From the INSTITUTE OF PHYSICAL CHEMISTRY OF THE POLISH ACADEMY OF SCIENCES
Evaporation for review — and with it global warming
The process of evaporation, one of the most widespread on our planet, takes place differently than we once thought – this has been shown by new computer simulations carried out at the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw. The discovery has far-reaching consequences for, among others, current global climate models, where a key role is played by evaporation of the oceans.
They all evaporate: oceans and seas, microdroplets of fuel in engines and the sweat on our own skin. For every one of us evaporation is of paramount importance: it shapes the climate of the planet, it affects the cost of car travel, and is one of the most important factors controlling the temperature of the human body. So common is it that it seemed that evaporation was a phenomenon that had been stripped of any more secrets. In the renowned scientific journalSoft Matter physicists from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw, Poland, prove that this belief was erroneous and the mechanism of evaporation must operate differently than had previously been assumed.
“Science copes badly with descriptions of processes occurring in nature. We are perfectly able to describe the states at the beginning of the process and at its end. But what happens in between? How does the given process really take place? For so many years we have been asking ourselves this question in relation to the phenomenon of evaporation – and we are coming to ever more interesting conclusions,” says Prof. Robert Holyst (IPC PAS).
In scientific and technical deliberations we use the Hertz-Knudsen equation, known for over a hundred years, to describe the evaporation rate. What follows from it is quite an intuitive prediction: that at a given temperature the rate of evaporation of the liquid depends on how different the actual pressure at the surface is from the pressure which would be present if the evaporating liquid were to be in thermodynamic equilibrium with its environment.
“The further the system is from equilibrium, the more dynamically it should return to it. It’s so intuitive! So we checked the Hertz-Knudsen equation – because we like to check. In order to do this we prepared exceptionally accurate computer simulations which allowed us for the first time to take a closer look at the process of evaporation,” explains Dr. Marek Litniewski (IPC PAS).
Advanced computer simulations carried out using molecular dynamics showed that the values of some parameters describing evaporation are even several times larger than those predicted by the Hertz-Knudsen equation. However, an even more interesting effect was noted: the stream of gas being liberated from the surface of the liquid during evaporation changed very little despite significant fluctuations in pressure.
“There could only be one conclusion from this observation: the rate of evaporation and the vapour pressure, that is, the physical quantities that were previously considered to be closely related, were not so. For more than a century we had all been making a serious error in the theoretical description of the phenomenon of evaporation!,” says Dr. Litniewski.
The hitherto model of evaporation was based on the principle of conservation of mass: the mass of molecules released from the surface of a liquid had to respectively increase the mass of the gas in its surroundings. Physicists from the IPC PAS noticed, however, that since the particles released from the surface have a certain velocity, in order to describe this phenomenon what should be applied is the principle of conservation of momentum.
“We realized that to some extent evaporation resembles shooting from a cannon: the missile flies in one direction, but the overall momentum of the system must be maintained, so the gun recoils in the opposite direction. The same happens with the molecules of evaporating liquid. Since there is an increase in momentum, there must be recoil, and if there is recoil, the pressure felt by the molecules on the surface of the liquid will be different,” says Prof. Holyst.
The new computer simulations were also used to measure the velocities of the molecules released from the liquid surface. They proved to be small, of the order of hundreds of micrometres per second, which corresponds to only a few kilometres per hour. This fact means that practically any naturally occurring flow over the surface of the liquid has to strongly interfere with the evaporation process. The evaporation cannot thus be described by an equation derived for a very specific case, for liquid that is in thermodynamic equilibrium with the environment.
The discovery of the IPC PAS researchers is of the utmost importance for, among others, the understanding of the real mechanisms responsible for global warming. Contrary to common belief, the most abundant greenhouse gas in the atmosphere of our planet is not carbon dioxide but water vapour. At the same time, it is known that the speed of flow of air masses over the oceans can significantly exceed one hundred kilometres per hour and therefore they will certainly affect the rate of evaporation. The hitherto evaluation of the rate of evaporation of the oceans must therefore be subject to error, which will certainly affect the accuracy of the predictions of contemporary models of the Earth’s climate.
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The researchers from the IPC PAS are investigating evaporation in collaboration with the Institute of Physics of the Polish Academy of Sciences in Warsaw, where experiments are being carried out to verify the correctness of the simulations.
