Do gasses obey ideal gas law?

[Dimitri]

I've read on the wiki that atmospherics in this game act according to the ideal gas equation, but I'm having trouble getting it to work in game.

I built a closed system of pipes, and injected CO2 into it. I then isolated a section of pipes, and pumped the gas into it at 10x pressure of the previous section. You'd expect temperature to rise with pressure, since the volumes are equal, but the temperature stays the same. Any ideas on why that might be happening?

[Darzan]

That is according to ideal gas law. That seems counter-intuitive but pressurizing does not directly affect temperature of gas, PV = nRT . Pressure increases while volume decreases. However you might get hotter gas if something in work process emits heat.

[Dimitri]

Originally posted by Darzan:

That is according to ideal gas law. That seems counter-intuitive but pressurizing does not directly affect temperature of gas, PV = nRT . Pressure increases while volume decreases. However you might get hotter gas if something in work process emits heat.

Does having the gasses in similar vessels (IE sections of pipe of similar length) not make sure the volume stays constant?

[Korin]

It does apply in everything but the ability to displace/store energy using pressure.

If you have a think about how much of this game would be useless if IRL refrigeration functioned in Stationeers you quickly come to the 'why' of that decision. For me it makes sense and adds to the game.

If i were able to cool and heat everything with pumps well ... thats too easy.

So if you negate the temperature variant of pv=nrt you can apply the equation to any PID type controller you like.

[Dimitri]

Originally posted by Korin:

It does apply in everything but the ability to displace/store energy using pressure.

If you have a think about how much of this game would be useless if IRL refrigeration functioned in Stationeers you quickly come to the 'why' of that decision. For me it makes sense and adds to the game.

If i were able to cool and heat everything with pumps well ... thats too easy.

So if you negate the temperature variant of pv=nrt you can apply the equation to any PID type controller you like.

Yeah that's what I was trying to do with the new heat exchanger. Thanks for the answer.

[Celery Man]

Originally posted by Korin:

If i were able to cool and heat everything with pumps well ... thats too easy.

damn this really sucks and is counter-intuitive in the extreme. a hard sci-fi game that intentionally breaks the rules of physics in such a way that a proportional / inversely proportional relationship only works in one "direction"? that's so ♥♥♥♥♥♥♥ confusing. that's like what Space Engineers did with thrusters imparting zero torque around centres of gravity and giving a game about *space travel* a universal maximum speed of a 100m/s. it's not fun, interesting, or elegant to have like 4 different slightly-overlapping options for heat exchange. if "easy" is a problem then:
- (a) that's a symptom the game is far too simplistic and needs more mechanics to interact with the temperature/pressure mechanics to give depth, and
- (b) simply split the pumps, radiators/exchangers, insulators, pressure vessels, coolants/refrigerants etc. into technological tiers with different rates / capacities / efficiency (which they've kinda done here, but not as sensibly or consistently as in, say, Oxygen Not Included or Rimworld).

edit: just discovered user Elmo's Atmospheric Realism Overhaul mod which fixes this whole problem: https://steamcommunity.com/sharedfiles/filedetails/?id=2882541343

[Harbingerman]

I just play the game/sim ... the idea behind it works for the most part and automation is where its at ... its more difficult than it was over a year ago and I want to see if they fixed some things which I know they didnt but we see ... I also play because very few people play it and it is challenging for my brain

[Dunkurtin]

Your confusion is probably based on incorrect use of the law. If you are taking gas from a larger pipe and putting it into a smaller pipe at higher pressure, your Volume IS changing. Your n is staying the same. So you move 10 mol gas at 375k from 10 pipes to 1. You go from
P=(10*R*375)/1000 = 31.16 to 311.6 = (10*R*T)100. Rearrange T=(311.6*100)/(10*R) = 375

Increasing pressure by moving to a smaller container, or adding more gas, doesn't just magically increase temperature. That's a backwards interpretation of causation. When you increase the temperature of a sealed gas you get higher pressure. It doesn't work in reverse because you can't magically increase pressure without changing another variable. Unfortunately half the wiki and guides are written by people who don't actually understand physics or how to use the formulas correctly.

