I have a setup where everything in my factory outputs 300 degree Used Coolant to the transport network. Said fluid is transported to a Coolant Processing facility where it's processed from 300 -> 200 -> 100 -> 25 degree used coolant.

The 25 degree used coolant is filtered to new, fresh coolant and output to the transport network.

The only place where less than 300 degree used coolant exists is within this processing facility. The transport network never sees anything but Pure Coolant and 300 degree Used Coolant.

In spite of this, when I output from the Requester Depot into a buffer tank of Used Coolant, I get less than 300 degrees. Right now, for instance, I have a tank full of 274 degree coolant.

I think it's a case of the transport network not knowing how to deal with the same fluid at different temps so it outputs random temps, making a mix. This breaks the coolant processing facility since it requires specific temperature spans to work.

He is aware of this. Don't know if there is any priority to fix it.

https://forums.factorio.com/viewtopic.php?f=23&t=85271&p=495563&hilit=seablock+transport+drones+temperature#p495563
https://mods.factorio.com/mod/Transport_Drones/discussion/5ecb8d9cb7d53d000c4856f3

However, the latest updates to Angels stretches the temperature spans so there are no longer any gaps... finding a way to get it to the right one would be the problem.

I gave up and started processing coolant locally at each smeltery.

I've been considering just pumping the coolant with pipes and relocating the coolant processing facilities more centrally. I still like the idea. But it would be nice if the drones worked too :)

I'm sure it will get fixed eventually.

You can easily mix the different used coolant into the same pipe and connect all 3 cooling tower to it.
the used coolant with always change its temperature, but if all 3 cooling tower are connected the coolant will automatically be processed by the correct tower.

Thats how I solved this issue. I dont bother anymore about the temperature and different stages.

Update:

issue still there. It worked for quite some time but it is still there.
I also removed all temperature related coding, but after some time the temperature still gets wanky between the outside and inside of the factory.
Maybe someone with more knowledge over LUA can find more.

Update:

issue still there. It worked for quite some time but it is still there.

Update2:
I did some further testing and it looks like sometimes when the drones come back to the requester they don't know the temperature anymore. And it defaults to 25C.

I put some debug lines in the transport_drone:process_return_to_requester() in the transport_drone.lua to write the item name and temperature of the returning fluid.
In most cases the used coolant comes back with 300C, but from time to time it comes back with nil. But I could not yet figure out why this happens.

That's what I've been observing too. It doesn't look like the coolant "cools off" on-route, but drops to 25C. Like you, I haven't been able to figure out why yet either.

Yes that is the issue. I gave up trying to fix it and just built my main (seablock) base as a grid TSM train base without transport drones and processed the coolant at each smelting block, importing Base Mineral Oil to top up. Once I had all the production blocks set up, I just removed Transport Drones. Interestingly enough, the sandfill that was under the roads turned from sand to grass, leaving an interesting pattern behind.

I think I figured it out, please let me know if it works now

Neat! I'm not using Transport Drones in my current AngelBob game (trains only), but I plan on restarting once all the mods catch up to 1.1 and I'll give it whirl again then! Thanks Klonan!

I also finished my seablock run, but thank you for fixing this!