Heat

Heat and Temperature

Terminology

Relative Enthalpy: In real-world physics, enthalpy is the total amount of thermodynamic energy you'd need to put in to create a system out of nothing, including the pressure needed to displace whatever would be in the volume otherwise. In this mod, the "relative enthalpy" measurement (abbreviated H because it's steamy and weird), is the amount of heat energy added over the ambient ground state. Ground state in the Nether is very different from ground state in the overworld, but in common practice it doesn't matter. When we say "heat" in this mod, we're referring to H.

One unit of H is exactly equal to the heat energy released during one furnace fuel tick. Therefore a piece of coal would eventually release 1600H, and a Note Block (poor thing, what did it ever do to you?) would release 300H. There is no more heat energy to be had in these objects, even with more efficient burning, so please don't violate energy conservation in your mods.

Specific Heat: The heat capacity of a system. In real-world physics, it's the amount of energy you'd need per mass to raise the temperature by one degree. In this mod, it's the total number of H that can "fit" into a device before triggering a phase change (not including energy you'd spend on the phase change itself. Ice stays the same temperature as it melts, for instance. Energy is invested in the phase change instead).

Specific Enthalpy: In the real world, this is the amount of enthalpy per mass invested into the system. In this mod, it's quite similar: The amount of H divided by the heat capacity of the block or device. Think of it as the "percent full". This is what governs diffusion through heat systems. Blocks with huge capacities are like big water reservoirs: you need to push a lot of water into it to raise the waterline by just a little for any river it feeds.

Temperature: An absolute thermometer reading. These are almost always expressed in Kelvin. There's a nontrivial, somewhat-fudged conversion between relative enthalpy plus ground state, and temperature. In this mod, if you see a temperature number, it's for casual estimation, not mechanical purposes.

Diffusion

Heat diffusion is the star of Thermionics. It's one of the first things you encounter, and has many intrinsic properties one normally uses a machine for. For instance, one might normally use a magma crucible to melt metals or make lava from stone. A radiator has the same function in-world. Just make sure you have adequate clearance away from flammable objects.

You can store heat, to some degree, in blocks with high specific heat. Cast iron and brick are great substances for this. Bricks heat up quite slowly, but as the system cools down, it slowly releases heat back into it. Iron heats up faster, and releases its energy faster, but this allows higher temperatures to be sustained while enough energy remains.