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I've corrected the attached spreadsheet. It doesn't take account of changes in pressure in my enclosed volume pod. Would pressure effect the air's Specific Heat, Thermal Conductivity or Dynamic Viscosity...

Here's the spreadsheet with the correct speed. I think the friction formula is mis-typed.http://files.engineering.com/getfile.aspx?folder=990986c2-b435-49c2-8966-a78bf1a042dc&file=forced_convection_r02.xls

The velocity should be higher eg 10 m/s

I've put the turbulent equations from Thermal Wizard into Excel (attached) but I'm not getting the right values for friction.http://files.engineering.com/getfile.aspx?folder=bae1d82b-54eb-4e46-b7c0-bc5d6fc99048&file=forced_convection.xls

Thanks Htlyst, the Thermal Wizard website has given me an answer. I'd been trying to calculate the Nusselt number for myself but haven't managed that yet.

The Efunda calculator unfortunately only works for laminar flow. My flow is turbulent. I'm not convinced by Jmiles formula; it asks for the conductivity of the external fluid while I am looking at the fluid inside the pipe. I've downloaded Lienhard but haven't found a useable formula for this in it.

Yes, it's near the surface of the water. To compare liquid cooling to air cooling I still need to answer my original question; how to calculate the convection coefficient.

Thanks Jmiles, I know the temperature of the water outside the pipe; that's what I'm calling TempWater. Thanks IRstuff, The generator is in an environment sealed at atmospheric pressure, so the pressure depends on the temperature. Pressure = PressureAtmos x Temp / TempAtmos Water cooling would...

I have a problem similar to a thread I found here: thread391-227383 I am designing a generator cooling system. The generator is in a sealed steel tube which is air filled and under water. I intend to weld a steel channel to the side of the tube and blow air down it to power circulation. So I...