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Author Topic: Why Does It Feel Colder Being In Water That Is The Same Temp As Air ?  (Read 12320 times)

neilep

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Dearest Klevur Peeps Whom Are Authorities On the Stuff They Know ,


As a sheepy I of course luff to swim.....out of all the immersing my body in water and splashing about activities that there are..swimming is my all time fave.

look, here I am enjoying some swimming fun !


Me Swimming Yesterday.


Don't be fooled, ewe know how the light can fool ewe in water  ..that's bona fide me alright !


Now that water was a very nice 23 degrees. .....thing is...so was the air temperature. So, when I got out of the pool and had dried myself off I felt considerably warmer than when I was in the water of the exact same temperature.

Why's that then....despite the temperatures being exactly the same ...why did I feel colder in the water ?


I so wish I knew !...I plan to have a pool party and I need to be ready to answer this kweschun should any of my sheepy pals ask it !..and they are a curious bunch..I am sure when they notice that the pool and air temp are the same that they will be queuing up expecting explanations !



Hugs et shmsihes


mwah mwah mwah



Neil
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RD

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With water or air at 23oC your body temperature is at least 13oC higher, so either in water or air  you’re  going to loose heat to the fluid surrounding you, (air is a fluid).

The thermal conductivity of water is over twenty times greater than air, so if all other variables are equal then in water you’re going to lose heat much faster to your surroundings than in air.

The movement* of the fluid surrounding you would affect the rate of heat loss: moving through the water when swimming will result in faster heat loss than if the colder fluid surrounding you was still.

If you’ve ever fallen asleep in a bath which has gone cold you may have experienced this phenomenon: when you wake up the bathwater doesn’t feel too cold but gets much colder immediately when you move. The comparatively still water next to your skin has been warmed up by your body.  Disturbing the water by moving brings colder water in contact with your skin and results in more rapid heat loss.

[* cf wind chill]
« Last Edit: 28/08/2009 12:50:02 by RD »

Karen W.

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Wow Neil.. What a cool question and applicable to my pool days also.

Rd that is interesting! How long would it take for your body to warm the entire tub of water?

RD

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How long would it take for your body to warm the entire tub of water?

If the bath water is colder than you then you will warm it up a tiny bit as soon as you enter it.

The heat output of the human body is only 100 watts, a water tank heater will be a few thousand Watts.

[BTW The water in the bath would not all be at the same temperature].


 
« Last Edit: 01/09/2009 10:21:04 by RD »

neilep

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RD is great...thanks RD for being RD.

Karen W.

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With water or air at 23oC your body temperature is at least 13oC higher, so either in water or air  you’re  going to loose heat to the fluid surrounding you, (air is a fluid).

The thermal conductivity of water is over twenty times greater than air, so if all other variables are equal then in water you’re going to lose heat much faster to your surroundings than in air.

The movement* of the fluid surrounding you would affect the rate of heat loss: moving through the water when swimming will result in faster heat loss than if the colder fluid surrounding you was still.

If you’ve ever fallen asleep in a bath which has gone cold you may have experienced this phenomenon: when you wake up the bathwater doesn’t feel too cold but gets much colder immediately when you move. The comparatively still water next to your skin has been warmed up by your body.  Disturbing the water by moving brings colder water in contact with your skin and results in more rapid heat loss.

[* cf wind chill]


Thanks RD.

Geezer

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Wait a minute! What about all that wool? Woold it not act as a thermal insulator?

Karen W.

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:) You may have a pint..as wool even warms when wet! Still shouldn't change the surrounding water though would it? When the water moved again would it not have to reheat its perimeter water just as before...or what?

Geezer

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Thanks Karen! Make it Guinness if you don't mind.

Karen W.

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Thanks Karen! Make it Guinness if you don't mind.
Whoops, forgot my "o"...LOL.Sorry!

Geezer

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Rats! I thought you were serious.

BTW, what stroke is Neil doing there? It can't be the doggie paddle. Maybe it's the sheepy paddle?

Nizzle

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I believe it's what we call the "brick stroke"
It's like diving without going back up

Karen W.

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Rats! I thought you were serious.

BTW, what stroke is Neil doing there? It can't be the doggie paddle. Maybe it's the sheepy paddle?


LOL....Come by some time I'll buy you a Guinness but I don't like beer! YUCKKY! Your welcome to it....

LOL,, Sheepy paddling! LOL...
« Last Edit: 02/09/2009 05:23:55 by Karen W. »

Karen W.

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 Poor sheepy...

Karen W.

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Dearest Klevur Peeps Whom Are Authorities On the Stuff They Know ,


As a sheepy I of course luff to swim.....out of all the immersing my body in water and splashing about activities that there are..swimming is my all time fave.

look, here I am enjoying some swimming fun !


Me Swimming Yesterday.


Don't be fooled, ewe know how the light can fool ewe in water  ..that's bona fide me alright !


Now that water was a very nice 23 degrees. .....thing is...so was the air temperature. So, when I got out of the pool and had dried myself off I felt considerably warmer than when I was in the water of the exact same temperature.

Why's that then....despite the temperatures being exactly the same ...why did I feel colder in the water ?


