When wind is like a convection oven
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Date: 2026-07-10
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Comments and reviews: 20
justsomeguy2886
I love that you mention near the end that your a human person not an object, I think a core thing people keep forgetting about evaporative cooling is that for human meat people (not machines or slabs of stone) 99. 99% of the time you cool off because of contact cooling with your sweat, it being a liquid with more room to move naturally draws out heat while contacting your skin and drips or rubs off well before any significant amount can evaporate (hence the instinctual need to wipe sweat off ourselves even in dry heat, I remember way back in the day (high school) this very subject was used to demonstrate how easy it is for people to hyper fixate on their understanding of a concept without understanding the mechanism in the field, yes the cycle of evaporative cooling works on humans but unless your completely still and butt naked you'll likely never actually cool off significantly with it alone, it was actually pretty funny how they got the point across in the classroom, 1 put water on skin 2 wiped off with a towel 3 recorded how it felt cooler then told us to do the same with our sweat in gym and we were like wow, in hindsight it was a great way to show just how many additional X factors there are to even the simplest of questions on a scientific level when applied to the real world and the immense importance of reproducing studies to try and catch as many as you can: D
sorry for the wall of text this was just a super neat blast from the past for me on a very specific topic (0>0)/
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I love that you mention near the end that your a human person not an object, I think a core thing people keep forgetting about evaporative cooling is that for human meat people (not machines or slabs of stone) 99. 99% of the time you cool off because of contact cooling with your sweat, it being a liquid with more room to move naturally draws out heat while contacting your skin and drips or rubs off well before any significant amount can evaporate (hence the instinctual need to wipe sweat off ourselves even in dry heat, I remember way back in the day (high school) this very subject was used to demonstrate how easy it is for people to hyper fixate on their understanding of a concept without understanding the mechanism in the field, yes the cycle of evaporative cooling works on humans but unless your completely still and butt naked you'll likely never actually cool off significantly with it alone, it was actually pretty funny how they got the point across in the classroom, 1 put water on skin 2 wiped off with a towel 3 recorded how it felt cooler then told us to do the same with our sweat in gym and we were like wow, in hindsight it was a great way to show just how many additional X factors there are to even the simplest of questions on a scientific level when applied to the real world and the immense importance of reproducing studies to try and catch as many as you can: D
sorry for the wall of text this was just a super neat blast from the past for me on a very specific topic (0>0)/
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stevenneiman1554
As someone with a physics degree, I would say that your explanation is pretty faulty, and I also feel like you get a bit lost in a metaphor that makes things more confusing. Selecting for the most energetic molecules is actually a quite small part of why evaporation cools a surface, and if it wasn't evaporative cooling wouldn't actually work well because you'd be surrounding yourself with hotter air than your own body temperature and that hotter air would tend to conduct its energy back into your skin/sweat. Similarly, misters wouldn't cool you like sweat or hose water because you'd be getting blasted with a mixture of cool drops and scalding-hot steam.
The actual answer is that it costs energy to vaporize. There's intermolecular forces holding the water together (which is the whole reason why it's water at all and doesn't just turn into a gas instantly, and when the mass of water puts enough heat into a given molecule for it to get away, it becomes vapor, but cold vapor because the energy that was making it hot has been used up breaking it free from that mass of water. The result is that the water is colder but the air isn't any hotter, just more humid. The same principle is also why water takes time and continued heat to boil away after reaching the boiling point, rather than just flashing to steam all at once when you hit 100C/212F
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As someone with a physics degree, I would say that your explanation is pretty faulty, and I also feel like you get a bit lost in a metaphor that makes things more confusing. Selecting for the most energetic molecules is actually a quite small part of why evaporation cools a surface, and if it wasn't evaporative cooling wouldn't actually work well because you'd be surrounding yourself with hotter air than your own body temperature and that hotter air would tend to conduct its energy back into your skin/sweat. Similarly, misters wouldn't cool you like sweat or hose water because you'd be getting blasted with a mixture of cool drops and scalding-hot steam.
The actual answer is that it costs energy to vaporize. There's intermolecular forces holding the water together (which is the whole reason why it's water at all and doesn't just turn into a gas instantly, and when the mass of water puts enough heat into a given molecule for it to get away, it becomes vapor, but cold vapor because the energy that was making it hot has been used up breaking it free from that mass of water. The result is that the water is colder but the air isn't any hotter, just more humid. The same principle is also why water takes time and continued heat to boil away after reaching the boiling point, rather than just flashing to steam all at once when you hit 100C/212F
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Mason265
Hey Adam, physicist here. You made a very nice explanation, but unfortunately I'm going to have to be that guy and correct the record. Evaporative cooling is actually a little different from what you described. It's not just about the most energetic atoms leaving, and causing the average temperature to sink (though that effect does happen as well. When you evaporatively cool a dense interacting liquid like water though, that's actually not the main contributor to the cooling.
