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Post by radiant on Oct 15, 2009 10:50:29 GMT
1. Humidity is a relative measure. When it is hot, the air can hold more water. "Dry" hot air probably holds as much water as my current surroundings (20C and 58% humidity). It is the amount of water vapour, not the humidity, that determines how effectively the air absorbs radiated heat. 2. I'm sure I've read quite often on sceptic blogs that even CO2 absorbs "to saturation" in a short distance near the surface. While it is a strawman argument I assume it may be true, and as H20 is a more effective absorber, it presumably absorbs to saturation as well. 3. Do you *know* how much heat is transferred by conduction as compared with radiation? My understanding and experience is that air is a good insulator. After all, you can fry an egg on the ground, but the air temperature may only be 35C. No I haven't said anything about it being "ultra hot". The radiation from a material is proportional to its temperature to the power 4. That is a big exponent! And as I followed up, even if the atmosphere cannot lose heat, this means that conduction from the earth will slow down (conduction is proportional to temperature gradient). This means the earth will warm and radiate more, so bypassing the atmosphere. I've only considered the first 10km to be honest. It was not clear to me whether you agreed that rising air would cool. Yes it will cool at a slower rate because it is radiating less. But an equilibrium *will* build up because eventually the surface will stop warming (at somewhere near to 250K) which means the atmosphere near the surface will stop warming which means there is no increase in the energy being transferred to the atmosphere. At this point the *rate* of conduction to the atmosphere will be constant. The rate of net radiation transfer between surface and atmosphere will be constant (ie. the atmosphere doesn't absorb much and doesn't emit much). So the atmosphere won't warm any more. As I said, I do not know what the properties of the upper atmosphere will be. And the properties of an atmosphere with convection will be very different from one without convection. As I've studied stellar atmospheres I know this to be true. i can breathe the air and live while in an unpressurised glider without oxygen at 14000 feet, do you really think that a hot element at the bottom of a room 14000 feet high is going to warm the air much other than near the ground unless the heat continues without radiation from the atmosphere, when by night and for most of the day the ground is not so hot it can fry an egg? Warm air rises But can you fry and egg on the ground most of the time in arizona? Here is somebody who tried and failed. phoenix.about.com/od/arizonapicturesandphotos/ig/Fry-an-Egg/Fry-an-Egg-12.htmI thought dry air was a good insulator if convection is inhibited but apparently Argon is better for double glazing and is used in double glazing Which majorly seems to reinforce Kiwis argument for at least n2 02. www.boccryospeed.co.uk/cryospeed/applications/double_glazing/index.aspAn argon gas fill reduces heat loss in sealed units by slowing down convection movement in the space between the panes of glass. The insulation properties of argon are a result of it having a greater density than the density of air. The density of Argon is 1.784g per liter Air is 1.29 But presumably there is a mass of science out there on how to reduce convection in gas mixtures for double glazing? Anyway........ Desert surfaces and near ground air cool rapidly at night because there is such low water vapour present even though they are covered with warm air. The santa ana wind begins cold and dry in the high deserts. Consider these points please
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Post by steve on Oct 15, 2009 11:51:44 GMT
The warm air will rise as long as it continues to be warmer than the air around it. I am not and have never disagreed that convection is an important way in which energy is transferred around the atmosphere.
If the air at 14000 feet were colder than normal, then convection would be allowed to build up which will warm it. If the air at 14000 feet is warmer than normal (descending air in high pressure, or a temperature inversion), convection is suppressed. That is why the atmosphere temperature profile is *dependent on* the rate at which a rising parcel of air cools down.
If the air loses part of its ability to cool because it contains no greenhouse gases, then the atmosphere may act to suppress convection compared with an atmosphere *with* greenhouse gases.
This means the air at the surface won't rise as quick, or it will take longer for the ground to warm it enough to make it rise. In either case, the result is that the ground warms a bit more. If the ground warms it loses more energy to space so gets to equilibrium by that method rather than by transferring more energy to the atmosphere. This means that the warming process does not continue to warm the atmosphere forever.
So, as I said at the very start, I think convection will continue in this greenhouse-gas free atmosphere which means that I think that the temperature profile of the atmosphere will follow the profile of our atmosphere in falling about 10C per 1km gain in altitude (up to the point where convection remains important).
