Water chill factor

[divad]

How is it calculated (vis a vis wind chill factor)?

 

[Steve_C]

Cold water chills faster than air but I have not heard of a Water Chill factor.

Wind can speed up evaporation and carry heat away.

Water can hold/take on much more heat than air can.

I think that the main parameter is just the temperature of the water, and perhaps whether it is salty or not since that effects density and hence heat capacity.

Are you perhaps asking how much faster water, for a given temp difference, can take up heat than air?

 

[Akimbo]

I have never seen a factor for water moving past your skin, probably because the water thermal conductivity is about 25x faster than air.

 

[divad]

Are you perhaps asking how much faster water, for a given temp difference, can take up heat than air?

Yes, in part.

---------- Post added February 6th, 2015 at 08:27 PM ----------

I have never seen a factor for water moving past your skin, probably because the water thermal conductivity is about 25x faster than air.

Sorry, I meant static in fresh water @,say, 46 degrees, what is the equivalent temperature on land with no wind.

 

[Kharon]

The temp is exactly the same - the temp loss is not. Wind chill is a measure of how much temp loss occurs due to air movement (wind). In water your temp loss is much greater than in air. Water chill makes no sense. There is no additional temp loss - except perhaps in current.

 

[tursiops]

The temp is exactly the same - the temp loss is not. Wind chill is a measure of how much temp loss occurs due to air movement (wind). In water your temp loss is much greater than in air. Water chill makes no sense. There is no additional temp loss - except perhaps in current.

I fixed this to be a bit more accurate....

The temp is exactly the same - the heat loss is not. Wind chill depends on how much heat loss occurs due to air movement (wind), and how equivalently cold that would feel if there were no wind. In water your heat loss is much greater than in air, even without current. The additional heat loss in non-moving water -- cmpared to non-moving air -- is considerable, because the thermal conductivty of the water is much higher than that of air...so you lose heat (as if the wind were blowing in air) and feel colder.

It is actually pretty good question from the OP, but I don't think there is a known answer. If I get motivated, I might try and work out an approximation.

 

[DaleC]

I get what you're asking:

If you stand in calm air at 46F you will chill to hypothermic levels in X time.
If there is a 20mph wind you will chill to hypothermic levels in Y time.
If you are submerged in 46F water you will chill to hypothermic levels in Z time.
What is Z?

I don't know the answer.

 

[RJP]

I get what you're asking:

If you stand in calm air at 46F you will chill to hypothermic levels in X time.
If there is a 20mph wind you will chill to hypothermic levels in Y time.
If you are submerged in 46F water you will chill to hypothermic levels in Z time.
What is Z?

I don't know the answer.

I have never seen a factor for water moving past your skin, probably because the water thermal conductivity is about 25x faster than air.

Seems as if Z= 25x faster than X

 

[eponym]

EVAD: are you asking "How much colder does it seem in 10C/50F water than in 10C/50F air?"

It would make sense to say the answer depends on how long we are immersed, yes?
But anyone who's dropped into 80F water from 80F air (without thermal protection) feels a difference "immediately", no?

 

[divad]

If wind chill can be calculated, then why can't water chill be calculated? I'm a simple person and I can't figure it out.