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Re: Plumbing Through the Heater Core Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 12 Dec 2008 06:01:13
In Reply to: Plumbing Through the Heater Core, Arabiflora  [Profile/Gallery]
, Thu, 11 Dec 2008 17:53:39
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This opinion is not based on actual examination of a core, but on design practices.
It would make sense that the core would be branched, not serpentine. The key to heat transfer is surface area of the hot coolant to core material. For that reason, you want more, smaller diameter tubes than one big tube. You're pushing fluid, and the volume goes up with the square of radius, but the surface area only goes up proportional to radius. Or put it another way - in a fat tube, the coolant in the middle of the tube isn't heating anything.
OK, thin tubes are better. If you have one long, serpentine run, that is a massive pressure drop. If you have a lot of parallel tubes, you have a much lower pressure drop. If you want good flow, especially far from the water pump, you want a low pressure drop.
Lastly, with a serpentine flow, one blockage stops up the whole heater. In parallel flow, a stoppage only kills one path; the rest keep going.
Based on design needs, I'd be surprised if it was one serpentine flow. It is likely a large branch or manifold at one end, feeding a number of parallel paths, with an accumulating manifold at the output.
Now, the downside is lower pressure and smaller tubes, so over time they'll clog up. You'll get gradual loss of heat. And you never get perfect pressure balance, so some tubes will always get lower pressure/flow, and be more prone to clog.
The failure mode is corrosion, which turns the metal into a different material, thicker than before. This captures crud and further corrosion. You can flush a core and that will mechanically remove the loose stuff. But unless you chemically scour the corrosion away, the flow will never be the same as new.
posted by 99.159.103...
, Thu, 11 Dec 2008 17:53:39, Fri, 12 Dec 2008 06:01:13 <-- Viewing This Message
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