Rapid heat transfer during condensation?

[TeraV]

I was building a Liquid Oxygen condensing chamber (using gas Hydrogen as coolant) and noticed that the bottom row of cells in the chamber (using Insulated Tiles constructed from Mafic Rock) dropped in temperature rapidly as the Oxygen condensed.

The chamber has been running continuously for about 10-15 cycles, the rest of the chamber walls have only cooled down to around -10 C. Each tile in the bottom row drops in temperature by about 0.5-2.0 C each time a Liquid Oxygen droplet falls on it.

Is this a bug, or just bad design? Will replacing the bottom row with Airflow Tiles (with a second row of Insulated Tiles) prevent this heat loss?

[blakemw]

Yes, in the community this is called flaking or partial evaporation where 5 kg chunks of a liquid or solid boil or melt off, and it results in rapid heat transfer between solid tiles (even if insulated) and liquid.

The best fix is using an inner liner of a low heat capacity tile like lead metal tile which will rapidly and cheaply cool down. There is no way for rapid heat transfer to happen (directly) between a solid tile and an insulated tile, and in many cases it is actually reduced to 0 heat transfer (such as with Ceramic and Igneous Rock Insulated Tiles).

You don't strictly need the metal tile lining where liquid is not intended to contact it, though gas:solid has a 25x heat transfer multiplier which is a lot higher than solid:solid, it's still much much less than occurs via flaking, to fully minimize heat transfer use a full metal lining but it's especially important to have the lining where liquid will contact the tiles.

Edited Sunday at 06:09 PM by blakemw

[TeraV]

Ah, I didn't originally think it was flaking since there was less than 5kg of Liquid Oxygen, but I now realize it would start flaking once more Oxygen condenses, raising the liquid's mass above 5kg.

I was originally concerned about using Metal Tiles for the bottom row since they could increase regular heat transfer between themselves and the other Insulated Tiles, is that true? Is it still negligible in this case?

And if I use Airflow Tiles instead, does the Oxygen there prevent flaking, or does it introduce any other heat transfer issues I can't think of?

[blakemw]

3 hours ago, TeraV said:

I was originally concerned about using Metal Tiles for the bottom row since they could increase regular heat transfer between themselves and the other Insulated Tiles, is that true? Is it still negligible in this case?

No it's not true. For heat transfer with insulated tiles, the lowest thermal conductivity is used and the higher thermal conductivity is ignored, so it's completely irrelevant what the thermal conductivity of the other tile is, then if the other tile is gas, a 25x multiplier is applied - but the thermal conductivity of the gas still doesn't matter, doesn't matter if it's hydrogen or chlorine, it's simply 25x higher for gas than solid/liquid.

Edited Sunday at 10:58 PM by blakemw