time I thought I was wrong I was mistaken.

[removed]

[removed]

materials have different emissivity. Plastic on wire is ~1, metals are way different.

Metals also reflect heat from different sources. You can tell if you're measuring a reflection by moving yourself around and measuring from different angles. reflections will change but the emited ir wont

You need to put a bit of black insulation tape on the metal and use that for temperature. Or use it to work out the emissivity of the metal.

Theres another setting for specular reflectance. You crumple up some tinfoil and take a reading from that for background reflectance

[removed]

[removed]

Otherwise known as the square-cube law!

Another great (but completely unrelated) example of this law explains the design differences between large and small animals. As a creature gets larger, its mass increases at a cubic rate (volume, m^3) but muscle/bone strength is proportional to their cross sectional area (m^2). This is why an elephant has such massive muscles/bones when (proportionally) compared to a dog.

It also impacts body temperature--since heat generation is proportional to body volume, but the ability to reject heat is proportional to the skin area. This explains the elephants' massive ears, and also why most cold blooded animals are very small.

If you scaled a dog up to elephant size it would collapse under its own weight before dying of heat. If you scaled an elephant down to dog size it would probably freeze to death. All because of math!

From the very beginning of the article on Wikipedia:

"Wind chill or windchill (popularly wind chill factor) is the lowering of body temperature due to the passing-flow of lower-temperature air.

It's a non-scientific term with no agreed exact formula and has nothing to do with inanimate objects.

Edit: Of course wind cools things - didn't mean to be nit-picking, I just don't like "windchill" because it's poorly defined. I mean there could be moisture on inanimate objects, that could be removed by dry air and cool further.. but there are good terms for those phenomenon such as evaporative cooling, convective, etc.

This isn't true. I also just looked on Wikipedia and it explains the same thing I explained. Wind chill is the additional cooling effect that wind brings. Not necessarily from evaporation, it still included conduction. So you're dry computer is still experiencing wind chill by definition.

Windchill is a human experience and does not apply to physical objects like a computer. No matter how fast the wind is blowing over your dry computer, it cannot reduce the temperature below the temperature of the air making up the "wind". What it can do is reach an equilibrium temperature faster. At least in my experience (and wikipedia) this phenomenon is called "air cooling your computer" and not wind chill.

edit for clarity: wind definitely cools things off faster than no wind :)

That's correct. Windchill annoys me. It's often misused and confusing. There are Reddit posts saying things like "Here I am in Michigan in a T shirt, it's -60F today". but it's actually 0F with windchill of -60F. And yes, wind does not cool things below ambient unless they are wet (or unless the wind itself is bringing in colder air)

[removed]

Because that determines how much energy the water has (volume is equivalent of mass). That energy has to be lost to friction, which doesn't increase as a cube.

[removed]

[removed]

[removed]

As others have said, the metal part isn't cooler - it's an artifact of the thermal camera.

It comes down to emissivity, and reflections.

A "thermal camera" or "(non-contact) IR thermometer" measures the radiated heat (long-wavelength thermal energy) emitted by the object you're pointing it at.

All objects emit the same spectrum (strictly spectral distribution) of radiation, depending only on their temperature - look up Blackbody radiator and colour-temperature.

The absolute amount of energy ("brightness") also varies strongly with temperature, but depends also on a property of the material, known as its emissivity.

For simplicity, IR cameras typically only measure the strength of emission at one wavelength (usually somewhere around 3-12µm), and determine the temperature by the "brightness" at that wavelength.

For most common matt/dielectric (non-metal) materials, the emissivity is 97-99% - which is the default calibration for an IR thermometer.... but metals, especially polished shiny ones, and especially gold has a lower emissivity, so the IR thermometer will under-read.

You can look up the emissivity for different materials and set the IR thermometer calibration accordingly, to get correct readings ... but be aware that metals can also look like mirrors, and you may "read" the temperature of the thing in the reflection in the metal, rather than the metal itself - or somewhere between the two.

If you wear a metal ring (especially a gold one) on your finger an point the thermal camera at your hand, you'll see the ring is darker (and reads "colder") - even though its true temperature is likely to be close to that of your fingers.

This is something that not enough people know about IR thermometers and IR cameras.

It's a physics thing! :-)