[Soondead]

Originally posted by Dunkurtin:

Your confusion is probably based on incorrect use of the law. If you are taking gas from a larger pipe and putting it into a smaller pipe at higher pressure, your Volume IS changing. Your n is staying the same. So you move 10 mol gas at 375k from 10 pipes to 1. You go from
P=(10*R*375)/1000 = 31.16 to 311.6 = (10*R*T)100. Rearrange T=(311.6*100)/(10*R) = 375

Increasing pressure by moving to a smaller container, or adding more gas, doesn't just magically increase temperature. That's a backwards interpretation of causation. When you increase the temperature of a sealed gas you get higher pressure. It doesn't work in reverse because you can't magically increase pressure without changing another variable. Unfortunately half the wiki and guides are written by people who don't actually understand physics or how to use the formulas correctly.

Umm... If I pump more gas into a pipe, the pressure increases but the volume does not. The heat energy stored in the added gas must go somewhere, so into the pipe it goes too. How does this not increase the temperature? I thought this was the very premise that made everything from refridgerators to air conditioners work; radiate the excess heat, then release the gas back into the loop at low pressure so the temperature drops and it will absorb heat from whatever you want cooled.

I can clearly see that it doesn't work that way in the game, but I thought that was how it was supposed to work in real life.

[ulzgoroth]

Originally posted by Soondead:

Originally posted by Dunkurtin:

Your confusion is probably based on incorrect use of the law. If you are taking gas from a larger pipe and putting it into a smaller pipe at higher pressure, your Volume IS changing. Your n is staying the same. So you move 10 mol gas at 375k from 10 pipes to 1. You go from
P=(10*R*375)/1000 = 31.16 to 311.6 = (10*R*T)100. Rearrange T=(311.6*100)/(10*R) = 375

Increasing pressure by moving to a smaller container, or adding more gas, doesn't just magically increase temperature. That's a backwards interpretation of causation. When you increase the temperature of a sealed gas you get higher pressure. It doesn't work in reverse because you can't magically increase pressure without changing another variable. Unfortunately half the wiki and guides are written by people who don't actually understand physics or how to use the formulas correctly.

Umm... If I pump more gas into a pipe, the pressure increases but the volume does not. The heat energy stored in the added gas must go somewhere, so into the pipe it goes too. How does this not increase the temperature? I thought this was the very premise that made everything from refridgerators to air conditioners work; radiate the excess heat, then release the gas back into the loop at low pressure so the temperature drops and it will absorb heat from whatever you want cooled.

I can clearly see that it doesn't work that way in the game, but I thought that was how it was supposed to work in real life.

So yes and no.

Your description of why it should happen is wrong. When you pump more gas into a pipe, you're increasing the n and the P, while the V and the T don't necessarily change. It's true that the heat energy in the gas you added can't go away, but it doesn't - it just stays with the added gas in its new location. More thermal energy shared across more gas doesn't require a change in temperature!

However! When you compress gas, you are doing work on it, and that added energy goes into gas temperature (there is nowhere else a gas can store it). When you decompress gas it does work and loses heat! These effects are real, but aren't part of the ideal gas law and are not included in Stationeers.

[Decius Brutus]

Originally posted by Soondead:

Originally posted by Dunkurtin:

Your confusion is probably based on incorrect use of the law. If you are taking gas from a larger pipe and putting it into a smaller pipe at higher pressure, your Volume IS changing. Your n is staying the same. So you move 10 mol gas at 375k from 10 pipes to 1. You go from
P=(10*R*375)/1000 = 31.16 to 311.6 = (10*R*T)100. Rearrange T=(311.6*100)/(10*R) = 375

Increasing pressure by moving to a smaller container, or adding more gas, doesn't just magically increase temperature. That's a backwards interpretation of causation. When you increase the temperature of a sealed gas you get higher pressure. It doesn't work in reverse because you can't magically increase pressure without changing another variable. Unfortunately half the wiki and guides are written by people who don't actually understand physics or how to use the formulas correctly.

Umm... If I pump more gas into a pipe, the pressure increases but the volume does not. The heat energy stored in the added gas must go somewhere, so into the pipe it goes too. How does this not increase the temperature? I thought this was the very premise that made everything from refridgerators to air conditioners work; radiate the excess heat, then release the gas back into the loop at low pressure so the temperature drops and it will absorb heat from whatever you want cooled.

I can clearly see that it doesn't work that way in the game, but I thought that was how it was supposed to work in real life.

Heat pumps don't use only gases, they add a phase change and use the latent heat of vaporization to manage temperatures.

