[Mike] works in a 50+ year old building with unreliable air conditioning. It often reaches 80°F inside during the summer, and he once measured it at 98°F. Rather than burn sick days, he became the envy of the office when he built this awesome desktop air conditioner.
The problem with knocking holes in the office walls and installing window units is that they must vent heat somewhere. [Mike] has overcome adversity and harnessed the power of the heatsink, only in reverse. His desktop a/c unit is made from two 28oz cans plus a 20oz can for the ice bucket. [Mike] used a side-vented CPU fan, which is vital to his design. He secured the heatsink to the base of one 28oz can with a self-tapping screw. This can is the upper chamber. [Mike] made a base from the other 28oz can, drilling holes for the CPU fan wires, the power cord, and a sweet light-up rocker switch. He used Gorilla Glue to affix the CPU fan to the base can.
Hot, stale office air is drawn through the ice in the 20oz can, which is nestled in aluminum foil to maximize heat transfer to the heatsink. The heat in the air gets absorbed by the heatsink, and the CPU fan kicks out cool air in 20-30 seconds.
“I can’t wait for the ice to melt outside and the heat to start just so I can test this puppy out. ”
Ice has a cooling capacity of 333 kJ per kilogram. He’s going to be sorely dissapointed.
A kilo of ice can offset his own body heat for about 40 minutes. Actually cooling the room by any amount for the whole working day is going to require buckets and buckets of it.
Indeed! So many people have “cute” ideas but fail to understand the basic physics…
I’m not sure what you mean by “fail to understand the basic physics…”. It is a desk top air conditioner, all it has to do is blow some cold air at him to make his job more bearable not cool the entire office. They sell similar products that use a 2L pop bottle filled with frozen water and they are good for and hour so this guys idea is so cute that people can make money selling it.
My thought exactly. The concept is using this as a personal cooler. It’s like sticking a cold drink on your face to “cool” you off, but not entirely. It just feels nice.
Thing is..where is he getting the ice? From the office freezer most likely. Overall this will make the office hotter.
And the generator that powers the freezer may be making the world hotter.
@tactileninja
Won’t the freezer be generating heat regardless of this solution?
Why do anything these days?
If no water is being frozen, the freezer’s compressor doesn’t run as much. If you put water in the freezer, the compressor turns on and pumps the heat it takes out of the water out the back of the freezer and into your office.
It’s a losing game unless your freezer is outside.
I promise I understand the “basic physics” of the problem. No, this doesn’t cool the whole office, neither does a desk fan. If you have ever worked in an office when the temp approaches 80F you would be able to appreciate the cool breeze. I have made other similar devices and each was much appreciated, I just felt sharing the build might help someone else in the same situation.
The problem with your basic physics is that it doesn’t even cool your face in any significant amount.
Alright, let’s suppose you have a kilogram of ice, and you melt the ice in 60 minutes, which gives you 5.6 kJ per minute minus about 0.2 kJ due to extra heat added by the fan. Let’s say the fan blows air at 35 cubic feet per minute, or approximately 1 cubic meter per minute. The specific heat capacity of air is roughly 1 kJ per kg and the density at 35 C is 1.1455 kg/m3 which means the air coming out of the cooler is approximately 4.5 C colder than what went in. This is of course assuming that it isn’t very humid, because water in the air increases the specific heat capacity. 35 cfm is also kinda slow and feeble for a desktop fan, but increasing the fan speed would result in less of a temperature drop.
So instead of basking in 98 F heat, you’re basking in maybe 92-95 F heat if the air was dry to begin with, which is still hot as hell. The only thing really going on here is the fact that you have air blowing onto your face which makes it more tolearble.
The further problem is that his can only fits about half a kilo of ice, so if he is getting any significant cooling effect from the ice itself, that means he has to keep refilling the can every 15 minutes.
I guess you have never cooled yourself with an ice cube or cool drink of water. The ice in previous coolers usually lasts around an hour, maybe two if its a can of solid ice and in an office situation getting up to walk around once an hour would be suggested for good health anyway. Granted if it reaches 98F in the office again this won’t make it a peachy experience but when it’s 78F or 82F it is very much a refreshing cool breeze. This is not a totally new device for me, just a new design. You should take a few minutes away from the physics book and give it a try. If you get hot easily I promise you will be pleasantly surprised.
