Thermal Conductivity

This article contains outdated information that is inaccurate for the current version. It was last updated for LU-356355. Unreflected changes in the discussed game mechanics are detailed here: EX1-463874

This article contains outdated information that is inaccurate for the current version. It was last updated for LU-356355. Unreflected changes in the discussed game mechanics are detailed here: EX1-463874

Thermal Conductivity is the property of a material that determines how quickly it heats or cools as it comes into contact with objects of different temperatures. Although the game states that between two objects, the lowest thermal conductivity is used, this is not true for all cases.

Equations

The calculation of Heat Transfer $q$ in $DTU$ is mainly a product of:

• $\Delta T$ the Temperature difference in °C
• $\Delta t$ the passing time , which, in any case is one tick is $0.2s$
• $k$ the applicable thermal conductivity in $DTU/(m\cdot s\cdot {\text{°}}C)$
  • $k_{lowest}$ is the lower of the two
  • $k_{average}$ the average of the two: $0.5(k_{1}+k_{2})$
  • $k_{geom}$ is the geometric mean of the two: ${\sqrt {k_{1}\cdot k_{2}}}$
• as well as additional Factor, like:
  • $C$ the real heat capacity $C={\text{mass}}\cdot ({\text{specific heat capacity}})$ of the hotter material
  • $A$ the buildings area

Equations

Scenario		Formula
Cell to Cell	Solid → Solid	$q=\Delta T\cdot \Delta t\cdot k_{geom}\cdot 1000$
	Solid → Liquid
	Gas → Liquid
	Solid → Gas	$q=\Delta T\cdot \Delta t\cdot k_{geom}\cdot 1000\cdot 25$
	Liquid → Liquid	$q=\Delta T\cdot \Delta t\cdot k_{geom}\cdot 1000\cdot 625$
Entity inside of a cell		$q=\Delta T\cdot \Delta t\cdot k_{lowest}\cdot 1000$
Debris on top of a solid cell		$q=\Delta T\cdot \Delta t\cdot k_{lowest}\cdot 62.5$
Insulated pipe and its contents		$q=\Delta T\cdot \Delta t\cdot k_{lowest}\cdot 50$
Other pipes and their contents		$q=\Delta T\cdot \Delta t\cdot k_{average}\cdot 50$
Building and the cells it occupies		$q=\Delta T\cdot \Delta t\cdot k_{building}\cdot k_{cell}\cdot {\frac {1}{5}}\cdot {\frac {C}{A}}$

Any Tiles, be they normal, insulated metal, plastic, bunker, glass or carpeted tiles, as well as doors, Farm Tiles, Heavi-Watt (Conductive) Joint Plates, and Tube Crossings count as Solid Cells, not as buildings.
Insulated Tiles reduce the thermal conductivity of their building material by a factor of 100.

Note: in real life, the units would cancel out, but surface area plays no role in ONI's calculation, therefore an additional $[m]$ meter needs to be multiplied to the product to have the equation result in DTU. (Not just meter, but a large string of units when calculating buildings.)

Another way to interpret this is that the units of Thermal Conductivity are given in-game as $DTU/(m\cdot s\cdot {\text{°}}C)$ while the unit is actually interpreted as $DTU/(s\cdot {\text{°}}C)$.

Limits of Heat Transfer

Lower Limits

Heat Transfer will not occur if:

• the temperature difference is less than 1 °C
• the calculated thermal flow is less than 0.1 DTU
• either of the masses is less than 1g

Upper limits

Heat Transfer has two caps:

• If the calculated heat transfer would result in a temperature jump of more than a fourth of their temperature difference $(T_{1}-T_{2})/4$ in either material.

  $q_{{\text{max }}1a}={\frac {T_{1}-T_{2}}{4}}\cdot m_{1}\cdot c_{1}\quad {\text{or}}\quad q_{{\text{max }}1b}={\frac {T_{1}-T_{2}}{4}}\cdot m_{2}\cdot c_{2}$

  Simply said: if the temperature difference is 40 °C, a materials temperature can change at most 10 °C per tick

• If the calculated heat transfer is larger than an eighths of the total heat difference $(Q_{1}-Q_{2})/8$, where the total heat $Q$ is a product of its temperature $T$, mass $m$, and specific heat capacity $c$: $Q=T\cdot m\cdot c$

  $q_{{\text{max }}2}={\frac {Q_{1}-Q_{2}}{8}}={\frac {(T_{1}\cdot m_{1}\cdot c_{1})-(T_{2}\cdot m_{2}\cdot c_{2})}{8}}$

Thermal descriptors

There are 4 thermal descriptors in the game, and they get attached to elements when their thermal characteristic reach a certain threshold. These descriptor does not affect the element any further.

