PCM Testing Update

Toward the end of July, Saad and I took an afternoon to try out some improvements to our PCM encapsulation process. Specifically, we wanted to try a simple method for securing the empty PCM packet in place while pouring in the paraffin, which we melted in an aluminum can "crucible" of sorts using a hot water kettle as a double boiler.

Here's an informal video overview of the process:

Materials

Electric hot water kettle, paraffin wax, empty PCM packets, 1/2" bore steel 'flask-filling' funnel, small spring-loaded clamps, cardboard box, pop/soda can, sharp scissors, long-stem digital thermometer, heating pad, handheld heat sealer, tabletop heat sealer, electrical access, water access

Process

1. Place a few cm of water in a typical electric hot water kettle.
2. Cut the soda can open at the top and squeeze one of the edges to make a little spout.
3. Place a few hundred grams of paraffin wax in the aluminum can.
4. Place the can in the kettle along with the thermometer, and turn the knob until you reach a water temperature of at least 65C (which is way above the 40C paraffin melting point but will speed up the filling process).
5. Wait until the paraffin is completely melted, perhaps 10 minutes. Meanwhile, cut off the top of the cardboard box and clamp the empty PCM packet to the sidewall, with the heating pad also clamped, behind it. The PCM packet should rest against the heating pad. Plug it in and turn it to a medium heat setting (say around 40C).
6. Place a heavy-ish object like a full 1L bottle of water in the box as a counterweight.
7. Insert the spout of the funnel into one of the PCM packet lanes and hold it in place.
8. Carefully pour paraffin up to the marked "fill line" on the PCM packet.
9. Repeat until all of the PCM packet lanes are full.
10. Wait until paraffin has solidified partially (so that it resists movement when squeezed) and use the handheld heat sealer to seal the top edge of the PCM packet.
11. Or, wait until paraffin has completely solidified and use tabletop heat sealer to seal the top edge of the PCM packet.

Some Conclusions

From this brief experiment we were able to extract a few salient points:

1. We need to design a rack that can hold multiple PCM packets at once so that filling, solidifying and sealing can be completed in parallel.
2. Alternately, we could design an easily replicable PCM packet filling rack for each packet.
3. Refrigeration would of course speed up the solidification step.
4. The heat pad may not be adding much here. Its intended purpose is to reduce premature freezing of the wax ("self sealing") that sometimes occurs during filling. It seems that this can be accomplished fairly well by increasing the molten wax temperature. However, the heating pad may in fact be useful in colder environments; this experiment was carried out in a room that with an ambient temperature of around 27C.