On Sun, Jun 28, 2009 at 8:50 PM, shochschild@att.net<shochschild@att.net>
wrote:
> Wow, so if I piped a radiator into the system and pumped through it at
> night, it would cool? B Great, this is just the kind of thing I would like
to
> try.
> Givens: B Say it is 100 during the day, and drops to 80 at night. B My pool
is
> about 92 right now and getting warmer daily. B If I could get it down to 85
> it would be well worth it.
>
> I have at least two car radiators in the junk pile, rather, I meant to say,
> in inventory.
> How much radiator surface? B Would 4 be twice as effective as 2? B Should I
> spray them black?
> Do I need to run a fan through them; in other words how important is air
> flow to the heat transfer?
>
I didn't mean car radiators. I meant exactly the same sort of system
that is being talked about in the heater thread. You'd need a couple
hundred square feet, exposed to the sky, not just to air. The idea is
that the panels radiate heat into near space, not conduct it into the
air (though you'll do that too, the amount of heat shed that way will
be very low.) You just run the pump at night, not during the day
(though, you can use it as a heater, and heat the pool when it's not
hot. How cold are you "winters"?). This is actually a pretty
standard thing to do with a solar pool heater; there are any number of
thermostatic controllers that do this as a built in feature. (You set
a desired temperature. If the panel is warmer than this, and the pool
cooler, the valve opens and the pump comes on, heating the pool. If
the panel is cooler than this, and pool warmer, the valve opens and
the pump comes on, cooling the pool.) I bet you there's someone local
who installs the things. (Though, there's nothing hard about
installing them. It's just plumbing, and a bit of wiring.)
Nighttime radiative cooling is something that very few people get.
It's been used for thousands of years. (Indians and Romans used it to
make ice in places like India and North Africa. During the summer.)
The clear night sky is really cold.
--
David Scheidt
dmscheidt@gmail.com
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