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need help with heat pipe layout, pls

Posted: Sat Feb 11, 2023 1:45 pm
by Cyrilis
I need help with a heat pipe / heatexchanger / turbine layout, pls!
I made this very compact ~10GW nuclear reactor core, but due to the small size and the restrictions in heat pipe length, I haven't found a working layout for heat pipes, water, heat exchangers and turbines yet. I have been tinkering around with it for days (ingame) spread over several months but I could not come up with a solution ... any suggestions? Or is it impossible at all to make this thing work?

This is my setup: 72 reactors, input: iron plated & 235U, Kovarex Fuel Cell assembly and recycling on site, steam meter controls fuel cell input.

BP in attachment, here is an overview picture


before you ask... No, I do not want to us e a 2N setup or bots. I want to find a way to make THIS particular reactor work and produce 9GW+

comments and suggestions appreciated.

Re: need help with heat pipe layout, pls

Posted: Sat Feb 11, 2023 3:51 pm
by astroshak
Unless I fat fingered something entering the numbers into my calculator, that setup should produce 10,600 MW (10.6 GW).

Since each Heat Exchanger takes in 10 MW of heat, that means you need 1060 HE’s.

With it looking like you are pumping water in from elsewhere (as opposed to landfilling in a small ocean) that means you are limited to 11 HE’s per offshore pump (23 if you pair them up; but with the flow rates of pipe-to-ground->pump->pipe-to-ground being capped at 3000/sec, I would not try to get 3 offshore pumps per supply line). You basically need 97 lines of HE’s each taking in one offshore pump’s worth of water. That would be reduced to 47 lines of HE’s if you were doubling the offshore pumps per water feed line.

Each line of 11 HE’s could feed 19 Steam Turbines with steam.

Try to avoid having multiple paths for heat, water, or steam to travel.

My own reactor BP was built on landfill, 2x4 setup extendable out to any 2xN with N being a multiple of 4. My design has one row of heat pipe, one row of heat exchanger, and one row of (steam) pipe, which then gets repeated, and I get 5 of those per iteration of the BP on either side of the reactor column. Each one is 13 HE’s long, due to that being all I needed them to be, and it is workable by having Offshore Pumps right there at both ends of each heat exchanger column.

If you double the offshore pumps up per water feed line, feeding 47 heat exchanger columns, you should have room for them all around your reactor core. It looks to me like you have room for 13 such columns straight up and down from the reactor core, and 11 such columns to the left and right of the reactor core (would make a giant + symbol). That would be 48 columns in total available to you; and a couple tiles of additional space besides, per side, that you could use for uranium and iron feeding. You could then feed the water in between rows of the steam turbines.

I’d suggest that such columns be fed directly from the reactor core, without that wide band of heat pipes you currently have surrounding the core. Treat heat like any other fluid : only give it a choice of flow path when you absolutely must.

Re: need help with heat pipe layout, pls

Posted: Sat Feb 11, 2023 7:08 pm
In the design pictured, I suspect the heat pipes are simply too long, as they have fairly limited throughput, which you start noticing when you stack up reactor neighbor bonuses. For example, in a 2-wide arbitratily tall (any number N units tall) column of reactors, heat pipes cannot carry heat far enough to be able to fit enough heat exchangers, without reaching 1000C in the core and wasting energy. There simply isn't enough space. You would think that parallel pipes help, and they do, but only so much.

However there is one solution, as happens to be the solution for the 2xN problem I just outlined: Using empty reactors as "long" heatpipes. A single reactor conducts heat as well as a single pipe, but a reactor reaches 5x further (by virtue of having a 5x5 footprint), and thus you can sustain sufficient heat throughput for a much larger distance.

By moving some of the elements in your build, and replacing large amounts of the heat pipe in the middle with empty reactors, you can significantly increase heat flow and probably make your build work.

Now this does requiring producing extra reactors just to act as mere heatpipes, but I would argue it is worth it if you want to make the reactor work properly.

Re: need help with heat pipe layout, pls

Posted: Sat Feb 11, 2023 11:18 pm
by Tertius
Your setup wastes possible neighborhood bonus for many reactors. The optimal reactor setup is a long row of double reactors. Such a row provides every reactor except the 4 reactors at the two ends with 3 sides of neighborhood bonus, and the 4 reactors with 2 sides of neighborhood bonus, so for n reactors, you get (n-1)*160 MW power.

Your 72 reactors would be one row of 2x36 reactors. This gets (72-1)*160 MW = 11360 MW, while according to astroshak your setup only gets 10600 MW. This is 1130 MW wasted, the power of 7 more reactors or roughly 10%.

A row of 36 double reactors offers a structure itself: connect rows of heat exchangers perpendicular to the reactor row. If the reactors row goes north-south, the heat exchanger rows go east-west, one field east of the reactors and one field west of them. After the heat exchangers, connect the turbines.
You might create a tileable setup, not limited to a length of 2x36 reactors. For example, a row of 2x6 reactors with corresponding heat exchangers and turbines is the smallest row that can be tileable. Tiled 2 times gets you 2x12 reactors, 3 times 2x18 reactors, 6 times 2x36 times - your size.

The real challenge of such big reactor fields is the water supply. Most designers (including me) "cheat" by placing such setups on lakes covered with landfill and leaving holes for offshore pumps exactly at the water inputs of the heat exchangers.

I don't want to post spoilers, but if you want to see examples of such setups, browse the "Show your creations/Energy production" forum, or search for "factorio tileable nuclear reactor" with Google. I don't ask you copy these setups, but it always helps to just see how other people did it conceptually, so you can create your own version of it.

