Re: Cooling attic (and home) by spraying water on roof (shingles)- good/bad?

["Phil Scott" <philscott@xxxxxxxxxxxxx>]

"Some Guy" <Some@xxxxxxx> wrote in message
news:42BF3E57.659FD057@xxxxxxxxxx
> Phil Scott wrote:
>
> > > Doesn't a mister waste water by atomizing it and then
the
> > > wind will blow it away?
> >
> >      The latent heat of evaporation for water ...
>
> I still don't see an effective way to arrange a residential
cooling
> system based on the evaporation of water.
>
> I don't think you can concentrate and deliver a substantial
amount of
> heat to a surface you can cool via evaporation.  Evaporative
cooling
> would be effective if the heat inside a house could be
brought to an
> out-door device who's surface temperature is well above
boiling and
> the application of water would result in evaporative
cooling.
>
> > Evaporative cooling would be limitlessly popular if it
> > did not add an equal amount of humidity in the form of
> > 'steam' to the air it was cooling to *sensibly lower
> > termperatures.
>
> So what you're saying is to mistify the air circulating in a
house in
> order to cool it.  I don't think that would work once you've
saturated
> the air (ie humidity > 75%) not to mention the effects of
saturated
> air on items in the house, the wood, the machinery, etc.

I am a mechancal engineer doing these sorts of calculations
and systems for over 40 years.. and you are entirely correct
if the humidity is say 50% and the outside air is 90F... you
can cool the air to 75 or so but the humidity is then up into
the 80% range and all the problems you mention manifest.
Thats why evaportive cooling is not used in many cases.

However in areas where the relative humidity is in the 20 to
30% range, and the outside air is over 90F... then the supply
air can be cooled to 70F and 50% relative humidity..that works
very well/


>
> I think only the roof makes a workable item to cool with a
water
> cooling.  It's designed to get wet, to collect runoff, and
gets very
> hot in the summer, and cooling it can lead to reduction in
cooling
> requirements of the house.

     Its workable...but there are problems ..its seldom used
because of those problems.   You get to do whatever you wish
though its yer house.  Have fun.


>
> The only thing that makes more sense is a temporary tarp or
canopy to
> cover the roof during the summer (to be taken down during
nasty
> weather, storms, etc).

  Oh please.


Phil Scott