If you design a cooling system which features an air stream under the body shell of the car you have to provide a heat exchanger, access and exit for the air. So your question makes little sense without further explanation of the specifics that you want to know.
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Ok that didn't turn out well. Let's say you have an intake and an exhaust already. You need to cool it more. Can you just stick on a bigger/more exhaust pipes? (I'm referring to the physics here, not the actual regulations) Or should you have a bigger intake instead? Let's say you could only choose between the two, and not both.
raymondu999 wrote:Ok that didn't turn out well. Let's say you have an intake and an exhaust already. You need to cool it more. Can you just stick on a bigger/more exhaust pipes? (I'm referring to the physics here, not the actual regulations) Or should you have a bigger intake instead? Let's say you could only choose between the two, and not both.
There is no simple answer here. What you need is a pressure difference in the cooling system; a lower pressure at the outlet than in the inlet. You can't just put a big air intake on the car and choke the flow in the outlet, or the other way around. You need a balanced approach. Mass flow in equals mass flow out.
As Edis implies, heat rejection in a liquid-to-air heat exchanger is all about relative temperatures and mass flows. If the air ducting is the only variable that you can adjust to increase your heat rejection rate, then you want to make whatever changes produce the greatest air mass flow improvements for the least weight and drag penalty.
A well designed duct has a minimum area at the inlet. Diffuses and slows the airflow gradually up to the heat exchanger core face, increasing it's pressure and density. Then gradually converges the hotter, more energetic airflow in the exit duct, reducing it's pressure and increasing its velocity, which provides an extractor effect across the exchanger core.
If you can only change the entry/exit area of the inlet or exhaust duct, a larger exhaust exit area would probably be my first choice.
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