Factorio Forums

I was wondering about making a mod that follows more closely the laws of thermodynamics, for instance having boilers/steam engines follow the Carnot efficiency of η = 1 - Tc/Th

(Tc and Th in Kelvin)
so for Tc=15+273 Th=165+273 (boiler + steam engine), that's η=34%(edited)
for Tc=15+273 Th=500+273 (nuke + turbine), that's η=63%(edited)
Or maybe this, which seems closer to real-life?
https://en.wikipedia.org/wiki/Endorever ... modynamics
(might be a bit too complex though, thermodynamics are already hard enough!)

(funny, in the example they give, the coal powerplant has a higher temperature than the nuclear one!)
(I guess because coal is safer?)
Now, if it's the steam engine/turbine that uses this efficiency calculation, wonder how then to calculate boiler efficiency (to be close to real life) ?
Otherwise there's also the issue that Factorio's Steam engines don't lose efficiency as the steam they receive gets colder...
(and there doesn't seem a way to change efficiency on-the-fly?)

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for a "realistic" boiler, I'm probably going to run into the issue that :
In Real Life :
Water :
Specific Enthalpy at Atmospheric pressure at 1,01325 bar, i.e. normal atmospheric pressure on the sea level at 0°C.:
100°C : 0.419 MJ/kg , 0.958 kg/L => 0.401 MJ/L
15°C : 0.063 MJ/kg, 0.999 kg/L => 0.063 MJ/L
Heating 1 L of water from 15°C to 100°C => 0.338 MJ
(on average a Specific Heat of 3.98kJ/°C/L or 3.56kJ/°C/kg)
https://www.thermexcel.com/english/tables/eau_atm.htm

*Factorio : heat_capacity : 0.2kJ per degree per liter (was same for all fluids, doubled for steam and water in 0.15.0)
https://wiki.factorio.com/Version_history/0.15.0#0.15.0 *

Heat of Water Vaporization : 2.26 MJ/kg => 2.25 MJ/L
(yes, that's indeed several times more than what is required to heat it from 15 to 100 °C!)
* No equivalent in Factorio *

Steam :
Well, there's an issue here, as when Water is vaporized, its volume (and pressure) increases **significantly** (1 694 times for volume at 1 atm.!), typical Rankine cycle boilers seem to run at 30 atm. pressure?
(This is actually what creates mechanical work in a steam engine.)
https://en.wikipedia.org/wiki/Rankine_cycle
So to keep some consistency, I'm going to rather work in kg.
At constant pressure, at 1 bar (~1atm) the Specific Heat of Steam is around 2 kJ/°C/kg
With the Specific Enthalpy of Superheated at 165°C Steam of 2.81 MJ/kg. => +2.75 MJ/kg from 15°C water
With the Specific Enthalpy of Superheated at 500°C Steam of 3.49 MJ/kg. => +3.43 MJ/kg from 15°C water (1.25 times more)
http://www2.spiraxsarco.com/esc/SH_Properties.aspx
*(Again, Factorio's steam heat_capacity is now 0.2KJ per degree per... kg??
So, total, that would be :
for 165 °C steam : 0.2KJ/°C/kg*(165°C-15°C) = 30 kJ/kg from 15°C water
for 500 °C steam : 0.2KJ/°C/kg*(500°C-15°C) = 97 kJ/kg from 15°C water (3.23 times more)
)*


You can also notice that the Rankine cycle injects the water under such pressure that it boils only at ~270°C !
*(Another way in how Factorio differs...)*
Yeah, I'm going to have to redo these calculations...
The normal Rankine cycle also sends the steam to the turbine as soon as the water has been copletely vaporised (no superheated steam)
The other Rankine cycles (with superheat, reheat, regenerative) seem to have higher efficiencies, and would allow for higher tier boilers (like the current nuke unlocked turbines?) that would work *both* for realism and gameplay !