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Post by radiant on Oct 15, 2009 12:11:00 GMT
The warm air will rise as long as it continues to be warmer than the air around it. I am not and have never disagreed that convection is an important way in which energy is transferred around the atmosphere. If the air at 14000 feet were colder than normal, then convection would be allowed to build up which will warm it. If the air at 14000 feet is warmer than normal (descending air in high pressure, or a temperature inversion), convection is suppressed. That is why the atmosphere temperature profile is *dependent on* the rate at which a rising parcel of air cools down. If the air loses part of its ability to cool because it contains no greenhouse gases, then the atmosphere may act to suppress convection compared with an atmosphere *with* greenhouse gases. This means the air at the surface won't rise as quick, or it will take longer for the ground to warm it enough to make it rise. In either case, the result is that the ground warms a bit more. If the ground warms it loses more energy to space so gets to equilibrium by that method rather than by transferring more energy to the atmosphere. This means that the warming process does not continue to warm the atmosphere forever. So, as I said at the very start, I think convection will continue in this greenhouse-gas free atmosphere which means that I think that the temperature profile of the atmosphere will follow the profile of our atmosphere in falling about 10C per 1km gain in altitude (up to the point where convection remains important). I agree the earth and its atmosphere will be colder at the surface layers!!!!!!!!!!!!!!!!!!!! Allow that idea to enter your brain The earth will be cooler!!!! Then consider what temperature is measured by a molecule in a vacuum that strikes a thermometer with enormous energy And then think about some of your answers here Are the most energetic hot molecules of the atmosphere going to be near the (50%cold 50% hot) and therefore warm surface if they can never be cooled unless they are at the 50% cold surface or they are warming the atmosphere and hot air rises?? You have already agreed the air will rise if it is warmer than the air around it. No heat can leave the atmosphere unless it reaches the surface and hot air rises For example in the morning is it going to be colder at the surface? Or is this some law of the new climate science that it can never be possible because overnight the entire warm atmosphere reaches the earths cold surface???
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Post by radiant on Oct 15, 2009 12:40:48 GMT
I thought dry air was a good insulator if convection is inhibited but apparently Argon is better for double glazing and is used in double glazing. Which at first sight majorly seems to reinforce Kiwis argument for at least n2 02. www.boccryospeed.co.uk/cryospeed/applications/double_glazing/index.aspAn argon gas fill reduces heat loss in sealed units by slowing down convection movement in the space between the panes of glass. The insulation properties of argon are a result of it having a greater density than the density of air. The density of Argon is 1.784g per liter Air is 1.29 But presumably there is a mass of science out there on how to reduce convection in gas mixtures for double glazing? So heat loss from a hot surface via the airs convection is significant even for tiny layers
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Post by steve on Oct 15, 2009 13:57:04 GMT
The above is ambiguous. Do you mean:
"I agree the earth and its atmosphere will be colder at the surface layers than higher up in the atmosphere"
or
"I agree the earth and its atmosphere will be colder at the surface layers on my hypothetical N2/O2 planet than on the real earth"
Because I agree with one of these statements but not the other.
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Post by byz on Oct 15, 2009 16:01:47 GMT
I thought dry air was a good insulator if convection is inhibited but apparently Argon is better for double glazing and is used in double glazing. Which at first sight majorly seems to reinforce Kiwis argument for at least n2 02. www.boccryospeed.co.uk/cryospeed/applications/double_glazing/index.aspAn argon gas fill reduces heat loss in sealed units by slowing down convection movement in the space between the panes of glass. The insulation properties of argon are a result of it having a greater density than the density of air. The density of Argon is 1.784g per liter Air is 1.29 But presumably there is a mass of science out there on how to reduce convection in gas mixtures for double glazing? So heat loss from a hot surface via the airs convection is significant even for tiny layers Please don't use any of the rubbish calculations around double glazing they don't work. I covered this in "A" level physics in the early 1980's (when "A" levels meant something) if you do the standard calculation it works out that there is no point having windows at all as the glass panes would allow the heat to transfer out in seconds. The the gap in double glazing is far too small it needs to be about 4 cm to make a difference. The