[Equest-users] How do you think about the no electricityEco-Coolers from Bangladesh

Fri Jul 15 15:57:06 PDT 2016

Fun question!

I believe there is definitely a degree of misinformation here, but I see some potential for improving thermal comfort (not for reducing the supplied air temperature).

Let¡¯s run with the idea of this being applied in a very hot climate where you would otherwise have open windows to facilitate natural convection, and you have a substantial amount of other solar envelope conductive loads building as the day progresses (the graphic mentions a ¡°tin hut¡±).

To start, this measure could substantially reduce direct solar gains through the opening (while introducing indirect conductive gains)...  It might be more effective/simple to install a permanent shading device (or just board up the window), but we should consider this effect as part of the whole package.

This assembly would also clearly restrict & reduce the quantity of natural convection that would otherwise occur with a totally free opening ¨C we have much less free area to work with.  How hot the interior environment temperature climbs, and how quickly it gets there is dependent on a number of fixed and variable conditions, but this net reduction in air changes per hour, all things being equal, will likely result in ¡°cooling design day¡± temperatures rising at a faster rate and to a higher maximum as far as a drybulb thermostat inside the room would be concerned.  Less air changes should result in a larger delta between inside and outside peak temperatures.

Independent of drybulb temperature measurements, there¡¯s one other ¡°saving grace¡± (perhaps more cynically, a means to fool someone into buying a product):   If there exists a substantial pressure differential between the indoor space and outside environment (due to mechanical or natural wind driven forces pushing/sucking air through the opening), these ¡°nozzles¡± might produce a relatively higher velocity for a projected area in front of the window.  I expect zero measurable effects on supply air or room air temperatures from this higher velocity, but someone standing in front of this device would enjoy improved evapotranspiration rates (sweat evaporation) due to the relative increase in air movement ¨C same reason we use circulating fans to improve thermal comfort.  In a similar fashion, we do not expect space circulation fans to reduce room temperatures. 

Would the combination of reduced direct solar gains, decreased air changes, and increased air velocity result in lowered space temperatures?  I highly doubt it, unless the wall opening was sorely wanting for a shading means to begin with.  

Could this combination of effects improve thermal comfort?  Sure, under the right conditions (likely hinging on the hourly windspeed & prevailing direction).  

I¡¯m more interested to find out if flipped around this device could function as a creative ¡°howling windchime¡± and what that might sound like¡

~Nick

Nick Caton, P.E.

  Senior Energy Engineer
  Energy and Sustainability Services
  North America Operations
  Schneider Electric

D  913.564.6361 
M  785.410.3317 
E  nicholas.caton at schneider-electric.com <mailto:nicholas.caton at schneider-electric.com> 
F  913.564.6380

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of ???? via Equest-users
Sent: Thursday, July 14, 2016 9:22 PM
To: Equest-users
Subject: [Equest-users] How do you think about the no electricityEco-Coolers from Bangladesh

Recently,I read the news about the zero air cooler,which is made with re-purposed plastic bottles.And the new claims that it helps reduce indoor temperature by 5 degrees centigrade.

The making process is shown as following:

I dout that very much.

the Joule-Thomson Coefficient for air (mostly nitrogen) at 300K (27¡ãC/80¡ãF) is about 0.36K/bar. This means that at 300K a 1bar change in pressure equates to a 0.22K. The change in pressure required to get the 5¡ãC (5K) reduction would therefore be:

5 / 0.22 = 22.7bar

So I think it is impossible the temperature drop will be up to 5  degrees centigrade after the air through the bottle.

What do you think?

------------------ 

Yongqing Zhao

Changsha Green Building & Energy Saving Technology CO.,LTD
NO.438,Shaoshan Road,Changsha,Hunan,China
Telephone:13574805636

Email:zhaoyongqing1987 at 126.com

         503271081 at qq.com 

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