Maximum evaporative cooling from sweat?

[shane c]

After your sweat evaporates and cools immediate skin it was upon, is the ideal then to have that resultant vapor whisked away as quick as possible, so to be promptly replaced with new hot/dry air, or not?

 

Can one be expelling and replacing it too quickly, like when hot/dry windy with no shirt, then wasting some of your sweat evaporating ‘coolth’ potential?

And, if so, would it not be best, <span style=”text-decoration: underline;”>if you could do it</span>, that all sweat evaporates directly off skin rather than some getting shirt wet and then that portion always evaporates off it, often billowing away at a distance, and much of it directly cooling to the outside of the shirt being whisked away and not even to the inside of the shirt, closer to skin?

If that’s all true, then would not this be best to maximize cooling from sweat, to have it evaporate where you want and keep cooler vapor from being too quickly whisked away, replaced with hotter coming in, <span style=”text-decoration: underline;”>if it could be done</span>;

Naked, or nearly so, body under 3/4 length, just below knees, loose wind or rain poncho, that was effectively largely held away from skin, especially at top chest, shoulders and around head so incoming air from below, aided by movement, could freely circulate up all the way to and around neck and head and then exhaust out at neck and around face? Maybe adjustable slit opening in back of neck, too.

Again, <span style=”text-decoration: underline;”>if it could be done</span>, to where enough air circulated freely up and out fast enough, would that not achieve the maximum cooling per ounce of sweat, as long as it wasn’t dripping off to the ground first?

BTW, I’m thinking more for in hot/dry desert where I rarely ‘wet’ sweat anyways, where humidity often so low it evaporates too fast, shirt is never wet, just my back from pack and under belt.

Also, garment would be close to white for reflecting solar radiant heat and being wind proof, that’d cut down on hot dry wind excessively adding to internal heat load.

To aid more air more freely circulating, I was thinking a lightweight curved U of any flexible slim rod coming out a couple inches at 45 degree angle near top front of shoulder straps to hold loose poncho or wind/rain jacket both up off shoulders and out a bit in front of chest.

Anyways, tell me what I’m missing here, or why only rare occasions where it might maybe help, thus too little potential cooling gain for the effort expended. Thanks for any thoughts.

[Mina Loomis]

Kind of like a Bedouin robe?

[shane c]

Mina, yes, but lighter, single layer, not absorbent and, most importantly, more airspace around shoulders and chest for higher volume of air to move more freely up from bottom to next get out around neck and head.

[David Thomas]

My mind, like Mina’s, immediately went to a Bedouin robe.  I theorize that it works by insulating the wearer from the high temperatures outside (air temperature, but also solar input on the outer layer) while allowing enough dry air through to provide evaporative cooling of sweat off one’s skin.

Without the insulating layers, though, I don’t think it would work.  Consider how hot a tent gets in the sun.

Maybe a bigger, whole-body version of this, a solar-powered fan:

[shane c]

David, where you’d written; “Without the insulating layers, though, I don’t think it would work.”

I was thinking similar, that it might help if cooler evaporated air inside was insulated from hotter air outside, but with added bulk/weight ideally it needs to also then be duel use. like as part of sleep system and/or cold weather garb that you then could reduce need for them some.

[David Thomas]

I think insulation from the high heat outside might work in a very dry environment and when you’re not doing a lot of work.  If you’re hiking in the heat of the day, I don’t think it will work, because you’ll be generating so much heat that needs to be dissipated somehow.

When hiking in the heat, what works best for me is light-colored, thin cotton clothing (LS shirt and short pants), keeping those moist with sweat or, preferably, with stream water, and creating my own shade with a large hat if need be, but a UL umbrella is more effective and more comfortable.

[Ben H.]

I think naked is best, if you only want to maximize cooling.  I think the Bedouin robe is very cool for being fully clothed, but I doubt it is cooler than being naked.  The Bedouin robe has a second function of protecting your skin from the sun.  Hot, sunny climates people prefer large billowy clothes to protect you from the sun, but also promote circulation to whisk away sweat.  Hot, shady climates (like the jungles of Africa, South America, or South East Asia) people tend to dress nearly naked.  They have to deal with the heat but not the sun.

It is possible to protect yourself from the sun and to allow enough circulation to not trap heat: the noble umbrella.  So if you have to deal with sun and all you care about is being as cool as possible, then I suggest walking around naked with an umbrella (pictures not needed!).

[David Thomas]

Staying cool and avoiding solar exposure (while nearly naked) has long been figured out.  And, yes, it involves an umbrella.

Mine, however, weights 8 ounces and I can secure it in my chest pocket and through a strap on my pack to hike with it, hands-free (someone else’s photo):

[Author]

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