Sucking or Blowing?

Spin off from current thread, what is your opinion? Please state why if you have a strong opinion....

The difference is negligible, but for the sake of the fan its better to blow. Sucking hot air through the fan will shorten its life span.

If i got money , i will go forcpu cooler AIO water cooling for each cob.
Got now 7 cob , 4x50w and 3x80w so 7 x ~60$, a liitle bit expensive to cool 7 cob

redi jedi said:

The difference is negligible, but for the sake of the fan its better to blow. Sucking hot air through the fan will shorten its life span.

Click to expand...

Will shorten seriously or what ?

i vote "sucking" just cuz heat wont blow on the plant .
but mines blow, if they sucked air, i will win at least 3 degrees ....which is not negligible

I always seem to have heat issues, meaning not enough heat. Maybe I just keep my basement too cool....

Sucking makes only sense if you have a radiator like the ones used in water cooling systems or if you want to pull heat from a housing.
In most other cases blowing is the better mode of operation.

You never ever push air though a filter or a light.. Always pull air!!!!!!

Pushing air will produce less cfm's and push through any dust or debris in the room through the fan, filter or light

@hyroot
We are talking here about heatsinks and not some filters, cool tubes or what ever.

hyroot said:

You never ever push air though a filter or a light.. Always pull air!!!!!!

Pushing air will produce less cfm's and push through any dust or debris in the room through the fan, filter or light

Click to expand...

If any dust or debris makes it through the filter, it really doesnt matter if its pushed or pulled...its going through anyways

Once you add the friction the air encounters moving through the duct, the whole push or pull is moot.(in regards to cfm)

http://sound.westhost.com/heatsinks.htm#s18

18 - Fan Cooling
...
..
"At first glance, you might think that it doesn't matter much whether the fan sucks or blows air into the tunnel. In reality. there is usually a big difference, with blowing (as shown) giving much better cooling. The reason is simple ... the air leaving the fan blades is turbulent, and it swirls around vigorously as it leaves the fan blades. This allows the airflow to 'scavenge' otherwise non-moving air from against the fins. The fins therefore get a continuous supply of cool air which aids heat removal.

Remember that the effectiveness of a heatsink depends on the temperature difference between the heatsink itself and the adjacent air. If the air is warm (right against the fins) then the heatsink must run hotter than it would with cooler air against the fins. This is a simple relationship, and determines the thermal rating of any heatsink.

Should the fan be connected so it sucks air into the tunnel, the airflow will be mostly laminar - moving fastest in the centre, with comparatively little movement at the surfaces of the fins where it's needed most. Without the turbulence that stirs up the airflow and making laminar flow impossible, the performance is reduced dramatically. The same applies to a conventional heatsink with a fan attached to the outside of the fins. The heatsink temperature difference between blowing and sucking can be 10-15°C or more, depending on the heat load [7].

The golden rule of forced air cooling is that you want (and need) the greatest airflow and turbulence possible, so the fan should always blow air onto the heatsink. Neverset up a fan to suck air across the heatsink, because as a method of cooling ... it sucks

."

I'm using two in-line fans in my grow room one 8" blowing fresh air in and a 6" sucking out. I'm using an inline fan speed controller on the 8" to keep them balanced.

tomate said:

@hyroot
We are talking here about heatsinks and not some filters, cool tubes or what ever.

Click to expand...

My bad. I couldn't see the pic in the first post. I was sitting in a BMW parking lot in the sun waiting for a friend to finish paperwork.

guod said:

http://sound.westhost.com/heatsinks.htm#s18

18 - Fan Cooling
...
..
"At first glance, you might think that it doesn't matter much whether the fan sucks or blows air into the tunnel. In reality. there is usually a big difference, with blowing (as shown) giving much better cooling. The reason is simple ... the air leaving the fan blades is turbulent, and it swirls around vigorously as it leaves the fan blades. This allows the airflow to 'scavenge' otherwise non-moving air from against the fins. The fins therefore get a continuous supply of cool air which aids heat removal.

Remember that the effectiveness of a heatsink depends on the temperature difference between the heatsink itself and the adjacent air. If the air is warm (right against the fins) then the heatsink must run hotter than it would with cooler air against the fins. This is a simple relationship, and determines the thermal rating of any heatsink.

Should the fan be connected so it sucks air into the tunnel, the airflow will be mostly laminar - moving fastest in the centre, with comparatively little movement at the surfaces of the fins where it's needed most. Without the turbulence that stirs up the airflow and making laminar flow impossible, the performance is reduced dramatically. The same applies to a conventional heatsink with a fan attached to the outside of the fins. The heatsink temperature difference between blowing and sucking can be 10-15°C or more, depending on the heat load [7].

The golden rule of forced air cooling is that you want (and need) the greatest airflow and turbulence possible, so the fan should always blow air onto the heatsink. Neverset up a fan to suck air across the heatsink, because as a method of cooling ... it sucks

."

Click to expand...

guod nailed it!

came in to post blowing because of turbulence but you covered that already

moving volumes of air sucking is always better
conducting heat from a surface blowing is always better

Sucking and blowing are too vague. All that matters is that air is being pushed ONTO your heatsink rather than off.