Rather, the most important part of the process is the binding energy of the water. Water consists of a bunch of electrically charged ions binding eachother together very tightly, and the process of pulling a water molecule out of that tightly bound soup involves breaking those intermolecular bonds. In order to break these bonds, you need to supply energy, and that energy ends up coming from the kinetic heat energy of the molecule, that then gets stored in the potential energy of the now broken bond, so the total amount of heat drops.
This turns out to be a much bigger contibutor to the coolness you feel when water evaporates on your skin.
The term to search for here to read more on the subject is latent heat.
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Hey Adam, physicist here. You made a very nice explanation, but unfortunately I'm going to have to be that guy and correct the record. Evaporative cooling is actually a little different from what you described. It's not just about the most energetic atoms leaving, and causing the average temperature to sink (though that effect does happen as well. When you evaporatively cool a dense interacting liquid like water though, that's actually not the main contributor to the cooling.
Rather, the most important part of the process is the binding energy of the water. Water consists of a bunch of electrically charged ions binding eachother together very tightly, and the process of pulling a water molecule out of that tightly bound soup involves breaking those intermolecular bonds. In order to break these bonds, you need to supply energy, and that energy ends up coming from the kinetic heat energy of the molecule, that then gets stored in the potential energy of the now broken bond, so the total amount of heat drops.
This turns out to be a much bigger contibutor to the coolness you feel when water evaporates on your skin.
The term to search for here to read more on the subject is latent heat.
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Zondrais
The one most important change I would make to Adam’s explanation is to explain that there are all kinds of ways a collision can move energy from a slower moving molecule to a faster one, like a slow bumper car hitting a fast bumper car from a side angle. It’s a small fraction of collisions, but in a densely packed lot with trillions of bumper cars it still happens a lot.
The moment a bumper car gets a lucky enough series of hits it gets shot out of the pit where it can never bump again, leaving behind a pit of slower cars.
You could also analogize it to money randomly moving around in a group of people. In a large enough group someone is always getting a lucky break. If everyone who gets lucky immediately leaves the group then the group as a whole losses money very quickly. I think Adam explains the second part well but is missing the first part (the way it’s described makes it seem like lucky breaks don’t happen all the time. 19: 54
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The one most important change I would make to Adam’s explanation is to explain that there are all kinds of ways a collision can move energy from a slower moving molecule to a faster one, like a slow bumper car hitting a fast bumper car from a side angle. It’s a small fraction of collisions, but in a densely packed lot with trillions of bumper cars it still happens a lot.
The moment a bumper car gets a lucky enough series of hits it gets shot out of the pit where it can never bump again, leaving behind a pit of slower cars.
You could also analogize it to money randomly moving around in a group of people. In a large enough group someone is always getting a lucky break. If everyone who gets lucky immediately leaves the group then the group as a whole losses money very quickly. I think Adam explains the second part well but is missing the first part (the way it’s described makes it seem like lucky breaks don’t happen all the time. 19: 54
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creshiell
I eat lunch in my car with the windows down and yesterday I almost put the windows up because the wind was just blowing HOT AIR on me.
After that debacle, I decided to skip my car and go for a walk during lunch until the heat advisory ends. I saw the heat advisory warning today said make sure to bring water with you and I thought oh I'll just go for a half hour walk during lunch instead of an hour in that case. 20 minutes in, the sidewalk in front of me started to streeeeeeeeeetch, and I was like oh no I need to sit So I sat on a bench in full sunlight wishing I had some water. In business attire and a wig, mind you.
Plucked up the energy to get back inside the office before they fired me for taking a long lunch and my back was DRENCHED and I had to force myself to drink the water once I got some.
So, long story short, it's hot y'all
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I eat lunch in my car with the windows down and yesterday I almost put the windows up because the wind was just blowing HOT AIR on me.
After that debacle, I decided to skip my car and go for a walk during lunch until the heat advisory ends. I saw the heat advisory warning today said make sure to bring water with you and I thought oh I'll just go for a half hour walk during lunch instead of an hour in that case. 20 minutes in, the sidewalk in front of me started to streeeeeeeeeetch, and I was like oh no I need to sit So I sat on a bench in full sunlight wishing I had some water. In business attire and a wig, mind you.
Plucked up the energy to get back inside the office before they fired me for taking a long lunch and my back was DRENCHED and I had to force myself to drink the water once I got some.
