On Aug 24, 7:12 pm, "stu" wrote:
wrote in message

...



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

Why use Aluminium? I wouldn't have thought it would be hard to find an old
copper one which will.
A. Be a little more efficient
B. Won't have the corrosion problems Aluminium may have.
As you wont be running it under pressure even a leaky one should be easy
enough to patch up.

As for Aluminium corroding, if it's the only metal in the system I don't
think you will have a problem. If I was making something like this (and
someday I'd like to) and using second hand stuff I think I'd suck it and see
what happened.
Stuart

Be patient Nick, George will answer all.

Until then, consider the following. The radiator is based on the
constant flow of the water pump and the thermostat, which opens and
closes on a regular basis. If one were to take the engine, measure the
block and head temperatures, as well as the radiator fluid
temperatures, one would find the relationship between all of them.
Now, we know that a automobile engine with a failed thermostat will
malfunction in some way. If the thermostat is stuck open, the engine
will never ever warm up, thus giving us an indication that a typical
auto radiator is over designed for the application with a wide open
flow. If stuck closed, it will overheat.

Another similar way would be to take say, 200 degree water heated at
an even rate and flow it through the radiator and measure the
difference between the inlet and outlet at a given flow of fluid and
air through the radiator. I would suspect that you will need a much
lower flow than you expect to extract a given BTU without flow
regulation.

Feel free to take all of that out of context in any way you see fit.