Why is it warm

February 10, 14:14

"Moisture-absorbing heat-generating fiber" underwear that warms up when worn.

It's a reassuring ally that survives the cold of winter.

But do you know why it gets warmer?

Challenge the problem!

Problem

"Moisture-absorbing heat-generating fibers" are clothing that utilizes the conversion of water vapor emitted from the human body into water.

Please answer the reason why wearing "moisture-absorbing heat-generating fiber" is warm, referring to the sentence below.

Reference: When the body gets wet, when the water evaporates, it receives heat from the surroundings and feels cool.

(Shirayuri Gakuen Junior High School 2019 renamed)

This kind of science that is used in daily life can also be traced from the knowledge of science.

The reference sentence is a hint.

"When the body gets wet, it feels cool when the water evaporates."

This is related to the "heat of vaporization."

What is heat of vaporization?

Have you ever heard of the word "heat of vaporization"?

If you deepen that knowledge, you will be able to understand the mechanism of "moisture-absorbing heat-generating fibers".

We asked Yayoi Satsumoto, a professor at Yokohama National University, who is studying clothing materials and comfort.

First of all, from the heat of vaporization.

What kind of heat of vaporization is there in daily life?

Mr. Satsumoto:

"When it's hot in the summer, you'll sprinkle water. When you sprinkle water on the ground that has been warmed by sunlight, the phenomenon of evaporation is called" vaporization, "and at that time, the heat is applied to the ground. The heat that is taken from the surroundings is called "heat of vaporization". "

When liquid water turns into water vapor, or gas, it draws heat from its surroundings.

The heat at this time is "heat of vaporization".

As heat is taken away, the surrounding temperature drops.

From steam to water, then ...

But what happens when water vapor turns into water?

Mr. Satsumoto

"What was water vapor releases energy and becomes water, that kind of phenomenon occurs."

When water vapor turns into water, it "releases" heat.

The heat at this time is called "condensation heat".

Based on the principle of "heat of condensation", here is the secret of "moisture-absorbing heat-generating fiber".

In fact, the human body emits water vapor even if it is not originally sweating.

The water vapor is associated with warming the underwear.

Why is wool warm?

This is an experiment conducted by Mr. Satsumoto.

Dry sheep's hair and wool to a humidity of 30% and put them in a glass container.

If you put this in a room with 70% humidity ...

The temperature was 20.5 degrees immediately after it was put out, but it reached 24.6 degrees in about 10 minutes.

Humidity, that is, the amount of water vapor around the wool, increased by more than 4 degrees.

That's how it works.

Water vapor "adsorbs" to the fibers.

In other words, the fibers gathered water molecules on a part of the surface and made them immobile.

As a result, the energy used when moving was released as heat.

Humidity is important for this phenomenon, and it is said that it occurs regardless of room temperature.

Mr. Satsumoto

"The fact that the moving water vapor cannot move means that excess energy is being released there. The energy released is in a state where it is released as heat. The opposite of the heat of vaporization when water is sprinkled, something similar to the heat of condensation is occurring. "

So, the answer to the entrance exam question is,

"Because we use the principle of generating heat to the surroundings when the water vapor emitted from the body turns into water

.

"

Other other futon secrets !?

This "hygroscopic heat generation".

Mr. Satsumoto told me that it is actually happening even with "dried futon".

Mr. Satsumoto

"What the sun is doing is the action of blowing water vapor. Since the" seat "where waiting for water vapor was vacant, the water vapor that came out of the human body was moving freely. It happens that the person is restrained and releases heat. That causes the phenomenon of "warmth". "

The reason we feel warm when we sleep on a dried futon is not because the warmth of the sun remains.

Of course, it is warm due to the heat of the sun immediately after it is taken in, but if it is taken in a little, it will reach the same level as room temperature.

To briefly explain ...

"When a person enters a futon that has dried and dried in the sun, the water vapor that comes out of the body is absorbed, and the reaction called" hygroscopic heat generation "that is the theme of this time occurs. Because ".

As with the mechanism of underwear in winter, there are many things that we don't know yet.

In "Migake, Curiosity!" Of "Weekly Maru-Knowledge News" (broadcast at 9:00 am on Saturday), we will delve into the news every week on the subject of current affairs presented in the entrance examination.

Let's think of "why?", In fact, "in the first place" that you want to know as a Kamakura caster!

You can also review the past on the homepage of the corner.

Please take a look from the link below!

https://www3.nhk.or.jp/news/special/maruwaka-migake/