use min 100cfm and ~3000 rpm (pwm). But I suggest to use 2 fan. One is connected to the miner and regulated with pwm mode.
Other is placed on opposite side, soaking air out and powered direct from PDU molex at highest speed (its silent so it wont be so laud).
Or you can power them both at higest speed and from PDU, no need of connecting to the miner fan connector and pwm regulation.
i need silent ones so i can sleep, so replacing the standard ones is a must , thanks for telling me