Originally Posted by Greenback
a quote from martins fan tests
2 fans Push/Pull vs others - It was very clear that when using two fans per radiator section, that the radiator intself acts as a flow spreader and provided great benefit to straightening out the air for the second fan in a push/pull configuration. Just like doubling up with a pump, there is a pressure benefit to doubling up on fans and this translates to about a 20-30% performance gain. The added fan pressure simply means and added gain in air flow and corresponding performance. None of the experimental pull/pull or push/push configurations provided any noteworthy benefit as it seams the air is simply too disturbed from the first fan to allow the second to perform properly when air is moving.
I would always recommend a push/pull configuration for two fans and add a shroud to both sides if space allows.
Adding a shroud to the push fan adds about 3-4% performance gain from what I've seen around. (I'll have to find the sauce for you)
Altho, it's been proven time and time again that a shroud on the pull fan is pointless as the dead-spot doesn't affect it as much due to the fact it's only really assisting the push fans static pressure.
Altho, from what I'm gathering from the OP, he wants to know if 2 functioning fans together would increase performance. Which I can't answer as I've never tried it. Logics tell me no it wouldn't help. Or if it did, it wouldn't be worth the additional noise created from a fan blowing air into another fans moving blades. *shudders the thought*