[Lammy]

I dont understand.

What is a single pass/dual pass heater core?

[Raider84]

a single pass heater core has water enter one side of the core and leave on the other side. The water goes through the core in one pass. As opposed to a two pass heater core like the chevette, where the water enters and leaves on one side of the core, the water travels to the end of the core, and then passes back through it to leave.
Usually a the two pass cores will cool the water more effectively, but the single pass cores are less restrictive.

[Since87]

Originally posted by Raider84
Usually a the two pass cores will cool the water more effectively, but the single pass cores are less restrictive.

Why do you think a dual pass heatercore will cool the water more effectively? I don't know of any reason why this would be true.

[UberBlue]

Single pass. Fedco 2-342



Dual pass. Fedco 2-261 (Chevette, D-tek Pro core)

A dual pass can be thought of as two single pass rads in series.

[BigSmokey]

I would think a double pass forces the water to contact more of the exposed radiator surface by creating a tighter channel for the water to travel. A single pass could have dead spots. This is just a guess, I also would wager this is a stereotype, true to an extent but if you get a good single pass it would work better than a bad dual pass.

[Altima]

does single series split up and run in parallel though? this would still be effective, and lots less flow restriction.

[UberBlue]

Originally posted by BigSmokey
I would think a double pass forces the water to contact more of the exposed radiator surface by creating a tighter channel for the water to travel.

Can you extrapolate on this some more? I'm not getting what you are trying to say. If you mean by increasing water contact via turbulence via increased water velocity, kinda so. Duals tend to be alot more restrictive than singles. Two 3-342 rads in series have slightly less than the same total flow restriction of a single 2-261 core.

Originally posted by BigSmokey
A single pass could have dead spots.

If you look at the 2-342 pic in my previous post, you will notice the inlet/outlet are diametrically opposed ensuring no dead spots.

Originally posted by Altima
does single series split up and run in parallel though? this would still be effective, and lots less flow restriction.

You hit the nail right on the head.

[UberBlue]

Further reading

Further, further reading.

[Raider84]

Originally posted by Since87


Why do you think a dual pass heatercore will cool the water more effectively? I don't know of any reason why this would be true.

because it travels twice the length as the single pass, therefore enabling the water to have more time to be cooled by the air running over the fins.

[BigSmokey]

The dead spots would be on the sides. Like I said though, I have no facts, just gueses. As someone pointed out in another post, water is like electricity, and to add to their analagy it will also travel the path of least resistance.

It would seem that a "single pass" would mean single channel and "double pass" would indicate a U shape. This assumption could be most non-scientific though, since often things are named for how they appear and not how they work. For instance, a double pass could be a W patern and a single pass could be an S.

It would depend on how they are made...Any mechanics out there that have discected a couple of these things to see where the water is channeled?

[Since87]

Originally posted by Raider84
because it travels twice the length as the single pass, therefore enabling the water to have more time to be cooled by the air running over the fins.

But, if the water flowrate is the same with each heatercore then any given quantity of water has the same amount of time to cool regardless of the radiator. Please read the flowrate sticky.

All else being equal, using a single pass heatercore will result in a higher flowrate. A higher flowrate will in turn result in the waterblock performing better. I doubt that many involved in watercooling, other than BillA, could detect the performance difference in the heatercores themselves.

[Since87]

Originally posted by BigSmokey

It would seem that a "single pass" would mean single channel and "double pass" would indicate a U shape. This assumption could be most non-scientific though, since often things are named for how they appear and not how they work. For instance, a double pass could be a W patern and a single pass could be an S.

They are built as they appear. A single pass has a plenum chamber on each end with a pipe in each plenum for inlet/outlet.

A dual pass has a single plenum chamber running the full width on one end, and two smaller chambers on the other end with a pipe in each for inlet/outlet.

[ILikeMy240sx]

The time that water stays in the radiator doesnt increase the performance as much as having greater flowrate due to greater deltaT. As the water stays in the radiator deltaT starts to decrease so the amount of heat removed from hot water is decreased. This is why single-psas heatercore will perform better than dual-pass given that othere components in your system is not restrictive

[Raider84]

i humbly stand corrected