[singron]

What you describe is kind of like a theoretical heat exchanger that only averages temperature at a single point.

You can improve this by exchanging heat across a continuous length along opposing flows. Imagine two parallel pipes thermally bonded where fluids flow in opposite directions. Each point still averages the temperatures, but the average temperature varies across the length and approaches the interior temperature on the interior side and the exterior temperature on the exterior side.

[ilyagr]

Yeah, I think this makes sense. If you connect many of my heat exchangers in series, the temperature gradient increases; only the middle one will work at the average of the inside and outside temperature (the example of 3 in a row makes sense to me). At the limit, it becomes what you described.

Thanks!

[vanderZwan]

The mechanism described is called a countercurrent exchange. One fun detail is that it's quite commonly found in biological systems in nature too!

https://en.wikipedia.org/wiki/Countercurrent_exchange

[open_erv2]

It's actually a regenerative heat exchanger: https://en.wikipedia.org/wiki/Regenerative_heat_exchanger.

[lsaferite]

The person you are replying to was discussing "exchanging heat across a continuous length along opposing flows", which is countercurrent exchange. Regenerative exchange is, at least to my understanding, more of a cyclical store and release process.

[vanderZwan]

Yes, which is what OpenERV is. I can understand why they might have thought I was talking about their system, my wording was a bit ambiguous there. So it doesn't hurt that they cleared that up :)