# Air velocity in a double-skin facade

I was wondering how the air flows in a double skin facade? Say I have a glass facade with a depth of 1m, a height of 200m and a width of 10m. It is a single vertical shaft all the way up with openings at the bottom to let air in and at the top to let air out:

There is a solar radiation of 100W/m2 hitting the outside of the facade and the air velocity at ground level is 1m/s. Can I expect the velocity of the air to increase as it travels through the shaft? and to what degree?

-

Yes, it may wel be possible that the fluid accelerates, this due to the expansion of the air. Suppose you have a steady state situation, then the mass flow in at the bottom (which you can calculate) should equal the mass flow rate at the top. Due to the heating, the air will expand, thus the density is decreased. As the massflow is $\int \rho v dA$, decreasing $\rho$ has to increase the velocity.

The physics behind this, includes buoyant forces due to gravity and density differences. Also, since you facade is 200m high, you should include ambient pressure difference between top and bottom (which is the reason that we have chimneys)

-

The answer is yes, and your system is called a solar cheminey. You will find all the necessary calculations in this paper: http://streaming.ictp.trieste.it/preprints/P/95/331.pdf

-
Answers consisting of only a link are less useful than those that explain or summarize what is on the other end of the link. – dmckee Jul 23 '12 at 2:40
When a paper exactly answers the question and is freely available, what's the point of copying the paper ? – Shaktyai Jul 25 '12 at 7:45
Stack Exchange sites aim to be repositories for answers, not just a link farm. Nor is it necessary to reproduce the whole of what is on the other end of your link, just give enough information about the direction the calculation takes. What are the key observations? What approximation simply the math? What kinds of limiting case are identified? That kind of thing. – dmckee Jul 25 '12 at 14:58