Microsoft announces Lumia 950 and 950XL water-cooled Windows Phones
...
The Snapdragon 810 has a reputation for heating up rapidly, which might be why Microsoft has opted to bring the phase-change liquid cooling technology from the Surface tablets over to its phones. We can surmise a bit about how this will work based on the Surface. In these devices, the liquid cooling system consists of a thin copper heatpipe connected to the processor. There’s water inside the heatpipe, which turns into vapor as the CPU ramps up. That vapor travels through the heatpipe to a fan that cools it off and lets it condense into liquid water again.
... If Microsoft can keep the Snapdragon 810 cool, it might be a worthwhile upgrade over the 808. In many Android devices, the 810 has to throttle down aggressively as it heats up, ending up not much faster than the 808. Windows on phones is already a snappy experience, even on mid-range devices. With a full-speed Snapdragon 810, it might be completely lag and stutter free.