Is the Stack Effect Effective for Small Electronic Enclosures?

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Discussion Overview

The discussion revolves around the feasibility of utilizing the stack effect, or chimney effect, to enhance heat dissipation in small electronic enclosures. Participants explore the implications of natural convection, airflow calculations, and design considerations for the enclosure's structure.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes using a chimney effect by hollowing out the vertical ends of the enclosure to create airflow for cooling, questioning the effectiveness of a 0.09 Pa pressure difference and 4.0E-6 m3/s airflow.
  • Another participant asks if the approach is aimed at leveraging natural convection for cooling and inquires about familiarity with natural convection calculations.
  • A participant expresses limited knowledge of natural convection calculations but mentions a rough estimate of surface area needed for heat dissipation, indicating that their estimate may be insufficient for practical applications.
  • Concerns are raised about the effectiveness of airflow generated by the proposed chimney design, particularly regarding the balance of pressure difference and gravity in vertical tubes.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the effectiveness of the stack effect for cooling in this context, and multiple viewpoints regarding the calculations and design considerations remain unresolved.

Contextual Notes

Participants express uncertainty about the calculations involved in natural convection and the impact of airflow rates, indicating potential limitations in their understanding and the assumptions made in their designs.

mhjerde
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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?
 
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So you're basically trying to take advantage of natural convection for cooling? Are you familiar with natural convection calcuations?
 
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.
 
mhjerde said:
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.

mhjerde said:
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?

mhjerde said:
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.