4 ms·

Because steam is warmer than the surrounding air, and thus rises. Anyway, https://en.wikipedia.org/wiki/District_heating https://en.wikipedia.org/wiki/District

• fulafel 4y ago
  Other parts of the world with district heating don't leak steam. Is it just because they use (liquid) water and not steam? The water is still plenty hot enough for steam to form in leaks, so there's perhaps some factor that makes leaks more tolerable in steam systems? Different corrosion concerns perhaps, air leaking in is less corrosive?
  • wongarsu 4y ago
    Our smallish city has district heating with hot water, and no steam rising from the streets.
  • tedunangst 4y ago
    I think it's an American thing. Our pipes are just that much freer. New York and Philadelphia systems leak steam, too.
  • mangecoeur 4y ago
    Steam based systems are just obsolete, steam under pressure leaks easily unless you do plenty of maintenance. Most district heating systems use liquid water in a closed loop. In fact most operators today are looking to further reduce temperatures to reduce losses and improve efficiency. You only let this much steam escape if you really dont care about saving energy/money
    • bobthepanda 4y ago
      The issue is generally for these large historic systems, the capital cost of replacement is larger than the savings. Because the streets of New York had many utilities laid out very early, there’s poor mapping and everything underground is haphazard, and disrupting somebody else’s utility system will get them to sue you.
      • mangecoeur 4y ago
        Well it's more a infrastructure policy issue than a technical one. Steam systems are so wasteful its hard to lose money upgrading them. As you say though, if you have different utilities under different ownership, some state owned and some not, it's more a problem of managing the upgrade as part of a long term infrastructure program if its not coordinated through a central utility provider.
        • bobthepanda 4y ago
          That, and that even if there was a central utility, documentation was not a priority at the turn of the 20th century, and so the locations of infrastructure are either not even mapped or incorrect.
• maxbond 4y ago
  I have a fun tangential story about when steam doesn't rise. In college I would walk past a steam stack on campus every day, because I could see it was always on the verge of making rings (pretty much any cylinder with steam or smoke passing through it or around it is, I've seen rings from incense, boiling rice [the cylinder here is the column of steam bubbles], dropping food coloring into water - if you look for them you start finding them. The craziest example I've seen, which works much like the food coloring, is an airplane contrail.). I thought if I kept it up, one day the wind would blow in just right right way and there would be a beautiful train of rings. I never did see it. But on a hot day[1], I saw the steam settle into the narrow alley next to the building. It formed into a tiny roll cloud, about six feet long. I watch it stunned for about fifteen seconds, and then it dispersed. [1] I'm pretty sure it was a hot day, what I remember clearly was that it was an unusual temperature. I surmise the air was very warm and so the steam was denser than the air. But it may have been a cold day and the steam cooled and then sank, unfortunately I can't say for sure because I didn't write it down.