I see there is a solid in the bottom left fluid block. That might also be acting like a heat sink too. Whats the mass/temperature/material of that solid? Also the big coal chunks? I’m guessing they’re still in the process of getting heated up.

Also, I think the minimum temperature for steam turbine inputs is 125? I think for maximum efficiency you also need at least 200C w/ all 5 vents open.

My point is that you probably want your system quite a bit hotter anyways.