I have. The point I was trying to make is that the difference in the air temperature this thing makes is not large enough to compare it to a cool drink or an ice cube on your face. If your room is 82F then it might with good luck cool the air to 75F which is still hot by any standard.
It’s just wafting slightly less hot air gently towards you, because the faster you make it blow the less the temperature of the air actually drops, and the longer you make the ice last, the less of an effect it has.
Besides, the condensation of water from the air eats up most of its cooling power anyhow.
You just can’t cool air down very well with half a liter of ice. It would be better to put the ice in a plastic bag, the bag inside a couple socks, and stuff it down your shirt.
forget body heat, my computer pumps 300W into the room (700+ under load), and another 100W for my router/modem/NAS. humans are around 100W equivalent I seem to remember, so in all there’s a good half a kilowatt just lying around idling.
The smallest AC units you should be bothering about have a capacity around 500 – 600 Watts. They aren’t really made any smaller than that, because even white window blinds on a sunny day can still leak a kilowatt into the room.
It depends on the window area. Sunlight is on the order of 1kW/m^2 on a sunny day if the surface is exactly perpendicular (a window probably won’t be) and if all the light was absorbed (it definitely won’t be).
If the humidity is low enough, an evaporative cooler would work great.
Not sure what PC would give off 300W just idling. Mine idles at about 90W (it’s a 6 core, though I generally don’t just leave it idling), peaks at 400W at worst case load, and averages 200W when tuned for performance per watt. The Dual CPU servers (fairly new Sandy Bridge E Xeons) I worked with at a previous job were similar, idling at about 120-150W. I suppose a Bitcoin miner can really pull lots of power, but who would leave one just idling?
I wouldn’t base your numbers of pure CPU data alone – remember that the rest of the components give off significant amounts of heat as well. My desktop (quad core 2.66GHz Xeon – packed memory bay with 8x2GB modules) gives off at least 350 – 400W of *heat* (not just idle power consumption) and that’s not counting the heat dissipated by the PSU and circulated through the room.
Regardless of how much, it’s obviously more than a trivial amount.
Wow, power must be free where you guys live. My desktop pulls about 50W (true RMS) when idle, which includes an ivy bridge quad-core, a souther islands graphics card and a water pump.
Really, though, if it would need any more power, i’d upgrade to some more modern hardware and watch it pay itself of with just the difference in power consumption.
Eh.. electricity is included in the rent. ;)
Plus, I don’t leave it running. It just gets too hot in my tiny little office.
Think lots of AMD cards. They’re beasts with their power consumption. It’s more like 250W I think, but I was going for hyperbole.
@v665f6atu3. Yeah, what you posted isn’t true. Spec on ivy bridge is 49w idle. Standby it is less than 5w, but that isn’t idling now is it? Mere waste from a very efficient power supply will push that up past 60 with ease.
So either misinformed or a liar. I reckon both.
Gaming & workstation type PCs can do 300W easily. My desktop PC + monitor uses 100W on idle.
@dkjnujb: I’ll just leave this here: http://www.anandtech.com/show/7003/the-haswell-review-intel-core-i74770k-i54560k-tested/2
Don’t call people liars and misinformed when the same thing is only true for you.
The cheap(ish) commercial dehumidifiers seem to use peltier effect coolers and just let the condensation drip from the heat sink. I should imagine with a carbon filter and a flyback or other high voltage supply one could produce a rather efficient air purifier with this sort of tin can design, at a fairly reasonable cost, especially if most of the components are waiting in junk boxes already.
If you had lots of money, you could buy a ton of peltiers and run them derated at 20-30% the voltage and current. For small temperature differences up to 20-30 K, a good peltier can achieve a CoP higher than 4 which means you can pump four times as much heat as the electrical input. They can make a fairly efficient, if rather expensive, solid state AC unit – the main problem being efficient heat transfer in and out to maintain the small temperature difference, and the size of the stack.
At the rated power and voltage even the best peltier has a CoP is just slightly over 1.
No way are they that efficient at 30 dT… More like 1-1.5 if you’re lucky.
Placebo air conditioning?
It’s the same as using a regular fan, except the air coming out is cooler.
It won’t cool the room, it might make the room hotter. BUT the user of the device will be cooler with the hot air blasting directly at them.