calculations never take into account that cold air tends to stay closer to a cold surface (try blowing smoke across a cold surface and you will see that the smoke floats 1-2cm above the surface) this is why curtains work as they trap the cold air and more importantly stop drafts. Having lived in a house without double glazing and one without the main benefit is that the inner surface of glass in double glazing is not as cold and so you don't get as much condensation (as long as the glass doesn't make contact with the aluminium frame, in which case it doesn't work very well). Sorry to go off topic slightly but please please don't use the standard calculations as they ignore the real physics. The standard calculations for double glazing said that the class in which we were studying (which had windows completely down two walls) would require a 100 KW heating system which was complete B*ll*cks!! Buy thick long curtains or even better wooden shutters
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Post by radiant on Oct 15, 2009 20:28:48 GMT
I thought dry air was a good insulator if convection is inhibited but apparently Argon is better for double glazing and is used in double glazing. Which at first sight majorly seems to reinforce Kiwis argument for at least n2 02. www.boccryospeed.co.uk/cryospeed/applications/double_glazing/index.aspAn argon gas fill reduces heat loss in sealed units by slowing down convection movement in the space between the panes of glass. The insulation properties of argon are a result of it having a greater density than the density of air. The density of Argon is 1.784g per liter Air is 1.29 But presumably there is a mass of science out there on how to reduce convection in gas mixtures for double glazing? So heat loss from a hot surface via the airs convection is significant even for tiny layers Please don't use any of the rubbish calculations around double glazing they don't work. I covered this in "A" level physics in the early 1980's (when "A" levels meant something) if you do the standard calculation it works out that there is no point having windows at all as the glass panes would allow the heat to transfer out in seconds. The the gap in double glazing is far too small it needs to be about 4 cm to make a difference. The calculations never take into account that cold air tends to stay closer to a cold surface (try blowing smoke across a cold surface and you will see that the smoke floats 1-2cm above the surface) this is why curtains work as they trap the cold air and more importantly stop drafts. Having lived in a house without double glazing and one without the main benefit is that the inner surface of glass in double glazing is not as cold and so you don't get as much condensation (as long as the glass doesn't make contact with the aluminium frame, in which case it doesn't work very well). Sorry to go off topic slightly but please please don't use the standard calculations as they ignore the real physics. The standard calculations for double glazing said that the class in which we were studying (which had windows completely down two walls) would require a 100 KW heating system which was complete B*ll*cks!! Buy thick long curtains or even better wooden shutters I am in Finland and people in scandanavia know about glazing to prevent heat loss. We have triple glazing We have an outer layer of glass with a ventilated space to outside with a 12cm gap to the double glazing unit. A bit like a narrow greenhouse outside each double glazing unit. The ventilated space has a white venetian blind Both the walls and windows here both appear to have a similar very high ability to not feel cold in the coldest -30 air But no doubt it is possible to make a look alike system that does not perform this well
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Post by radiant on Oct 15, 2009 20:33:16 GMT
The above is ambiguous. Do you mean: "I agree the earth and its atmosphere will be colder at the surface layers than higher up in the atmosphere" or "I agree the earth and its atmosphere will be colder at the surface layers on my hypothetical N2/O2 planet than on the real earth" Because I agree with one of these statements but not the other. I agree the earth and its atmosphere will be colder at the surface layers on my hypothetical N2/O2 planet than on the real earth So the next question is and one i just asked, Do you agree it will be colder at the surface of the planet and the atmosphere in the morning and the heat of the atmosphere will still be there higher up?
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Post by stranger on Oct 16, 2009 0:01:48 GMT
Unless you have a vacuum between the panes, double glazing will not do much of anything to decrease heat transfer. Triple glazing is somewhat better but it is about on par with a quarter inch of fiberglass. That is the reason "energy efficient homes" have relatively small windows.
The main advantage of double and triple glazed windows is the relative absence of air intrusion. A little cold air will cool a lot of room temperature air.
Argon is used because it displaces air, including the water vapor. And since it is denser than "air" it's a bit easier to work with.
