Temperature Guide: Cooling, Heat Pipes & Steam Energy Tips
Temperature controls how heat is stored and transferred in Factorio and determines what machinery (boilers, heat exchangers, steam turbines, reactors) can do. This page summarizes how temperature is represented, how heat is carried by fluids and heat pipes, practical limits, and simple formulas for planning heat networks.
Temperature basics and energy content
- Fluid temperature is measured in °C. Ambient reference used by the game is 15°C.
- Energy per unit of fluid per degree Celsius is 200 J / unit / °C. That is: raising 1 unit of fluid by 1°C stores 200 J.
- Example: 1 unit of steam at 165°C stores (165 − 15) × 200 = 30,000 J. A 25,000-unit tank of steam at 165°C holds 750 MJ. The same-size tank at 500°C holds 2.425 GJ.
Steam temperatures used by machines
- Heat exchangers must reach 500°C before they can produce steam.
Heat pipes: stored heat, throughput, and temperature drop
- Heat pipes carry heat energy along connected heat-pipe segments. Each segment stores some heat and also imposes a limit on how much temperature drop occurs for a given power flow.
- For a straight heat-pipe connection with one input and one output, the temperature drop across a single segment depends on the power P flowing through it (P in MW):
- Temperature drop per segment = 1 + (P / 15) °C.
- This formula gives an effective maximum length for a line of heat pipes between a source temperature and a sink temperature because the total drop cannot exceed the available temperature difference.
- Example: A heat exchanger must be at 500°C to make steam and the maximum source temperature available from a generator is 1000°C, so the maximum temperature difference is 500°C. For P = 40 MW, maximum straight-line length ≈ 500 / (1 + 40/15) ≈ 136 segments.
- Heat pipes do not have separate flow rates like fluids; they instead model thermal resistance as the per-segment temperature drop formula above.
Special heat-transfer behavior of reactors and other entities
- A nuclear reactor used merely as a passive heat conduit (even unfueled) imposes a different temperature drop than a heat pipe:
- For power P in MW passing through a reactor, the reactor drops temperature by 1 + (P / 387) °C. This makes reactors comparatively lower-resistance thermal links than a single heat pipe segment for large P.
- Heat exchangers and heat generators (reactors, boilers, heat producers) have maximum operating temperatures:
- Heat exchangers need 500°C to generate steam.
- Heat generators (e.g., reactors) can go up to 1000°C.
Planning heat networks: practical rules
- When designing a heat network, compare the source temperature and required sink temperature and divide the available delta-T by the per-segment drop to estimate how many segments you can place in series.
- Use drop per segment = 1 + (P / 15) for heat pipes.
- For networks that include reactor blocks as conduits, use the reactor drop formula where appropriate.
- Keep high-power links short or use multiple parallel paths to reduce P per path and thus reduce the per-segment temperature drop.
- Heat exchangers must receive sufficiently hot fluid (≥500°C) at their input. Ensure enough temperature headroom after pipe/segment drops when routing heat to steam generation.
Energy accounting and efficiency
- There are no thermal losses to storage or piping for fluids: a fluid sitting in a pipe or tank retains its heat energy (the only losses are those intentionally modeled via temperature drops through heat pipes and transfers into machines).
Quick reference formulas
- Fluid energy stored: energy (J) = 200 J/unit/°C × units × (T − 15°C).
- Reactor used as conduit drop: ΔT_reactor = 1 + (P (MW) / 387) °C.
- Max straight-line heat-pipe length (given ΔT_available): length_max ≈ ΔT_available / (1 + P/15).
Use these numbers to size heat-pipe runs, estimate how much steam a given hot-fluid inventory represents, and ensure heat exchangers receive ≥500°C.