汉堡包可以挽救您的烟斗吗?

温馨提示:全文约4228字,阅读全文大约需要5分钟

德克萨斯州的天气状况是一场可怕的灾难。寒冷的温度,以及断电,意味着许多人被困没有热量的屋子里。最重要的是,得克萨斯州的大多数房屋和建筑物并非设计用于长期低于冰点的温度。这意味着也有许多冻结和破裂的水管。

但是每个人都试图使事物发挥作用。您知道什么使橡胶泡沫如此出色的绝缘体吗?

德克萨斯州的天气状况是一场可怕的灾难。寒冷的温度,以及断电,意味着许多人被困没有热量的屋子里。最重要的是,得克萨斯州的大多数房屋和建筑物并非设计用于长期低于冰点的温度。这意味着也有许多冻结和破裂的水管。不好。

但是每个人都试图使事物发挥作用。您可能已经Twitter上看到了这张照片,数据和社会科学家Rumman Chowdhury休斯敦郊区的一家快餐店外抢购,那里显然有一些聪明的人试图用一堆汉堡包将管道绝缘。

我们打电话给这个特定机构的经理,他说他们对此一无所知。因此,如果没有任何intel,我们想知道:这真的有效吗?为什么寒冷的天气里水管会破裂?让我们开始吧。

我们生活一个水世界(H 2 sub> O)中。水以气体(水蒸气),液体(湿的东西)和固体(冰)的形式存。但是水很奇怪。它可以做大多数其他物质无法做到的事情-它作为液体的密度大于它作为固体的密度。

但是,不仅仅是当冰变成冰时水会漂浮。它冻结时会扩展。它必须扩大。如果您有1克液态水,但变成1克密度较低的冰,则它必须占用更多的体积。当液态水变成冰时,这种膨胀是如此强大,以至于它可以从容器中弹出。如果您不小心将一整瓶水留冰箱中,则可能已经看到了这一点,但它也可能破坏诸如钢之类的金属。

这是我实验室中发现的较旧的物理演示。它被称为冰弹-不是因为它是用冰制成的,而是因为冰使它爆炸了。一探究竟。

这是一个很小的钢制容器,顶部装有螺母。将水注满(不留气隙),然后将其冻结。当内部的液态水变成冰时,压力就足以使钢制容器破裂。我一直想这有多棒,因为您通过去除而不是添加热能来使某物爆炸。

因此,想象一下这个钢制容器是进入您家的水管。 (除非收集雨水或由氢气和氧气制成水,否则您可能只有一个。)如果天气太冷,水可能会冻结并实际上使管道破裂。那很糟。现是一些问题和答案。

住宅供水管线几乎总是地下,这是一件好事。尽管从夏季到冬季,气温会发生巨大变化,但地面温度要稳定得多。南部各州,地面温度不太可能低于冰点-因此管道中的水也将超过冰点(并保持液态)。

但是也有一些例外。一些气候温暖的地方,并非水管系统的所有部分都会地下,并会通过空气区域。 (哎呀,我的阁楼上有水管,我住温暖的地方)。尽管冷水(假设为1摄氏度)和暖冰(0摄氏度)之间的温差很小,但能量差异却很大。将水从固相转变为液体需要大量的能量。我们称其为融合的潜热。对于水,其值为每克344焦耳。这可能很难理解,那么举个例子呢?

