Optimizing Evaporative Cooling via Sweat in Dry Desert?

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shane2
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Assume a nearly full length thin robe open at top and bottom and largely, somehow, held off a couple inches away from bare naked skin underneath to maximize unrestricted vertical airflow.

Assume desert 120F hot and very dry air can enter/exit at either bottom around ankles or at top around open neck.

When sweat evaporates or vaporizes off skin, cooling the skin there, that resultant vapor exits and more 120F dry air is drawn into replace it.

Is that sweat created moist vaporized air likely to be warmer or cooler than the outside 120F dry desert air?

Which way does it want to naturally flow, up or down?

If vapor is cooler than 120F, would it be preferable then to not move it out too overly fast, which would only draw in even more 120F against skin even faster, adding even more heat load to skin?

I understand additional evaporation requires more dry air replacing that moist vapor, but am trying to optimize just how fast/slow you'd want to do so.

Just fast enough that all sweat presented gets fully evaporated before dripping away to ground, but not so fast that skin gets excessive 120F desert air blast that adds even more heat to skin even quicker, is my thinking here.

Am I missing anything so far?

Next, if any sweat does get onto inside of garment, would it be more efficient for micro-environment there, in cooling skin, if it was impermeable to where when garment sweat evaporated that cooling process (and vapor) was contained onto the inside?

Finally, if from above impermeable garment we could expect the air temp inside garment to be cooler than outside 120F air, would there then not be additional benefit maintaining that cooler micro-environment temp if garment was also insulated against conductive heat gain, too?

Thank you for any thoughts.
 

Answers and Replies

  • #2
Tom.G
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Is that sweat created moist vaporized air likely to be warmer or cooler than the outside 120F dry desert air?
Cooler.

That's the basis for "Swamp Coolers", or Evaporative Coolers, used as a cheaper alternative to Air Conditioning in desert areas.
 
  • #3
Drakkith
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Cooler.

That's the basis for "Swamp Coolers", or Evaporative Coolers, used as a cheaper alternative to Air Conditioning in desert areas.

I thought the cooling of the air was because of the air being blown past the now-cooler surface, not because the evaporated water cooled the air it evaporated into.
 
  • #4
shane2
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I'm a little unclear about that process, too.

When a swamp cooler has hot/dry air blown through it, it cools that air that went through that wet medium via evaporation, yes?

When sweat on skin evaporates from 120F hot/dry desert air moving atop it, if that vapor created then is cooler than 120F, wouldn't we want to have that not whisked away too quickly?

Quick enough for new dry air to evaporate more sweat, yes, but not so quick skin heats up from excessive blast of more hot/dry air?
 
  • #5
Drakkith
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I thought the cooling of the air was because of the air being blown past the now-cooler surface, not because the evaporated water cooled the air it evaporated into.

I'm a little unclear about that process, too.

After a bit more reading, I think that evaporation cools both the surface and the air itself when it evaporates. But I'm really not certain.

When sweat on skin evaporates from 120F hot/dry desert air moving atop it, if that vapor created then is cooler than 120F, wouldn't we want to have that not whisked away too quickly?

If evaporation cools the surface of the skin, then yes, we would want to whisk away that now-humid air so that more sweat can evaporate.
 

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