Here is another link.
Looks like these are mounted in the existing Windows. I think.
Rechecking the video, there do not appear to be any chimneys (or even roof vents).
Sad … the money spent on this bullshit would have fed that village for a year.
So, this is flawed. I direct your attention to the diagram in the video. The red arrows show the hot air entering the wide part of the plastic bottle and blue arrows show the cooler air jetting out the narrow part. This looks like Bernoulli’s principle, but it’s not because there’s nothing holding the output in the jet as is shown in the diagram. Whatever compression occurred will very very quickly decompress as soon as it exits the plastic bottle. Bernoulli’s principle can only be used in a single fluid flow, like in a pipe, never fluid flow in a medium of the fluid.
Any heat loss the air experiences would be immediately regained upon exiting the system. The First Law of Thermodynamics says energy must be conserved, if we take heat energy out of the air, it must go someplace, here it would have to be absorbed by the plastic. The Second Law of Thermodynamics says everything wants to be the same temperature, so if we increase the temperature of the plastic, it will want to give it right back to the air. Thus, this system does no good a’tall. Worster, it would impede the air flow into the dwelling, making it hotter inside.
You tell them blokes at that other message board this contraption violates ALL the Law of Thermodynamics.
Third Law says nothings can be 0 K, so this thing won’t work then either
I remember Chronos quoting Homer Simpson: “In this house we follow the Laws of Thermodynamics!”
“In this house we obey the laws of THERMODYNAMICS!”.
I once had the opportunity to use this exact line (with “program” swapped for “house”) in a contentious discussion with a disingenuous contractor making bullshit claims about the fundamental physical mechanisms of their particular widget, to an audience that included a brigadier and major general. This is to date, and seems likely to remain, my highest practical career accomplishment.
Stranger
I’m thinking that there may be “jets” of faster local airflow , at the expense of total airflow through the window. Maybe these feel subjectively cooler to people, who are next to the device.
The five degree drop is difficult to explain, unless ambient conditions are poorly controlled.
Some suspect that the baseline temp was measured with the window closed. In which case, I’m sure the device is a significant improvement on a wall.
That temperature drop is inexplicable … that heat energy has to go someplace … or we have a felony offense punishable by up to five years attending freshman physics classes.
However, if the air outside the tin shack was 5ºC cooler, then simply opening the windows and lets the breeze flow though would replace the hotter air. If you’ll notice in the video, the “before” scenes show calm, the “after” show distinct air movement. It’s subtile but there, little bits of cloth flapping around and such.
So, did some checking … average high temperatures at the Dhaka, Bangladesh airport during the hot season is 31ºC {Cite} … a far cry from the 40ºC the video claims … such rot …
Faster than what? The jets from the bottlenecks cannot be faster than the ambient wind (and in fact are probably slower).
My explanation, absent well-documented data to the contrary, is that it’s bullshit.
The two relevant temperatures are:
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the temperature of the jet of air shortly after it exits the bottleneck, and
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the temperature of the ambient wind approaching the contraption.
Anybody care to test this right now? You’ll need a co-conspirator, with one of you driving a car and the other holding the experiment out the passenger window. Slice up a 2-liter bottle as described, and while the car is screaming down the highway, hold it out the window. Hold a digital meat thermometer in the unimpeded slipstream until it reports a steady temperature; make a note of it. Now hold the thermometer just downstream of the bottleneck, and record the temperature there. My claim is that there will be no temperature difference.
I have a meat thermometer, but I can’t be bothered to buy two liters of soda just to try this. If you’ve got a bottle and a thermometer and a friend with a car, this is your moment. Do the experiment and report back here.
To get air temperature to drop from 86F to 77F without actually transferring heat out of it, you need to expand it, which means you need to lower the pressure on it. How much? If your starting point is air at 86F and 14.7 psi, then you need to lower the pressure to 13.9 psi. If you’re doing this by decreasing the pressure downstream of an orifice, then the flow through the orifice will be accelerated to 217 MPH.