So, long story short, it's hot y'all
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seanoconnell7080
Chemistry student here, I think there may be a minor misunderstanding/misleading phrasing at 22: 21
Air can only hold so much water vapour before the water comes dripping out, we call that rain.
When air becomes saturated with water vapour, the water vapour condenses into tiny liquid droplets or ice crystals, this process forms clouds, not rain.
These tiny droplets or ice crystals form clouds, it is through a separate process that they can grow larger and eventually fall as rain or snow.
The droplets or ice crystals grow larger through collisions, merging with each other. As they increase in size, gravity becomes stronger than the upward forces from air currents and air resistance, causing them to fall as rain or snow.
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Chemistry student here, I think there may be a minor misunderstanding/misleading phrasing at 22: 21
Air can only hold so much water vapour before the water comes dripping out, we call that rain.
When air becomes saturated with water vapour, the water vapour condenses into tiny liquid droplets or ice crystals, this process forms clouds, not rain.
These tiny droplets or ice crystals form clouds, it is through a separate process that they can grow larger and eventually fall as rain or snow.
The droplets or ice crystals grow larger through collisions, merging with each other. As they increase in size, gravity becomes stronger than the upward forces from air currents and air resistance, causing them to fall as rain or snow.
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Mason265
I think the easiest way to see how this explanation doesnt tell the whole story is to observe that if you took an insualted box with very dry air in it and a thermometer, and then put a bucket of water in that box, as the water evaporates you will observe the total temperature of both the water and the air drop.
If your explanation here was the only effect, you would see the total temperature of the system stay the same as the water evaporates.
What's happening though is that water is bound tightly with intermolecular bonds, and it takes energy to break those bonds and make vapour. The energy necessary to break those bonds comes out of the heat energy of the molecules, so there is actually a total cooling of the whole system.
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I think the easiest way to see how this explanation doesnt tell the whole story is to observe that if you took an insualted box with very dry air in it and a thermometer, and then put a bucket of water in that box, as the water evaporates you will observe the total temperature of both the water and the air drop.
If your explanation here was the only effect, you would see the total temperature of the system stay the same as the water evaporates.
What's happening though is that water is bound tightly with intermolecular bonds, and it takes energy to break those bonds and make vapour. The energy necessary to break those bonds comes out of the heat energy of the molecules, so there is actually a total cooling of the whole system.
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TheBudderWizard
As a physicist, I’m very happy with your explanation of phase change!
I’ll also add that another way to explain the phenomena is like this:
You are at a loud college party (because you are not a physicist) and you can hear people talking over the music, but the music is loud. Then someone drunkenly stumbles (partying much harder than the rest of the party) into the power cord and music abruptly stops. People are still talking when it happens, but suddenly the volume of the party has decreased rapidly and is noticeable, especially as the rest of the confused party goers quiet to see what happened.
Glad to be seeing more videos like these again!
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As a physicist, I’m very happy with your explanation of phase change!
I’ll also add that another way to explain the phenomena is like this:
You are at a loud college party (because you are not a physicist) and you can hear people talking over the music, but the music is loud. Then someone drunkenly stumbles (partying much harder than the rest of the party) into the power cord and music abruptly stops. People are still talking when it happens, but suddenly the volume of the party has decreased rapidly and is noticeable, especially as the rest of the confused party goers quiet to see what happened.
Glad to be seeing more videos like these again!
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robinbaylor2672
It’s a great analogy for evaporative cooling. Refrigeration/heat pumps, are a bit more complicated. You have a compressable gas that gets squeezed, which makes it even hotter, but you keep the squeezed gas where you want the heat to go. Then you the gas expand into the area you want to cool (have you ever used canned compressed air to blow dust off something The can, as well as the air from it, gets cooler as you work. The cooler gas then absorbs heat, and when some heat has been absorbed, it gets routed to where you want to dump the excess heat and squeezed again. You cannot use mechanical refrigeration without making more heat somewhere else.
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It’s a great analogy for evaporative cooling. Refrigeration/heat pumps, are a bit more complicated. You have a compressable gas that gets squeezed, which makes it even hotter, but you keep the squeezed gas where you want the heat to go. Then you the gas expand into the area you want to cool (have you ever used canned compressed air to blow dust off something The can, as well as the air from it, gets cooler as you work. The cooler gas then absorbs heat, and when some heat has been absorbed, it gets routed to where you want to dump the excess heat and squeezed again. You cannot use mechanical refrigeration without making more heat somewhere else.
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brendancurtin679
it just won't ever be humid enough to make a noticeable difference when it's cold outside
Definitely not true. High humidity can definitely make it feel noticeably colder.