Even if the device doesn’t reduce the temperature by much over a significant area, it will probably still make the air in its immediate vicinity more comfortable to breathe. That alone is worth something. And, of course, moving air is almost always preferable when the temperature is high, even if it’s all the same temperature.
There might be a bit of a placebo effect at play too, I suppose, but this is more than a “cute” failed idea. At worst, it won’t be as effective as he hoped and he’ll learn something from it. At best, he will have built a cheap device capable of making his job more comfortable.
I work offshore in West Africa. On deck we go up to 86F, 85% humidity, but inside the living quarters it reaches over 90F and even higher humidity. So I have a usb notebook cooler hanging over my bed, blowing past a cool bottle of water to cool me down. YES, I am an engineer with a firm grasp of thermodynamics, so I know in the long run I’m NOT saving energy and I’m NOT cooling the world, I’m just increasing entropy, BUT, that’s not what I worry about, and I’m sure [Mike] would agree, it’s about what happens on YOUR skin. So I agree with nate here, if it makes it easier to work, why not.
Although I would not call this air conditioning unless you live in an extremely humid area. Here the cold bottle of water helps with condensation a lot, but back home where it’s very dry, not even an AC can condense water out of the air.
[Mike], enjoy your jealous co-workers until the first polar bear comes knocking on your door :)
For once, it would be great if all those on the internet with a “vastly superior grasp of phsycis” actually used their talent to actually improve something and contribute rather than simply beat their hairless chests.
Are we all really THAT insecure that we need to make a bunch of anonymous people on the internet think we are smart, by derating others? Do you realize that this DISCOURAGES others from projects and especially about sharing them. Is that the goal here?
Some people sit around quoting textbooks (or worse… science fiction) and doing nothing while others are actually doing things. Which ones do you think drives innovation? How many ideas that made no sense with known physics at the time have resulted in breakthroughs?
Complaints without solutions are worthless. If your minds are so much more superior, where is YOUR solution?
I read these comments sections every day, and over and over again it is just a bunch of whiny people trying to knock down anything they can find no matter how small – from the grammar and spelling of the authors on this site to simple conceptual errors in the projects. Does this really make you feel smarter?
“How many ideas that made no sense with known physics at the time have resulted in breakthroughs?”
I think none.
Well, then clearly you are an idiot, David.
Are you proposing that current laws of thermodynamics are flawed and therefore someone can come up with a new invention that will cool a space without moving heat from one place to another? Because “known physics at the time” for our time is a little better than the knowledge that existed in the nineteenth century. The easy inventions are mostly done, new inventions are getting harder and harder because we are not discovering new physics principles, we are bumping up against the limits of physics.
There is a good chance that our laws for gravity are wrong, I ‘m not sold on the whole undetectable except through gravity dark matter.
Clearly, science is bullshit!
“new inventions are getting harder and harder because we are not discovering new physics principles”
I wonder why that is? Could it be because we think we know everything? Don’t you think we thought we knew everything 100 years ago? Do you REALLY believe that in 100 years, people won’t look back and laugh at how primitive we are?
Of course I am not suggesting that this guy stumbled on anything groundbreaking. I am commenting on the constant complaining and chest beating going around here. He DID something. Explain to him why it doesn’t work, suggest improvements, or just don’t comment. But being an intellectually insecure bitch on the internet is useless.
The laws of thermodynamics are solid and true (as far as I am aware) and the heat is being transferred via the ice. The flaw in most of the attacks on this project seem to be around the title “Air Conditioner” and relating that to a standard AC unit the refrigerates an entire office. Maybe I should have named it “Desktop Personal Cooler” as all it is intended to do is provide a cool breeze. I promise it is quite refreshing in a stuffy office as I have built several devices like this in the past. My eagerness to test is a matter of testing this iteration as others were functional but not as clean looking. You can get a similar effect by putting a cup of ice in front of a small cpu fan but I believe using the heatsink to be a bit more efficient and directed. The cool air also works with the evaporative cooling your skin already provides and the lower temperature magnifies this effect. In HVAC terminology the differential on this $2 doo-dad is about 20F which is actually better than most AC units. This project was never meant to challenge physics and re-write science it was simply sharing an easy (and proven) way to keep cool in the office.
