Radiator design reference 1

[TChronos]

I am designing a series of downflow radiators. It's been suggested that the radiators would work best if the inlet and outlet were at opposite corners. The best "fit" solution would have the inlet and outlets both on the left side of the radiator. I understand that there will be pressure loss across the header tanks, but I'm not sure if it will be significant enough to cause a distribution problem. FWIW, I see many automotive radiators which have been designed with apparant disregard for this issue. I can't be the first one to encounter this. Is there a reference on radiator design that discusses inlet and outlet placement?

 

[patprimmer]

When confronted with this problem when making a radiator for a 1912 model car I was restoring, I ran the pipe into the bottom header, then across inside the header.

The pipe was capped off. but had small holes drilled in it.

These holes had a total cross sectional area equal to the pipe, and were uniform. holes were on the bottom side i.e. opposite side to the cores to help prevent short cuts and increase mixing and improve distribution.

The original that we were trying to replicate overheated easily, but the tubes close to the inlet and outlet side were very noticeably hotter than the far side.

The poor distribution may have been exacerbated by the fact that the system was thermo-cycle i.e. no water pump at all.

We used 1/2' air conditioning condenser tube as the cores, as it looked original.

The distribution manifold hidden inside the header worked fine, it now never overheats and all cores seem to be similar in temperature.

Point is, you may need some method inside one tank to distribute flow.

On a modern radiator with relatively small id of the cores vs inlet pipe size, on a system with a pump, the differential might not be nearly so great as in my case.


Regards

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[mauner]

If you consider pressure loss along the inlet and outlet headers then opposite corners will provide better distribution through the radiator.

Fluid that first leaves the inlet header has to travel a greater distance along the outlet header. This evens out the pressure loss and promotes evenly distributed flow.

When my old Dodge B200 van with a 318 V8 was overheating my automechanic told me to feel the radiator - if a section was cold (which it was) then it needed to be boiled clean or replaced. Opposite connections didn't help when corrosion was present. Fluid short cycled straight down the radiator near the inlet and then along the header to the outlet - about 50% of the radiator was fouled.

I would expect this to have happened much sooner if inlet and outlet were on the same side. Low flow conditions at the far end of the radiator will probably collect corrosion products faster.

 

[Fabrico]

Both connections on one side is what's known as a double pass radiator. There are lots of them around. Someting to keep in mind is that for a given flow, it takes 4 times the pressure to equal a single pass radiator.

http://www.stewartcomponents.com

has some good info on this subject.