If it comes to the question how long should be the heat pipes between reactor and the first heat exchangers, you might consult the wiki article: ... Heat_pipes
Short answer: as short as it can be.
Smallest practical distance is 4, as far as I remember. Up to 6 is ok, but if you go much beyond that, your reactor needs to heat up near to 1000 °C to make the heat reach the last heat exchanger in the line, so you don't have much buffer margin to use the heat capacity of the reactor to buffer heat if your consumption is less than the maximum power of the plant. Your web of heat pipes is not feasible. It wastes material but doesn't actually help distributing the heat.

Re: need help with heat pipe layout, pls

Posted: Sun Feb 12, 2023 8:58 am
by mmmPI
If you want to keep the shape of the core, i suggest you rework the fuel insertion to happen in the "gaps" inside the large square (red circles) rather than outside in some areas, so as to use other reactor as heat conveyer on the outside.
reactorsareheatpipes.png (4.73 MiB) Viewed 1787 times
from this other page on the wiki, the distance that heat can travel is explained differently with the formula rather than table,it may help illustrate the difference when using reactors as heat pipes given the original shape :)
For any heat pipe entity with one input connection on one side and one output connection on another, this entity with lower the temperature by 1 + (P / 15) °C with P being the power going through this entity expressed in MW.
As surprising as it may seem, an unfueled nuclear reactor can also be used as a heat pipe.
In this case, it will drop the temperature by 1 + (P / 387) °C, with P again being the power in MW going through the entity.
You already know you need P at around 9GW+ or 9000 MW, in the theorical case of having just 1 connection to transfer heat. If you were to make 9 connections, such as in the edited picture, the order of magnitude for the temperature loss is made decently small. to a drop of 1+[(9000/9)/387] per reactor. This is about 3.5°C. With heat pipes it would be 67°C.

This matches the value at the end of the wiki page
The nuclear reactor will thus lower the temperature 5 times less with near-zero power going through it, and nearly 26 times less when approaching infinite power, compared to those lines of heat pipes.
As an example, a single line of 100 nuclear reactors (or 500 tiles) will only lower the temperature by about 360°C while carrying 1GW.
With heat pipes it would be only 100 tiles since they are smaller, and the temperature would be lowered by : 6700°C, which is not possible since the maximum difference allowed between the hottest point ( 1000°C) and the coldest point (500°), is 500. This means you are only allowed
500/[1+(1000/15)]= 7.4 so really 7 heat pipes.

Why then the wiki says the distance is 0 when power is >302 MW on the other page ? I suspect this is because in a real game, you can't "consume" 1GW power with heat exchanger connected to a single heat pipe, you would need to connect 100 of them which takes some space, which require additionnal heat pipes, and if the 7th heat pipes is >500°C the 8th is not. Which, like what seem to be the problem in your case, doesn't allow all the heat to be converted to electricity.

In a real game though, the 8th pipe can show 500°C, this may be happening to you, this is because the pipe may reach 500°C temperature at some point in time in game, and then never goes lower again since heat exchanger stop functionning at 500°C. The heat exchanger will be a 499°C,and some rare times during a fraction of second, the heat pipe will have a temperature of 501; the heat exchanger 500°C, and some steam will be produced during times where the utilization of reactor is 100% of its capacity. It may be confusing to debug that it is a heat throughput problem. Given the picture i think everyone assumed it is the case, me included but it may be useful that you confirm the symptoms are a lack of heat in some exchanger at the end of their lane ?

The more general purpose of having a blueprint that does the recycling and the enrichment and the power production all in one place can be achieved more easily with smaller reactor as the main constraint seem to be the heat transfer in your case, but it is also often time, as mentionned the water input which are both made easier when scaling down a little, even though you may lose the ability to place the production facility in the middle which looks cool and is often an underated thing :)

It may help fiddling with the blueprint in the map editor and import the satisfying result blueprint ingame later to speed up development as there are option to make copy/paste instant and it alleviate the frustration of running into pipes all the time in those compact designs where you want to modify the middle island of production :)

Re: need help with heat pipe layout, pls

Posted: Sun Feb 12, 2023 10:09 am
by Cyrilis
Hey guys, thanks a lot for the input. I will try to tweak the core first and then go to the heat pipe layout again. I wasn't aware you can use empty reactors as heat pipe... that's an interesting solution.
Further comments appreciated, I will keep you informed on my progress!

Re: need help with heat pipe layout, pls

Posted: Wed Feb 22, 2023 11:47 pm
by vangrunz
Just to throw in...heat pipes can also be used as an energy buffer which is also described on the wiki page about heat pipes. I have built a large buffer around the "unused" spaces left & right of my setup as well as beneath them (the heat exchangers are on top of my setup), so should I ever run dry with uranium fuel cells there'll be, depending on the layout, a lot of time until the steam runs dry completely. Of course, every heat pipe consumes heat. But once heated, it will keep its temperature unless there's a greater difference. As what I have watched, the only cases your temperature decreases are either a high electric energy consumption or your fuel runs dry.

To prevent a complete run-dry you can watch your supplement with uranium ore/uranium fuel cells via circuit network and alert you with speakers so you get a message, no matter where you are.

I agree that a 2xN setup provides the most energy you can get because you do not waste neighbour bonus. Currently, there's no possibility supplying automatically a nuclear reactor which has other reactors to all of its sides directly adjacent (this would "only" boost another 40 MW if I calculated correctly, 200 MW instead of 160).

Also, don't forget to buffer water & steam in storage tanks. One each line (which should always be separated) would be sufficient, depending on the amount of energy buffer you'd like to have. The maximum steam temperature is 500°C, no matter how much you're cascading.

And, whereever you can, use pumps instead of pipes, especially directly from an output or directly into an input, such as heat exchangers, steam turbines and storage tanks. This ensures the most constant flow possible.