Re:Canada weather: Dozens dead as heatwave shatters records
by JeremyNT on Wednesday June 30, 2021 @10:23AM
(#27688912)
How lasting is this effect though compared to evaporative cooling (which lasts for as long as you stay hydrated due to the replenishment of moisture from sweat)? The volume of liquid you're adding to your garment can't be all that much, and if you combine your body heat with a high ambient temperature it seems like the water should reach equilibrium rather quickly.
I don't doubt it helps in the short term - I live in the southeast and I've done this when hiking many times (once my shirt's already soaked from sweat and I can find a cool stream) - but it only provides a temporary respite.
Re:Canada weather: Dozens dead as heatwave shatters records
by phreeza on Wednesday June 30, 2021 @02:28PM
(#27691924)
Here are some numbers: the evaporation enthalpy of water is 2,260 kJ/kg at room temperature. The specific heat of water is 4.2 kJ/(kg*K). So for a given amount of water, the evaporation is "worth" about 500
Kelvin of cooling in terms of energy absorbed.
Re:Canada weather: Dozens dead as heatwave shatters records
by phreeza on Wednesday June 30, 2021 @10:11AM
(#27688758)
If that is the effect you are going for, would wearing a camelback water bladder have a similar effect? It has slightly less surface area to interface with your body, but you can carry a much larger amount of water.
Re:Canada weather: Dozens dead as heatwave shatters records
by mrkstu on Wednesday June 30, 2021 @11:40AM
(#27689839)
And put it in the freezer intermittently...
Re:Canada weather: Dozens dead as heatwave shatters records
by klyrs on Wednesday June 30, 2021 @02:00PM
(#27691605)
Tap water is colder than the inside of the house. Bringing it into the house reduces the heat inside. Putting it into the freezer heats the room that the freezer is in. You're better off replacing the water when it gets warm. Kinda fucked in a drought, though.
In high humidity by wearing a shirt doused in tap water you cool down by heating up your t-shirt. This method does not work if water comes out of your tap already hot. This only happens rarely. In dry environments evaporative cooling helps but it is not necessary to be effective.
I recommend using shirts made of elastic breathable material such as under armor shirts for comfort. Cotton tends to stick to your skin extra and feel really nasty.