Lighting Why blow into the light when you could blow out? Makes no sense to me

[Groff]

Right, so this is basically the standard for most, if not all LED's

But this makes absolutely no sense to me. It's much more efficient to have the passive intake, that semi-passive outtake. It creates much more noise, turbulence therefore less flux, increased pressure inside the casing therefore lower heat dissipation, harder for the fans to work so life expectancy is lower, actively encourages dust all over the place… I simply don't get it.

Flip the fans upside down and you get much better cooling all round. All other gear I use blows outwards. PC fans don't blow into the CPU heatsink! Maybe I'm missing something logical here, but I'm completely stumped.

For heavens sakes, we don't lower the temps by blowing cool air into it, that's totally inefficient. What we do is blow the heat out, and most of the time passively let cool air in, or actively will a smaller fan.

 

[Yunglord]

Right, so this is basically the standard for most, if not all LED's

But this makes absolutely no sense to me. It's much more efficient to have the passive intake, that semi-passive outtake. It creates much more noise, turbulence therefore less flux, increased pressure inside the casing therefore lower heat dissipation, harder for the fans to work so life expectancy is lower, actively encourages dust all over the place… I simply don't get it.

Flip the fans upside down and you get much better cooling all round. All other gear I use blows outwards. PC fans don't blow into the CPU heatsink! Maybe I'm missing something logical here, but I'm completely stumped.

For heavens sakes, we don't lower the temps by blowing cool air into it, that's totally inefficient. What we do is blow the heat out, and most of the time passively let cool air in, or actively will a smaller fan.

That's why all of us have to switch the direction of the fan's in ufo led's and stuff ahahah

 

[Corgy]

I too asked myself this question, and actually came across an explanation that I no longer can find.....there's sound non-intuitive reasons........it has to do with the airflow space and pathways inside the cabinet, what kind of chips is used and laminar flow.........there's some hints in these links to why and when vertical or horizontal airflow is chosen....someone with google skills as opposed to me would likely quickly find the scientific explanation.......

https://www.msi.com/Graphics-card/R9-390X-GAMING-8G.html#hero-overview

https://en.wikipedia.org/wiki/Thermal_management_of_high-power_LEDs

https://en.wikipedia.org/wiki/Nusselt_number

http://www.mechatronix-asia.com/How..._passive_free_air_convection_LED_cooling.html

https://www.researchgate.net/public...e_by_Natural_Convection_An_Experimental_Study

But why not ask one of the LED vendors on here, there's plenty........ahem.......

 

[Site]

I believe if the fans were just drawing it through the unit, so it would be intaking at the sides then sucking the air over the heat sinks, the air wouldnt actually flow into the fins of the heat sink....if the air was dragged up and through it would follow the easiest air path and bypass the fins, and not giving a good, even transfer of heat....so you would lose efficiency of the heat sink...might be more theory behind it but thats my thoughts off the top of my head....so when it is blown into the heat sink it will find its way into the fins and find a way to get out again...

 

[BigSm0]

I believe if the fans were just drawing it through the unit, so it would be intaking at the sides then sucking the air over the heat sinks, the air wouldnt actually flow into the fins of the heat sink....if the air was dragged up and through it would follow the easiest air path and bypass the fins, and not giving a good, even transfer of heat....so you would lose efficiency of the heat sink...might be more theory behind it but thats my thoughts off the top of my head....so when it is blown into the heat sink it will find its way into the fins and find a way to get out again...

This would be my explanation as well. It may miss the heatsinks in doing so. It would be quieter and may make the fans work less hard but not as efficient. Not unless there was some sort it chase way for the air to travel through.

 

[KapScot]

You can see this effect is you place a PC Fan (I use 3 in my small grow cabinet and that's without those in the LEDs) close to a surface - the closer to the surface (intake) you get the less air gets moved - fans for component cooling always blow from a (hopefully) clear intake space around whatever fan is required - it takes a lot of oomph to get air mooving around a constricted space which is why we need bigger fans to pull thru filters - the amp load at startup on a big Ruck type fan will give you an idea as to extra power required to get moving.

Personally I thought especially for LEDs the thing to do would be to put a sort of false ceiling in the cabinet whereby all the led cooling (side panel external vents) - and external fan intakes were located on the exposed side to the room/cabinet - which would only leave the LED temps at the surface as heating agents. Maybe next year if I rebuild my cabinet lol - the only down side I would see would be an increase in room dB from the exposed LED fans but that might be counteracted in less cooling required (usually means less fan extraction noise).

 

[rshackleferd]

Put your hand on the back side of a fan and now put your hand in front of the fan. Which side would you use to cool stuff down?

 

[BigSm0]

Put your hand on the back side of a fan and now put your hand in front of the fan. Which side would you use to cool stuff down?

It's the same amount of air movement on both sides.

 

[thetreeman]

I think you need to think on a more molecular level. Heat is absorbed by molecules hitting a surface and the energy transferring to those molecules. The best insulator is empty space, thats why thermoses are filled with a vacuum chamber often to keep things warm or cold. Pushing air into something causes more molecules to hit that surface and will absorb much more heat than pulling air away from something, unless the air is forced to contact the surfaces before it gets to the fan that is sucking, as is the case in a laptop or whatever where there is a very defined course the air must travel going through the case and heatsink before reaching the fan. Make sense?

 

[rshackleferd]

That might work in a pipe or tube but the front side of the fan is slamming against other air causing more circulation. Instead of a small area of suction you have a large area of flow.