404
New York bridge gets stuck open after getting too hot
(www.bbc.com)
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
this post was submitted on 09 Jul 2024
404 points (99.0% liked)
News
36628 readers
592 users here now
Welcome to the News community!
Rules:
1. Be civil
Attack the argument, not the person. No racism/sexism/bigotry. Good faith argumentation only. This includes accusing another user of being a bot or paid actor. Trolling is uncivil and is grounds for removal and/or a community ban. Do not respond to rule-breaking content; report it and move on.
2. All posts should contain a source (url) that is as reliable and unbiased as possible and must only contain one link.
Obvious biased sources will be removed at the mods’ discretion. Supporting links can be added in comments or posted separately but not to the post body. Sources may be checked for reliability using Wikipedia, MBFC, AdFontes, GroundNews, etc.
3. No bots, spam or self-promotion.
Only approved bots, which follow the guidelines for bots set by the instance, are allowed.
4. Post titles should be the same as the article used as source. Clickbait titles may be removed.
Posts which titles don’t match the source may be removed. If the site changed their headline, we may ask you to update the post title. Clickbait titles use hyperbolic language and do not accurately describe the article content. When necessary, post titles may be edited, clearly marked with [brackets], but may never be used to editorialize or comment on the content.
5. Only recent news is allowed.
Posts must be news from the most recent 30 days.
6. All posts must be news articles.
No opinion pieces, Listicles, editorials, videos, blogs, press releases, or celebrity gossip will be allowed. All posts will be judged on a case-by-case basis. Mods may use discretion to pre-approve videos or press releases from highly credible sources that provide unique, newsworthy content not available or possible in another format.
7. No duplicate posts.
If an article has already been posted, it will be removed. Different articles reporting on the same subject are permitted. If the post that matches your post is very old, we refer you to rule 5.
8. Misinformation is prohibited.
Misinformation / propaganda is strictly prohibited. Any comment or post containing or linking to misinformation will be removed. If you feel that your post has been removed in error, credible sources must be provided.
9. No link shorteners or news aggregators.
All posts must link to original article sources. You may include archival links in the post description. News aggregators such as Yahoo, Google, Hacker News, etc. should be avoided in favor of the original source link. Newswire services such as AP, Reuters, or AFP, are frequently republished and may be shared from other credible sources.
10. Don't copy entire article in your post body
For copyright reasons, you are not allowed to copy an entire article into your post body. This is an instance wide rule, that is strictly enforced in this community.
founded 2 years ago
MODERATORS
Dumb question, but why is the water cooler than the bridge? Because it was underground? Or does the evaporation help because it's endothermic?
It's a good question. Steel is very good at absorbing and retaining heat. Water on the other hand isn't. Metals in general have way better thermal conductivity than water.
Exposed to the sun at the same time, a piece of metal will warm up a few times faster than the water. I believe steels can be somewhere around 8-10 times less energy required than to heat a similar mass of water.
The water could even start out slightly warmer than the bridge. Evaporative cooling would also work here since there is plenty of ventilation around the bridge. But that can slow down based upon humidity level.
Because metals have way better thermal conductivity, they aren't good at retaining heat.
Heating equal masses of steel and water the same amount takes exactly the same energy, it just might take longer for the insulator vs. the conductor.
Specific heat of liquid water is around 4. Steel is like .45-.50 or around there. So it would take 450-500 joules to increase 1kg of steel 1C. Would take around 4k joules to increase 1kg of water by 1C.
Isn't your wording on the previous post a bit wrong? Metal isn't good at retaining heat, quite the opposite but it is a lot easier to heat it up in terms on temperature causing the issue in question. The issue isn't that it is retaining heat but the temperature raising quicker as environment gets hotter.
I should have added "compared to the air around it" because that's what I was thinking in my head.
I entirely forgot about specific heat. I am an idiot.
Both. Even the river water below the surface will be cooler than steel that's been sitting in the sun. And putting that cool water on the bridge absorbs some of the heat and is removed in evaporation, just like sweating.
Water also needs a substantial amount of energy to evaporate, hence it will sip some heat from the environment around it when it evaporates. Combined with the good thermal conductivity of steel, the bridge cools off.
You get a similar effect when walking out of a hot shower. The hot water evaporates and cools you down.
I'm learning so much from this post.
Touch the roof of a car in the sun. Shit's hot.
Probably because the metal absorbed heat from sunlight and heated up considerably, but the water was room temp only.
Probably both. Definitely evaporation will remove the most heat if both substances are at the same temperature initially.
Simplified: Energy is stored as heat in matter (the jostling of atoms and molecules) and there are many more water molecules under the bridge than there are molecules/atoms in the bridge. So both the water and the metal heat up during the day and cool down at night, but since there is much more water, the water has a much more stable temperature. In short: Larger volumes of atoms have larger heat capacities.
If the water under the bridge was stagnant and a shallow puddle, then it's temperature would vary much more throughout the day as well, but it would still warm up less than metal or soil, since a body of water loses some of it's heat through evaporation.
This is also why coastal climate is a thing: the huge mass of water in the ocean makes it so that coastal areas are warmer in the winter and cooler in the summer.