I live in New Orleans (but have lived in Philly, Boston, etc, and even high 30s or low 40s can feel closer to freezing with how humid it can be. Moist air absorbs heat from your body much more efficiently than dry air. Also, your clothes trap moisture better/don't dry out as well in humidity, which makes your clothes less able to trap warm air and insulate you as well. It just further enhances the wicking away of heat from your body.
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it just won't ever be humid enough to make a noticeable difference when it's cold outside
Definitely not true. High humidity can definitely make it feel noticeably colder.
I live in New Orleans (but have lived in Philly, Boston, etc, and even high 30s or low 40s can feel closer to freezing with how humid it can be. Moist air absorbs heat from your body much more efficiently than dry air. Also, your clothes trap moisture better/don't dry out as well in humidity, which makes your clothes less able to trap warm air and insulate you as well. It just further enhances the wicking away of heat from your body.
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teddysuplex
I used to love when I lived in a slightly drier climate and when I’d walk out of an AC’ed building the air that hit me felt like opening an oven. It was nice but I feel like the sun was less hot Now the air temp feels similar but the sun beats down so hard even with a hat and sunscreen that I can’t stay outside long just because of the sun, not the air temp.
I grew up in a 100% humidity environment and now I live in a 60%-70% humidity environment and it’s definitely more miserable now. Being outside even briefly from May-November gives me what feels like heat stroke and I’m younger than Adam.
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I used to love when I lived in a slightly drier climate and when I’d walk out of an AC’ed building the air that hit me felt like opening an oven. It was nice but I feel like the sun was less hot Now the air temp feels similar but the sun beats down so hard even with a hat and sunscreen that I can’t stay outside long just because of the sun, not the air temp.
I grew up in a 100% humidity environment and now I live in a 60%-70% humidity environment and it’s definitely more miserable now. Being outside even briefly from May-November gives me what feels like heat stroke and I’m younger than Adam.
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aggies11
Body is weird. It produces it's own heat. In a vacuum the body would overheat and cook itself. It doesn't need the air from a convection oven. It's why water slightly under body temp can still feel warm. We need the air to cool us. If air is cooling us too slowly (but still cooling us) then we overheat and cook ourselves. But not exactly the same as a convection oven, which requires air temp above object temp.
Interesting question would be, what temp in still air, what temp in moving air, and what temp in high humidy sill/vs moving (to ignore benefits of sweat evaporation)
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Body is weird. It produces it's own heat. In a vacuum the body would overheat and cook itself. It doesn't need the air from a convection oven. It's why water slightly under body temp can still feel warm. We need the air to cool us. If air is cooling us too slowly (but still cooling us) then we overheat and cook ourselves. But not exactly the same as a convection oven, which requires air temp above object temp.
Interesting question would be, what temp in still air, what temp in moving air, and what temp in high humidy sill/vs moving (to ignore benefits of sweat evaporation)
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TrogdorBurnin8or
You missed an evocative science method. Wet bulb globe temp isn't calculated. It is tested experimentally by swinging that wet bulb around the tester on a sling at speed. It is a wet bulb globe temp of 35c (later revised to 31c with more conservative assumptions about human biology) that is lethal to everyone. The elderly, with reduced heat elimination capability, start dropping like flies five degrees before that.
This video is great, because everybody understanding this is Important if we want there to still be at least 8 billion people here in fifty years.
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You missed an evocative science method. Wet bulb globe temp isn't calculated. It is tested experimentally by swinging that wet bulb around the tester on a sling at speed. It is a wet bulb globe temp of 35c (later revised to 31c with more conservative assumptions about human biology) that is lethal to everyone. The elderly, with reduced heat elimination capability, start dropping like flies five degrees before that.
This video is great, because everybody understanding this is Important if we want there to still be at least 8 billion people here in fifty years.
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logicalparadox2897
The best way I heard this described is by Veritasium: what we perceive as hot and cold is not temperature itself, but heat transfer. This touching highly conductive surfaces (like an aluminum pole) will feel hotter or colder than their temperature alone would have you guess. Add in convection (wind, radiation (sun beating down on you and reflecting from surfaces around you and hit things around you radiating their own hear, and you have the thermodynamic trinity. Factor in evaporative cooling and you've got a more or less complete working knowledge of heat
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The best way I heard this described is by Veritasium: what we perceive as hot and cold is not temperature itself, but heat transfer. This touching highly conductive surfaces (like an aluminum pole) will feel hotter or colder than their temperature alone would have you guess. Add in convection (wind, radiation (sun beating down on you and reflecting from surfaces around you and hit things around you radiating their own hear, and you have the thermodynamic trinity. Factor in evaporative cooling and you've got a more or less complete working knowledge of heat
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eliahabib5111
One correction, even if your AC works on renewables there is an efficiency issue.
