Quote:
Originally Posted by fanamingo
Can you elaborate? My google searches have turned up empty.
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I remember Korff's book ** that Aerohead keeps on bringing up, and conveniently, he scanned in a part where Korff made a diagram with a summary of the details of "ideal" sealed ductwork for a radiator.
- Inlet duct should be equal to the radiator height.
- (inlet) entrance height need only be 1/6th of the radiator height IF duct length is equal to radiator height
- Duct must be sealed airtight on both sides of radiator to hold pressure.
- No air leaks between duct and radiator.
Note that aerohead said AREA, not height like the book's diagram mentions. More precisely, you should be figuring that ideal openings are 1/6th the AREA of the radiator behind.
Most cars have too short a nose to have the 1/6th radiator slit up front. Unless you're going to fab up a nose cone like basjoos' Aerocivic, that would mean you'd have to have a larger than 1/6th opening, because of that shorter space.
My car's the same as what trebuchet03 is modelling in his CFD thread, and I think that flow is typical for most cars:
Just look at the front where trebuchet03 did more detailed modelling of the opening with the grill slats, the bumper, and how the air eddies and has to move around the irregular shape of the engine before exiting out. And note that he didn't (yet?) try modelling how the fans (two on this model of Jetta) will make the airflow even more turbulent in the bay.
- The bumper splits the airflow to the radiator
- The nose to radiator distance is FAR shorter than needed for Korff's Ideal Radiator Duct
- No clean exit for airflow from the radiator
- Fans and fan shrouds restrict and "dirty" the airflow after the radiator (but ARE necessary for additional airflow, like when you are travelling at low speeds after cruising on the highway for a length of time)
Here's a compromise idea: two inlet ducts - one fitting the upper half of the radiator, one fitting to the lower half. This reduces the area / height for each duct, which MIGHT allow for Korff's ideals of width/height/area to work.
Splitting an 18" tall radiator into two 9" halves would mean an ideal 9" depth for a duct. For your own car... you'll have to measure to see!
**
Walter P Korff's book: Designing Tomorrow's Cars: From Concept Step by Step to Detail Design (1980) ISBN: 9780960385003