Re: Ambient temperature control

On 7/1/2024 7:34 AM, legg wrote:

On Sun, 30 Jun 2024 18:14:32 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:
 

Assuming you can keep a device in its "normal operating (temperature)
range", how advantageous is it (think MTBF) to drive that ambient
down?  And, is there a sweet spot (as there is a cost to lowering the
temperature)?

>
If all you're thinking of is MTBF, adding the complexity of an active
cooling element is a big step in the wrong direction for the system.

Shifting the reliability burden into a (relatively) low-tech, ubiquitous
subsystem allows failures to be maintained by "non-technical" people.
It also allows for easier redundancy -- you can add another AHU "in parallel"
with an existing unit a lot easier than redesigning the electronic
system to be more reliable over a larger operating range of temperatures.

Reducing the thermal impedance of the source, to ambient is the
usual way to go, when addressing a specific aging factor.

If ambient approaches the limits of the design, then what?
You design something to be able to operate at 50C (on paper).
It gets deployed *at* 50C.  What sort of failure rate do you expect
at that elevated temperature vs. operating that same piece of kit
at 30C by introducing active cooling?  (the assumption being that said
cooling can be maintained/repaired by a local run-of-the-mill agency)
The question tries to address that issue -- and, the consequences of
how "well" you strive to maintain a "better" operating environment.
E.g., cooling the environment to 10C and then letting it creep back
up to 50C before repeating the cycle would be different than keeping
the device "at" 30C.
Why set a cold aisle temperature of 20C and not 30C?  40C?  Why not
operate the devices at their specified ambient limits?
     Continuous Operation: 10C to 35C, 10% to 80% relative humidity (RH).
     10% of annual operating hours: 5C to 40C, 5% to 85%RH. 1% of annual
     operating hours: -5C to 45C, 5% to 90%RH.
I.e., the cited device CAN operate at 45C.  But, at what cost
(reliability)?

https://ve3ute.ca/2000a.html
 If you're thinking of performance, It's cheaper and more reliable
to concentrate on reducing the temperature of the point source, not
the rest of the planet.
 RL