” You can get a similar effect by putting a cup of ice in front of a small cpu fan but I believe using the heatsink to be a bit more efficient and directed. ”
What you get is a placebo effect, because a cup of ice can only sink so much heat and you’re nevertheless attempting to cool several cubic meters of air with it.
Again. Suppose you have a cup or 250 grams of ice. That has the thermal capacity to remove ~100 kJ of heat. A typical 120 mm computer fan moves about 3 cubic meters of air per minute in free air, the mass of which has a thermal capacity of ~3.6 kJ per Kelvin.
What happens is that the ice takes about 30 minutes to melt because the cup is somewhat thermally insulating, and the temperature of the airstream does not drop one degree, and what you have there is a perfectly ordinary small table fan that just happens to sit in front of a melting cup of ice that practically speaking does nothing to cool you down.
When you try to increase “efficiency” by adding a heat exchanger, you may get the airstream to cool enough to notice it, but then your cup of ice melts in five minutes. For 5K or 9F of cooling, 5.55 minutes to be precise.
Its not a placebo effect, its a stream of air roughly 20F cooler than the air around it. I am not cooling several square meters of air, I am cooling the air that is blowing directly on me. This is not theory, I have built similar coolers before and this one seems to do a better job of focusing the cold from the ice to the air stream. It would be better with some insulation in the cooling chamber and a lid so that an even higher percentage would go to the air. It also takes considerably longer than 5 mins to melt (haven’t tried it at 98F yet though).
” its a stream of air roughly 20F cooler than the air around it. I am not cooling several square meters of air, I am cooling the air that is blowing directly on me.”
Yes you are. The fan is continuously moving air at a rate of several cubic meters per minute. A typical computer fan does about 3 cubic meters per minute, and a proper desk fan moves 15 cubic meters at the lowest setting.
That means you /are/ trying to cool a significant mass of air anyhow, and the cooling rate provided by the ice is distributed into that mass flow.
If you are measuring a 20 F drop in temperature at the outlet, your ice has to be melting at a very rapid rate, or your fan is barely moving any air at all. That is the basic physics of the situation.
OK, then name one.
The battery, fire, lightbulbs, boats, airplanes, radio transmission, photography, space travel, nuclear energy….
Physicists are typically morons. For centuries they have stood around arguing and discrediting others while inventors actually proved them wrong over and over again. Physicists thought the world was flat at one time, that there was a belt of invisible and impenetrable matter in space, and even that our eyes emitted light rays which allowed us to see. And in every case, they thought they knew everything there was to know. Of course, they are quick to take credit for those innovations and pretend they didn’t laugh.
Imagine if the Wright brothers had posted their attempt to build a flying machine on the internet and succumbed to all the “vastly superior intellects” laughing their project down.
A good 40% (statistic made up out of my ass) of all physics are THEORIES. Unproven theories. Yes, in this case, I do believe we understand enough about thermodynamics to know this is isn’t going to work. Not my point at all. We don’t know everything and without experimentation, we will never advance.
A wise man knows that he doesn’t know everything. Innovation stops when we think we do and people just get dumber.
TL&DR: STFU
“For centuries they have stood around arguing and discrediting others while inventors actually proved them wrong over and over again.”
You forget the thousands and thousands of charlatans, crooks, snake-oil salesmen, overunity inventors and plain loonies who outnumber the successful inventors by at least a thousand to one.
The point of science and the scientific method is to weed out what works from what doesn’t, and frankly the vast majority of ideas or inventions just don’t. That’s where you get the illusion that physicists just keep poo-pooing and putting everyone else down.
I’ve been watching this debate from the sideline.
justice099 said “How many ideas that made no sense with known physics at the time have resulted in breakthroughs?”
David replied: “I think none.”
David is SO wrong.
The most obvious for me is sailing upwind. Going from those Square rigs to fore-aft rigs. It was noticed that some pirates had such rigs as early as the 15th century but the Europeans couldn’t understand or work out why they sailed a good 20% closer to the wind. They said it defied the laws of physics. Hmm…David?
SO..that’s just the first one.
Laser was perceived as a fun and silly parlour trick at the time.
Oh, and my solution was to say “My office is too hot, I’m going to work from home until you fix it.”
Your solution, then, is to burn up your sick leave, as mentioned in the article.
Some jobs, as unicorn rare as they may be in your world, allow people to do work from home, and have it count as work.