Stranger
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Post by radiant on Oct 16, 2009 3:16:39 GMT
Unless you have a vacuum between the panes, double glazing will not do much of anything to decrease heat transfer. Triple glazing is somewhat better but it is about on par with a quarter inch of fiberglass. That is the reason "energy efficient homes" have relatively small windows. The main advantage of double and triple glazed windows is the relative absence of air intrusion. A little cold air will cool a lot of room temperature air. Argon is used because it displaces air, including the water vapor. And since it is denser than "air" it's a bit easier to work with. Stranger Do you have a reference for this? Argon is used probably because it has a lower thermal conductivity than air and so it reduces convective mixing and therefore heat transfer across the glass gap. BOC say this low conduction property is related to density. www.engineersedge.com/heat_transfer/thermal-conductivity-gases.htmHumans can comfortably survive horribly cold temperatures by wearing clothes such as furs that trap air. When air is cold it holds almost no moisture content so the trapped air is dry air Dry air is a known insulator So you have glass which is a poor ir transmitter then gas which is a poor conductor and ir transmitter followed by glass again. Providing the gas does not travel from side to the other heat cannot be easily transferred or radiated thru the glass. In dry conditions heat will radiate out from a room to the coldness of space if there is no protection from this. Importantly U-Value measures how well a material will conduct heat which is different to how well ir radiation passes thru it R values also include the U value part but include radiative transfer thru the glass also Therefore if you blow warm air against a glazing unit then conduction thru the unit is more important than a colder average radiation passing thru it to cold space. Test conditions and theories might then get a result which is not necessarily accurate for the realities of the problems encountered in the real world. All i know is that my triple glazing provides great comfort in very cold sub -20C conditions
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Post by steve on Oct 16, 2009 9:55:43 GMT
So the next question is and one i just asked, Do you agree it will be colder at the surface of the planet and the atmosphere in the morning and the heat of the atmosphere will still be there higher up? I expect the surface of the planet will be 250 degrees or so on average (though the diurnal cycle will be more extreme due to more rapid cooling at night which makes it harder to think about "average temperatures"). I agree that if the atmosphere is warmed, then it will lose the energy more slowly because of its much lower emissivity. But I think the atmosphere will probably obtain and maintain a balance in which it gets about 10C colder for each km rise in height (due to adiabatic cooling) because the low absoptivity means the amount of radiative heating at the surface will also be reduced.
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Post by steve on Oct 16, 2009 10:08:05 GMT
From a UK perspective I would imagine that double glazing helps in three ways:
1. Better sealing compared with single-glaze which tends to imply old-fashioned, draughty units. 2. Possibly better glass that restricts passage of infrared. 3. The gas that fills the units presumably also helps - though when I've had units where the seal has broken, the difference is not so noticeable.
Incidentally, in the UK, a lot of people will spend £5000 on new windows, but they won't spend £2-300 on much more effective cavity wall insulation and loft insulation, which I guess is a triumph of marketing and dodgy statistics over practicality.
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Post by poitsplace on Oct 16, 2009 11:03:36 GMT
Incidentally, in the UK, a lot of people will spend £5000 on new windows, but they won't spend £2-300 on much more effective cavity wall insulation and loft insulation, which I guess is a triumph of marketing and dodgy statistics over practicality. Yep, this is one of my big beefs with most current alternative energy projects. Everyone's going for high tech stuff that costs WAY too much to be of any practical use...and ignores things that are sometimes essentially free. Everyone shrinks away from any hint of practicality and demands ENTIRELY "carbon free" technologies. Why the heck won't they settle for solar-thermal electric plants with a natural gas/oil/coal backup? Why won't they add simple forced air solar heat or solar water heaters to their homes? They just keep demanding crazy, virtually useless nonsense as if it was a "solution" and then pregnant dog that "big oil" is just being evil and lying...when energy companies are actually just being practical. They DO have some experience with these things, after all. They know all too well that energy is useless unless it's there when you need it.
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Post by nemesis on Oct 16, 2009 11:13:22 GMT
My parents' Victorian built house had very large windows. The single glass panes were much thicker than those made today and proved to be very good insulators of noise and temperature. I have no scientific explanation why this should be so.
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Post by radiant on Oct 16, 2009 12:51:08 GMT
So the next question is and one i just asked, Do you agree it will be colder at the surface of the planet and the atmosphere in the morning and the heat of the atmosphere will still be there higher up? I expect the surface of the planet will be 250 degrees or so on average (though the diurnal cycle will be more extreme due to more rapid cooling at night which makes it harder to think about "average temperatures"). I agree that if the atmosphere is warmed, then it will lose the energy more slowly because of its much lower emissivity. But I think the atmosphere will probably obtain and maintain a balance in which it gets about 10C colder for each km rise in height (due to adiabatic cooling) because the low absoptivity means the amount of radiative heating at the surface will also be reduced. According to your own words the surface is going to be incredibly hot because it is not cooled either by significant conduction or any of the agreed none radiation. So according to you the surface is going to be very hot but the atmosphere colder 500 feet higher? So all that heat for 5 billion years and local higher atmosphere is mysterious cold when it can never cool unless it for some reason can descend against gravity to cool? Meanwhile even double glazing with air or with argon has issues with conduction and convection in a tiny layer of gas, argon being used because it has almost half the conduction of air due its mass.
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