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Im trying to build pc cabinet such that there is 3 fan input to cabinet, and just one output which is the smps inbuilt fan. Then seal off all other air gaps.

Q. Will the smps fan break due to receiving 3x its capability?

Or reprase as, Will using different fan size in same duct system break the smaller fan?

iuofk
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    There will probably be no damage unless the 3 other fans are huge. People have been building PCs with unbalanced fan directions forever. – vir Jul 20 '22 at 17:24

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There are 2 criteria. CPU core temp, other hotspot temp and fan noise level that determines your design targets.

There is also a CPU fan that just circulates heat usually and often Graphics card fans that exhaust directly.

Pros:

  • reduce CPU temp, remove PSU heat

Cons:

  • accumulate dust on CPU fins, MOBO, inside Tower case and PSU case,
  • add noise with eddy noise interference on a mesh.
  • spread circulate heat rather than exhaust directly
  • transfer CPU heat to PSU heat.

The best cooling rate is > 3m/s velocity directly over the hotspot not 50~100 CFM into the box.

Room dust tends to fall after a while of still air. so floor-mounted towers will collect more dust.

  • 3 input fans that you have will collect more dust but have low velocity over the hotspots.

The velocity of eddy currents on fan intake creates lots of noise and reduces air velocity significantly. With a plenum with a small cross-sectional area, airspeed increases with eddy currents near the surface collecting more radiated heat.

It would feel the same as you being sheltered by houses in a wind storm. So you want to design the heat flow, somewhat like a laptop with a thin plenum of air to exhaust with air intake not forced. If the fan has no finger protection grid, it will run much quieter. When mounted inline with a plenum, it gets muffled even more.

So rather than recycle the CPU heat into the PCU, why not create a plenum over the CPU and remove the heat directly from top to rear, so the PSU does not accumulate more dust and operate with warmer air. Dell used this method about 25 yrs ago to make towers extremely quiet and cool using inline CPU fans with axial exhaust and radial intake.

These are just some experiences, I've had with fan designs using smoke, lasers, and thermocouples.

Tony Stewart EE75
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  • the smps fan (or smaller fan) will not break due to forced dynamo spin from excess air flow? – iuofk Jul 20 '22 at 21:02
  • No. that does not prevent failure.. if sealed the flow is limited due to overall box pressure and vent restrictions. So the 3 fans could be reduced to the PSU fan flow rate. But again that does not mean significant CPU temp reduction – Tony Stewart EE75 Jul 20 '22 at 21:24