I don't understand how heat exchangers work

[SilentSam]

I see a reactor generates 40 MW. I see it gets a adjacency bonus of x% which multiplies that output. I see reactors have a temperature and that temperature transfers to to heat exchangers via heat pipes and as long as they are over 500C they make 500C steam which can be consumed by turbines. All well and good.

What I can't figure out though is how I can tell when a particular reactor is overtaxed for heat exchangers. I've read the various ratio threads here and on reddit and I know each heat exchanger says "Energy Consumed = 10MW". But I can't actually see this at work in any way - as far as I can tell, heat exchangers just keep on trucking no matter how many I put on a heatpipe.

Check out this setup:

Capture.PNG (895.25 KiB) Viewed 13243 times

(The bottom middle and right most reactors are not yet fueled - let us ignore them)

So the top left reactor has a single heatpipe attached to it. It has 2 active neighbours so we get a 200% bonus so 40MW + 40MW * 2 = 120MW @ 10MW/heat-xc = should support 12 heat exchangers, which is exactly how many it gets.

The bottom left reactor however only has one active neighbour. So we would expect it to support a maximum of 8 heat exchangers, but as you can see, it has far in excess of that (36 to be exact) all running on the same heatpipe, which should lose it additional heat due to length (and sure enough, the last heatpipe segment 553C compared to the first one which is 993C. HOWEVER, I can't for the life of me figure out what difference that actually makes in steam production. In the screenshot you can see I've attached a storage tank to one of the top heat exchanger's outputs (which should not be over-taxed) as well as one of the bottom most ones (which should be extremely over-taxed, right?)

So we would expect the top tank to fill up with 500C steam at a good clip and the bottom one to basically do nothing at all, right? Well they both seem happy to produce 500C steam at the same rate. Is this a bug? (I'm on 0.15.12 btw, playing with only one mod: Bottleneck, which really shouldn't interfere with mechanics at all...) Am I totally missing something here? Some core misunderstanding perhaps? E.g. I assume turbines only care about the volume of steam and the temperature it's at right? Any 500C steam is as good as any other? I.e. the two heat exchangers being samples really should be producing the same amount of electricity given they are producing the same temperature steam at (apparently) the same volume per second?

Things I've checked:

• The super long heat pipe is being fully utilized - 2 separate offshore pumps are supplying it with fresh water and all their steam has somewhere to go.
• The heat pipe they are on is not connected to anything else.
• The other 2 reactors are fully utilized as well (with 16 and 12 heat exchangers each) - just in case heat travels through the reactor block or something. (incidentally, does it? i.e. are reactors erm... conductive?)
• I'm super low on power so all the steam is getting used up by a big turbine farm (not pictured)

[DaveMcW]

are reactors erm... conductive?

Yes they are.

[Kelderek]

Mouse over each reactor, are the neighbor bonuses being applied even for the unfueled reactors? For example is the bottom left showing 100% or 200%? If it shows 200% then I would assume that to be a bug, I would expect the bonus to apply only for fueled reactors. If it shows 100% for the bottom left one then that may be an issue with it displaying correctly, but the "under the hood" mechanics of it could be bugged and allowing a higher neighbor bonus even though all your reactors are not fueled.

By my calculations you should be able to run 44 exchangers based on the reactors you have fueled (12 each for the top 3 reactors and 8 for the bottom left one). If all 6 of those reactors had fuel I would expect you to be able to run 80 heat exchangers (12 each for the corners and 16 each for the ones in the middle)

[Aeternus]

Neighbour bonus means: bonus energy generation equal to the neighbour bonus. If it's 100%, the reactor produces 80MW. 200%: 120MW and 300%: 160MW. That's the cap.
The cluster in your screenshot has 800MW of heat generation (2x 160 and 4x 120).
Heat exchangers work once they reach a temperature above 500 degrees. Before that, they are offline and do nothing.
Above 500 degrees, they will transfer up to 10MW of heat energy to steam.

Reactors have a specific heat of 10MW, which means they need 10MW per degree of temperature raised. Heat pipes and heat exchangers have a specific heat of 1MW, which means they need 1MW of heat energy to raise their temperature by 1 degree. Thermal energy as of 0.15.11 only transfers from a higher energy source to a lower energy source. Heatpipes have a maximum transfer rate of 1GW of energy. Reactors can transfer up to 10GW between eachother. In practise, this means that a reactor row can be seen as a single heatsource. The temperature difference between them will be minimal. It also means that a row of (offline) reactors can be used as an expensive but very efficient heat pipe and heat storage buffer.

When is a reactor overtaxed? If the heat exchangers furthest away from the reactor do not have temperatures above 500 degrees once the system has found it's balance (and the reactors no longer increase in temperature).

[Shokubai]

It sounds like you are making a simple error in part of your logic. The heat pipes essentially pass THROUGH the reactor. So just because your pipe is only connected to 1 reactor its actually connected to ALL of them.

[Kelderek]

Keep in mind the OP is only putting fuel in 4 of those reactors, not all 6.

[Aeternus]

Ahh... right. Then it's 80*3 + 120 = 360MW in heat generation.

[SilentSam]

Reactors have a specific heat of 10MW, which means they need 10MW per degree of temperature raised. Heat pipes and heat exchangers have a specific heat of 1MW, which means they need 1MW of heat energy to raise their temperature by 1 degree. Thermal energy as of 0.15.11 only transfers from a higher energy source to a lower energy source. Heatpipes have a maximum transfer rate of 1GW of energy. Reactors can transfer up to 10GW between eachother. In practise, this means that a reactor row can be seen as a single heatsource. The temperature difference between them will be minimal. It also means that a row of (offline) reactors can be used as an expensive but very efficient heat pipe and heat storage buffer.

Is this energy use / transfer exposed in the UI at all? Or is it like fluid flow rate where you can only really notice by the things that stop working on the other end?

[Aeternus]

It is not exposed in the UI but the values can be retrieved from the game files. The transfer rates and/or formula used to transfer heat I'm not sure of, but the maximum transfer rates are set in the configuration files for the buildings.