Describe the bug

Using heat pipes, it's impossible to outperform directly attached heatsinks no matter how many heatsinks or air grates are used. Same with using compressed iron blocks; the heat transfer speed is just not fast enough.

How to reproduce the bug

Setup 1: Advanced air compressor, 5 speed upgrades, 4 directly attached heatsinks, 3 air grates.
Setup 2: Advanced air compressor, 5 speed upgrades, 4 sides attached with heat pipes extended several blocks away, as many heat sinks as you can fit on the heat pipes, 3 air grates.

Expected behavior

Setup 2 should outperform setup 1 because there's vastly more surface area for the heat sinks to dissipate heat.

Additional details

No response

Which Minecraft version are you using?

1.18 - critical bugs only

Which version of PneumaticCraft: Repressurized are you using?

3.6.0-19

Crash log

No response

After additional testing using the advanced air compressor, it doesn't exchange heat with surrounding blocks like blue ice or even air. The temperature in open air with the compressor hot but off does not change without heat sinks. Attaching compressed iron blocks to the compressor also equalizes the temperature between the two blocks but doesn't dissipate any.

I think that this is not a bug, and it's working precisely as intended (for the most part). The Heat Pipes could perhaps do with a tweak that makes heat travel a bit faster, but the problem is that there is no simple solution like 'just change the numbers' because the way the heat works in game is a byproduct of a few smaller systems working together (involving temperature, thermal resistance and thermal capacity of the blocks involved, what the temperature differential between them is, what the physical distance is, etc), not a system of its own that can be individually adjusted. So, changing something to improve the way heat dissipates through Heat Pipes could have adverse effects elsewhere in the mod and would require a lot of scrutiny in testing to get right and make sure everything is balanced correctly. Whether or not desht agrees or even gets around to it (though I wouldn't be surprised if he has already made adjustments here and there) doesn't mean we can't have properly cooled setups, it just requires a bit more thought.

For a bit of history, when PNC first released, it had no Thermal Lagging and no Heat Pipes. There were Heat Sinks, and for moving heat around you would use Compressed Iron Blocks. Compressed Iron Blocks are not insulated, so to prevent the heat from escaping, you also had to encase the Compressed Iron Blocks with something else, like Trapdoors because they can be opened/closed (which you still have to do now if you're using Compressed Iron Blocks). As the mod became more popular, and got more attention, the need for a better looking and more convenient to use insulation block resulted in Thermal Lagging getting added. There was also a rebalancing proposal after 1.12 where the material/iron cost of progression was reconsidered as it was too expensive for the planned shift of moving PNC from a mid-late game mod to an early-late game mod, and one of the ways this cost was reduced was the introduction of the Heat Pipe, which has its own built-in insulation, making Thermal Lagging unnecessary for just moving heat around.

A Heat Sink doesn't just cool whatever block it's attached to. Think of it (loosely) as a block which absorbs and voids temperature (either hot or cold) until ambient temperature is reached, as long as some preconditions are met. In all cases, the most overlooked precondition is that the Heat Sink must be facing an Air Block. The precondition for voiding heat is that the Heat Sink itself must be passively (i.e. by biome ambient temp) or actively cooled. Conversely, the precondition for voiding cold is that the Heat Sink must be passively or actively heated (note however that a Heat Sink cannot be actively heated with the items present in the base mod, but if it could, that's how it would work - this can be seen by observing the behavior of a Heat Sink placed on a block with heat properties that are less than that of the ambient temparature). That until ambient temperature is reached bit is probably the most important detail: a Heat Sink that is optimally cooled will never cool anything below ambient temperature. It will only ever find equilibrium at ambient temperature. This means that if the ambient temperature surrounding the Heat Sink is 57 degrees (as it is in a Desert biome) and the Heat Sink is being used to cool something, then the Heat Sink will never fall below 57 degrees, no matter how much Air Grate cooling you throw at it. You really have to consider the placement of your setups which produce heat in this mod if you want to heat or cool stuff efficiently. This means either building it in a cold biome, a cold dimension, or a higher altitude (these are all ways of finding reduced ambient temperature - if you right click an Empty/Air Block in front of you while holding the Manometer, it makes it a lot easier to find an optimal temperature spot).

If you want the convenience of being able to place your heat-producing setup anywhere you want, or making it look neat, then using just Heat Sink + Air Grate cooling will not be enough, I'm afraid. You would need to use a more involved cooling setup involving placing down Ice, Snow or some other coolant, but this can be made more efficient by also using an Air Grate and Heat Sink setup in tandem with the coolant method.

Speed upgrades inside Compressors also make this sort of cooling a lot harder to do. There are two important things to consider with speed upgrades - if they are used inside Compressors, those Compressors will operate at faster speeds, but exponentially reduced efficiency. They will also produce a lot more heat (if they produce heat at all) than they would without the speed upgrades. It's fine to use a few speed upgrades here and there, but a lot of them is going to make your time with PNC a lot more unmanageable. Note that this only affects compressors, max speed upgrades in other machines is totally fine.

Note also that Speed upgrades aren't the only way to increase the speed of air generation (and thus the speed of temperature increases). The type of fuel you're using matters too. Something like Gasoline will produce higher temperatures in a shorter amount of time than LPG. This is because Gasoline has a shorter burn time than LPG does (LPG produces more air over a longer period of time).

Despite all this, it is possible to still fully cool an Advanced Liquid Compressor with max speed upgrades (even inside a Desert Biome) as long as you build it close to max world height, and you will have a little bit of leeway with where you place the heat sinks, but not much.

Another tip is that there needs to be a full Air Block between the Air Grate and the Heat Sink. Even though there is a visual gap between the blocks in the Air Grate's 3D model, it still considers the Air Grate as being placed directly onto the Heat Sink - and a Heat Sink will only void heat if it is facing an Air Block.

So, to summarize how to get the temperatures you want:

• Build closer to optimal ambient temperature by either being in a cold biome, cold dimension or high enough altitude
• If the above is not enough or you can't, consider reducing the amount of speed upgrades you're using
• If the above is not enough, try switching to a more efficient, slower burning fuel.
• If the above is still not enough, then consider using an active supply of coolant in addition to Heat Sinks + Air Grates.

And some general tips:

• An array of many Heat Sinks attached to a series of Heat Pipes is generally fine, just bear in mind that heat has a travel time. Heat will travel towards cold, and the bigger the temperature difference is between both ends, the shorter the travel time duration is (meaning it will travel faster). So your Heat Sink array should be as close to the block you're cooling as you can possibly get it.
• An array of many Air Grates is not quite necessary and I'd even go so far as to say that if you're using more than 6 of them (assuming default PNC balancing), you've probably overlooked something - and that's me being generous. For cooling an Advanced Liquid Compressor, in the right conditions, you can get away with just one (even if that one is pointing at a flat plane of 3x3 Heat Sinks that are not immediately attached to the compressor)

If you want a cool project to make some time, try making a pressure generation setup which involves using Soul Campfires to generate pressure via the Thermal Compressor. This particular setup benefits (or actually even requires) a long segment of Heat Pipes (you'll need as many of them as you have campfires). This type of project helped me have a better understanding of PNC's heat mechanics and how the Heat Pipes can really be put to effective use. It's also useful, because when you consider modded items from other mods that have heat mechanics like this with more useful thermal properties (like the Soul braziers in Decorative Blocks), it's also a feasible pressure generation strategy for midgame in any modded playthrough.