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Venturi-Style Eco Cooler From Bangladesh

Venturi air-conditioning

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#1 boblalux

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Posted 20 July 2016 - 07:34 AM

Apparently works very well, and has already been installed in 25 000 households.  No energy input (eg electricity) required.

My question, where does the dissipated heat go to?  The flow of entrant air is narrowed, thus giving rise to a cooling of the air projected into the room. 

 

To view, Google with   "  eco cooler bangladesh  "

 

Bob



#2 CraigD

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Posted 21 July 2016 - 07:37 AM

To view, Google with " eco cooler bangladesh "

Links are allowed and encouraged – hence our name hyp[erlink]ography. Here’s the video that comes up first in a google search:

 

Apparently works very well, and has already been installed in 25 000 households. No energy input (eg electricity) required.

The “Eco-cooler” doesn’t use electricity, but since it only works if there’s enough wind speed to force air through it’s cut-off plastic bottles, it does require energy, though wind energy costs nothing (‘til some enterprising capitalists can figure a way to make folk pay for it ;) ) and wasted if not used.
 

My question, where does the dissipated heat go to? The flow of entrant air is narrowed, thus giving rise to a cooling of the air projected into the room.

It goes the same place heat goes when air made to move faster by a Hand-paddle and rotary blade electric fan – that is, it isn’t dissipated, heating some other place, at all.

What I think’s happening here is a common “thermal illusion”, the same one that makes us feel cooler when air is moving over our skin than when it is still, which happens when we ride in a moving vehicle or stand in the stream of a fan. The Eco-Cooler slightly increases the speed of the wind that blows against it (it would be interesting to see someone measure this), causing the moving air to carry off more evaporated sweat, which really cools a person’s body, and dries the skin and stimulates its nerves, which gives the perception of coolness, even if little or no cooling, or even heating, (which, if the air is really at 40 to 45 C as in the videos, would happen to a dry 37 C human being) is really occurring. Ordinary fans produce the same effect, without relying on the ambient wind.

The video suggests to me that this is the main effect people are feeling from the Eco-Cooler. Notice that people seem most please with it when they put their faces close to its nozzles, the effect. This is not to say the effect isn’t real – being more comfortable, and actually having less heat, are related but different phenomena.

Because the Eco-Cooler is nearly opaque, it also blocks the sun from entering the window it covers, which can dramatically reduce the temperature in a room. In the main room of my house, which has a large glass west-facing window, blocking the incoming sunlight by closing it Venetian blinds reduces the typical temperature from 32 to 25 C. This, I suspect, is most responsible for the before and after thermometer readings showing the Eco-Cooler making a room 5 C cooler.
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#3 boblalux

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Posted 21 July 2016 - 12:12 PM

Interesting, thanks.

Still, I don't think that the "cooling" effect is solely due to forced perspiration by wind.  The supporters of the gadget state that the cooling is similar to, when blowing onto your hand with a widely open mouth, and then continuing but slowly closing your mouth, the temperature felt goes from warm to cool.

Also, if you measure the pressure in a venturi system (which the gadget is) 1 in the wider portion, and 2 in the narrower portion, the relatively large difference in pressures has the effect of lowering the temperature in the narrower portion (inside of window);  so again the question arises, if there is a cooling inside the room, it must be linked with warming elsewhere, but where?

Bob


Edited by boblalux, 22 July 2016 - 09:49 AM.


#4 CraigD

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Posted 24 July 2016 - 01:47 PM

Still, I don't think that the "cooling" effect is solely due to forced perspiration by wind.

The video’s show, a drop from about 45 C to 40 C, which I think is an accurate report. However, they don’t show that the drop is greater than it would be if an opening were made with a panel that blocked as much light and admitted as much airflow as the Eco-Cooler, without using funnels to increase the speed of the air. If they did, I believe the same change in thermometer reading would occur, but the panel would not be as easy to build, nor as be enjoyed as much by the people inside.
 

The supporters of the gadget state that the cooling is similar to, when blowing onto your hand with a widely open mouth, and then continuing but slowly closing your mouth, the temperature felt goes from warm to cool.

I think this explanation is wrong.

The reason your hand feels, and actually is, warmer, when you blow on it with a wide open vs partially closed mouth is due to entrainment, where the stream of about 37 C air from your mouth drags surrounding room temperature (standard room temperature is 25 C) air with it. This NakedScientist page has a good description of this.

In air that’s warmer than your breath, like the 45 C air mentioned in the videos, the effect would be the reverse of in standard 25%, your hand feeling warmer when blown on with pursed your lips than open mouth. Notice that in the videos, they do the blowing demonstration outside, where the air is presumably cooler than inside a hot steel-walled shack.

It would be fun to confirm this hypothesis experimentally. If I get a chance, I’ll try using a portable heater to heat a small isolated room in my house to 38+ C, and give it a try.
 

Also, if you measure the pressure in a venturi system (which the gadget is) 1 in the wider portion, and 2 in the narrower portion, the relatively large difference in pressures has the effect of lowering the temperature in the narrower portion (inside of window);

A venturi produces lower air pressure in the narrow part of it where air flows faster. I don’t think, and can’t find anything with a web search suggesting, that this would cause a thermometer in the narrow part of a venturi to show a lower temperature than one in the wide part or outside it. In any case, since the Eco-Cooler venturi is narrow only in the neck of the plastic bottle that passes though the panel, not inside the house, I don’t think the venturi effect has any effect on the house’s inside temperature.
 

so again the question arises, if there is a cooling inside the room, it must be linked with warming elsewhere, but where?

If, by installing the Eco-Cooler, more air flows through the house than before, and the air outside the house is cooler than air and objects inside the house, then heat is being carried from these warmer surface to the outside by the moving air.

I think the Eco-Cooler works by a combination of increasing total airflow through the house, and reducing the amount heating by sunlight.
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#5 boblalux

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Posted 24 July 2016 - 02:58 PM

Thanks, all of you.  It's all great fun.  So to confirm one way or other, I am constructing a panel of 45 bottle parts, and will report back.  First, I have to drink another 35 x 1.5L of bottled water, and as I prefer beer, it may take some time, but I hope to report back before winter!

Greetings

Bob

 

By the way, I protected my hand with thin cling film, and then blew on it with wide to narow closed mouth.  Cooler with narrow closed mouth, thus, it does not seem to be a forced evaporation of perspiration effect.


Edited by boblalux, 07 August 2016 - 01:20 PM.

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