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 0.25x800x746x3.41/(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 0.1
"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?

Nick