Well I’m glad we got that settled. Now we can stop wasting billions of dollars on the green house effect and move on to studying the green horse effect. It was surmised that human CO2 emissions are causing horse sh** to turn greener at an alarming rate. A new “combating sh**” budget was proposed by the White House yesterday. NASA’s director Charles Bolden replied that new facilities will need to be constructed because, in his words, “We’re already up to our eyeballs in this green sh**”.
The Gaudyan reported of a scientist at Penn State University who decided to take an early step into studying of the severity of the green horse sh** problem in terms of determining the rate at which fewer and fewer people are able to notice it on the ground resulting in an alarming increase of tragic slip and fall accidents worldwide. It was noted that the greatest number of injuries are occurring in the poorest countries who are asking the UN to compensate them for the disproportionately larger expense they must bear compared to that of rich countries who unfairly delight in their excesses while burning most of the fossil fuel.
Here is interesting article describing new theory of evaporation- http://arxiv.org/abs/1406.2261
All interesting stuff.
Now what happens if they add some impinging thermal photons to the model?
Does the water get warmer, or does it just increase the rate of evaporation?
Probably both…. Absorption of sun flux causes the temperature increase, which causes evaporation rate increase, that contributes to cooling of the near surface layer, that, if forced mixing is present, contributes to convective cooling of lower layers of water… And all this may reach equilibrium or may always be in transient state… But who, except for us, cares? Definitely the funding agencies don’t care, as they spend huge money on some exotic or Armageddon outcome research. All this evaporation is trivial science that was settled (ha!) last century.
If I put a drop of washing-up liquid onto the surface of a bowl of water will the water evaporate more quickly/slowly or stay the same, assuming no other changes in the environment? It certainly reduces the surface tension.
And as a rider, with all the soapy effluent pushed into the oceans, has the rate of ocean evaporation increased or decreased?
From the above comments, I see I am late in saying color me unimpressed. I guess until now, Polish Academy of Science must have thought that hanging a water bag on the front of landrovers in hot countries was a cultural affectation and not a practical practice. BTW why do all these modern scientific press releases use vague descriptors? Don’t say a moving air mass interferes with evaporation, say it increases evaporation!!
And before the Academy waits for another century, I will advise them that conservation of mass still DOES apply as well as the omnipresent conservation of momentum. While I’m at it, molecules of air masses traveling over the surface of the water collide with the surface and jar loose molecules of H2O. It gets better. Some H2O in the air mass also bumps into the water and joins itself on, too! The surface of the ocean with a hundred km wind has its exposed surface much more than doubled with the corrugation of waves and spray. I have a favorite small beach in Dom. Republic where I go down on a rough water day and breathe in the visible dry salt mist that blows on shore from evaporated spray.
And how about:
“Contrary to common belief, the most abundant greenhouse gas in the atmosphere of our planet is not carbon dioxide but water vapour.”
We have a daily serving of this in the climate science discussions.
I’ve got some 60 year old engineering textbooks somewhere that I could contribute to the academy. Since the progressives have reduced the Nobel Prize to ISO-Crackerjack quality, I guess they could be up for the prize for baroque physics.
Perhaps Polish scientists deserve respect and support. These days it is almost impossible to do research of ubiquitous phenomena like evaporation or substances like water. Science funding agencies look for exotic, Armageddon, or very near term outcome research. That’s why, in particular, the Nobel is reduced to “ISO-Crackerjerk” quality.
Walt, I take your point. But if one has modeled the whole thing, why would it be a surprise that momentum is conserved (and mass, too, of course). I visualize molecules of water oscillating with heating until momentum outstrips the restraining bonds and some of them pop up into the atmosphere – analogous to an ‘escape velocity’ in a gravitational context.. They rightly must have modeled the pull back of the adjoining molecule still in the water for that nanosecond. Presumably they also modeled the cooling effect that would reduce the amplitude of the oscillations of those still in the water. Certainly, wind as a factor in evaporation is huge, not only for the energy of it at the boundary layer but also because of manifold increase is exposed water surface in a roiling sea.
Perhaps they have discovered something but they should isolate exactly what this is. It certainly isn’t that the Hertz-Knudsen equation is inapplicable to situations where it is windy – this was known.
I am sure they could use them. Was looking at the MIT Open Courseware Courses. They are closer to (actually below) the level of my HS courses in Chem, Physics, and Math. It appears College is now Advanced High school.
Aw gee.
So every time I evacuate a refrigeration system to remove water vapour I guess I’ve been wasting my time…cause like water isn’t affected by pressure. (or lack thereof).
Thank God these people remain in the ‘theoretical realm’….please keep them there.
