Volume of 1 fluid unit

[Hyperbar00]

Greetings everyone

I was wondering how many liters 1 fluid unit is worth.
The question may sound strange, I just like to make calculations and wanted to know.
For convenience, one may consider that 1 unit = 1 L
If we take in account the energy needed to heat 1 unit of water then 1 unit would be roughly 48 mL yet it would imply that a fluid tank could only hold 1,2 cubic meter of water.

Has anyone any suggestion ?

[5thHorseman]

Factorio is a game and therefore the units don't need to make sense so much as provide interesting gameplay.

Fluid volumes make as much physical sense as storing 50 cars in the trunk of another car.

The answer to "What is the volume of 1 fluid unit?" is "1 fluid volume unit." The only other reasonable answer is "Volume doesn't mean anything in this game."

...which is actually probably the better answer, considering you can store 50 cars in the trunk of another car.

[darkfrei]

Has anyone any suggestion ?

1 unit of water will be vaporized into 1 unit of steam, so it's mass unit, not the volume.

[Jap2.0]

1 unit of water will be vaporized into 1 unit of steam, so it's mass unit, not the volume.

Interesting point.... That would mean that pipes and tanks have a certain weight limit that they can handle, which could (not really) explain the volume differences. That said, if that were the case it should probably be pressure of some form, not weight.

[Hannu]

1 unit of water will be vaporized into 1 unit of steam, so it's mass unit, not the volume.

Some mods use it as amount of substance. There will not be consistent answer without contradictions.

[spike35540]

Have you considered using the energy of steam at a specific temperature to find the volume?

The specific enthalpy (h_g) of the steam is used to calculate the stored energy. We'll use a full storage tank of 25k fluid units for saturated steam. The stored energy is given by:

E = v ⋅ ρ ⋅ h_g

where:

E is the total stored energy,
v is the volume of the tank,
ρ is the density of the steam,
h_g is the specific enthalpy of the steam.

According to steam tables, the properties of steam at 165°C are:

Saturation Pressure: Approximately 700 kPa
Specific Enthalpy of Saturated Steam (h_g): Approximately 2776 kJ/kg
Specific Volume of Saturated Steam (v_g): Approximately 0.272 m³/kg

The stored energy (E) is related to the mass (m) and specific enthalpy (h_g) by:

E = m × h_g

​Rearranging to solve for mass:

m = E / h_g = 750,000kJ / 2776kJ/kg ≈ 270.2kg

The volume (v) is the product of mass (m) and specific volume (v_g):

v = m × v_g = 270.2kg × 0.272m³/kg ≈ 73.5m³ ≈ 73,500L

Now we know the capacity of a storage tank. To get the volume of a single fluid unit, divide the storage tank volume by its maximum fluid units:

73,500L / 25,000 fluid units = 2.94 liters / fluid unit.

Let's round up and say that a unit of fluid in Factorio is about 3 liters.