Re: HVAC questions

[Bernard Cleyet <anngeorg@PACBELL.NET>]

In An Anthology of Partly-Baked Ideas, one writer suggested collecting humid air with
a sheet of plastic over the edge of a cliff overlooking the ocean or lake.  (I think
(s)he was an Israeli, so the Mediterranean.)   I forgot how he expected to condense
it;  maybe at night it would dew the sheet.

bc

cliff parker wrote:

> I was speaking with my brother who is a mechanical engineer working w=
> ith HVAC design in large buildings.  As we discussed some of the phys=
> ics involved with his work he told me that one of the factors that mu=
> st be considered when designing ventilation systems is that humid air=
>  tends to rise to the ceiling.  As I pondered why this may be a few q=
> uestions came to mind that I am having difficulty answering on my own=
> .  The first comes directly from the conversation with my brother. =
> =20
>
> 1) Why should humid air in a building tend to rise to the ceiling?  T=
> he thought that comes to my mind is that the source of humidity is ge=
> nerally people breathing hot air.  Hot air rises and therefor the hum=
> idity goes along for the ride.  However, I am not satisfied with this=
>  answer because it would seem that the air breathed from people would=
>  mix with the room air too quickly to cause much convection movement.=
>   Is there more that I am missing.  It seems like there must be.
>
> 2) Why is hot air less dense than cool air?  I basically understand b=
> ut my ideas need a little polishing.  In a balloon the hotter air wou=
> ld collide with the balloon surface with more kinetic energy and ther=
> efore stretch the balloon to a larger size.  Larger size and same # o=
> f particles =3D less density.  Less density =3D greater buoyant lifti=
> ng force than gravitational force.  However when hot air is unconfine=
> d in the atmosphere what acts as the surface of the balloon?
>
> 3) If the air I am breathing right now was trapped into a well insula=
> ted tightly sealed container and was allowed to sit on a shelf for a =
> period of time would that various molecules settle into layers.  Heav=
> y molecules on the bottom and light on the top?
>
> Any answers pointing me in a useful direction would be appreciated.
>
> Cliff Parker
>
> Never express yourself more clearly than you can think.  Niels Bohr=
> =20
>
> This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.