[time-nuts] LPRO Heat Sink?

Hal Murray hmurray at megapathdsl.net
Wed Sep 23 17:07:51 UTC 2009

> 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? 

The heater is for the physics package.  The heat sink is for the electronics.

> 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? 

It doesn't take much.  What do you have handy?  (Don't forget goop or 
whatever to connect the baseplate to your heatsink.)

If you need some guesstimates to get started, try a 8 inch square of 1/8 
aluminum.  I don't think that will need a fan if you mount it vertically.

> 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.

Yes, but an LRRO doesn't need much.  A typical noisy fan will be way overkill.

Is there a rule of thumb for a flat plate mounted vertically so convection 
provides the air flow?

These are my opinions, not necessarily my employer's.  I hate spam.

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