Convection heat transfer

[rgduck]

In ONI, the air doesn't appear to move around much at all... at least not compared to real life, where cold air will quickly change places with warm air below it. Does this mean that doors don't do much to insulate rooms from their surroundings?

[YOLO KNIGHT]

Doors still transfer heat. Metal ones do, at least. They can be a considerable heat leak without a vacuum seal

 

edit: i thought insulation was an option for mechanized airlocks but maybe not?

[rgduck]

16 minutes ago, YOLO KNIGHT said:

Doors still transfer heat. Metal ones do, at least. They can be a considerable heat leak without a vacuum seal

Yeah, that's what occasioned my question. I've got a gap I don't want too much heat flowing across, but I don't care about germs or gases, and I don't want to set up a vacuum. I'm wondering whether I'd do better to put a door in or just leave the gap empty.

[Gurgel]

It really depends. Gas does not flow from convection as things in Oni do not expand when warmer, but gases do flow from pressure differentials although slowly. A door will give you one tile with very good heat conductivity but will prevent gas flow when closed. If there is gas flow, putting in that door is probably better. 

[rgduck]

9 hours ago, Gurgel said:

It really depends. Gas does not flow from convection as things in Oni do not expand when warmer, but gases do flow from pressure differentials although slowly. A door will give you one tile with very good heat conductivity but will prevent gas flow when closed. If there is gas flow, putting in that door is probably better. 

I notice that deodorizers tend to produce horizontal lines of cleaned oxygen (or leave behind horizontal lines of polluted oxygen). I'm guessing from this that gases flow left-right more easily than they flow up-down?

If so, maybe my choice should depend on the orientation of the gap.

[tuxii]

Gases sort themselves out in ONI based on density.  O2 and PO2 have identical densities so this unique layering behavior happens between them that doesn't happen with any other gases.

This also provides for an easy solution:

The carbon dioxide lock.  Thanks to CO2 being the heaviest room temperature gas in the game and having a low thermal conductivity makes this a good, easily implemented method of thermal isolation and mixture prevention.

[Gurgel]

9 hours ago, rgduck said:

I notice that deodorizers tend to produce horizontal lines of cleaned oxygen (or leave behind horizontal lines of polluted oxygen). I'm guessing from this that gases flow left-right more easily than they flow up-down?

If so, maybe my choice should depend on the orientation of the gap.

Good point. I guess I have been playing too many Oni as I sort-of implicitly assumed that. 

[yoakenashi]

ONI does have rudimentary convection as hot packets of gas will rise. I tested this a few months ago.

[6Havok9]

On 3/5/2023 at 9:45 PM, rgduck said:

In ONI, the air doesn't appear to move around much at all... at least not compared to real life, where cold air will quickly change places with warm air below it. Does this mean that doors don't do much to insulate rooms from their surroundings?

Sim convection is very fast and somewhat reliable. It's not real convection, there are no currents: packets of the same gas aggressively trade places with colder/warmer packets, when they can. You can cool just the top of a room and have a homogeneous temperature across that room, or a nice gradient if the room is large.

Full doors are made of metal, metal is a conductor, a much better conductor than gases. So doors are not insulators, they are exceptional conductors.

@tuxii already explained how gas density determines layering. O2 and pO2 will compete for the same layer. Left-Right bias was "fixed" a long time ago.

BTW, I still don't understand the correlation between the two sentences. Why would the lack of convection make doors worse insulators? I can't understand it, neither in real life nor in the Oniverse. So I refrained from answering until now. Like a good man taught me, when in doubt, don't post.

(still trying to understand  felt like a @Saturnustroll. Don't trust that guy, he's Evil!)

[wachunga]

1 hour ago, 6Havok9 said:

Why would the lack of convection make doors worse insulators?

I think the question was feeling out how significant a role gas movement plays in the transfer of heat energy. A door will stop gas movement and eliminate that avenue of heat transfer. Without convection, doors are less useful then one might think they would be if there was convection. IRL, a refrigerator door is critical as all the cold air inside will just fall out without the door. Like a bucket of water turned on it's side. Chest freezers are great because the cold air stays inside with the door open or even without a door. In the absence of convection, a standing freezer would work just as well as a chest freezer. The importance of the door being greatly reduced or made worse if you choose to phrase it that way.

 

As had been said, there is convection of a sort in ONI. But using a door to stop that doesn't work very well. Doors are super conductive with gases because of a hidden 25x gas<->solid multiplier. Heat will just transfer through the door and what convection ONI does simulate occurs regardless. To stop convection, you put the opening to your room on the top (like a chest freezer) or on the bottom. A door is not only superfluous for such a design, but harmful as heat transfers through cells faster when it is gas<->solid<->gas than when it's gas<->gas<->gas.

Without knowing the scenario it's hard to say more.

 

[rgduck]

3 hours ago, wachunga said:

I think the question was feeling out how significant a role gas movement plays in the transfer of heat energy.

Yes, that's what I was after. And the rest of your post is also exactly what I was thinking about in the OP... I just neglected to fully explain.

FYI my original scenario was this:

It's hot above and I'd like to delay the room below heating up. Do I put in a door or not?

[blakemw]

In ONI convection is fast sideways and slow upwards, and upwards it only occurs if the gas type is uniform because density based tile swapping takes precedent over temperature based tile swapping.

Convection is mainly a significant driver of heat transfer at higher gas pressures, like when you have 100 kg/tile in a steam chamber, those steam tiles swapping place can move huge amounts of heat. But it's certainly noticable at normal gas pressures.

A practical example is growing Sleet Wheat in a simple insulated tile pit, just relying on convection to keep the cold in  the pit, or contrarily growing a heat-loving plant like Pepperplants in an inverted pit.

Doors usually increase heat transfer, if you really want to have a door then make it out of Gold Amalgam which has the lowest thermal conductivity (similar to rock), but it's still not that low compared with gas tiles. Gas locks (like the common liquid lock but allowed to fill with CO2 instead of being filled with liquid) are very good thermal barriers.

[Gurgel]

On 3/7/2023 at 12:44 AM, yoakenashi said:

ONI does have rudimentary convection as hot packets of gas will rise. I tested this a few months ago.

Interesting. I never noticed. May explain some things though.