Any machine will create some excess heat as part of its function. So regardless of how the AC is powered after netting the cooling you get inside and the heating your AC cause outside there is more heat in the system that there was before you used your AC.
This is not a reason for now using AC, nor a reason not to switch to renewables (nuclear included.
Fossil fuel will have additional heating effect ON TOP of what your AC would do.
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One correction, even if your AC works on renewables there is an efficiency issue.
Any machine will create some excess heat as part of its function. So regardless of how the AC is powered after netting the cooling you get inside and the heating your AC cause outside there is more heat in the system that there was before you used your AC.
This is not a reason for now using AC, nor a reason not to switch to renewables (nuclear included.
Fossil fuel will have additional heating effect ON TOP of what your AC would do.
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deathhimself1653
Huh, this one I already knew for some tragic circumstances. There have been many cases of heat waves where people turned on fans, only for that to speed up heat stroke and death.
Unfortunately this has happened in prisons quite a lot, because of course, those deemed to have committed crimes don't deserve the 'luxury' of AC or easy access to cool water. The other place this happens is nursing homes, for much the same reason. (We as a society failing to uphold the values we often say we do)
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Huh, this one I already knew for some tragic circumstances. There have been many cases of heat waves where people turned on fans, only for that to speed up heat stroke and death.
Unfortunately this has happened in prisons quite a lot, because of course, those deemed to have committed crimes don't deserve the 'luxury' of AC or easy access to cool water. The other place this happens is nursing homes, for much the same reason. (We as a society failing to uphold the values we often say we do)
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randomnerd6709
The other part of the cooling of evaporation comes from the fact that all the water molecules have bonds with each other, which are especially strong because water is polar so it’s charges are uneven. It takes energy for the bonds to break so some molecules can drive off into the sunset and that energy comes from slowing down the other molecules which adds to the cooling, like if several cars smash into a still car to send it away and then they all end up staying still in a pile up
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The other part of the cooling of evaporation comes from the fact that all the water molecules have bonds with each other, which are especially strong because water is polar so it’s charges are uneven. It takes energy for the bonds to break so some molecules can drive off into the sunset and that energy comes from slowing down the other molecules which adds to the cooling, like if several cars smash into a still car to send it away and then they all end up staying still in a pile up
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tonycz1592
In addition consider your micro-environment and radiation heat transfer. In open spaces seek shade. If no shade make your own by hats loose flowing clothing and parasols. For your greenhouse use the fan to exhaust the sun heated air and add a son shade over all the surfaces exposed to sun during the day. Engineering nerd in Phoenix. Good job explaining g the science that my best teachers have transferred since high school college and associates work g around this earth
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In addition consider your micro-environment and radiation heat transfer. In open spaces seek shade. If no shade make your own by hats loose flowing clothing and parasols. For your greenhouse use the fan to exhaust the sun heated air and add a son shade over all the surfaces exposed to sun during the day. Engineering nerd in Phoenix. Good job explaining g the science that my best teachers have transferred since high school college and associates work g around this earth
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Acc_Expired
I think an important aspect of your traffic analogy is that the reckless driver gets to go fast because he is cutting other people off, which then slows them down!
Energy is conserved, so for every bit more kinetic energy an evaporating molecule gets, it has to take it from another molecule. It isnt just that the fastest molecules evaporate, its that those molecules used to be slow, took energy from their neighbors, and then absconded with that energy.
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I think an important aspect of your traffic analogy is that the reckless driver gets to go fast because he is cutting other people off, which then slows them down!
Energy is conserved, so for every bit more kinetic energy an evaporating molecule gets, it has to take it from another molecule. It isnt just that the fastest molecules evaporate, its that those molecules used to be slow, took energy from their neighbors, and then absconded with that energy.
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CamelCaseCam
Your evaporative cooling explanation is missing something important: it takes extra energy to turn something from a liquid to a gas.
In a liquid, water molecules have a bunch of weak forces tying themselves together. This is why the water doesn't just fly away. When you turn water into a gas, you need to put in extra energy to push against these forces. This energy comes from the heat of the surroundings, which cools you and the remaining water.
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Your evaporative cooling explanation is missing something important: it takes extra energy to turn something from a liquid to a gas.
In a liquid, water molecules have a bunch of weak forces tying themselves together. This is why the water doesn't just fly away. When you turn water into a gas, you need to put in extra energy to push against these forces. This energy comes from the heat of the surroundings, which cools you and the remaining water.
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