Stack effect on small scale

  • Thread starter mhjerde
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Main Question or Discussion Point

Does it make sense to try to use the chimney effect/stack effect to increase heat dissipation for a smallish electronic enclosure?

I'm thinking that if I hollow out the two vertical ends of the enclosure, I can get a 100mm high 5x5mm "chimney" on each side. On paper I get about 0.09 Pa pressure difference and a airflow of about 4.0E-6 m3/s. That does not look like much, but I have very little experience with this topic.
Does it matter if the chimney is straight or conical? Is there an ideal shape?
The enclosure is made from 6061 aluminium, dyed and anodized.

I'm hoping someone could offer an opinion on this. Is it worth pursuing?
 

Answers and Replies

  • #2
Mech_Engineer
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So you're basically trying to take advantage of natural convection for cooling? Are you familiar with natural convection calcuations?
 
  • #3
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I can't say I'm too familiar with natural convection calculations. I managed a rough estimate of the surface area needed to dissipate heat for the prototype in an upright position, without really understanding all the intricacies of natural convection. It also turned out to be a bit on the low side for real world use.

I was hoping I could avoid having to increase the size or add cooling ribs to the outside. I might get some added cooling by hollowing out the vertical parts of the frame, but I don't know how much of an effect an airflow 4.0E-6 m3/s gives me.
 
  • #4
Mech_Engineer
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I can't say I'm too familiar with natural convection calculations.
If you're wanting to use passive cooling in an electronics enclosure, this is what you'll have to use.

I managed a rough estimate of the surface area needed to dissipate heat for the prototype in an upright position, without really understanding all the intricacies of natural convection. It also turned out to be a bit on the low side for real world use.
What calculations did you use to determine this?

I was hoping I could avoid having to increase the size or add cooling ribs to the outside. I might get some added cooling by hollowing out the vertical parts of the frame, but I don't know how much of an effect an airflow 4.0E-6 m3/s gives me.
You also mention that you plan to use 100mm tall vertical tubes to create a 0.09Pa pressure difference (which I'm assuming you calculated using the standard atmospheric model) but the pressure difference in a vertical tube is balanced by gravity- it doesn't just start flowing air by itself.
 

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