120VAC 120mm x 38mm fan blade question

[eplebnista]

How does the number of blades a fan has affect its airflow capabilities?

I am replacing a 120mm x 38mm 120vac fan and have matched the specs pretty closely in regards to voltage, size, cfm, rpm, and amp draw but noticed a detail when I received the new fan I may have overlooked as being something very important in the application the fan is being used for (an air hockey table fwiw). The new fan has 7 blades whereas the old fan only has 5.

Any opinions or insights would be greatly appreciated. :beer:

 

[Billb2]

Originally posted by: eplebnista
How does the number of blades a fan has affect its airflow capabilities?

I am replacing a 120mm x 38mm 120vac fan and have matched the specs pretty closely in regards to voltage, size, cfm, rpm, and amp draw but noticed a detail when I received the new fan I may have overlooked as being something very important in the application the fan is being used for (an air hockey table fwiw). The new fan has 7 blades whereas the old fan only has 5.

Any opinions or insights would be greatly appreciated. :beer:

You really want to look at the PQ curves for fans. These curves describe the relationship between airflow and pressure for a particular fan.
A doubt that a 5 blade and a 7 blade, even if they deliver the same maximun CFMs, will operate the same against a backpressure.
http://www.actrx.com.tw/technical_pq.html

 

[eplebnista]

Thanks for the link. It will probably take me a little while to read through it.

I probably should have included the info below to better define my question.

Original Fan KA-1238HA1SAT Static Pressure .23/.26

Replacement Fan GAA1238-115BB Static Pressure .37


From the link:

However, the fan with curve A is much better than the fan with curve B. Why, because if you need the flow rate of Q, Fan A has more ?power? (higher pressure) to overcome the resistance. Or, you may think, if there is a specific resistance to overcome, Fan A can deliver more air flow than Fan B

I guess that sums it up. The static pressure is greater on the new fan. Hopefully it will be close enough to the original to work.