• Thermally Reactive: Elements have a specific Heat Capacity of less than or equal to 0.2
• Slow heating: Elements have a specific Heat Capacity of greater than or equal to 1.0
• Insulator: Elements have a thermal conductivity of less than or equal to 1.0
• High Thermal Conductivity: Elements have a thermal conductivity of greater than or equal to 10.0

Pipes list

Liquid Pipes

Pipe	Material	Thermal Conductivity
Insulated Liquid Pipe	Insulation	0.0000003125
Liquid Pipe	Insulation	0.00001
Insulated Liquid Pipe	Ceramic	0.019375
Insulated Liquid Pipe	Obsidian	0.0625
Insulated Liquid Pipe	Igneous Rock	0.0625
Insulated Liquid Pipe	Sedimentary Rock	0.0625
Insulated Liquid Pipe	Sandstone	0.090625
Insulated Liquid Pipe	Granite	0.1059375
Insulated Liquid Pipe	Wolframite	0.46875
Insulated Liquid Pipe	Tungsten	0.46875
Liquid Pipe	Ceramic	0.62
Liquid Pipe	Obsidian	2
Liquid Pipe	Igneous Rock	2
Liquid Pipe	Sedimentary Rock	2
Liquid Pipe	Sandstone	2.9
Liquid Pipe	Granite	3.39
Insulated Liquid Pipe	Thermium	6.875
Liquid Pipe	Wolframite	15
Liquid Pipe	Tungsten	60
Radiant Liquid Pipe	Lead	70
Radiant Liquid Pipe	Niobium	108
Radiant Liquid Pipe	Steel	108
Radiant Liquid Pipe	Iron	110
Radiant Liquid Pipe	Copper	120
Radiant Liquid Pipe	Tungsten	120
Radiant Liquid Pipe	Gold	120
Liquid Pipe	Thermium	220
Radiant Liquid Pipe	Aluminum	410
Radiant Liquid Pipe	Thermium	440

Gas Pipes

Pipe	Material	Thermal Conductivity
Insulated Gas Pipe	Insulation	0.0000003125
Gas Pipe	Insulation	0.00001
Insulated Gas Pipe	Ceramic	0.019375
Insulated Gas Pipe	Mafic Rock	0.03125
Insulated Gas Pipe	Obsidian	0.0625
Insulated Gas Pipe	Igneous Rock	0.0625
Insulated Gas Pipe	Sedimentary Rock	0.0625
Insulated Gas Pipe	Sandstone	0.090625
Insulated Gas Pipe	Granite	0.1059375
Gas Pipe	Ceramic	0.62
Gas Pipe	Mafic Rock	1
Gas Pipe	Obsidian	2
Gas Pipe	Igneous Rock	2
Gas Pipe	Sedimentary Rock	2
Gas Pipe	Sandstone	2.9
Gas Pipe	Granite	3.39
Radiant Gas Pipe	Gold Amalgam	4
Radiant Gas Pipe	Iron Ore	8
Radiant Gas Pipe	Copper Ore	9
Radiant Gas Pipe	Pyrite	9
Radiant Gas Pipe	Wolframite	30
Radiant Gas Pipe	Aluminum Ore	41
Radiant Gas Pipe	Niobium	108
Radiant Gas Pipe	Steel	108
Radiant Gas Pipe	Thermium	440

Tips

• When cooling or heating an area it's better to run pipes through tiles than through atmosphere. in both cases the equation for "Building and the cells it occupies" is used which multiplies both Thermal conductivities, and in general, gasses have a much lower thermal conductivity than liquids, which have lower conductivity than solids.
  • However, if drastic cooling is desired, then Steam Turbines and Aquatuners will have to be involved, which means a cavity filled with Steam will have to be used.
• To jury rig insulate without building new Insulated tiles, it's therefore better to run pipes through atmosphere and have the pipes therefore changing less heat with the environment.
• Since Insulated Tiles have a factor of 1/100, and pipes a factor of 1/32, less heat is transferred if a regular pipe goes through an insulated Tile than when an insulated pipe goes through a regular Tile. Though, of course, Insulating both has an even better insulating effect.

References

https://forums.kleientertainment.com/forums/topic/84275-decrypting-heat-transfer/