Coolant
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| Specific heat | Varies |
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| Autoignition temperature | Varies |
Description
Coolant is a gas or liquid being used as a medium to transfer heat, typically in order to maintain temperature in a room or cool a heat-generating machine. This can be done as simply as placing the gas or liquid in uninsulated pipes in a pressurized environment, but can be augmented through more active means, such as Radiators or Air Conditioner units, or by directly thermally linking two pipe networks, such as using a Heat Eexchanger. This is especially vital for machines that generate heat but require a cooler environment to function, such as Gas Fuel Generators and Stirling Engines, and is also important for maintaining the temperature of rooms used as living spaces or for growing plants.
Types of Coolant
The choice of coolant comes down to several factors. The specific heat of the fluid, which can be found in the Stationpedia, indicates how much energy (in joules) it takes to heat a specific quantity of the fluid by 1 degree (Kelvin or Celsius). The higher the specific heat of the fluid, the more energy it can absorb before rising too much in temperature to be useful, so fluids with a higher specific heat are often better coolants.
Liquids almost invariably have superior energy storage density compared to gases, but can be more difficult to work with due to phase change mechanics. For example, liquid Pollutants have 25 moles per litre, meaning a single 10L pipe segment can hold up to 250 moles of liquid pollutants. To pack that much gaseous pollutants into a single 10L pipe segment, assuming the gas is at 20°C, it would need to be at a pressure of ~61 MPa, which is more than gas pipes are capable of supporting. However, the lower density the liquid, the lower pressure the gaseous form would need to be at to match. Silanol has a liquid density of only 6.25 moles per litre, meaning gaseous Silanol would only need to be at a pressure of ~15 MPa to match.
When using either liquids or gases as a coolant, it is important to remain aware of the phase change thresholds for the fluid. Not only does phase changing change the temperature of the fluid, impairing coolant efficiency, but it can very easily break pipe networks. Gas pipes are put under stress when liquids are present in them, ultimately rupturing if too much liquid accumulates, and liquid pipes have 1/10th the maximum gas pressure limit as gas pipes, potentially causing liquid pipes to burst if too much of the liquid boils off. Both types of pipes break instantly if the fluid in them freezes. As such, selection of coolant relies heavily on the temperature band one is working with. While Carbon Dioxide can be a solid coolant, its relatively high condensation point (as high as -6.8°C) and freezing point (-55.3°C) make it ill-suited for working in low-temperature environments and cooling situations.
From a raw specific heat perspective, Silanol has highest readily available (Sodium Chloride has higher, but is much more difficult to acquire, being only partially implemented at this time, and is only useful in very high temperature applications). In addition, it has a very wide liquid range (-130°C to 550°C), making it very effective in cooling setups that require a broad temperature range. However, it is difficult to acquire (being available only from medium and large liquids traders, and rocket mining), and has a quite low density in liquid form (only 6.25 moles per litre, compared to 55.6 for water), limiting its usefulness as a coolant. Other good options include:
- Pollutants - Relatively mediocre from a statistics perspective (mid-range specific heat, below average latent heat), but are very easy to acquire (most combustion reactions create them) and are otherwise essentially useless. Note that they has a very wide liquid range (-99.8°C to 161°C), are quite prone to condensing when pressurized in gas pipes and require a fairly high pressure (~3.6 MPa at 20°C, versus the maximum 6 MPa for liquid pipes) to keep them in liquid form, so dealing with unwanted phase changing is a common issue when using pollutants as coolant.
- Carbon Dioxide - Has the highest specific heat of the fluids that are gases at room temperature and are relatively easy to acquire. Unfortunately, also has an unusually high condensation point amongst said commonly-available gases, and has an extremely narrow liquid range before freezing in pipes, limiting its usefulness as a coolant to higher-temperature use-cases, or to very specific temperature ranges in liquid form.
- Water - Has a very high specific heat (72, third highest amongst the available fluids in the game, behind only Sodium Chloride and Silanol and a fairly wide liquid range, but also has a number of other important uses (including drinking it), can be difficult to acquire on some worlds, and can be difficult to manage due to how little pressure is required to start condensing it at room temperature.
- Hydrogen or Helium - Jave fairly poor specific heat (~21 J/K), but can be used as a gaseous coolant even at very low temperatures (in the case of Helium, it never changes phase and cannot exist as a liquid), making them good options for coolant cryogenic cooling setups, such as condensing Oxygen for use with a liquid-fueled rocket engine.
- Nitrogen - Has a similarly poor specific heat, but has a fairly low max liquid temperature (-83.1°C), is generally quite readily available (being found in both Nitrice and as a combustion output when using NOS as an oxidizer)), doesn't have as many other uses as some other fluids, and is inert from a combustion perspective.
| Name | Specific Heat | Fluid Density (mol/L) | Max liquid temp (°C) | Freezing temp (°C) | Notes |
|---|---|---|---|---|---|
| Oxygen (O2) | 21.1 | 33.3 | -111°C | -217°C | |
| Nitrogen (N) | 20.6 | 28.7 | -83.1°C | -233°C | |
| Hydrogen (H2) | 20.4 | 35.7 | -203°C | -258°C | Lowest condensation and freezing point of any phase-changing fluid. |
| Methane (CH4) | 20.4 | 25 | -78.1°C | -192°C | |
| Pollutant (POL) | 24.8 | 25 | 161°C | -99.8°C | Cannot condense at standard pressure, requires at least 1.8 MPa. |
| Carbon Dioxide (CO2) | 28.2 | 25 | -6.8°C | -55.3°C | Cannot condense at standard pressure, requires at least 517 kPa. |
| Water (H2O) | 72 | 55.6 | 371°C | 0°C | Highest liquid density of any fluid in the game (tied with Polluted Water) |
| Polluted Water (PW) | 64 | 55.6 | 361°C | 3°C | Highest liquid density of any fluid in the game (tied with regular Water) |
| Nitrous Oxide (N2O) | 37.2 | 38.5 | 158°C | -21.7°C | Cannot condense at standard pressure, requires at least 800 kPa. |
| Ozone (O3) | 38.6 | 38.5 | 31.5°C | -222°C | |
| Silanol (SiOH) | 101 | 6.25 | 550°C | -130°C | Lowest liquid density of any fluid in the game, by a significant margin. |
| Hydrazine (N2H4) | 48.4 | 33.3 | 248°C | -26.9°C | Extremely toxic. Auto-combusts with itself at 247.7°C, resulting in pure Pollutants. |
| Alcohol (ALC) | 33 | 17.2 | 150°C | -41.5°C | Only exists as a liquid, evaporates into Methane. |
| Helium (He) | 20.8 | N/A | N/A | N/A | Only exists as a gas, cannot phase change. |
| Hydrochloric Acid (HCl) | 37 | 35.7 | 158°C | -25.9°C | Extremely toxic. |
| Sodium Chloride (NaCl) | 130 | 25 | 2526°C | 333°C | Only exists as a liquid, evaporates into Pollutant. Highest max liquid temperature and specific heat of any fluid. Freezes into Salt. |
See Also
Gases and Liquids
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