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Calc's check please

I am working with an engineer in the USA who has problems cooling a large diesel (9 cylinders 24" bore 29" stroke) and we have now got down to checking the 'new' radiators.

I have done some figures but I'd like my maths checking:

We are assuming that all pipe sizes are ID for the purposes of the excercise)

Inlet/Outlet pipe is 4" - cross sectional area, I make that 12.568 sq in Radiator branches are 2 X 2" pipe, total cross-sectional area I make 6.284 sq in Radiator pipes are 44 X 0.375" pipe, total cross-sectional area I make 4.86 sq in

If we assume OD sizes:

4" pipe assuming 1/4" wall thickness - 11 sq in 2" pipe assuming 1/8" wall thickness - 2.40 square inches X 2 = 4.80 sq in 0.375" pipe assuming 1/16" wall thickness - 0.05 square inches X 44 = 2.160 sq in.

The problem is that the engine overheats with the 'new' radiators, and as far as I can tell, the flow is just not sufficient. Each radiator tube length is about

108" and has 3 X 180 degree bends per pipe.

My feeling has been all along that the radiator design is wrong for the engine, but the guy I am dealing with has no engine experience and needs a helping hand.

I'd just like my basic maths checked out please :-))

TIA

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

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Reply to
Peter A Forbes
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You only took of one wall thickness for the 4" pipe, should be 9.621 sq in. Other numbers look ok.

What are the air and water inlet and outlet temperatures on the radiators?

Mark Rand RTFM

Reply to
Mark Rand

Peter you are almost right. A quick go with Excel shows that the only one wrong is the 4" OD which I make 9.62

Henry

Reply to
Dragon

Thanks for that, also to Martin P and Henry.

It's a bit involved, but basically the engine had a new radiator system installed in 2000 and hasn't had proper cooling since then.

From what we have deduced after a week of email exchanges and pictures of the installation, is that the system doesn't seem to have the flow rate required to get the heat out of the water, it just moves too slowly through the cores.

The tubes are 108 FEET long each, not inches, so you can imagine the water resistance in that for a start. Having 44 tubes in parallel does help, but the pressure drop in the system is quite high, something like 30psi with one pump running and 45psi with the second pump going. Outlet pressure remains almost constant, just the inlet pressure goes up with the second pump running.

The tubes and sizes in the radiators look more suitable for air conditioning than engine cooling, but I have the documents for the original quotation so I can go through their figures.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

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Reply to
Peter A Forbes

So, if there is enough heat exchanger area, your friend may be looking at splitting the radiator pipes half way along and running the halves in parallel? nice little welding job for someone

After a panic about legionella, we re-plumbed our diesel (17 1/4"x21" 12 cyl) to use the cooling pond instead of evaporative cooling. The site didn't accept my suggestion to shut down the oil fired heating boilers that the site used and use the diesel instead. Said diesel will never be run again. Anyone want a

6MW gen set for the back garden. needs a little work, but has only had one careful owner (the makers).

Mark Rand RTFM

Reply to
Mark Rand

The radiator are the tubes? Ummm, you know that real radiators have a significantly bigger area for dissipating heat?

Nick

Reply to
Nick Mueller

Where is that please? just checking the trailer suspension....:-))

Had an email this morning, the intercoolers have 100 X 3/8" pipes through them and 8" inlet and outlet, roughly what we originall told the guy they should be on the rad's.

Peter

-- Peter A Forbes Prepair Ltd, Luton, UK snipped-for-privacy@easynet.co.uk

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Reply to
Prepair Ltd

If I remember correctly, everything else remaining equal, the flow rate is proportional to the length of the pipe. If the 44 M shaped pipes could be reconfigured as 88 U shapes you would get twice the flow. In practice it would probably be a bit less than twice if the pumps are centrifugal as the pressure drop would decrease.

Bob

Reply to
BobKellock

That is what we reckon also. Most radiators for water cooling have fairly short runs but lots of them in parallel, this system has very long runs and not many of them.

We also found out overnight that there is a GE gas turbine cooling system in parallel somewhere, I am just finding out where and how this is connected into the loop.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

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Reply to
Peter A Forbes

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