Your irony is understandable. But picture this: Hertz-Knudsen model says that below the temperature that corresponds to vapor saturation there is no evaporation at all! So, clothes hang out in -10C temperature should not dry. And this is foundational model for all modern theories that include evaporation. The Polish scientists show that the evaporation rates can be much higher than expected by H-K model. This is step in correct direction.
There is a water vapor saturation even at -10C. Or even at 30C. Hertz-Knudsen assumes no wind – a condition usually found in a laboratory.
Thanks Walt, I was aware of that. I’m also aware that too powerful a vacuum can have the same effect. However; perfectly dark, perfectly still, perfectly cold circumstances do not occur on this planet…nor do deep vacuums…far as I know.
As a side issue I wonder how many know that the word vacuum has its origins in the Green word for calf?!
Look, this new evaporation theory may be correct, or not, but
The new computer simulations were also used to measure the velocities of the molecules released from the liquid surface
is not true. A computer simulation is NOT a measurement. The simulation is built on a theory and therefore it confirms that theory.
How about some empirical science.
An unknown unknown!
so they discovered wind chill basically.
This could also cast doubt on the validity of Henry’s Law as regards CO2 exchanges with the oceans.
There is no discovery, yet. We should wait for experimental verification. Patiently.
Wind also makes sea spray, increasing surface area of water-air interface by many orders of magnitude. Which is kinda significant.
The wind does not deed to get up that much to create breaking waves, 15 knots or so, which in turn creates ‘white water’ with lots of surface area. Waves break when their slope gets to about 1 in 7. The mechanism also filters energy into the larger, faster waves which survive as ocean swells.
I see Earth as a battery it charges under high pressure systems and discharges from the ground up while under the influence of a low pressure system http://www.av8n.com/physics/anode-cathode.htm
Ocean currents are driven by the flow of electrons and it’s electric charge that drives wind and ocean evaporation https://www.youtube.com/watch?v=wwGx7qqQe-Y
Well duhhhh!
When it evaporates, 1 kG of water draws in enough energy to cool the adjacent 2200 cubic metres of air by 1˚C or thereabouts. As a mechanism it is a few orders of magnitude more intense than the CO2 “greenhouse” effect. And the “Models” have ‘missed’ that. LOL
The “science sure is settled it is pretty clear but the big question folks is just where the hell, in what godforsaken swamp or cess pit, did it settle?
Pretty sure the modelers are aware of heat of vaporisation.
“Every water molecule (H 2 O) consists of one atom of oxygen and two atoms of hydrogen, as shown below. Each hydrogen atom is attached to the oxygen atom by a covalent bond in which the hydrogen atom shares an electron with the oxygen atom. The shared electron is slightly closer to the oxygen atom than to the hydrogen atom.
Fresh Water, Physics and Chemistry of
A water molecule has no net charge because the number of positively charged protons equals the number of negatively charged electrons. However, because the hydrogen ends of the molecule have a slight positive charge and the oxygen end has a slight negative charge, it is called a polar molecule. The negative and positive ends of different water molecules slightly attract each other, forming hydrogen bonds . These hydrogen bonds are about twenty times weaker than the covalent bonds between hydrogen and oxygen.”
Read more: http://www.waterencyclopedia.com/En-Ge/Fresh-Water-Physics-and-Chemistry-of.html#ixzz3pKwmK45x
http://www.waterencyclopedia.com/En-Ge/Fresh-Water-Physics-and-Chemistry-of.html
What makes you think that we can read?
It’s even more complicated than you suggest.
“In the renowned scientific journalSoft Matter physicists from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw, Poland”, Soft Matter seems to be a psuedonym for soft head. Can someone advise these trogdolites that the UN IPCC budget is overspent and to look elsewhere for possible funding?
“The process of evaporation, one of the most widespread on our planet, takes place differently than we once thought – this has been shown by new computer simulations”
Ah. Computer simulations. Right.
( And it should be “takes place differently from the way we once thought”. “Different/ly than” is wrong.)
So these guys got this idea in a bathroom clustered around a hand dryer. A truly novel observation that requires a sophisticated computer model that can not be falsified. My observation is that my hands don’t dry quickly if the blow dryer isn’t turned on. Give me a break! OMG!
“They proved to be small, of the order of hundreds of micrometres per second, which corresponds to only a few kilometres per hour.”
Rewrite the first part as 0.1 mm/s, which equals 0.36 m/hr. One of the measures is off by a factor of 10,000!
These scientists should read Professor Gerald Pollack’s book The 4th Phase of Water, they’re still missing some big points. bit.ly/4thphaseofwater
George E Smith
“Surely people have been measuring evaporation rates under varying conditions for eons.”
