I believe it's called "Buoyancy-driven ventilation". Natural airflow will occur when there is a large difference between interior and exterior air. All you would need is to poke some holes in the outer case for cold air to get in and other holes for hot air to get out. So for example if the exterior air is 17C, and the interior air of the phone (which is in thermal contact with the chipset though some aluminum or graphite sheet) is 45C, you'd no longer have to see the phone throttle its performance to lower its temps. It would cool itself through natural ventilation like a woman in a burqa. You can run a game at constant 60 fps indefinitely on this phone while all other phones start at 60 fps and end up at 25 fps after just 5 to 20 minutes of gameplay. Why can't this be done? What are the physical limitations of a smartphone preventing it?
closed as off-topic by John Rennie, Jon Custer, ACuriousMind♦ Dec 16 '16 at 0:38
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For a chimney to work effectively, it needs to be tall: then, a small difference in density can provide a reasonable change in pressure. Secondly, the chimney needs to have an appropriate aspect ratio. For small channels, slow flow follows Poiseuille's equation, in which the flow rate goes as $\Delta p a^2$ - make the channel half as big, and you need 4x more pressure to get the same air flow. And you need air flow in order to carry the heat away.
The bottom line is - the size of a phone is too small for this to work effectively at the temperature difference you can tolerate on the processor.