I so wish I knew !...I plan to have a pool party and I need to be ready to answer this kweschun should any of my sheepy pals ask it !..and they are a curious bunch..I am sure when they notice that the pool and air temp are the same that they will be queuing up expecting explanations !



Hugs et shmsihes


mwah mwah mwah



Neil
I like Wet Things
xxxxxxxxxxxxxxxx


Doesn't water evaporation from skin make the water feel colder also.. as the evaporation is happening from the start when ever the air hits the skin?
« Last Edit: 03/09/2009 06:57:54 by Karen W. »

Geezer

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Must have taken Neil a long time to get dry with all that wool, or maybe he went through a carwash and stood in the blow dryer section for a while  ;D

Back to the question: I think the reason you feel a lot warmer in air than water of the same temperature (assuming that temperature is lower than your body temperature) is simply because water is a better thermal conducter than air. Soooo, water can "pull" heat from your body more quickly than air can.

RD

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... water is a better thermal conducter than air.

I refer the honorable gentleman to the answer I gave a few posts ago ...
Quote
The thermal conductivity of water is over twenty times greater than air,
so if all other variables are equal then in water you’re going to lose heat much faster to your surroundings than in air.
http://www.thenakedscientists.com/forum/index.php?topic=25242.msg272381#msg272381
« Last Edit: 02/09/2009 21:43:38 by RD »

Geezer

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Guilty as charged, your Honour  B)
« Last Edit: 02/09/2009 22:34:55 by Geezer »

lyner

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The thermal capacity must also be relevant. Water has a high specific heat capacity and is more dense than air. A given volume of water in contact with your body will remove a lot more heat than the equivalent amount of water for that reason. Of course, the effect will be short lived unless there is some convection. It would only be in wet suits / dry suits that the benefit of air's conductivity would dominate, I feel, because the two fluids are captive. Once there's convection the water is far more effective at cooling because you can get more mass of it in contact and then carry it away.
This explains why there are so few air cooled cars than water cooled. SHC and density count.
« Last Edit: 03/09/2009 07:58:36 by sophiecentaur »

Geezer

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I think you are correct SC regarding heat capacity. We might say that large masses of air or water have enormous heat capacity relative to the heat a sheep can produce, so heat capacity is not relevant, but there must be localized effects as you suggest that are significant in the heat transport mechanisms.

Does "wind chill" depend on the heat capacity of air? I suspect it does.

BTW, I know at least some air cooled engines "cheated" to some extent because they relied heavily on the lubricating oil to remove heat. The oil circuit included an oil cooler. VW advised against the use of multigrade oil in their air cooled cars for a long time. I believe this was because "straight" mineral oil recovers its lubricating properties, even after reaching rather high temperatures, whereas the additives in multigrade oils break down at high temperatures, and the oil's properties are permanently altered. Because of this, I installed an oil temperature gauge in my first VW, but it didn't prevent it from dropping a valve which went on to wreck the entire engine! (I think that was really more to do with the fact that the engine was completely worn out - what do you expect for 35 quid?)

lyner

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Wind chil? Absolutely. It's forced convection.

Geezer

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Wind chil?

Karen W.

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I think you are correct SC regarding heat capacity. We might say that large masses of air or water have enormous heat capacity relative to the heat a sheep can produce, so heat capacity is not relevant, but there must be localized effects as you suggest that are significant in the heat transport mechanisms.

Does "wind chill" depend on the heat capacity of air? I suspect it does.

BTW, I know at least some air cooled engines "cheated" to some extent because they relied heavily on the lubricating oil to remove heat. The oil circuit included an oil cooler. VW advised against the use of multigrade oil in their air cooled cars for a long time. I believe this was because "straight" mineral oil recovers its lubricating properties, even after reaching rather high temperatures, whereas the additives in multigrade oils break down at high temperatures, and the oil's properties are permanently altered. Because of this, I installed an oil temperature gauge in my first VW, but it didn't prevent it from dropping a valve which went on to wreck the entire engine! (I think that was really more to do with the fact that the engine was completely worn out - what do you expect for 35 quid?)

I have owned so many Volkswagon's it is not funny!

Karen W.

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NEILY... STILL WHEN ONE IS IN THE WATER THERE IS A CERTAIN AMOUNT OF EVAPORATION HAPPENING WHILST MOVING AROUND AND SPLASHING WHICH WOULD CREATE A COLDER FEELING IN THE POOL CAUSE WHEN YOU GOT OUT YOU ABSORBED THE WATER INTO A TOWEL ELIMINATING THE EVAPORATION FACTOR WHICH MADE THE SKIN COOL.. wHEN COMPLETELY SUBMERGED THOSE PARTS OF THE SKIN WERE PROBABLY WARM UNTIL YOU MOVED  AND CHANGED THE WATER ON THE SKIN ALLOWING SOME AREAS TO BECOME COOL AS EVAPORATION BEGINS IMMEDIATELY WHEN EXPOSED TO THE AIR.

I HAVE THE SAME THING HAPPEN EVERY DAY IN THE POOL.

Oh poop..sorry about the caps!

lyner

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Wind chil?
Save energy - avoid double leters.

 

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