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Still confused about heat transfer


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Game says about thermal conductivity that "Between two objects, the rate of heat transfer will be determined by the object with the lowest thermal conductivity."

In case of radiator system, heats transfered from liquid to pipe and then pipe to gas (or vice versa). Liquids and gases are always has lower thermal conductivity than whatever the pipe material is. Then why granite or wolframite, which has high thermal conductivity, is the best choice of material? Aren't thermally reactive materials such as obsidian or igneous rock a better choice?

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I don't know about that rule:  "determined by the object with the lowest thermal conductivity " . I thought it was determined by the difference of the two materials.

Thermally reactive minerals are just thermally reactive relative to other minerals, not all things.  Metals are still way more thermally reactive than any mineral.

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2 minutes ago, Kermack said:

I don't know about that rule:  "determined by the object with the lowest thermal conductivity " . I thought it was determined by the difference of the two materials.

Thermally reactive minerals are just thermally reactive relative to other minerals, not all things.  Metals are still way more thermally reactive than any mineral.

ONI seems to use "thermally reactive" to mean "low specific heat," meaning that the material changes temperature more quickly for a given amount of heat energy gained/lost. The actual rate at which materials exchange heat energy with other materials supposedly depends on the thermal conductivity rule.

9 minutes ago, Kabrute said:

smaller packets more often vs larger packet less often, ultimately, pipes run through metal tile have highest tranfer from pipecontents to world cell

I don't understand. Smaller packets of what? At what rates? This is unclear.

If the rate of heat transfer really is clamped by the lowest conductivity involved, I would also think that you would prefer low specific heat materials for heat exchangers as long as the conductivity of the material is equal to or greater than that of either the working fluid or the environment. That way you combine maximum "bandwidth" of heat energy transfer with maximum responsiveness of the exchanger (so less lag after working fluid supply starts/stops).

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1 hour ago, tulkaz said:

Game says about thermal conductivity that "Between two objects, the rate of heat transfer will be determined by the object with the lowest thermal conductivity."

That is correct. Given two materials, the rate of transfer is limited to the lower rate material between some surface area or method of conduction. Consider the following real life values Table of Thermal Conductivities :

  1. Diamond: 1000 W/m*K
  2. Water: 0.6 W/m*K
  3. Styrofoam: 0.033 W/m*K

A styrofoam cup holding 90°C water will feel hot (but not scalding). However, if that 90°C water splashed onto your hand, you will flinch. Your skin has higher thermal conductivity than styrofoam. All that extra heat the water had quickly transferred over to your hand whereas you can hold styrofoam cup at 90 degrees.

1 hour ago, tulkaz said:

Then why granite or wolframite, which has high thermal conductivity, is the best choice of material? Aren't thermally reactive materials such as obsidian or igneous rock a better choice?

Their term Thermally Reactive is counter-intuitive but it's physics. The physics about how much energy is needed to change a substance's temperature is called SPECIFIC HEAT. Something that is thermally reactive are substances that change temperature quickly, NOT transfer heat quickly, which is THERMAL CONDUCTIVITY.

In order to change temperature quickly, you have to have a low specific heat. Obsidian's specific heat is 2.0 joules per gram*Kelvin. That means to raise 1 gram of Obsidian by 1 degrees, you need 2 joules of energy. In contrast for water, to raise 1 gram of Water by 1 degree, you need 4.186 joules.

If I used 10 joules of energy to heat up these substances, I will actually raise 5 degrees for Obsidian vs ~2.4 degrees for Water. AND Because I raised obsidian by 5 degrees, it is more THERMALLY REACTIVE, than water. Water is known to be a heat sink in the scientific world.

________________

Specific heat and thermal conductivity are intensive properties independent of each other but they don't fully describe how the game's heat works. Thermal Equilibrium, an extensive property, depends on these intensive properties. Every system equilibrates and at thermal equlibrium, all matters within that system have the SAME TEMPERATURE.

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7 hours ago, CodingKitteh said:

That is correct. Given two materials, the rate of transfer is limited to the lower rate material between some surface area or method of conduction. Consider the following real life values Table of Thermal Conductivities :

  1. Diamond: 1000 W/m*K
  2. Water: 0.6 W/m*K
  3. Styrofoam: 0.033 W/m*K

A styrofoam cup holding 90°C water will feel hot (but not scalding). However, if that 90°C water splashed onto your hand, you will flinch. Your skin has higher thermal conductivity than styrofoam. All that extra heat the water had quickly transferred over to your hand whereas you can hold styrofoam cup at 90 degrees.

