CFM required to maintain an air cooled engine at a specific temperatur

[kartingChamp]

Hello,

A long long time ago I took a few thermodynamic courses, during the first year of engineering. This is long forgotten though.

I would like to estimate the CFMs required to maintain an air cooled engine at a specific temperature. I googled and searched on this forum trying to find equation ready to be populated with parameters, but didn't really find anything.

If someone could get me started with this that would be greatly appreciated.

Things I know are:
- Engine HP
- Engine surface in contact with the air
- Surrounding/incoming air temperature
- Ideal surface temperature of the engine
- Engine material

Is there a way to massage these parameters to estimate the amount of CFM of air I need to blow onto that engone to keep it at a certain temperature?

Thanks!
KS

 

[VerneE]

The easiest methode to determine cooling air requirements is from the engine manufacturer - they usually have data on space cooling requirements.

Otherwise consider the engine at maximum output. From the engine manufacturer you should have things like exhaust gas discharge volume & temperature, cooling water volume and differential temperature, which can be used to calculate the heat energy per unit time from the engine that is not being used for power.

Convert the fuel usage into energy per unit time and subtract the power output (converting into same units). From this subtract the heat energy calculated above. The remaining amount is the heat being given off from the engine.

This is a rough calculation, not all energy is being accounted for, but it probably will be close enough. This is for maximum output of the engine and may be overdesign.