the guarantee may be limited to proofgrade materials, though i’m sure there’s some possible legalese that covers something like “safe, reasonable laser usage.”
FWIW, if those are regular computer fans you’re talking about, they probably don’t do very well at all with any substantial back pressure. They’re good at moving fair amounts of air relatively quietly. (My anecdote: the first time I tried to built a nozzle thingy to direct cooling air for my 3D printer, I turned it on and felt a significant airflow blowing backwards past the fan blades.) You likely want some kind of blower.
1 Like
One thing to note is suction airflow feels the same as blowing airflow. They both simply cool the skin. I often think a fan is blowing when it is sucking, so I hold a sheet of paper near it to see which way it deflects.
i lick a finger and feel which side gets colder
Not sure that works does it? The side with highest airflow will be coolest and that will always be the side nearest the fan, regardless of whether it blows or sucks.
These are the same form factor as a lot of computer fans but are 24V with optional PWM. They’re rated for about 70CFM each, but not that much pressure at only .09 inches of water.
Guess I’ll have to do an Experiment!
no, it’s a pretty reliable indicator of direction, i find.
edit: i don’t tend to work with very faint sources of directional air, so i don’t know how easy it is when barely detectable.
Why?
I have just tried it and it doesn’t work for me.
I have an 80cfm extraction fan that blows into a 22mm pipe via a funnel shaped duct. If I place my hand near the intake it feels like it is blowing. If I wet my finger the cold side is nearest the fan. If I place a piece a sheet of balsa wood anywhere near it it gets sucked onto the fan guard so it is definitely sucking, not blowing.
I often hear people say that air comes backwards over fan blades but I think they are all fooled as we have no way of detecting airflow direction with our skin.
okay, maybe it’s of limited use to you. i use it all the time when i take the window fans in and out to check for how the air is going through the room and it’s repeatable for me. i think the conflict here is scenario.
I think if the airflow is parallel, like wind, then the wet finger will work because the lee side will have less flow over it. Near a fan the air is cone shaped, so there is more flow at the fan side, regardless of flow direction.
1 Like