wetsuits and wool

[jviehe]

I recently had a discussion with someone in regards to the use of wool as a liner in wetsuits to keep you warmer. Im interested in the physics behind this. Im referring to specifically the Pinnacle line of wetsuits which use Merino wool. Pinnacle explains the benefits of the wool here:

http://www.digitaligual.com/pinnacleaquatics7/html5/merino.htm

Now, Ive always thought it was common knowledge that the water in your wetsuit is part of what keeps you warm, as well as the neoprene, though Ive never delved into the physics. Im told by others however that this is wrong, and wetsuit companies lie about it.

Ok, so now add wool, which absorbs water, effectively keeping more water in your wetsuit. Depending on the truth, this extra water will either make you warmer or colder. In addition, Pinnacle states that the wool is exothermic, that it generates heat when wet.

So, could someone try and explain what the truth about water and wool is, and explain the physics behind it?

 

[WarmWaterDiver]

I've never heard of an exothermic chemical reaction nor heat of mixing effect between water and wool - (unless maybe the wool was made from pure sodium???). I don't remember seeing any episodes of the X-Files with pyrophoric sheep in a rain storm, so I can't lay this at the feet of that show.

There are three mechanisms for heat transfer - conduction, convection, and radiation. The sun is an excellent example of radiation as heat transfer - so is a typical industrial furnace. Conduction is dependent on contact between surfaces of objects. Convection depends on fluid flow patterns, and is the only method dependant on fluids. A 'woolly' insulation layer restricts fluid movement and therefore heat transfer via conduction - whether it's home attic insulation, a blanket on your bed, or wool inside a coat liner. That's why good insulation is very fibrous - it restricts the mean free path for any fluid current before distrubing the flow.

A wetsuit, if properly fitting, lets a thin layer of water inside between the skin and inner wetsuit surface, and then minimizes further flow of that water, minimizing heat transfer via convection. The wetsuit material itself helps minimize heat transfer via conduction, but in a fluid environment (whether air, water, or other fluid) convection is usually the predominant mode heat transfer is accomplished.

Hope this helps!

 

[SoCalOffshore]

All I know is that their suits are very nice and work great.

 

[Bob3]

The only way it could have any possible benefit would be to take up room in loose areas, & eliminate some "sloshing". Basically they're trying to scam the folks that slept through physics class in high school, just like the "radiant foil lining" that supposedly reflected your body heat back, another impossibility.
I don't do business with companies that are that full of BS. :wtf:

 

[bob1dp]

Wool is one of a handful of materials that maintain body warmth when wet. I went dry caving a couple of years ago. Knowing I’d get wet I went to a thrift store and loaded up on wool clothing. We cam across an underground lake and swam the 30 yards across it. The water was 50 degrees and didn’t seem cold. I continued with the caving a soaking clothes for another hour with out feeling chilled. Go Figure.

 

[jviehe]

The only way it could have any possible benefit would be to take up room in loose areas, & eliminate some "sloshing". Basically they're trying to scam the folks that slept through physics class in high school, just like the "radiant foil lining" that supposedly reflected your body heat back, another impossibility.
I don't do business with companies that are that full of BS. :wtf:

We arnt in the regular forums here, we are in the physics forum. If you have something to contribute related to the physics of this, please do. Otherwise, keep your negative comments to yourself.

 

[Mako Mark]

Merino wool is particularly known for its insulating properties and durability, the Merino sheep is particularly well adapted to cold wet high country weather, so there must be something in it.

I think the idea of preventing "sloshing" is probably a large part of how it works too. We all know that water movoement in a wetsuit compromises its thermal properties.

Regarding the foil or titanium linings, I think these actually work too. I have had wetsuits with and without the foil, and there is definately a feeling of warmth when the skin is kept in contact with the lining.

 

[jviehe]

Oddly enough I came across this on Rodales which states the water and wool thing are myths. Not too many details, but it makes some kind of sense.

http://www.scubadiving.com/gear/exposure_protection/wetsuit_hype:_10_big_lies/0/

They dont address the exothermic claim, but the practical aspect of all this seems to be get whatever has the least amount of water in it. Which would translate to better fit, and no fibers.

 

[WarmWaterDiver]

They missed the boat though in Rodale's article though stating conduction between water and your skin is the dominant mode of heat transfer. In a fluid media, warm fluid rises and cool fluid sinks (in a gravity well like planet Earth). Even if your completely still while immersed, the film of water against the skin rises when warmed, and is replaced by cooler fluid which rises when warmed, which . . . this is called natural convection. Add motion such as descending, swimming, ascending, etc. to what comprises 'scuba diving' and it's easily demonstrated that convection dominates.

Cancun Mark is right on that the 'skin on skin' fit feels warmer, as this is minimizing gaps for fluid mobility to occur.

The 'absorbency' of wool is the same mechanism as anything else 'wooly' that provides insulation - restriction of fluid movement to restrict convective heat transfer. Absorbed fluid doesn't move - but 'free' fluid does. I'm still quite puzzled on the exothermic claim - anyone seen this at home in their sink with Woolite and their 'fine washables'? Unless, of course, they are adding something that chemically reacts with water to the wool, like pure metallic sodium, but once it would be all reacted, it would stop providing the exothermic reaction, and provide a few issues with fit testing, shipping, and storage. This part of the claim to me is Marketing folks not knowing what the words they're using mean - see Scubapro and 'overbalanced diaphragm' claims for Mk16 & MK18 first stages now vs. 'balanced diaphragm' just a few years ago with the same internal mechanical design - and I once had a supplier for industrial equipment claim 'uniform randomness' as a quality of their product. I'm still puzzled how, even if one could achieve 'uniform randomness', a Zen concept if I ever heard one, how one would measure it, much less consistently repeat it??

Maybe we should make suits with black lining that are attached to a polar bear fur liner. One of my college Thermodynamics professors was a bit more research focused than industrial applications focused, and taught us polar bears are invisible on ultraviolet photography film. Their hides are black, and hairs are hollow acting like fiber optic fibers, conducting UV radiant energy to the skin. This is why they have to 'pant' sometimes above water and need to submerge to cool off (there's that conductive heat transfer stuff again . . .) Since the red end of the spectrum is the first to go underwater . . . Oh, wait, the UV has to penetrate the outer layer of such a suit's skin - darn, science over marketing claim getting in my way again - must be why I still work in a technical occupation and not a king of infomercials.

 

[Mako Mark]

'uniform randomness' .

:lol:

and I have been thinking that the worlds greatest oxymoron was JUMBO SHRIMP....

Maybe we should make suits with black lining that are attached to a polar bear fur liner. .

This would only work if you turned the suit inside out, now, if anyone can get me such a polar bear suit, I would definately be in for a seal scaring expedition. Who is in?