Free convection of horizontal circumferential fins

[mrpi]

Ok, I have designed an electric motor housing to operate with forced cooling. For demonstration purposes, our customer would like to operate the motor without the cooling system.

The cooling system consists of fans and shrouds to duct the cooling air over the fins on the housing.

I need to provide some estimate of how hot the motor is going to get during minimum-loading demonstration use.

So my question is about estimating the convection heat-transfer coefficient of the housing in free-convection mode.

For reference, the aluminum housing has circumferential fins 5mm thick on 14mm center-center spacing. The fins are 30mm long.

Free convection tables I've looked at show values ranging from 3~7 W/m^2*C in air. Are these reasonable?

Given the relatively close spacing of the fins, should I err on the low side since buoyant movement of the air is restricted?

Beat to fit, paint to match.

 

[IRstuff]

I would definitely go on the low side. The fin spacing is a bit tight, for free convection.

TTFN

FAQ731-376

 

[gwolf2]

3-7 sounds reasonable, again I'd go for 3 as IRstuff says. The fins seem very thick at 5mm. If the temperature gets above 100C think about radiative heat transfer - it will help you if you have the correct surface coating.