Efficiency of longer heat pipes

[Periwinkle]

Just a small question about nuclear power. I was not able to find a conclusive answer in the wiki.

TL;DR: Does the temperature of a heatpipe connected to a heat exchanger actually matter, as long it is above 500 degrees?

As far as i understand, turbine need 500 degrees steam made in a heat exchanger, and if the heatpipe connected to the heat exchanger is not at least 500 degrees hot, it does not do anything.
But do higher temperatures at the heat exchanger matter?

If they do matter, i assume it would be better to pipe steam to the turbines and make the exchanger setup more compact.

At the moment my setup is as follows: From each reactor i have a single heat pipe going to a douple row of heat exchangers, and to each exchangers i have directly connected two turbines. This makes somewhat long heat pipes, at the furthest away i am at ~850 degrees,
According to the power statistics this seems to be able to produce the full amount, but i do not consume nearly enough at the moment to verify.

[Mashaa]

Two things you should consider:
1. It actually needs to be at least a few degrees higher than 500 so that the heat exchanger can take energy from it - something like 505-510.
2. The energy throughout of heat pipes reduces with distance, which can throttle your power production if they are very long. More info on this: https://wiki.factorio.com/Tutorial:Nucl ... Heat_pipes

[Tertius]

Heat needs a temperature difference for travelling from one point in a longer heat pipe to the other. And heat tries to even out the temperature. If a heat exchanger "consumes" heat, it cools down the connected heat pipe piece. Then heat from connected warmer heat pipes flow into that piece, up to the reactor.
So if a heat pipe is 500°C at a distant heat exchanger, it's 510°C at the next pipe piece, 520°C at the piece after that, and so on up to the reactor that may be perhaps at 750°C.
If the exchanger is working and continuously extracting heat and keeping its pipe at 500°C, this heat gradient stays the same: exchanger 500, reactor 750 (or whatever temperature achieves equilibrium).
The reactor can go up to 1000°C. So you need to make sure the heat is able to reach the farthest heat exchanger and make that exchanger work (more than 500°C) and the maximum of 1000°C of the reactor is sufficient for this. The complete gradient from reactor to farthest heat exchanger cannot be more than 500°C: from 500 to 1000.

There is a table how long heat pipes can go with a given amount of heat exchangers in the wiki: https://wiki.factorio.com/Tutorial:Nucl ... Heat_pipes

[Amarula]

TL;DR: Does the temperature of a heatpipe connected to a heat exchanger actually matter, as long it is above 500 degrees?

No. The actual temperature doesn't matter, as long as the heat pipe is hot enough.
The heat exchanger does not work faster or more efficiently or in any way better as the pipes get hotter. You don't get any bonus steam from having extra toasty heat pipes.

[gatetman]

TL;DR: Does the temperature of a heatpipe connected to a heat exchanger actually matter, as long it is above 500 degrees?

No. The actual temperature doesn't matter, as long as the heat pipe is hot enough.
The heat exchanger does not work faster or more efficiently or in any way better as the pipes get hotter. You don't get any bonus steam from having extra toasty heat pipes.

1. It actually needs to be at least a few degrees higher than 500 so that the heat exchanger can take energy from it - something like 505-510.

For reference, for anyone that appreciates a more precise and nuanced answer about the Heat Pipe temp -

• The Heat Exchanger(s) start producing steam when the connected Heat Pipe exceeds 501 C.
• Between 501 C and 501.67 C, output scales up linearly from 0 to ~103.1 L/s.
• At 501.67 C and above, output is at full steam (~103.1 L/s).

(Provided, of course, that there is adequate water input and that the steam output pipeline is not full.)

Interestingly, this is true whether there's one or two Heat Exchangers connected to the Heat Pipe in question, and whether or not it connects to more Heat Pipes that in turn connect to more Heat Exchangers.

According to the power statistics this seems to be able to produce the full amount, but i do not consume nearly enough at the moment to verify.

This can be a bit misleading if you're consuming less than you're producing.

The "maximum possible power production" in the Electric network info chart is based on your Turbines that currently have access to steam (ie, that are ready to produce electricity). That's not necessarily the same as the current steam production rate of the Heat Exchangers. For instance, if you double the number of Turbines, you'll see the max power production go up accordingly, without adding any Reactors or Heat Exchangers. Because those Turbines with access to some steam _can_ actually produce that much electricity for a while, though eventually they'll run out of steam.

If you want to see whether your Heat Exchangers are all producing full steam, hover over the ones furthest away from the reactors and they should say "Output: 103/s of 103/s" if they're maxed out.

Of course, that's all assuming the steam pipeline is not full. If you manage to fill up your steam pipeline (including the Turbines and any pipes and storage tanks) because you're consuming less steam than you're generating, the Heat Exchangers will slow down to match your actual consumption. (But meanwhile, Reactor, Heat Pipe, and Heat Exchanger temps will continue to rise in this case, until the Reactors eventually reach 1000 C.)

If they do matter, i assume it would be better to pipe steam to the turbines and make the exchanger setup more compact.

Yes well, one advantage of a more compact setup is it will take less time to "ramp up" heat in the whole system before the most distant Heat Exchangers operate at full capacity.