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on Gopher (inofficial)
URI Visit Hacker News on the Web
COMMENT PAGE FOR:
URI Why are smokestacks so tall?
nemo44x wrote 2 hours 37 min ago:
Important consideration when building an offset smoker for BBQ. Many of
the cheaper ones have stacks that are small and not very high. Taller
stacks make a better cooker because it pulls the air faster creating
better convection and therefore better bark; desirable characteristics.
a3w wrote 3 hours 27 min ago:
"politics of high smokestacks" was when e.g. Germany got higher
smokestacks, since we initially killed the local plant life when
burning coal. Now, we can kill the whole planet at once, but only a
tiny bit. Problem solved, until we later said "actually, use filters,
not (only) high chimneys".
Thanks for having been to my Ted talk.
Next up: Why climate change made the filter solution not work, either
â with cutting edge science claims back from 1856.
(Damn, the actual timeline for 1950-1980 and 1856 mixes these two issue
non-chronologically. Sorry, to be fair: we were completety certain of
climate change in 1990, when we saw that the 1970s era cooldown was not
a new trend, but just a decade of a brighter albedo due to particle
emissions.)
mcthorogood wrote 4 hours 23 min ago:
Calculating smokestack height was in my undergraduate chemical
engineering curriculum that I completed in 1976. Height is required so
that the National Air Quality Standards in the U.S. Clean Air Act are
not violated at the base of the stack.
h1fra wrote 5 hours 54 min ago:
as always, this channel makes your watch 20minutes of something you
couldn't care less and you always end up amazed
pfdietz wrote 7 hours 39 min ago:
There's a related technology that creates downdrafts by cooling air.
In a region with warm air near cold water (like, say, Los Angeles, with
cold ocean water), injection of the water at the top of a large tower
can cool the air, causing it to descend.
This was proposed to be used, again in Los Angeles, as a way to not
only generate power (via turbines at the bottom of large hyperboloidal
towers) but also clean pollutants from the air. I don't think it ever
went anywhere (probably too expensive) but it would work at least in
principle.
einpoklum wrote 9 hours 59 min ago:
I leafed through that page, and it still seems like the answer is: "To
make sure the pollutants are dispersed and/or carried away enough to
reduce exposure of people around the base."
Am I wrong?
kortilla wrote 8 hours 34 min ago:
Thatâs secondary. Smoke stacks were tall long before people cared
about pollution (1800s).
dweekly wrote 9 hours 47 min ago:
You're right, but the less intuitive part is that the stack makes the
air rise much more quickly; the exit velocity is higher the taller
the stack.
eulgro wrote 11 hours 18 min ago:
The amount of AI generated imagery in the video is baffling.
michaelt wrote 9 hours 21 min ago:
Except for the sci-fi city at the 40 second video mark, I'm pretty
sure it's almost all real video, just brought from a big stock video
provider.
If you want video of a drone flying over a power plant or hot air
balloons taking off, you can license them from stock providers, just
like with stock photos.
Of course, it does share some of the cues of AI-generated content -
but I suspect a lot of these AI companies buy a lot of stock content
for their training datasets.
Kye wrote 6 hours 37 min ago:
I assumed the city came from the same stock series as this meme
which predates generative AI:
URI [1]: https://knowyourmeme.com/memes/the-world-if
geerlingguy wrote 7 hours 54 min ago:
Some of the stock content providers are also polluting the waters a
bit as well, allowing AI generated stock clips to be added :(
Kye wrote 10 hours 3 min ago:
I didn't see any.
saagarjha wrote 12 hours 16 min ago:
Huh, I always assumed it was because wind speeds would typically be
faster higher up, creating lower pressure to draw up air.
potato3732842 wrote 8 hours 23 min ago:
At first that's true. That's why chimneys all have a more or less
minimum height above the roofline (and people can get away with
little to nothing for a house on a ridge line or like an ice fishing
shack or something).
Beyond the minimum the effect tapers off and what TFA is talking
about starts mattering.
rkagerer wrote 14 hours 1 min ago:
Some shorter, ELI5 answers: [1] I like the backgrounder about Sudbury.
URI [1]: https://www.reddit.com/r/explainlikeimfive/comments/p3m9fp/eli...
Mistletoe wrote 8 hours 19 min ago:
People hate on Reddit but this is why I love Reddit, I got the answer
in a few seconds as opposed to the original article pontificating and
padding forever about it.
tracerbulletx wrote 2 hours 58 min ago:
It's not an article. Its a transcript of an entertaining
educational video on one of the best engineering youtube channels
in the world and a gift to society. It says that it's a transcript
at the top of the text for goodness sake.
kelnos wrote 3 hours 45 min ago:
That's a bit uncharitable towards the article. If you're just
looking to answer a question as simply as possible, you're going to
want a different source than if you're curious about the background
and history of something.
lelanthran wrote 3 hours 34 min ago:
> That's a bit uncharitable towards the article.
I didn't think so; I also tried to read the article, but
spreading out a 20 word answer over what seemed like 2000 words
of navel-gazing got me out of there in a hurry.
lloeki wrote 13 hours 1 min ago:
That's basically what I remember: the leading reason is that a steel
furnace needs a lot of heat to build up a lot of pressure and push
carbon in, and higher chimneys help provide that.
Others like Japan found another way to achieve the necessary
temp/pressure, but it hardly scaled as it needed to during the
industrial revolution.
TBH the "let's avoid smoke" aspect sounds like a retcon, the mythical
London smog is a testament of that.
jodrellblank wrote 9 hours 42 min ago:
> TBH the "let's avoid smoke" aspect sounds like a retcon
Yes, thatâs what the article says:
â When you look at all the pictures of the factories in the 19th
century, those stacks werenât there to improve air quality, if
you can believe it. The increased airflow generated by a stack just
created more efficient combustion for the boilers and furnaces. Any
benefits to air quality in the cities were secondary. With the
advent of diesel and electric motors, we could use forced drafts,
reducing the need for a tall stack to increase airflow. That was
kind of the decline of the forests of industrial chimneys that
marked the landscape in the 19th century. But theyâre obviously
not all gone, because that secondary benefit of air quality turned
into the primary benefit as environmental rules about air pollution
became stricter.â
ErrorNoBrain wrote 14 hours 17 min ago:
i always assumed it was so the factory (and the neighbors and roads)
weren't covered in smoke
e40 wrote 4 hours 53 min ago:
Nah, they care not at all about the neighbors. They built the factory
in the bad part of town for a reason.
wahern wrote 3 hours 7 min ago:
More often poor people moved near industry because the land was
much cheaper on account of it being less desirable. There are some
high-profile modern examples where industry moved into existing
communities, but that's historically atypical.
Of course by the 3rd of 4th generation it becomes a distinction
without a difference. But understanding patterns of development is
important. If today you want to prevent poor people from tomorrow
living in polluted areas, rich people have to make it easier to
build affordably in nicer areas--e.g. allow increasingly dense
development so poor people don't get pushed toward industry.
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