Yes they have, for agriculture. Its called Class A Pan Evaporation and it only supports the claimed changes in surface temperature where wind speeds are high, e.g.:
http://onlinelibrary.wiley.com/doi/10.1002/joc.1061/pdf
http://english.cas.cn/bcas/2013_3/201411/P020141121530436552259.pdf
You get almost nowhere with this reasoning. How sensitive are climate models to the linear assumption of Hertz–Knudsen? Where does the equation even show up in models? How does the flux at the immediate surface compare to turbulent transfer in the boundary layer — if one is the bottleneck, the other doesn’t matter too much and you can assume an equilibrium. Who cares when the transfer coefficients are anyway empirically constrained? If you are saying that evaporation is less sensitive to temperature than previously thought, then okay, great, so is precipitation. http://www.nature.com/nature/journal/v419/n6903/fig_tab/nature01092_F2.html Balance is retained. What about empirical data about water vapor concentration sensitivity to temperature? http://www.sciencemag.org/content/296/5568/727.full So let’s say the latent heat flux is suppressed — great, now the ocean is just warmer, and the evaporation rate shoots up again, together with convective instability which further facilitates water vapor transport.
This is lightyears from making a judgement about climate model uncertainty. These new results are probably more important for new cloud droplet paremterizations (and soft matter physics — to be clear the original article doesn’t mention anything about climate, after all this is not climate science).
The H-K equation is irrelevant to the calculation of evaporation of water in the atmosphere–which is controlled by species diffusion and heat transfer,both described by continuum equations.An exception might be evaporation of ice crystals at high altitudes–which is not of “utmost importance” to global warming.Incidentally,I wrote a Ph.D dissertation on the application of the H-K equation to the evaporation of water(U.C.Berkely,1965),and relevant heat and mass transfer texts.
Puzzeling… Continuity equations are inaplicable on the interafe of water and within Knudsen layer since the continuity equations assume Maxwelian distribution function. H-K theory corrected by R.W. Schrage (1953) and then by S.I.Anisimov (1965) is the best that we have at the moment. Except,of course for, MD simulation work by the discussed here Polish group or analytical work that was not published in peer-reviewer literature – http://arxiv.org/abs/1406.2261
Reblogged this on Norah4you's Weblog and commented:
What shall we do with the drunken sailor, was a song heard in my youth….
Guess the Alarmist ought to learn the difference in using words. They need it to understand THEY ARE WRONG….
The story goes: On a ship the captain noticed that the Chief mate always returned in drunk condition no matter which harbor they visited.
The captain wrote in the log book: Chief mate drunk
Not once but several times.
The Chief mate took the oportunity to write when the Captain once visited the town they entered: Captain sober today
Walt:Continuum not continuity. The Schrage H-K theory is fine–but irrelevant since the”interfacial resistance” is negligible in this context.
Yes, continuum equations…. I am not familiar with the “interfacial resistance” concept. Where can I read about it? What do you think of this Arxive article?
Transport across the Knudsen layer can be represented by a mass transfer resistance with a potential difference of vapor pressure across the layer.This resistance is in series with the diffusion resistance into the bulk vapor-air mixture,which is orders of magnitude larger.Hence details of transport across the Knudsen layer are irrelevant in the present context(including the Arxive article).Some references:
Mills and Seban,Int.J.Heat Mass Transfer 10,1815-1827(1967).
Mills,A.F.” Heat Transfer” 2nd.Ed,Prentice Hall,1999,pp.719-730.
Thank you very much. I’ll read these refs.
Here’s a timely thing to consider, how much heat did it take to boil all of the water in that hurricane, and then carry that weight 500 to 1,000 miles.
When I think it was David came up out of the gulf, through Ohio and Indiana ending up in Canada, I estimated it carried 25-30% of the volume of Lake Erie.
How much heat did that pull out of the ocean to be radiated into space as the water condenses.
Water doesn’t boil in hurricanes or any process that takes place at ambient temperatures. Evaporate is still a liquid, it is not a gas. And it is heavier than dry air, so the notion that convection powers hurricanes is but a meterology based myth.
What’s the kinetic energy of a water molecule that has the energy to leave the liquid and become vapor, and why does evaporation cool the the liquid it leaves from?
Micro6500:
What’s the kinetic energy of a water molecule that has the energy to leave the liquid and become vapor,
Jim McGinn:
A single molecule cannot break off, except upon boiling, in which case many break off. (Beyond that I don’t know the answer to your question, sorry.)