Note that if the pressure inside your tin hut is 13.9 psi and the pressure outside is 14.7 psi, your tin hut will vigorously implode.
Other relevant temperature is the temp in a poorly ventilated tin hut (with window closed) vs temp in a (slightly) better ventilated hut (with device) in window vs a hut with open window.
Additional relevant temperatures are ambient temps at the time the shots of the thermometer were made.
These could illuminate careless errors or fraud. If there is deliberate fraud, then a bunch of other temperatures could be entertained as relevant.
An addendum to the experiment I proposed in post #28:
a water manometer, with one end of the tube pointed forward in the bottleneck and the other end of the tube pointed forward in the free slipstream (i.e. out in “clean” air), will allow a comparison of the stagnation pressures of the two airspeeds. My prediction is that it will show the bottleneck velocity being equal to the free slipstream velocity (possibly slightly below free slipstream, owing to friction/turbulent losses).
The inventors explicitly claim that the air exiting the device is cooler than the air entering the device (see here at 1:03). To assess this claim, the only two relevant temperatures are the temperatures of the air entering the device and the air leaving the device.
The inventors also explicitly claim that it reduces hut indoor temps by 5C (see above video at 1:21; oddly, despite the captioned claim, the thermometers show a 9C decrease). To assess this claim, yes, you’d need to know what the “before” condition of the hut is: closed window, open window with the sun streaming in, or open window with an awning to keep the sun from coming in.
If them peoples don’t have electricity, what the hell is running that electric drill?
There’s no careless errors here (other than 44ºC - 35ºC = 5ºC), it’s a complete fraud. The company that produced this video, Grameen Intel Social Business Ltd., writes software for impoverished rural areas in Southeast and Central Asia. Places without electric power …
Fraud implies gain for the fraudster. What would be the gain for GISB by promoting the eco cooler?
Maybe the YouTube & FaceBook promotion could result in donations?
Or maybe a secret program to clean up the streets from icky water bottles.
I agree with you that the results are bogus but I think your statement about change in state being critical for heat transfer is wrong.
Change in state may represent the limit of the thermal process but it isn’t necessary in order to pump the heat.
Anyone who has ever filled a scuba tank will tell you that the tank gets very hot as the air is compressed into it yet no air from the supply side nor the delivery side is liquefied.
In my OP, I was wondering if there was an element of this.
But my intuition tells me the heating from compression should be quite modest. Also, any exchange of heat from the flowing air through the bottle-neck to the ambient air should be small, both because plastic is a poor heat conductor and because the transit time is so fast (with little time for heat transfer), even with a light breeze.
So the proposed mechanism looks like baloney and my alternative explanation looks weak.
Maybe I’ll try to experiment with this this summer.
I suppose that if holding a single bottle in a strong wind by the neck causes perceptible warming of the neck, it would indicate some plausibility to a cooling effect downstream. That might be easy to do.
My engineering background tells me that it’s awfully close to zero. Assuming a 10-mph breeze, the math says that if you bring that wind to a dead stop it will compress just a smidge and heat up by about 0.02 degrees F. Cool that back down to ambient temp, then expand the air to get it back up to 10MPH, and it will now be about 0.02 degrees F below ambient.
Two factors working against achieving even that tiny temperature fluctuation are the fact that the air never comes to a dead stop (and so doesn’t warm up by the full 0.02 degrees), and as you note, it doesn’t have a lot of time, surface area, or temperature difference across which to shed heat before being expanded again.
A refrigerant with convenient phase-change properties makes for an efficient refrigeration system, but it’s not an absolute requirement for a refrigeration cycle. An air compressor puts out smoldering-hot compressed air (you can get severely burned if you touch the compressor’s output pipe when the tank pressure is high); cool that tank of air off to ambient temperature, and then expand it, and now you’ve got uncompressed air cold enough to give you frostbite, without the air ever having gone through a phase change.