Wax as a potting material?

[Inkidu]

Shot in the dark here. (Just a newbie)

After watching a show about the NASA moon rover and how they dealt with battery temp. control i.e. paraffin wax
Could this possible be used in a XM-L direct drive drop-in that is only on for a minute here and there.
Obviously would have to make sure the wax was fully enclosed but would this suck up heat any better than more traditional potting material?
The FETtie I just ordered is going to beg for amps.

U2 XM-L with a 3100 mAh Redilast with some copper tape on drop-in in a solarforce L2P

Any help would be appreciated.

 

[MikeAusC]

Paraffin is an Insulator - but when it melts it can start moving the heat away by Convection - just like a heat pipe.

 

[LukeA]

Do you mean a potting material or a heatsink? As a potting material over driver electronics it would be ineffective due to melting. As a phase-change material in a heatsink it might be effective if there is zero convection and if mass is a concern (like something being sent to space). Conducting the heat into the wax and containing its change in volume would be challenges.

 

[Inkidu]

The wax would be in the pill.
The idea being a quick way to transfer heat.
Going from a solid to a liquid requires heat/energy.
Something that if you were doing for more than a minute might not make sense.
For any kind of practical way you would go with a more traditional material, but what if you wanted to transfer heat quickly for a short period of time.
What change in volume?
Just thinking aloud, I could just buy a direct drive XM-L with an epoxy but what is the fun in that?

Thanks for any help.

 

[LukeA]

Liquid wax is less dense than solid wax, so the same mass of liquid wax is going to be volumetrically bigger than the same mass of solid wax.

If you want to drive an XM-L or any other power LED for any period of time more than just a flash you are going to need something to remove the heat from the LED. Potting the LED in epoxy would be a bad idea, but using a minimally thick layer of epoxy to attach it to some piece of metal is the usual way.

If I was trying to make a wax heatsink what I would do would be to find something like the "Heatsink, 8 Fin" on this page. Then I'd attach rectangular aluminum plates to each end of the slots, fill the slots with liquid wax, scrape the excess liquid off, let it cool, scrape maybe 3-5% of the solid wax out of each slot (to be more sure that it won't overpressure when the wax melts) and then bond another aluminum plate over the wax to seal it in. Then bond the LED to the heatsink's surface, wire it up and try it out. You might consider bonding the LED as an early step and taking some temp readings and pictures over time before and after adding the wax. CPF's nerds would appreciate it.

Ideally you would pull a vacuum over the wax after sealing it but that is probably beyond the scope of this device.