And how do you think we got that knowledge of physics? Do you think we sit around reading physics books just for kicks?
No. We built something. It didn’t work as expected. I have a failed experiment from last night sitting next to me right now. Sometimes we tried and failed many times before hitting the books to find out why it didn’t work. Or if there is some other potential approach that will work. Sometimes this helps. Other times all the intellect and books in the world doesn’t mean you can find a solution to a problem.
And then if we share what we’ve learned in hopes of educating, or sparing folks some wasted effort repeating known dead ends, we get ridiculed by folks like you. Who generally have never built anything, or read a book, and haven’t the intellect to distinguish between fact and fiction.
Really? Is that what you see here? People actually explaining why it didn’t work and offering suggestions for improvements? That’s not what I am reading here.
And people like me, huh? What do you know about me, Chris? Do you know what I do for a living? What I have built?
Generally, the knowledge of physics came from numerous people that didn’t listen to the “vastly superior intellects” and built and experimented anyway.
The irony of your post is that you are actually agreeing with what I said. But apparently your rage and hastened need to respond caused you to miss that entirely.
“There is no likelihood man can ever tap the power of the atom.”
— Robert Millikan, Nobel Prize in Physics, 1923
“But what is it good for?”
— Engineer at the Advanced Computing Systems Division of IBM, 1968, commenting on the microchip.
“640K ought to be enough for anybody.”
— Bill Gates, 1981
“The concept is interesting and well-formed,but in order to earn better than a ‘C,’the idea must be feasible”
— A Yale University management professor in response to Fred Smith’s paper proposing reliable overnight delivery service. (Smith went on to found Federal Express Corp.)
“Heavier-than-air flying machines are impossible”
— Lord Kelvin, president, Royal Society, 1895.
“Everything that can be invented has been invented”
— Charles H. Duell, Commissioner, US Office of Patents, 1899.
Yes, but none of those inventions violated the known laws of physics. So … what was your point again?
Obviously, slightly beyond your grasp…..
Alan, at the time the ideas were conceived they WERE violating known laws. Also, what was once perceived as impossible is not possible. I know this argument probably isn’t reasonable within scope of discussion, but since we’re off on a tangent, why not :)
*now possible”, not, “not possible”
All of those quotes have a reason to be, or are simply lifted out of context to look silly.
Mostly the reason is lack of advancement in the field, such as Lord Kelvin’s comment about heavier than air planes at a time when engines simply did not have the power density to lift themselves off the ground.
Many forget that the Wrights brothers weren’t only pioneering aerodynamics, but also ultralight engines, just as they forget that their first successful powered flight was teetering on the brink of being just a power-assisted glider instead of climbing by engine power. Some still argue they actually didn’t have enough power, and the first flight was simply too short to prove that they had, because well built gliders can take off from a slight gust and glide for minutes.
The thermodynamics of melting ice is not a vast uncharted territory with new discoveries to be made if one just keeps a dogged spirit despite the naysayers. It’s a well know subject where experiment like this is mostly just going to prove what is already known.
I would upvote you if I could.
Oh my god.. You guys are hilarious arguing.
Look, I am not a rocket lawyer surgeon, but it sure does feel good to have cold air blowing on my skin in the summer time. Who cares if the room is 90 degrees, all that matters is my skin temperature.
Alan says: “Yes, but none of those inventions violated the known laws of physics. So … what was your point again?”
How about sailing upwind? (for starters)
For-aft rigs, as opposed to square rigs…first seen on some pirate ships in the 15th century but Europeans couldn’t understand how they sailed 20% closer to the wind as they defied the Laws of Physics.(known at the time)
I’ve wondered about making my own ‘basic’ AC using peltier devices, I bought a couple of 100watt ones some years ago and never did much with them as I only had a 3A 12v power supply, but now I have a 16.5A 12V supply (203watt Xbox PSU) I’m going to be doing more testing when summer appears.
My basic idea was to use a fan and heatsink on the cold side of the peltier to blow cold air in the room, whilst the hot side is water cooled (think PC water cooling setup) with the reservoir being a huge bucket of water outside.
Feasable? Or just something to try when bored/fed up with the heat?
