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Old May 17th, 2008, 06:16 PM   #7121
harm123
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AIRCONDITIONING in burj dubai and Vanhenriks question:

Hello vanhenrik!

Always fun to read your post! You're a great contributer to this forum!
You just give it that little bit extra. I think a lot of users can appreciate it.

Where did you get the information that it took the airconditioning of the Burj Al Arab 5 months to cool the building down?

I doesn't even suprise me that it took that long, because the heat capacity of stone/concrete is sooooo big. Think of a big church in Europe, the temperature inside stays constant pretty much all year long, even if you just let the big doors open constantly!! Same goes for the temperature inside a bunker with walls of 0.5 meter thickness.

With normal airconditioning power, it would definetely take a very long time to lower the temperature of the concrete (all the way to the inside).
And Burj Dubai is far more concrete, then Al arab!!!!!!!!!!
So with all these concrete walls, the temperature inside the core is like: really tough to change. Maybe once they cooled the core down, they can shut the airconditioning off for a year!
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Old May 17th, 2008, 06:46 PM   #7122
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Quote:
Originally Posted by vanhenrik View Post

i wonder when they suld start cleaning the windows
end i wonder 1 mour thing that`s is when they have clost up the bulding whit all the windows then they start the ac end geting down the tempeture incide the bulding i wonder how long that will take ?
it took a bout 5 month for burj al arab
It isn't the same situation; Burj al Arab have 200 meters high atrium, and Burj Dubai floors are 3-6 meters high.
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Old May 17th, 2008, 07:00 PM   #7123
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BTW for skyscraperpage burj dubai, they lowered height from 819m to 807.7m. Well I guess its irrelevant
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Old May 17th, 2008, 07:08 PM   #7124
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Quote:
Originally Posted by Suren View Post
It isn't the same situation; Burj al Arab have 200 meters high atrium, and Burj Dubai floors are 3-6 meters high.
So therefore, it will take even longer to cool the BD with a greater surface area of thermal mass to contend with. A 200m atrium would only assist the cooling due to the stack effect of warm air rising therefore exhasting hot air fairly qucikly out the building.
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Old May 17th, 2008, 07:12 PM   #7125
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Quote:
Originally Posted by buildmilehightower View Post
BTW for skyscraperpage burj dubai, they lowered height from 819m to 807.7m. Well I guess its irrelevant
what are you talking about??
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Old May 17th, 2008, 07:14 PM   #7126
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Found similar photos from similar angle.

From november 2007:



From today:


Last edited by buildmilehightower; May 17th, 2008 at 07:20 PM.
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Old May 17th, 2008, 07:19 PM   #7127
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it looks very nice!!!!1
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Old May 17th, 2008, 07:26 PM   #7128
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Burj dubai looks really henge now. Sometimes find it cool that concrete in the bottom floors hasn't still cracked
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Old May 17th, 2008, 07:29 PM   #7129
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It depends on weight and not on height
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Old May 17th, 2008, 07:56 PM   #7130
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Of course, but lower buildings may weigh more than BD. So the question is about any massive building and not only tall ones, depending on the ratio height/footprint size, and other considerations like construction material .
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Old May 17th, 2008, 08:02 PM   #7131
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spectaculastic Imre

I just found out that there are more workers working on burj dubai then there are in the whole building industry in my country (roughly 6000), and the finished burj will be more then 10 times higher then my countries highest building that opened just recently (78meters here: http://www.veisluturninn.is/FileLib/...sidur/turn.jpg) for us that is a skyscraper
haha that is ridiculous

I will probably faint when I 'll see the mighty burj for real
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Old May 17th, 2008, 08:03 PM   #7132
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now it has hit the fans

it sems this is going to be an realety !




truley amazing !

http://www.alltomvetenskap.se/index.aspx?article=2204
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Old May 17th, 2008, 08:08 PM   #7133
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anything else to say? i still see open desert next to a 2700 ft tower. honestly its just so boring there they have to spend oil $ on making extreme architechtural wonders. I do however love its Cool design. I was merely questioning its location?!?!?
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Old May 17th, 2008, 08:15 PM   #7134
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Quote:
Originally Posted by Suren View Post
It isn't the same situation; Burj al Arab have 200 meters high atrium, and Burj Dubai floors are 3-6 meters high.
yes i now but it has to be a lot of moist when they are coling the tower ?
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Old May 17th, 2008, 08:45 PM   #7135
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wow..
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Old May 17th, 2008, 08:49 PM   #7136
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what if theres an earthquake
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Old May 17th, 2008, 09:33 PM   #7137
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Quote:
Originally Posted by harm123 View Post
AIRCONDITIONING in burj dubai and Vanhenriks question:


With normal airconditioning power, it would definetely take a very long time to lower the temperature of the concrete (all the way to the inside).
And Burj Dubai is far more concrete, then Al arab!!!!!!!!!!
So with all these concrete walls, the temperature inside the core is like: really tough to change. Maybe once they cooled the core down, they can shut the airconditioning off for a year!
Ill try a short calculation:
Floor-area: 334000 m
thickness: 40 cm (I think it is thinner, but there are also vertical columns)

Volume: 133600 m
Density: 2400 kg/m (Ill take just concrete no steel)
Heat-capacity: 1 kJ/(kg*K)

to cool it from 45 to 25 C you need 1.781.333 kWh cooling energy, sounds a lot.
I have in mind, that there is a total cooling capacity of 45 MW available.
I assume that just 2,5 percent (1,125 MW) of this capacity are effectively used to cool down the building (considering the heat transfer coefficent air->concrete) then it would take 1583 h or 65 days -> 3 month.

I think my calculation is very conservative. Any comments? Did I forget something important? What about my 2,5% of 45MW assumption (just a feeling)? Am I right that BD is just cooled by air? no activated floors or things like that?
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Old May 17th, 2008, 10:02 PM   #7138
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Quote:
Originally Posted by Johannes867 View Post
Ill try a short calculation:
Floor-area: 334000 m
thickness: 40 cm (I think it is thinner, but there are also vertical columns)

Volume: 133600 m
Density: 2400 kg/m (Ill take just concrete no steel)
Heat-capacity: 1 kJ/(kg*K)

to cool it from 45 to 25 C you need 1.781.333 kWh cooling energy, sounds a lot.
I have in mind, that there is a total cooling capacity of 45 MW available.
I assume that just 2,5 percent (1,125 MW) of this capacity are effectively used to cool down the building (considering the heat transfer coefficent air->concrete) then it would take 1583 h or 65 days -> 3 month.

I think my calculation is very conservative. Any comments? Did I forget something important? What about my 2,5% of 45MW assumption (just a feeling)? Am I right that BD is just cooled by air? no activated floors or things like that?
Hey Johannes!

Your calculation is EXACTLY the one I had in mind when i wrote that it would take several months to cool the whole burj dubai down (from 45 to 25 degrees celcuis) because of the large heat capacity of concrete and the large amount of concrete! There is even more concrete in the core walls!

You made very good assumptions!

But let's not get too much into physics here
I hope vanhenriks question is answered now!

But it was a really nice question about the burj Dubai in my opinion. 'Cause no one probably realised that!
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Old May 17th, 2008, 11:25 PM   #7139
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Quote:
Originally Posted by Nike12 View Post
what if theres an earthquake
Dubai is close to an active zone, but the area itself has never been hit by an earthquake so far. Look at this map:


http://upload.wikimedia.org/wikipedi...rs_1963-98.png
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Old May 17th, 2008, 11:27 PM   #7140
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and the BD could probably withstand a quite heavy earthquake because of its size
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