12 Jul 18
1 edit
Originally posted by @uzlessFor a similar reason I will suppose that rocks aren't colder in the breeze but we are.
...
The air is coming from your lungs so why isn't it at the same temperature?
edit: I forgot to say the temperature is the same, of course. So it is our perceptions that have changed.
12 Jul 18
1 edit
Originally posted by @apathistso you are saying, albeit rather incorherently, that the temperature of the air coming out is the same temperature regardless of whether you whistle softly or heave ho heavily and that the "perceived" temperature difference on our hand is simply due to wind chill? Is that it?
For a similar reason I will suppose that rocks aren't colder in the breeze but we are.
edit: I forgot to say the temperature is the same, of course. So it is our perceptions that have changed.
Well, if i blow at the same SPEED using the two different methods, the temperature on my hand still feels different, although you say it is the same.
if i told you i did this experiment using a thermometer and the temperature was lower when I whistled, would you believe it?
13 Jul 18
Originally posted by @uzlessSorry, I'm not getting the difference between the two cases. Are you saying that the temperature drop is independent of the force with which you expel air, but does seem to depend on how widely you open your mouth?
so you are saying, albeit rather incorherently, that the temperature of the air coming out is the same temperature regardless of whether you whistle softly or heave ho heavily and that the "perceived" temperature difference on our hand is simply due to wind chill? Is that it?
Well, if i blow at the same SPEED using the two different methods, the temper ...[text shortened]... eriment using a thermometer and the temperature was lower when I whistled, would you believe it?
If so then it's due to a greater pressure drop when you have your lips pursed. In each case the air has the same temperature just before it leaves your mouth, but is at a slightly higher pressure when you have your lips nearly shut. With your mouth open more widely there is essentially no pressure drop so the temperature doesn't fall either.
13 Jul 18
1 edit
Originally posted by @deepthoughtso to use your reasoning in an analogy, if you had a ziploc bag that was wide open, the pressure inside the bag would be the same as outside the bag, but if you closed 90% of the ziploc bag somehow the pressure inside the bag would be higher than the pressure outside the bag? even though the bag is not sealed?
If so then it's due to a greater pressure drop when you have your lips pursed. In each case the air has the same temperature just before it leaves your mouth, but is at a slightly higher pressure when you have your lips nearly shut. With your mouth open more widely there is essentially no pressure drop so the temperature doesn't fall either.
Ie even though your mouth is not closed there is a pressure difference between the air in your mouth versus the air when it leaves your mouth? A difference of at least 15`C?
13 Jul 18
Originally posted by @uzlessWell, that's my hypothesis. Bear in mind that the ideal gas law works with absolute temperature. So a temperature drop of 15 Celsius corresponds with a 2.5% change in pressure. I don't think that's unfeasible and I can't think of any other reason.
so to use your reasoning in an analogy, if you had a ziploc bag that was wide open, the pressure inside the bag would be the same as outside the bag, but if you closed 90% of the ziploc bag somehow the pressure inside the bag would be higher than the pressure outside the bag? even though the bag is not sealed?
Ie even though your mouth is not closed ther ...[text shortened]... the air in your mouth versus the air when it leaves your mouth? A difference of at least 15`C?
13 Jul 18
Originally posted by @uzlessNo, I wouldn't. I see no reason to think the tempurature of the air in your lungs changes because of the way you are holding your lips. But your case cannot depend on the way things feel to you. Wind chill proves that.
so you are saying, albeit rather incorherently, that the temperature of the air coming out is the same temperature regardless of whether you whistle softly or heave ho heavily and that the "perceived" temperature difference on our hand is simply due to wind chill? Is that it?
Well, if i blow at the same SPEED using the two different methods, the temperatu ...[text shortened]... experiment using a thermometer and the temperature was lower when I whistled, would you believe it?