Once you’re over about 100-150W, phase change cooling (think normal AC’s) is superior to peltiers in pretty much all but long time reliability…
Maybe if NASA released detailed plans for the free-piston stirling engine (mechanically very simple) they’ve been developing, even low-power cooling could be more effective :D
btw it would be interesting to try the same type of thermal management that spacesuits use – a very long thin (plastic/silicone?) tube that is woven into the first layer…
Something similar has been tried for the Leopard 2A6 MBT to help the crews in Iraq-type climates, where the temperature in the tank can go over 50°C…unsurprisingly the crew with the suits showed less fatigue and better combat readiness even in extreme heat conditions ;-)
Better than nitting ,especially if the flow is against your body. Everyone know that thican’t service enture room, but so frakin what ? ( thanks to all blessed persons with knowledge in physics :-D )
Despite all the math and physics, his perception of feeling cooler is all that matters. Yes, efficiently cooling his WHOLE body down for 40 minutes would require a significant amount more of ice, but the last time I checked, freezing a human being alive isn’t the goal here.
Point being that with half a kilo of ice in a can, it doesn’t really offer any noticeable cooling, or, it melts the ice in a matter of minutes.
If the ice melts in 40 minutes, it offers the same relief from heat as a 50 Watt lightbulb offers against cold. That is to say, not really.
It’s just an air blower at this point.
There is allready a goog solution to desktop air conditioning. Just running a small desktop fan will increase the convective heat transfer from the skin by an order of magnitude.
So most of the effect of the unit will be due to it moving the air and very little of it will be due to melting of the ice.
Stick to the little desktop fan and you will have a much cheaper, more efficient, quieter and more effective solution.
All humans come with evaporative coolers allready installed as part of the base level package.
You can buy small thermoelectric dehumidifiers for ~$50. They are small enough to fit on a desk, circulate enough air to replace a fan, cool the air slightly by nature of their operation, *and* the reduced humidity will help your sweat evaporate.
If you have a supply of tap water, this often comes in at 50 – 60°F and can be used in a heat exchanger (read “salvaged car radiator”) with a big fan. I did this years ago in graduate student housing (which prohibited real A/C units). Two observations:
1.) Condensation.
2.) Don’t skimp on the hoses/fittings, because if one breaks and you’re on the second floor, your life is going to be interesting for a while. Just sayin’ ;-)
Other than that, it kept things cool enough to sleep at night if a bit gurgly.
Our local Walmart does this in the auto-service garage. There’s a big radiator looking heat exchanger about 6 ft tall and 8-10 inches thick supplied by garden hoses and a big blower fan attached.
Something like this? http://portacool48.blogspot.com/2011/04/mobile-industrial-evaporator-to-cool.html
My dubious apparatus was a simple “chilled water” heat exchanger and a lot smaller – since I didn’t pay for water it could run all the time (see comment #2).
That might be it. I didn’t think it was using evaporation since summers here (Midwest) are pretty humid already but it might be.
You may be thinking of an evaporative chiller, which uses the evaporation of water to remove heat form the air..
http://en.wikipedia.org/wiki/Evaporative_cooler
I don’t think I have ever seen a more clueless bunch of know-it-alls.
It doesn’t work?! How does it not work? It blows cool air on him, seems pretty simple.
Then there is the group going on about needing all of this ice, he isn’t combating global temperature change. He wants some cold air on his face, because his office is hot.
Do you people even live in the same universe as most of us? You seem to have a basic grasp of physics but yet you can’t understand that the man wants some cold air and has achieved that?!
It works, but it doesn’t work any better than a fan without the ice, so there’s no reason for the cans etc. All he needed was the fan.
No, the ice cools the air that is blowing on him. Essentially you are saying he would feel equally cool if he let a hot air gun blow on his skin because it is still air that is heating the room.
Don’t take this too personally but saying the ice does no good is like saying the ice in your drink does no good. Two lumps of ice in a coke mean the difference between “a drink” and “a refreshing drink”. Same thing here; it’s the difference between a breeze and a refreshing breeze.
It makes such a small difference that a comparison to ice cubes would be like plopping two cubes into a 64 oz double big gulp.
The effect is mostly psychological because you think you’re doing something about the situation.
What babies. Heck I’ve worked physical labor jobs in 120F temperatures. I’d lose 5 pounds of weight a day and drink it back every night too!