Their term Thermally Reactive is counter-intuitive but it's physics. The physics about how much energy is needed to change a substance's temperature is called SPECIFIC HEAT. Something that is thermally reactive are substances that change temperature quickly, NOT transfer heat quickly, which is THERMAL CONDUCTIVITY.

In order to change temperature quickly, you have to have a low specific heat. Obsidian's specific heat is 2.0 joules per gram*Kelvin. That means to raise 1 gram of Obsidian by 1 degrees, you need 2 joules of energy. In contrast for water, to raise 1 gram of Water by 1 degree, you need 4.186 joules.

If I used 10 joules of energy to heat up these substances, I will actually raise 5 degrees for Obsidian vs ~2.4 degrees for Water. AND Because I raised obsidian by 5 degrees, it is more THERMALLY REACTIVE, than water. Water is known to be a heat sink in the scientific world.

________________

Specific heat and thermal conductivity are intensive properties independent of each other but they don't fully describe how the game's heat works. Thermal Equilibrium, an extensive property, depends on these intensive properties. Every system equilibrates and at thermal equlibrium, all matters within that system have the SAME TEMPERATURE.

 

Thank you for the explanation but still don't get it :(

When you make liquid oxygen with radiator system using hydrogen, heat would transfer oxygen > gas pipe > hydrogen. At oxygen > gas pipe stage adjusted thermal conductivity is 0.024, which is oxygen and at gas pipe > hydrogen stage would be 0.168, which is hydrogen. Those thermal conductivity will be same no matter what material is used for gas pipe because the lowest thermal conductivity among raw materials are 2.

Adjusted thermal conductivity of this oxygen-cooling radiator system will be always 0.024 and 0.168 then why the material of gas pipe matter?

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The statement "Between two objects, the rate of heat transfer will be determined by the object with the lowest thermal conductivity." isn't entirely correct.

Decrypting heat transfer.

Heat transfer from pipes to the cell in which they are located does depend on both the conductivity of the pipe and the cell. In theory, granite or tungsten pipes transfer heat the best. However, heat transfer from the fluid within the pipe to the pipe itself is indeed clamped by the lower conductivity material, which would be the fluid. So in practice, heat transfer is very strongly constrained by the working fluid. How much of a difference the pipe actually makes depends on the specifics of the situation, masses and temperatures and so on. It can range anywhere from "yes, granite helps" to "no, granite doesn't help".

Clear as mud?

I don't know if this working as intended, a bug, planning to be changed, or what. I do know that this is still the case as I just tested it in debug.

I assume this doesn't need to be said, but the bigger the difference in temperatures the greater the transfer. Polluted water has a lower conductivity than water, but it's better because you can make it colder. Petroleum is great in both regards.

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3 hours ago, tulkaz said:

 

Thank you for the explanation but still don't get it :(

When you make liquid oxygen with radiator system using hydrogen, heat would transfer oxygen > gas pipe > hydrogen. At oxygen > gas pipe stage adjusted thermal conductivity is 0.024, which is oxygen and at gas pipe > hydrogen stage would be 0.168, which is hydrogen. Those thermal conductivity will be same no matter what material is used for gas pipe because the lowest thermal conductivity among raw materials are 2.

Adjusted thermal conductivity of this oxygen-cooling radiator system will be always 0.024 and 0.168 then why the material of gas pipe matter?

 

In your example heat conductivity does not matter since gases conduct the heat way slower than the building material.

 

What does matter though is the specific heat capacity which allows you to reach higher differences in temperature faster which in return accelerates the heat transfer. The unit for thermal conductivity is (W/m)/K so the higher the difference in temperature, the faster the heat transfer until a thermal equilibrium is reached.

So sedimentary rock or obsidian are better than granite because they have a lower heat capacity --> shorter time until equilibrium is reached. However, once in equilibrium the material has no effect whatsoever.

 

That said, I'm not quite sure how the game calculates heat transfer between packets of fluid inside a pipe and the pipe itself. The meters in the thermal conductivity unit could be set to 1 or something lower which would influence transfer rates.

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