Quote from: philipma1957 on January 04, 2015, 03:11:31 PM

Quote from: visdude on January 04, 2015, 02:41:38 PM

Quote from: philipma1957 on January 04, 2015, 12:46:17 PM

Quote from: visdude on January 04, 2015, 07:41:54 AM

I'm surprised that the discussion about replacement fans are more focused on their airflow volume (CFM) rather than static pressure (mm/H2O) which is more significant in heat sink/radiator applications. High static pressure fans are more capable of penetrating through dense heat sink fins such as in the AntMiner devices. I think there's a reason why Bitmain engineers equip their units with very powerful industrial 12038s with high static pressure (directly proportional to loudness) instead of just mainstream consumer-oriented 12025s.

true in the case of one push fan only. but two high cfm fans as push pull get around that.

since neither one needs full penetration of the heat sink using high static pressure, but if you don't care about sound the stock fan with a good pull fan cools best.

Push-pull configuration is only effective in an enclosed unit (S3) and not in an open-chassis design (S5) though.

I ran the s-5 with the stock fan pushing and at freq 412 the temps crept up to 67 and 65 .

I ran the same freq with the 148 cfm 3 pin delta as a pull and temps never went above 58 and 56 at freq 412. so for overclocking adding a high cfm pull fan got beter results.

I am sure that a sealed box would have helped more.

In your scenario (adding a pull fan in an open S5 unit), the pull fan is able to help dissipate some hot air coming out at the other end of the heat sinks to a certain extent (hence the temperature difference), courtesy of the powerful high-static-pressure (loud) stock fan that is able to force air through the dense heat sink fins. The key is to have a high-static-pressure fan that is more efficient in pushing/forcing air through restrictive heat sink/radiator fins for optimum cooling, enclosed case or not. I did add pull fans to my S1s back in the day because it helped to a certain extent.