Large silent fan for cupboard ventilation

[octechno95]

I want to install a large PC case fan into a cupboard for ventilation. I want the fan to be as silent as possible so thinking that either a 200mm or 140mm size would be ideal. I know the fan will run at 12V but I want to run the fan off mains so is there a safe mains adapter that will allow the voltage to be stepped down safely so I can do this? The cupboad has a few passively cooled nework equipment so cool requirements are pretty low. It's already been working fine without ventilation for months so ventilation is just a small improvement.

The two that I were looking at were the Noctua 140mm or the Noctua 200mm I am slightly leaning towards the 200mm as it seems to run a lot quieter for comparable or better airflow.

Are there better options than these for around the same price? How can I connect these to mains?

 

[octechno95]

USB powered fan probably ideal with USB "phone charger" type of thing

Is it easy to power a PC case fan from USB? How would I do that for the Noctua 200mm? I need to mount the fan onto the inside wooden door. On the outside, I'll have a grilled vent cover.

 

[octechno95]

I've only got low powered fanless equipment. Cupboard has been fine without any fans for months so single fan feels like it will be enough of an improvement. Twin fan will be overkill. Cupboard isn't airtight so a single fan blowing out air will allow cooler air to be drawn in around the gaps of the cupboard.

Given a single fan, which direction should I mount it. Blow out air or pull in air?

 

[octechno95]

Cupboard is marginal warmer than the outside room. Makes sense, will point the fan blowing inwards. Thank you all