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13 Jul 18
2 edits
The temp is the same in both cases ( actually it should be minutely warmer in the case of the whistle from both the action of compression in your mouth, and viscous dissipation as the air passes through your lips ). The whistle "feels" cooler because the coefficients of convection and evaporation are dependent on fluid velocity ( the exact proportionality relationship is undoubtedly complex, but in a general sense its a direct proportionality. increase fluid velocity, increase both capacities to exchange heat.). There is also a time dependency that makes the whistle air "feel" colder. We are in a transient heat exchanging state over both these timescales ( the temperature of your lips is changing), but ask yourself how long the whistle blow is in comparison to the opened mouth puff? There isn't sufficient time to exchange heat through convection or evaporation in the puff, however the whistle blow is much longer per unit volume of air passing through you mouth ( probably even reaches steady state by the time you've expended your breath).
That's just my take on it.
15 Jul 18
4 edits
Originally posted by @uzlessThe air pressure is greater when you whistle. I'm assuming this squeezes heat from the air in much the same way an air conditioner compresses warm gas, causing it to release heat.
How come when you whistle, the air coming out feels coolish, but when you say something forcefully like "HA, HA, HAAAAAAAAA" the air coming out feels warmish?
The air is coming from your lungs so why isn't it at the same temperature?
But what happens to that released heat, where does it go?
The temperature of the surrounding air might also be a factor. If your room temperature is 40°F or 50°F, then whistling on the sensor of a digital thermometer should cause the number to rise rather than fall.
edit: I just now did a little experiment. I held my finger a short distance from my mouth and blew a tight stream of air on it. It felt cool, but then when I held the finger very close to my mouth the air felt warm. So maybe the released head is discharged away from the side of the tight stream of air.
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16 Jul 18
Originally posted by @lemon-lime"The air pressure is greater when you whistle. I'm assuming this squeezes heat from the air in much the same way an air conditioner compresses warm gas, causing it to release heat."
The air pressure is greater when you whistle. I'm assuming this squeezes heat from the air in much the same way an air conditioner compresses warm gas, causing it to release heat.
But what happens to that released heat, where does it go?
The temperature of the surrounding air might also be a factor. If your room temperature is 40°F or 50°F, then whistl ...[text shortened]... lt warm. So maybe the released head is discharged away from the side of the tight stream of air.
You're putting the cart before the horse. The air conditioner doesn't compress the air to "squeeze" out the heat leaving behind a cooler gas. What is happening in the air conditioner is the cool gas (refrigerant at atmospheric pressure and minus 20 ish deg F temperature) absorbs heat from the room, and is then compressed to raise its temperature SO it may exchange heat with a warm environment outside of the room. After the heat exchanger It is then reversibly expanded to restart the cycle.
16 Jul 18
1 edit
Originally posted by @joe-shmoThe comparison has to do with whistling, and what an air conditioner does to expel heat.
"The air pressure is greater when you whistle. I'm assuming this squeezes heat from the air in much the same way an air conditioner compresses warm gas, causing it to release heat."
You're putting the cart before the horse. The air conditioner doesn't compress the air to "squeeze" out the heat leaving behind a cooler gas. What is happening in the a ...[text shortened]... side of the room. After the heat exchanger It is then reversibly expanded to restart the cycle.
It isn't necessary to describe how decompressed gas gathers heat from indoor air, because the point of all this is:
Does whistling produce a stream of cooler air?
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16 Jul 18
1 edit
Originally posted by @lemon-lime"The air pressure is greater when you whistle. I'm assuming this squeezes heat from the air in much the same way an air conditioner compresses warm gas, causing it to release heat.
The comparison had to do with whistling, and what an air conditioner does to expel heat outside. It wasn't necessary to describe how the decompressed gas gathers heat from indoor air.
But what happens to that released heat, where does it go? "
These two statements taken together indicate a misunderstanding, I was trying to correct that...nothing more. Heat is absorbed in a compression, not released.
"Does whistling produce a stream of cooler air?"
I highly doubt it.