air flow calculation

The quantity of exhaust air, Q, is directly proportional to the extent of natural convective heating about the radiator - of course, unless you have forced cooling of the radiator - hence the size of the duct is determined by dividing the bouyancy-displaced air, Q, by the velocity of bouyancy of the natural convection and by pi (3.14...), and then taking the square root of the result, which should give you the radius of the duct.

Because nature abhors vacuum, the same quantity of air will attempt to flow into the closed room, so you may make the intake duct size also the same.

Forced air intake will simply increase the velocities through both ducts only but will have no effect on the generator unless forced convective cooling is maintained on the radiator, as well.

Calculating the quantity Q requires knowledge of the shape of the radiator, the temperature of the radiator fluid, etc, etc, all of which is known to you.

I hope that this is helpful

do you have any calculations sheet according to heat dissipiation

Do you have an exhaust fan already, or are you utilizing the fan on the radiator?

If you are utilizing the radiator fan to move the air, size the inlet to the fan at least the same area as the radiator inlet. I had always over-sized by about 25% to make up for dirt, debris, cottonwood seeds, etc. You do not want to put stress on the fan, assumming it is an axial fan. They are not built for back pressure systems. Check the equipment manufacturer for their recomendation.

The outlet should be the same!

Allow extra area if there are any turns in the ductwork. Use long-turn elbows with turning vanes.

You do not want to add any resistance to the air flow!

If you need to ask this question, you should confer with an expert that has experience in this area.

I would also take temperature measurements before and after the installation. This will help determine if there was a mistake made in the installation.

The manufacturer's literature on the generator will tell you the amount of cooling air required for the generator. It will also tell you the amount of air the colling fan provided with the generator will produce. If there is a deficit, then additional forced air must be provided by the use of fans or ventilators placed in the wall or ceiling of the room. Make-up air required for the combustion process is normally found within the cooling air stream. Therefore, no additional air need be required for that purpose. There may already be a turbo-charger on the combustion air intake that will deliver the required air to the cylinders for combustion.

The cooling air requirements, if not satisfied by the installed fan on the generator, can be calculated and adequately sized ducts can be determined with simple formulae used for airflow calculations in HVAC or other air-moving situations.