I here you pcf11, been there too, just prefer 70F over 120F.
The real solution to personal cooling would be to augment the ability of the human body to remove heat from itself. We spend so much energy cooling the air around us, when all were are really trying to achieve is cooling off our own bodies.
When the humidity is too high, our sweat can’t evaporate anymore into the saturated air and just clings to us, eventually acting like an insulator and trapping the heat in our bodies.
I admit that I am no expert on thermodynamics, but we have a built in heat source inside our bodies. It would seem that using a refrigerant that evaporated at a lower point than normal body temperature (alcohol and ammonia for example) and used the same principles of Einstein’s absorption fridge, we could develop something that extracted the heat directly from the human body much faster than sweat.
Obviously this does require a temperature differential and would only work when the ambient temperature is still lower than our core temperature. This is where my understanding of thermodynamics gets very sketchy.
Does anyone have any thoughts on how this could work?
Need to re-engineer the human body a bit so that when going into an air conditioned space from the hot outdoors that it doesn’t immediately start sweating like mad to shed heat.
“Hey! Stupid autonomic systems! It’s COLD in here. You do NOT need to sweat right now! Let convection and radiation do the job. I’m going to stay in here for at least two hours so quit soaking my back and armpits.”
You could swallow the heat exchanger half of a water cooled system and as long as the surrounding air is cooler than body temp. :)
They make gloves that circulate cool water over the back of your hands where the veins are close to the surface. That removes heat quite efficiently, and the problem you’re left with then is just to keep the water cool.
maybe you could use ice. :)
minature swamp cooler, fun comcept
There’s another much more efficient technique you could use to remove heat from the human body using ice. Eat it.
I saw an air-conditioning unit used in a welding shop. It was a HUGE fan (~4.5′ dia) with what amounted to a stack of corrigated cardboard to blow through. You hooked it up to a water faucet with a regular garden hose. The water soaked the cardboard, and the fan blew air into the cardboard. The result was cool water-saturated air blown into the room. It did help. This is in Indiana, where summer humidity is already fairly high. You didn’t use significant amounts of water either. I imagine this would NOT be the case in someplace like Arizona or New Mexico, where the relative humidity stays down in the single digits for most of the year.
Evaporative cooling is pretty efficient. You only need about a liter per hour to achieve 600 Watts of cooling.
Just barely learning more about this type of cooling method, myself. Does this mean your water usage is considerably higher?
From the prespective of this guy he will have fresh air, for a hour or half of it. The others, well, that’s their problem..
But if he gets the ice from the fridge in another room, that’s well played by the guy. Drawback in my opinion is the 20oz, ~0.6 liter, he will be walking around a few times to have a day of fresh air. Plus there must be a big fridge to generate ice for a entire day of work every day… plus the work of making the ice himself…
I’ve came across something with the same purpose but to refrigerating a small room, done with a styrofoam box, and some pc fans.. the option to use with a battery or another kind of power supply is up to you.. Of corse a proper ar conditioning is more efficient in energy consumption, but when it comes to cheap diy solution for a temporary solution well, with 5 ou 6 pets i bet this would last a day or almost, it all comes down to number of pets for the amount of hours/temperature to cool.
And remember, winter in brasil is like summer in other countries.. :P
link: http://www.youtube.com/watch?v=Hcek5D6Wn2E
The ice maker is in accounting and runs 24hrs a day anyway. I work in IT on a seperate (and highly defective) AC unit. Getting up once an hour is no problem especially when compared to sitting at your desk sweating.
I’ve worked at benches for a few years now with basically no climate control, so 45F winters and 85F summers pretty easily. Over the worst of this past winter I had a 300W heater blowing across the bench where my hands were and kept things pretty comfy. When it’s 90F a good fan does wonders, and I’ve considered ice coolers for the fan air but haven’t built anything yet. All the physics in the world explaining thermodynamically that it’s not an efficient idea still doesn’t dodge the fact that slightly cooler moving air directed on your face and hands will pretty much always make you more comfortable when working in a hot room. May be more psychology than physics, but it works. Comfort is comfort, physics be darned.
Why not just dump a bucket of water on your self (and get soaked), then let a fan blow air over you — that will keep you cool…
in a cube farm? don’t think that works
Well I guess you’d have the perfect excuse to wear those boat shoes while on the clock.