size radiator air inlet
size radiator air inlet
(OP)
How would I go about determining the required volume of air inlet for a radiator? I am tasked with determinimg if the air scoop opening is large enough for the Cummins diesel engine we are using.
I am assuming a simple bernoulli formula would be in order. Presure in would be atmosphere but would pressure out be the same? Velosity in would be 0, I'm not sure if P out would be as well. I assume volume out could be calculated from the opening of the radiator shroud. Is there a better method?
Thank you
Jim
I am assuming a simple bernoulli formula would be in order. Presure in would be atmosphere but would pressure out be the same? Velosity in would be 0, I'm not sure if P out would be as well. I assume volume out could be calculated from the opening of the radiator shroud. Is there a better method?
Thank you
Jim





RE: size radiator air inlet
Regards
Pat
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RE: size radiator air inlet
Whoever supplies the actual radiator should be able to provide you with application help for sizing the air-side ducting.
Rule of thumb: Any 'scoop' needs as much transverse area as the radiator core.
Mike Halloran
Pembroke Pines, FL, USA
RE: size radiator air inlet
Mike,
I was afraid that I would get the "same size the radiator" answer but was wondering if the size could be reduced with the fan pulling the air. I have sent a request to the radiator vendor but have not recived a reply yet.
Thank you
RE: size radiator air inlet
Another way to look at this is locomotives control the jacket water temperature by cycling the fan motors on and off. The radiators are horizontal so "thermo-syphon" works at idle but need everything going at full power.
The scoop area is a very sensitive design feature. You may remember that a lot of the WW2 fighter the P51 performance advantage over the P40 using initially the same engine, was that the cooling water scoop was about a third the area of the radiator and had a standoff from the fuselage out of the boundary layer. On the ground there was a flap that opened downstream of the radiator to keep things cool until the plane got into the air. In normal (flight) operation the ram air velocity was greatly reduced while passing through the radiator and the with the exhaust flap was adjusted so that there was an additional 300 lb. thrust due to the energy picked up from the radiator.
Anyway you probably should consut Cummins.
RE: size radiator air inlet
As far as the cross sectional area, you can get away with something smaller than the radiator. Depending on the fin design, fins-per-inch, and number of rows, your radiator is blocking a significant portion of the area. I would keep the ducting just in front of the radiator the same size as the radiator for 6" minimum, then start tapering.
Another factor: puller or pusher fan? You can get away with a cruder scoop design with a pusher fan, but they are less efficient. In my experience with B-series engines in tight engine compartments the cooling is reduced about 10%. Try to keep the shroud as long as you can, it helps quite a bit by getting air to move through the corners and very center of the radiator. When you put the fan within a couple inches of the radiator you loose a lot of effective surface area.
ISZ
RE: size radiator air inlet
The fan is a pulling fan and has a shroud on the outlet side to keep the air all comming through the radiator. The scoop actually is over the top of the engine pulling the air from the front of the machine and then directs the air to the rear of the unit turning it and then ends facing forward into the radiator with the engine sitting with the fan and radiator facing to the rear. I have given the dimensions and sketch to the radiator source for approval and cummings will be to approve everything before the unit is put into production. i was hoping to learn more to be able to better understand the requirements and maybe do some of my own work myself.
Again thank you for your insight.
RE: size radiator air inlet
Mike Halloran
Pembroke Pines, FL, USA