假设您有一升冰(重约1,000克)。如果要0 C下取冰并将其1 C下转化为水,则将需要344,000焦耳的能量(加上一点点的能量来提高水温)。那是多少能量?好吧,假设您有一台具有3,000 mAh电池(毫安小时)的智能手机。这相当于41,000焦耳。因此,它可能有足够的能量来使您的手机运行一整天,但是您将需要其中八到九个手机来融化所有冰块。

这实际上是一件好事。这意味着您可以使用融化的冰来冷却饮料,而实际上并不需要那么多冰。这也意味着您需要从管道中去除大量的热能以使其冻结。一个寒冷的夜晚可能不足以使管道破裂。

是的。好,假设您水管内。 (是的,您现很小了。)如果水是静止的,您可能会卡暴露于冷空气的管道的一部分中。实际上,您可能会冻结,然后您必须断开管道。但是现假设它是自来水,由稍微滴落的水龙头引起。您仍然是管道中的小人物,但现您也正移动。您穿过冷管部分时会变冷,但不会冻结。相反,您只需移至房屋的其他部分。

哦,可是,地下主要管道中的更多水正进入管道的较冷部分。它会冻结吗?可能性不大。请记住,水管处于地面温度,几乎可以肯定不低于冰点。因此,进来的水不是太冷,希望它不会结冰。

绝缘有帮助。如果将泡沫绝缘材料包裹任何裸露的管道周围,则其作用与冷却器或绝缘饮料杯相同。绝缘降低了通过热相互作用将能量从热的物体转移到冷的物体的速率。如果将冷饮放桌子上,能量会转移到饮料中,导致温度升高。另一方面,将饮料放凉爽的地方,会增加隔热效果,并降低能量传递的速度,从而使饮料升温所需的时间更长。

对于管道周围的泡沫绝缘来说,水比空气要热,因此这会降低能量从水中传递出去的速度。请记住,如果您从水中除去足够的热能,它将使液体从液相转变为固体,这是最糟糕的部分。所以,是的-绝缘那些管道。

现我们越来越认真了。这是您正寻找的答案,我将提供给您。我认为答案是肯定的。是的,将汉堡包放裸露的水管周围会增加隔热效果,并减少管子冻结(破裂)的机会。

但是那将如何工作?好吧,绝对最好的绝缘体之一是空气。它不如什么都没有(真空),但它仍然非常有效,并且比真空绝缘子容易制造得多。实际上,这就是大多数绝缘子的想法:通风。您知道什么使橡胶泡沫如此出色的绝缘体吗?是的,空气。泡沫内部有微小的空隙。那件漂亮的羊毛外套呢?是空气摇粒绒可捕集空气,因此使其成为良好的绝缘体。甚至您墙壁和阁楼上的玻璃纤维隔热材料实际上也只能捕集空气以使您的房屋隔热。


英文译文:

The weather situation in Texas has been a terrible disaster. Cold temperatures, along with the loss of power, mean that many people have been stuck inside their homes with no heat. On top of that, most of the houses and buildings in Texas are not designed for extended periods of below-freezing temperatures. This means that there have also been many frozen and busted water pipes. Not good.

But everyone tries to make things work with what they have. You may have seen this photo making the rounds on Twitter, which data and social scientist Rumman Chowdhury snapped outside a fast food restaurant in the Houston suburbs, where some clever person had apparently attempted using a bunch of hamburger buns to insulate a pipe.

We called the manager of this particular establishment, who said they knew nothing about it. So without any intel, we wondered: Would this actually work? Why do water pipes burst in cold weather anyway? Let's get to it.

We live in a world of water (H2O). There's water as a gas (water vapor), as a liquid (that wet stuff), and as a solid (ice). But water is weird. It does something that most other substances don't do—its density as a liquid is greater than its density as a solid.

But it's not just that water floats when it becomes ice; it expands when it freezes. It has to expand. If you have 1 gram of liquid water that turns into 1 gram of ice with a lower density, it has to take up more volume. This expansion of liquid water as it becomes ice is so powerful that it can break out of a container. You've probably seen this if you’ve accidentally left a full bottle of water in your freezer, but it can also break metals like steel.

Here is an older physics demo that I found in a lab. It's called an ice bomb—not because it's made of ice, but because ice makes it explode. Check it out.

This is a small steel container with a screw nut on the top. You fill it with water (leaving no air gap) and then freeze it. When the liquid water inside turns to ice, the pressure is great enough to break the steel container. I always think about how awesome this is because you make something explode by removing thermal energy instead of adding it.

