[time-nuts] LPRO Heat Sink?

J. Forster jfor at quik.com
Wed Sep 23 14:51:29 UTC 2009


Monsterously thick will NOT do it. All that does is increase the heat
capacity of the HS, not it's ultimate thermal resistance (W/deg).

You need surface area and air flow to cool something. The air flow is
needed because there is a "film coefficient" between the HS and the room
air. Even minimal air flow drastically reduces the film coefficient,
increasing heat flow per square inch.

-John

==============



> The heat sink requirements are in the LPRO manual that is available on the
> net.  My recollection is that the sink would require fins unless it was
> monstrously thick.  The requirement is to keep the base plate less than 70
> degrees C and the manual says this will require a heat sink with a thermal
> resistance of less than 2 degrees C per Watt in order to achieve this in
> an
> environment up to 50 degrees C.
>
> You can, however, turn it on to check it for a few minutes, without a heat
> sink attached.
>
> Joe
>
>
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of William Zimmer
> Sent: Wednesday, September 23, 2009 8:41 AM
> To: time-nuts at febo.com
> Subject: [time-nuts] LPRO Heat Sink?
>
> I am new to the Time-Nuts list and to the time standard area in general,
> so please excuse my questions if they has been asked and answered before.
>
> I just purchased an Efratom LPRO 101 Rubidium frequency standard.  As I
> understand it, I must mount it on a heat sink.
>
>  
>
> Question 1:  The lamp and chamber operate at a temperature around 100
> degrees C and we must provide sufficient power to heat the unit.  If we
> are heating the unit, why do we need a heat sink?  Doesn’t the heat sink
> defeat the heating process?
>
> Question 2:  Assuming that there is a reasonable answer to question1 and
> a heat sink is needed, how big a heat sink is required?  Are fins
> required?  Is forced air required?  In other words, what do I have to do
> to mount the LPRO 101 correctly?
>
> Thank you in advance for your assistance.
>
>  
>
> Bill Zimmer, N3VTW
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