奇趣物理实验——热血沸腾
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文献1中提到
By the year 1919, the published
methods for preventing bumping included the addition of chips or
bits of glass beads, porcelain plates, bricks, granite, coal, talc,
and pumice. One author noted that powdered coal was very effective,
while solid chunks were valueless. Another author claimed the exact
reverse. Not one author “measured” bumping; it was “observed”
only.
If a liquid is pure and its
container is clean, considerable superheating is possible as
discussed earlier. Under these conditions boiling could occur in a
cyclic manner: first a quiet, non-boiling period as the liquid
superheats; then an explosion when the nucleation rate becomes
large; and finally a sudden drop in the liquid temperature after
the superheat has disappeared as heat
of vaporization. The process would then repeat. If this view is
correct, cleanliness and purity are necessary for bumping. Addition
of most impurities would catalyze nucleation and decrease bumping.
Glaser's observations, that
superheat (of particular liquids) is destroyed by particles of high
energy radiation, are pertinent to bumping. Glaser calculated that
hard cosmic ray particles struck his small laboratory apparatus at
a rate of about one per half-hour. This would mean that a
large-scale industrial boiler would be struck by cosmic particles
continuously. Thus nucleation should be continuous, and bumping
should be absent in industrial equipment. Of course an alternate
explanation for the lack of bumping in large equipment is the great
difficulty in obtaining sufficient purity and cleanliness.
Before bumping can be studied, it
must be measured. A suggested method has been tried at the
University of Illinois. Bumping in a flask creates sudden pressure
fluctuations. These are used to vibrate a flexible diaphragm. An
electrical scheme is used to measure the amplitude and frequency of
the resulting deflections. Preliminary measurements with methyl
alcohol show quantitatively that a decrease in pressure increases
the severity of bumps, use of a smooth glass surface causes
stronger bumps than an etched glass surface, and emanations from
radium do not affect the course of bumping. The first two
observations are consistent with nucleation theory. The later
observation may mean that methyl alcohol does not ionize readily.
Additional quantitative tests are needed.
酒精灯加热
液体发生暴沸
随后
有个较长的平静期
接着是第二次暴沸
剧烈程度超过第一次
然后持续沸腾
直至烧干
这和自来水的顺序相反
自来水是先持续沸腾
后期出现爆沸
我没想明白
沸腾球持续沸腾时的凝结核
究竟是什么
撤去酒精灯后
停止沸腾
液面上飘着一颗液滴
这种现象也经常在水面出现
左侧玻璃球下方
突然出现一个气泡
迅速膨胀
并将右侧玻璃球内液体吹开
第一次暴沸的余波还未平息
就发生了第二次暴沸
我只观察到一次
将沸腾球竖直放置
也会出现暴沸
第二次比第一次剧烈
这是常见的摆放方式
加热单侧玻璃球
液体发生流动
无法实现暴沸
双侧同时加热
或许可以
打火机在左侧加热
液体却向左侧移动
有些奇怪
有兴趣的读者，可以参阅如下文献，进行深入了解
1：Westwater J W. Boiling of liquids[M]//Advances in Chemical
Engineering. Academic Press, 1956, 1: 1-76.
