EMHeatTube

Looking into how to trigger the SAT to crystalize when in supersaturated(?) state.

The main driver has been having a mechanism that can be activated with no pass-troughs, to aid sealing. Which lead to magnets as strong hard drive magnets are fairly easy to come by. 

First design had a moving ring with screws in it so a magnet could pull it up, with the spring of the disk pulling it back down. While the was some success with this design it wasn't reliable. The print direction meant the 2 rings would rub over each other and cause friction and the click disk didn't have enough strength to pull it back all the time. Also small mistake in that I forgot PLA softens at a low ish temp and totally deformed it.

Version 2 (or maybe 3 by this point) uses a single strip of metal but changes the magnet point to the side so the metal strip is the only moving part. This provides plenty of level advantage and almost no spring back resistance. There is a pivot point to concentrate the movement onto the part with the perforation to ensure maximum movement of them.

I don't really understand what triggers the SAT it doesn't seam to be well understood. I have tried to emulate the click disks that are used in the hand warmers. An interesting side is when assembling the V1 test too much movement of the SAT and trigger was setting it off without the disk moving. Could make transport interesting.

Initial investigations to see if we are barking up the wrong tree.

Assumptions

• SAT density: 1.46g/CM3
• SAT latent heat of fusion: 0.073Kwh/Kg (264kJ/KG low end 289KJ/KG high end)
• 60% SAT to water solution (volume?)
• ABS thermal conductivity: 0.1 W/m/K (SAT thermal conductivity not modeled ABS wall only)
• SAT temp 58C

First test pipe ( to be built)

• 43mm OD 1.5mm wall ABS 1m long
• 4.16Kg sodium acetate 1.91Kg water 6.07Kg total
• 0.30Kwh
• heat output @18C room: 257w
• heat output @20C room: 244w
• estimated 1h runtime

Full size pipe

• 75mm OD 65mm ID 5mm wall ABS 1m long
• 11.55Kg SAT, 5.31Kg water, 16.86 total
• 0.84Kwh
• heat output @20 room: 166w
• heat output @ 18 room: 175w
• estimated 4h runtime