So, imagine this steel container is instead the water line going into your house. (Unless you collect rainwater or make water from hydrogen and oxygen, you probably have one.) If it gets too cold, the water can freeze and literally burst your pipe. That's bad. Now for some questions and answers.

Residential water lines are almost always underground—and that's a good thing. Although air temperatures can vary drastically from summer to winter, the ground temperature is much more constant. In the southern states, this ground temperature isn't very likely to get below freezing—so water in the pipes will also be above freezing (and stay liquid).

But there are some exceptions. In some places with warm climates, not all parts of a water pipe system will be underground, and will pass through regions of air. (Heck, I have water pipes in my attic, and I live in a warmer location). Although there is a small temperature difference between cold water (let's say 1 degree Celsius) and warm ice (0 C), there is a huge energy difference. It takes quite a bit of energy to change water from its solid phase to a liquid. We call this the latent heat of fusion. For water, this has a value of 344 joules per gram. That might be difficult to comprehend, so how about an example?

Suppose you have a liter of ice (with a mass of about 1,000 grams). If you want to take this ice at 0 C and turn it into water at 1 C, it would take 344,000 joules of energy (plus a tiny bit more energy to raise the temperature of water). How much energy is that? Well, let's say you have a smartphone with a 3,000-mAh battery (milliamp-hours). This is equivalent to 41,000 joules. So, it might have enough energy to run your phone for a full day, but you would need eight or nine of these phones to melt all that ice.

It's actually a good thing. It means that you can use melting ice to cool off your drinks—and you don't actually need that much ice. That also means that you need to remove quite a bit of thermal energy from your pipes to get them to freeze. One cold night probably isn't going to be enough to make your pipes burst.

Yes. OK, imagine you’re inside of a water pipe. (Yes, you are super tiny now.) If the water is stationary, you might be stuck in a part of the pipe that is exposed to cold air. You could actually freeze, and then you would have to break the pipe. But now suppose it's running water, caused by a faucet that is slightly dripping. You are still a tiny person inside of a pipe, but now you are also moving. You pass through the section of cold pipe and you get cold—but you don't freeze. Instead, you just move on to other parts of the house.

Oh, but more water from the main underground line is coming into that cold part of the pipe. Would it freeze? It's not as likely. Remember, the water pipe is at ground temperature, which is almost certainly not below freezing. So, the incoming water isn't super cold, and hopefully it won't freeze.

Insulation helps. If you wrap some foam insulation around any exposed pipes, it does the same thing as your cooler or insulated drink cup. The insulation decreases the rate that energy is transferred from the hot thing to the cold thing through a thermal interaction. If you put a cold drink out on a table, energy is transferred into the drink to cause it to increase in temperature. Putting the drink in a cooler, on the other hand, increases the insulation and decreases the rate of energy transfer so that it takes longer for the drink to warm up.

For the foam insulation around a pipe, the water is warmer than the air, so this decreases the rate of energy transferred out of the water. Remember, if you remove enough thermal energy from the water, it will make a phase transition from a liquid to a solid—and that's the bad part. So, yes—insulate those pipes.

Now we are getting serious. This is the answer you are looking for—and I'm going to give it to you. I think the answer is yes. Yes, putting hamburger buns around an exposed water pipe will increase the insulation and reduce the chance of having a frozen (and burst) pipe.

But how would that work? Well, one of the absolute best insulators is air. It's not as good as nothing (a vacuum), but it's still pretty effective—and much easier to make than a vacuum insulator. In fact, that's the idea behind most insulators: Get some air. You know what makes rubber foam such a nice insulator? Yup, air. The foam has tiny air spaces inside of it. What about that nice fleece jacket? It's air. The fleece traps air and that makes it a good insulator. Even the fiberglass insulation in your walls and attic really just traps air to insulate your house.


Share this Post: