> >> Keith,
    > >> What's the difference between a radiator core and an
    > >> air-conditioning core.
    > >> George (down under)
    > >>
    > >> George,
    > >>
    > >> The major difference is around 300 - 400 psi in the a/c core v.s.
    > >> around 20 psi for a radiator. A/C cores are thicker walled round
    > >> tubes to prevent them from distorting when subjected to the hgh
    > >> pressures in the system. Radiator cores can use a rectangular
    > tubes
    > >> with thinner walls and will have more surface area per square inch
    > >> of radiator surface, hence better heat transfer.
    > >>
    > >> Joel
    > >
    > > Aircon cores are also generally a thinner package, while heater
    > cores
    > > are significantly thicker.
    > >
    > > Keith Wood
    >
    > Thanks Keith and Joel,
    > The reason I ask is that there are many GM aircon cores out there
    > being used
    > as radiators. Generally they appear thicker (not thinner), than the
    > rad
    > cores, perhaps 3 to 4" for the GM aircon cores and about up to 2"
    > for the
    > Rad cores.
    > I believe the suggestion to increase the pressure in the Radiator to
    > about
    > 24psi to protect against boil-over at altitude might put the
   radiator
    > at
    > risk, if it's rated at only 20 psi - would there be a safety factor
    > built
    > in or would it be running dangerously close to pressure limits.
    > George (down under)
    >
    >
    > ---------------------------------------------------------------
    >
    > It depends on which one you are talking about George.
    > There are two heat exchangers in AC systems. One inside the
    > vehicle and one up front next to the rad. The one up front has
    > large frontal area and is thin similar to a rad.
    >
    > The one inside the vehicle has frontal area constraints and
    > aerodynamic
    > drag or pressure loss is not a consideration. It is dumb to use it
    > in a way
    > it was not designed for. The typical car rad is a better match for
    > aircraft engine cooling use.
    >
    > Any air/fluid heat exchanger works better if thin. The ultimate heat
    > exchanger has infinite frontal area with infinitesimal thickness :)
    > The first half does three quarter of the work.
    >
    > So far nobody has blown a rad with up to 30 psi.
    > --
    > Paul Lamar ...No rotor no motor.


    > Most current radiators are for low pressures, ie approximately psi
    > 20 or less. Most are now using plastic tanks and connectors to the
    > cores instead of solder. As suggested elsewhere, a good radiator
    > repairman can fabricate a soldered radiator and tanks which can be
    > tested to much higher pressures which will give a good safety margin
    > and reliable service.
    >
    > A/C condensers may not have as good of a heat transfer due to their
    > high pressure design using thicker walls. I'm sure they would be an
    > excellent choice for oil coolers.
    >
    > Joel

   Joel,
   Th local aluminum radiator supplier recommends the plastic tanks (
   on his
   website) before I contact him, what is the recommendation on the plastic
   tanks - I heard they were prone to failure much more quickly than
   the full
   aluminum ones. I'm sure the racing people use full aluminum, perhaps for
   that reason.
   George (down under)

   George

   Plastic tanks are mechanically attached to the core with tabs and
   generally work well with the 12 - 16 psi pressures that new cars
   operate.  An occasional  failure caused the driver to pull over to
   the side of the road and call for a tow truck.  However this is
   generally NOT what pilots want to do.  The major problem with the
   plastic tanks is that they occasionally develop cracks and are not
   designed to operate at higher pressures.

   Aluminum radiators with aluminum tanks which are soldered (tig weld)
   together is the way to go obit more expensive.

   Good  old Green ethelyne glycol with additives  is the fluid of
   choice and should be changed during your annual.  Stay away from
   some of the newer antifreezes as they have problems with cold and
   altitude.

   Oil Coolers.

   Some of the oil coolers now have a baffle inserted into the tube to
   increase the interior surface area and increase heat transfer.
   Looks interesting.

   Joel

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