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This article contains outdated information that is inaccurate for the current version.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This article contains outdated information that is inaccurate for the current version.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: ${\sqrt {k_{1}\cdot k_{2}}}$

For heat transfer with buildings, additional factors include:

• $C_{hot}$ the thermal mass of the hotter object: $m\cdot c\cdot \left[{\frac {1}{5}}\right]_{\text{if building}}$ where $m$ is mass, $\,c$ is specific heat capacity (SHC), and divide by 5 if the hotter object is a building
• $A$ 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
	Gas → Gas
	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		$q=\Delta T\cdot \Delta t\cdot k_{lowest}\cdot 1000$
Entity 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		$q=\Delta T\cdot \Delta t\cdot k_{building}\cdot k_{cell}\cdot {\frac {1}{2}}\cdot {\frac {C_{hot}}{A}}$

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 (2/255)² (or 16 256) instead of 100 as stated in the game. It also uses $k_{lowest}$instead of $k_{geom}$for the purpose of cell to cell conductivity, which is mostly going to be the insulated tile conductivity. Solid to gas multiplicator still apply.

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 $DTU/(s\cdot {\text{°}}C)$.

Recap of Cell to Cell multipliers

				Gas	Liquid	Solid
Gas				1	1	25
Liquid				1	625	1
Solid				25	1	1

Because of the Gas to Solid x25 multiplier, it's recommended to add a double tiles layer or a thin liquid layer when trying to insulate two rooms, to instead get a x1 multiplier.

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 eighth 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 $c$: $Q=T\cdot m\cdot c$. This upper limit has been removed since 509629 (Fast Friends Update).

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

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
Radiant Liquid Pipe	Cobalt	200
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	Cobalt 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

Solid Tiles list

Tiles

Tile	Material	Thermal Conductivity
Insulated Tile	Insulation	0.0000001
Tile Carpeted Tile	Insulation	0.00001
Insulated Tile	Ceramic	0.00620
Insulated Tile	Mafic Rock	0.01000
Insulated Tile	Fossil	0.020
Insulated Tile	Igneous Rock	0.020
Insulated Tile	Obsidian	0.020
Insulated Tile	Sedimentary Rock	0.020
Insulated Tile	Sandstone	0.029
Insulated Tile	Granite	0.0339
Plastic Tile	Plastic	0.150
Plastic Tile	Solid Visco-Gel	0.450
Tile Carpeted Tile	Ceramic	0.620
Window Tile	Glass	1.110
Tile Carpeted Tile	Mafic Rock	1.000
Tile Carpeted Tile	Fossil	2.000
Tile Carpeted Tile	Igneous Rock	2.000
Tile Carpeted Tile	Obsidian	2.000
Tile Carpeted Tile	Sedimentary Rock	2.000
Tile Carpeted Tile	Sandstone	2.900
Tile Carpeted Tile	Granite	3.390
Metal Tile	Depleted Uranium	20.000
Metal Tile	Lead	35.000
Metal Tile Bunker Tile	Steel	54.000
Metal Tile	Niobium	54.000
Metal Tile	Iron	55.000
Metal Tile	Copper	60.000
Metal Tile	Gold	60.000
Metal Tile	Tungsten	60.000
Window Tile	Diamond	80.000
Metal Tile	Cobalt	100.000
Metal Tile	Aluminum	205.000
Metal Tile	Thermium	220.000

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/