How to make a two pass rad out of a one pass rad.

          Cut a notch in one header tank and insert and tig
          weld in a baffle. Then close up the hole and tig weld
          in the neck. The other end is just all capped off.
          --
          Paul Lamar ...No rotor no motor.

     Paul,

     Please doodle the water flow through a two pass radiator..


     Matt-

     OK Matt here it is.
     --
     Paul Lamar ...No rotor no motor.


How is that not only slightly better than having two smaller radiators
in series?  The second pass will be much less efficient than the first
pass section, right?  Didn't we just discuss not wanting to do this?


Matt-

On the face of it there is no difference. It is a compromise
to simplify  the plumbing at the slight expense of efficiency.
Perhaps the core volume may need to be 10% larger but in
terms of cost that is insignificant. There are fewer connections
(more reliable) and there is some heat conduction transfer from
the hot side to the cool side through the fins and the end tanks.
There is only one scoop and diffuser required instead of two.

The best way to do it is this. The top and bottom
sections must be thermally insulated from each other and supported
with plastic sides. It is called a counter cross flow heat exchanger.
Rather expensive to build and not available off the shelf.
Ed Klepies built one. He can build another upon request.
These are about 10% to 15% more efficient in terms of core
volume required.

http://www.rotaryeng.net/Counterflow-rad-core4.jpg
http://www.rotaryeng.net/cross-counter-flo-theory.gif


--------------------------------------------------------

I forgot to mention a couple of other things Matt.
Since the cross sectional area of the tubes is half of what
it is with the simple rad and their length is twice as long
there will be a higher velocity of coolant passing through
the tubes for a given flow rate at the expense of slightly more
water pump HP required. The higher velocity of the water enhances
the heat transfer from coolant to metal a bit. In the past this has
been the rational for use of two pass rads in race cars.

The cooling god giveth and the cooling god taketh away :)

Paul Lamar ...No rotor no motor.

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