Water’s polarity increases when one bond is broken, making the second very hard to break.
Evaporation doesn’t produce gas. H2O gas (steam) can only exist above its boiling point. Evaporation produces vapor, which is not a gas but small droplets.
BTW, this completely refutes meteorology’s notion that convection causes storms. There is no steam in earth’s atmosphere and only if it did exist would meteorology’s notion of convection make any sense at all.
Jim McGinn asserts:
A single molecule cannot break off, except upon boiling, in which case many break off.
So I guess evaporation is a myth?
Sorry, I haven’t read the thread, but that comment just stood out.
So do the insults about meteorologists. Why all the hating?
But you might be a smart guy, in which case I will defer to your knowledge. But I haven’t made up my mind yet.
” Jim McGinn:
A single molecule cannot break off, except upon boiling, in which case many break off. (Beyond that I don’t know the answer to your question, sorry.)”
So when I refer to all of the water in that hurricane being boiled out of the ocean (as evaporation ), you agree with me now, because for a water molecule in liquid form, it’s kinetic energy has to increase to the same as water turning to steam as it boils to escape. This is why evaporation cools the source of the water. BTW I never said the ocean boiled, just the water vapor is boiled out of the water. Next you mention that the jet stream powers a hurricane, not convection, and yet most people know hurricanes strength over warm water, and lose energy over cold surfaces, no jet stream needed.
Micro6500:
So when I refer to all of the water in that hurricane being boiled out of the ocean (as evaporation ), you agree with me
Jim McGinn:
I do not agree with that. The uplift in all storms is the result of low pressure energy delivered though/from jet streams. The energy of all storms comes from above, not from convection.
Keep in mind, meteorology’s convection model fails to explain the existence of jet streams. But jet streams, once explained, do not fail to explain the phenomena that has been mislabelled convection.
Meteorology is as dumb or dumber than climatology. They don’t do experiments or any quantitative analysis of any kind.
Micro6500:
now, because for a water molecule in liquid form, it’s kinetic energy has to increase to the same as water turning to steam as it boils to escape. This is why evaporation cools the source of the water. BTW I never said the ocean boiled, just the water vapor is boiled out of the water.
Jim McGinn:
You think that makes a difference? Honestly?
Micro6500:
Next you mention that the jet stream powers a hurricane, not convection, and yet most people know hurricanes strength over warm water, and lose energy over cold surfaces, no jet stream needed.
Jim McGinn:
Your, “most people know,” is a crappy rationale for an argument. But I’m not criticizing you, I’m criticising meteorology for never having done any empirical testing of that crappy argument. The energy of all storms comes from jet streams. IT DOES NOT COME FROM CONVECTION. That is but an urban legend.
Meteorologists don’t discuss storm theory just like climatologist don’t discuss CO2 theory. BECAUSE THEY ARE BOTH CRAPPY THEORIES.
Jim McGinn asserts:
A single molecule cannot break off, except upon boiling, in which case many break off.
So I guess evaporation is a myth?
Sorry, I haven’t read the thread, but that comment just stood out.
So do the insults about meteorologists. Why all the hating?
But you might be a smart guy, in which case I will defer to your knowledge. But I haven’t made up my mind yet.
Jim McGinn:
Good for you. Meteorology is a religion, not a science. Their convection model fails under the slightest scrutiny. Learn to ask the right questions. You won’t get answers, just evasiveness. They are bamboozled by storms and are trying to save face with the public by keeping their worthless theory vague. Just like climate scientists, they realize that as long as they keep it vague the public won’t realize how ignorant they really are.
The energy of storms comes from jet streams. It does not come from convection,.
And here I always thought storms are the result of the temperature differential; hurricanes can’t form unless the ocean is 80º.
And yes, the jet stream tends to suck storms along. But I don’t recall it providing the storm’s energy.
You learn something new every day here. Whether it’s true or not. ☺
dbstealey:
And here I always thought storms are the result of the temperature differential;
JM:
Temperature differential? Between what and what? Evidence? Analysis? Testing? Imagination?
Why is it you nitwits never ask these quesitons of meterological pretender?
dbstealey:
hurricanes can’t form unless the ocean is 80º.
And you think this proves what, exactly?
And yes, the jet stream tends to suck storms along. But I don’t recall it providing the storm’s energy.
Really? Evidence? Analysis? Testing? Imagination?
You learn something new every day here. Whether it’s true or not.
Why don’t you nitwits ask meteorologist to verify their dumb theory that moist air is lighter than dry air 🙂