[Elecraft] K3 Cooling

[Tom W8JI]

Let me throw a few things into the mix.

1.) About compression and temperature. There isn't enough 
pressure to make a difference. The fan in the K3 is not 
running at 40 PSI, or even at 0.4 PSI. I would bet the 
static pressure is less than 0.1 inches of water (.0036 
PSI). It takes a pretty big centrifugal blower to make .036 
PSI (1 inch of water), and the heating from that pressure is 
negligible.

2.) We really don't want laminar flow across a heatsink. We 
want some turbulence so the air isn't stagnant along the 
fins. The AL600 and ALS1300 have deflectors that add 
turbulence because the fins are 6" long, straight, smooth, 
flat, and far from the fans. Adding deflectors to create 
turbulence almost doubled the cooling. I doubt this is the 
case with the K3.

3.) I would not blow hot air from a heatsink or high 
dissipation area into the more sensitive electronics, nor 
would I do anything the engineers at Elecraft didn't suggest 
or approve. Generally people designing air systems know far 
more about the systems than casual observers. If I wanted a 
cooler heatsink and was left to my own devices, I would 
change to a higher airflow fan of the same style. I can see 
all sorts of problems that might occur from reversing, and 
even a few from adding a "blow into the case" helper fan.

The heatsink is probably warming the air with 150 watts of 
heat dissipation at times. I haven't looked at current drawn 
by the rest of the radio, but I doubt the other components 
in the radio dissipate 25 watts total. Why would I blow a 
150 watt heater into a 25 watt heated area? It would make a 
whole lot more sense to draw the slightly heated air across 
the heatsink than bake the rest of the radio.

73 Tom