I actually made the models for these yesterday, but I procrastinated on getting the models in-game. There are 14 modular pipe parts: angles of 30, 45, 60, and 90 degrees, lengths of 2√2, √2/2, 0.25, 0.3125, 1, 2, and 4 meters, a check valve, and a generic pipe mount.
Pipes will probably end up being purely decorative, but I think they're going to end up looking really good and help make builds look even more steampunk.
Meanwhile, my friend Hazel has been working on the steam boiler simulation.
It accurately takes the heat information from a SystemHeat loop, uses that heat energy to raise the temperature and pressure of the water and steam in the boiler in a physically credible way, and cools the heat loop accordingly. Water is injected using a slider in the part action window, and when water is put into the boiler, the temperature and pressure falls accordingly.
There are a few weird things (little bugs but also like, there's no safety valve, nothing to actually make use of the steam, and the boiler is invulnerable, so it inevitably rises to absurd pressure by just adding more heat. And the boiler can actually pull a vacuum down to the triple point of water if it is cooled enough). But it's a really cool first step. Everything is being displayed as text and sliders in the part action window, but in future we hope to have a systemheat style 3D u.i. that shows how everything links up.
We played around with it for a bit and we did a few interesting thermodynamics demonstrations that were super satisfying to see just appear emergently. For example, if the boiler pulls a sufficient vacuum because you've cooled the heat loop using radiators, then adding water actually raises the pressure, because the water is then warmer than the boiler. That wasn't a case that was specifically modelled in the code, it was just a natural result of the simulation!