alt.energy.homepower

wrote in message
news:fan5i1$jal@acadia. ...
> I'm thinking about using a recent Taurus auto radiator or a Ford or GMC
> pickup radiator to heat water with hot sunspace air, but I'm concerned
> that
> a) it's hard to find specs for radiator performance, and b) a mechanic
> says
> an aluminum core radiator might crud up with corrosion in less than a year
> with oxygenated water and no antifreeze.
>
> How many Btu/h can an auto radiator move from 150 F air to 140 F water,
> using its electric fan, with no wind? An engine that makes 200 HP at 25%
> efficiency (unlikely with no motion :-) would burn 800 HP of gas. If 25%
> of the heat leaves from 200 F water to 100 F air via the radiator, the
> air-
> water thermal conductance is /(200-100) = 5100 Btu/h-F,
> good compared to a 2'x2' all-copper $200 MagicAire 2347 duct heat
> exchanger
> that moves 45K Btu/h from 125 F water to 1400 cfm of 68 F air with a
> "H20 pressure drop.
>
> Antifreeze would be expensive for a 1000 gallon heat storage tank, and
> an antifreeze heat exchange loop would add to the cost and lower
> efficiency.
> How much antifreeze do we need just to prevent corrosion? Is there some
> corrosion inhibitor we can use at a low concentration?
>

One quick google suggests at least 25% ethylene glycol...
/support/

But that's still pretty high if you're talking about the whole storage tank
:-(

Another suggests that it isn't (corrosion) very bad if you can be sure to
use water that doesn't have any halides in it. But filling a whole storage
tank with demineralized water is probably about as expensive as doping it
with EG.

/Articles/

A general rule to reduce corrosion is to use water that has a low electrical
conductivity and not connect dissimilar metals. So if you use an Al
radiator, you might consider using short sections of hose to connect it to
copper piping. This helps minimize forming a galvanic cell that will
corrode the metal with a more negative potential.

daestrom