Numbers of cooling fan for a heatsink?

I am trying to figure out if I need only one fan for my heatsink or more?
I asking cause the fan that I have selected do not cover the entire heatsink area. Does it means that I need to have more fans
in order to maximize the cooling from the heatsink?

In that case, if my fan needs to have a speed of 9m/s, and I lets say I have 4 fans.
Does each fan still need 9 m/s ? or is it enough to have only 2.25 m/s for each /fan?

Thank you

mading2018 said:

In that case, if my fan needs to have a speed of 9m/s, and I lets say I have 4 fans.
Does each fan still need 9 m/s ? or is it enough to have only 2.25 m/s for each /fan?

Thank you

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Yes, more fans will maximize. Still needs 9m/s.

But really, whether you need it or not depends on application. Many heatsinks don't need fans at all.

dknguyen said:

Yes, more fans will maximize. Still needs 9m/s.

Click to expand...

Thank you for letting me know .

dknguyen said:

But really, whether you need it or not depends on application. Many heatsinks don't need fans at all.

Click to expand...

Yes, it is true.

Something came up, so I need to ask again regarding the heatsink.

I have some concern when it comes to wires that is connected from the mosfets, diodes, transformer (mounted on the heatsink) to circuit board, where there is 5-6 cm distance between them. Do you think it may be a problem with occurring interference? If it is a problem, do you have some suggestion on how to overcome it?

Depends on the frequency you're switching at and the rise-times involved.

Best way to deal with the problem (if there even is a problem) is to lay the board out differently and put things closer together and sandwich the offending traces between two ground planes.

Just a point about your original post. Your 9m/s is an air speed - fans are normally quoted in volume - 9l/s - Liters per Second. A 40mm fan may produce 9m/s but an 80mm fan will move 4 times as much air and a 120mm fan will move 9 times as much.

Mike.