Since the introduction of cotton, the problem of dressing in the people of the Tang Dynasty in winter has been greatly solved.

After years of development, the cotton planting area of ​​the grasslands in northern Shuozhou can basically meet the current use needs of the Tang Dynasty.

Of course, this planting area continues to increase every year, but the growth rate is not as exaggerated as it was at the beginning.

As the cotton planting area becomes wider, the price of cotton cloth will naturally drop.

Because the nobles in Chang'an City generally have their own cotton plantations in the northern part of Shuozhou, and most people have built their own cotton workshops.

Therefore, the competition in the cotton cloth market in Datang is very fierce.

Whether it was the cotton cloth workshop in Wang's Taiyuan that first introduced water trucks to improve production efficiency, or the use of steam engines later, the price of cotton cloth has been continuously reduced.

In this way, even if cotton cloth completely replaces linen cloth, it becomes the first choice for the people.

Cotton is no longer the expensive price at the beginning.

Dai Quan has the most full experience of this.

As the earliest eighth-level worker under Li Kuan, Dai Quan is now almost sixty years old.

In this era, I am definitely an older worker.

When he bought his first set of cotton coats, he spent about two cents of money before he grabbed one in the treasure pavilion.

Now the same cotton coat can be handled for only a few dozen cents.

However, the dressing problem was solved, Dai Quan still had a small trouble.

He usually doesn't drink tea or soup, but just drinks boiled water.

But in winter, boiling water will cool down quickly after it boils.

But his stomach is not good, and if he drinks cold water directly, he will often have stomachache.

After suffering many losses, Dai Quan no longer dared to drink cold water casually.

But this is also a trouble.

When you are at home, you can cook a pot of water on the honeycomb coal stove, and there is no problem when you want to drink it.

But when you go out, it is not that convenient.

Even if he goes to some workshops and wants to drink hot water, it is not that convenient.

As for the time being on the carriage, it is even more inconvenient.

So in recent years, he has been thinking of ways to see if he can make a heat-insulating device.

Although Dai Quan is old, he has always been easier to learn.

Live until you grow old and learn until you grow old.

This spirit can be fully exerted in him.

Some time ago, he saw a paper by a student from the School of Physics of Guanshishan Academy in the Journal of Science, which was about the transmission of heat.

In this paper, heat conduction is divided into several situations in detail.

"The phenomenon of heat transfer from part of the system to another part or from one system to another is called heat transfer. Heat conduction is three heat transfer modes, heat conduction, convection and radiation..."

Until now, Dai Quan clearly remembers the description at the beginning of this paper.

The problem that had troubled Dai Quan for many years suddenly became a clue.

Since heat is transmitted through heat conduction, heat convection and heat radiation, then make your own container and reduce these heat transfer methods to a minimum. Can you keep the hot water in the container in heat?

Once he had this idea, Dai Quan immediately took action.

After all, he was also a veteran craftsman in the workshops under the Prince's Mansion, and his status was extraordinary.

It is the kind of existence that can directly seek to see Li Kuan.

So it is naturally very convenient for him to make any test samples.

In Dai Quan's view, to make a heat-insulating device, it is necessary to start from the aspects of heat conduction and thermal radiation.

As for thermal convection, whether the water in the cup becomes cold or the water in the teapot becomes cold, it is obviously not the influence of thermal convection.

So he didn't start from this aspect.

However, it seems simple to think about it, but if you really want to do it, there are still many difficulties that need to be overcome.

Whether it is a glass cup, a tin-plated iron cup, or a cup made of bamboo tubes and wood, there is no way to avoid the occurrence of heat conduction and heat radiation.

Although the principles of heat conduction and heat radiation are not particularly clear.

However, based on the papers he has seen, he knows that the heat conduction efficiency of different objects is different.

In other words, if you use different containers to fill hot water, the time it takes for the hot water to cool is different.

Dai Quan went to Guanshishan Academy to find someone to ask for advice, but the results he got were a bit surprising.

In vacuum conditions, the efficiency of heat conduction is the lowest.

This made Dai Quan stumped this moment.

He naturally knew what vacuum meant.

He also went to see the experiment of pulling a bronze ball at the entrance of Shishan Academy.

At that time, I vacuumed the copper ball.

After much trouble, Dai Quan finally turned his attention to the glass workshop and porcelain workshop.

According to his idea, he directly used glass or porcelain to fire a double-layer bottle, and then found a way to vacuum it and see how it worked.

After many tests, Dai Quan finally found a relatively excellent result.

"Master Dai, these are just made double-layer glass bottles. A small hole has been opened at the bottom of the bottle according to your requirements to vacuum."

As an old hero in the stripping workshop, Dai Quan has a very high prestige here.

Even if Chen Dali, the current workshop manager, had to call out Master Dai obediently in front of him.

"Well, put it all there to see how the improvement of the vacuum equipment this time is."

Obviously, it is not the first time Dai Quan has come to prepare samples today.

After struggling for several months, he not only confirmed the best way to make glass bottles, but also asked the Steam Engine Institute to help create a steam engine equipment that can be used to vacuum.

However, due to various reasons in the previous few times, the final vacuum effect should not be very ideal.

Therefore, the thermal insulation effect of the thermos is not very ideal.

Today is the last confirmation he planned. If the hot water in the hot water bottle can remain hot after half a day and still have a certain temperature in twelve hours, then he will prepare to arrange for craftsmen to produce on a large scale.

Such a good thing shouldn't be enjoying it alone.

"From the last time, the insulation effect has been greatly improved after a layer of silver is plated on the inner wall of the glass bottle.

If the vacuum level is further improved, this thermos will definitely become a product that shocked Datang."

He is a part-time teacher at Guanshishan Academy of Geography. After consulting with others in the college, Dai Quan has already gained a deep understanding of the principle of heat transfer.

Vacuum is used to minimize the influence of heat conduction.

Silver plating is to minimize heat radiation, which is also the inspiration found in the principle that silver plating mirrors can reflect light.

Unexpectedly, the results were very good after trying.

After one hour of insulation, it basically dropped to room temperature.

However, after adding a silver plating process, the insulation effect immediately rose to several steps.

If you just put it in one go, you can already successfully push it to the market.

Dai Quan has full confidence that such products can already sweep the market.

But he is pursuing perfection and thinks he can do better with a thermos.

So during this period he has been preparing for how to better vacuum.

Whether it is redesigning the holes used for vacuum extraction in glass bottles or renovating special vacuum extraction steam, it is all for today's final confirmation.

Soon, a special double-layer glass bottle was placed on the vacuum equipment, and Dai Quan started to operate it himself skillfully.

After getting a bottle, there will naturally be a craftsman who will help heat it into it.

After just one hour of hard work, all 100 samples were filled with hot water.

Now I’m waiting to use three to confirm the temperature every half hour, and finally draw a temperature change curve.

If this change curve meets Dai Quan's idea, the glass workshop will be arranged to start mass production of this special double-layer glass.

In order to allow the thermos to be launched on the market faster, Dai Quan has already made people weave an outer frame with bamboo.

At that time, put the glass bottle in a bamboo basket and put cork at the opening, and a thermos that was most popular in the 1970s and 1980s will be born.

The reason why we need to wrap it in a bamboo basket is mainly because of the shock absorption and cost issues.

Later generations generally used iron sheets to make shells.

But the price of iron is naturally much more expensive than bamboo.
To be continued...