[Elecraft] KPA500 - Advantage of min fan speed?

[George Thornton]

>From a physics standpoint, heat is radiated from an object either by direct radiation of heat into space (photons) or by transfer of heat to an adjacent object with lower temperature.

For heat transfer to another object, the amount transferred depends substantially on the heat absorbing characteristics of the object.   Some objects are natural insulators and will result in little heat transfer.  Air is not an insulator but it is not as effective as water, which is 24 times as heat absorbing as air.  

The surface area of contact is also important.  Moving air across a hot surface increases the exposure of cooler air to the hot surface resulting in faster cooling.  In other words a faster fan will always cool more than a slower fan.




-----Original Message-----
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of Don Wilhelm
Sent: Monday, September 30, 2019 10:28 AM
To: Andy Durbin <a.durbin at msn.com>; elecraft at mailman.qth.net
Subject: Re: [Elecraft] KPA500 - Advantage of min fan speed?

Andy,

Physical fact related to any heat dissipating object -- if you apply an air stream across the object, it will not come up to a given temperature as quickly as having no air stream across it.

Specifically for the amp, if you run the fan speed minimum at 1, it will heat to the 55 degC threshold more slowly before switching  to level 2. 
Of course, from there on up to higher temperatures, there will be the same time period between the higher fan speed steps.

In other words, the fan minimum will NOT shift the entire range of thresholds, but it WILL delay the time to reach the level 2 threshold.

73,
Don W3FPR

On 9/30/2019 1:13 PM, Andy Durbin wrote:
> 
> I measured the fan speed thresholds over a year ago but that information doesn't answer the question about any operation advantage of running min speed  greater than zero.
> 
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