Hot, high pressure gas goes to the condenser, where it rejects heat to where heat is unobjectionable (or desirable), and as it loses heat the gas condenses to a high-pressure liquid. The liquid is metered to a low pressure and sent to the evaporator, where it evaporates and absorbs heat from where heat is undesirable (or available). The warm low-pressure gas is forced through a compressor, making it a hot high-pressure gas that continues the cycle.

The refrigerant is chosen to have large specific latent heat of vaporization and favorable phase curves; it is desirable that it absorb a lot of heat to boil at its boiling point and that there pressures at which it will boil at a lower temperature than the heat source and condense at a higher temperature than the heat sink are modest and within the capacity of the piping and compressor.

[ulzgoroth]

Originally posted by Decius Brutus:

Originally posted by Soondead:

Umm... If I pump more gas into a pipe, the pressure increases but the volume does not. The heat energy stored in the added gas must go somewhere, so into the pipe it goes too. How does this not increase the temperature? I thought this was the very premise that made everything from refridgerators to air conditioners work; radiate the excess heat, then release the gas back into the loop at low pressure so the temperature drops and it will absorb heat from whatever you want cooled.

I can clearly see that it doesn't work that way in the game, but I thought that was how it was supposed to work in real life.

Heat pumps don't use only gases, they add a phase change and use the latent heat of vaporization to manage temperatures.

Hot, high pressure gas goes to the condenser, where it rejects heat to where heat is unobjectionable (or desirable), and as it loses heat the gas condenses to a high-pressure liquid. The liquid is metered to a low pressure and sent to the evaporator, where it evaporates and absorbs heat from where heat is undesirable (or available). The warm low-pressure gas is forced through a compressor, making it a hot high-pressure gas that continues the cycle.

The refrigerant is chosen to have large specific latent heat of vaporization and favorable phase curves; it is desirable that it absorb a lot of heat to boil at its boiling point and that there pressures at which it will boil at a lower temperature than the heat source and condense at a higher temperature than the heat sink are modest and within the capacity of the piping and compressor.

While this is true as far as I know, it isn't necessary, merely helpful. You certainly can build a gas-phase-fluid-only heat pump that uses the same cycle without the phase change.

AFAIK non-phase-change cycles are mostly used for heat engines rather than heat pumps, though you might also use one for pumping if you can't get a phase change at the right temperature range.

[Decius Brutus]

Originally posted by ulzgoroth:

Originally posted by Decius Brutus:

Heat pumps don't use only gases, they add a phase change and use the latent heat of vaporization to manage temperatures.

Hot, high pressure gas goes to the condenser, where it rejects heat to where heat is unobjectionable (or desirable), and as it loses heat the gas condenses to a high-pressure liquid. The liquid is metered to a low pressure and sent to the evaporator, where it evaporates and absorbs heat from where heat is undesirable (or available). The warm low-pressure gas is forced through a compressor, making it a hot high-pressure gas that continues the cycle.

The refrigerant is chosen to have large specific latent heat of vaporization and favorable phase curves; it is desirable that it absorb a lot of heat to boil at its boiling point and that there pressures at which it will boil at a lower temperature than the heat source and condense at a higher temperature than the heat sink are modest and within the capacity of the piping and compressor.

While this is true as far as I know, it isn't necessary, merely helpful. You certainly can build a gas-phase-fluid-only heat pump that uses the same cycle without the phase change.

AFAIK non-phase-change cycles are mostly used for heat engines rather than heat pumps, though you might also use one for pumping if you can't get a phase change at the right temperature range.

Gas-only heat pumps are limited to a hot side being the heat of compression hotter than the cold side, and the heat of compression is also a lower bound on the energy consumption of the compressor.

I'm not familiar with any heat engines that use only gas, only condensing steam engines.

[ulzgoroth]

Originally posted by Decius Brutus:

I'm not familiar with any heat engines that use only gas, only condensing steam engines.

The Stirling engine, which is represented in the game, is an example.

Condensing in steam engines is also an optional feature, though I don't know if anybody has done closed-cycle steam engines without it. Doing so would probably require doing something weird and perhaps impractical with the heating systems - either pulsed heat or mechanically moving volumes in and out of them. (The Stirling engine does the latter, in effect - as it rotates its working gas chambers alternately come into contact with the heat source and heat sink.)