In fact, human use of refrigeration dates back thousands of years. If we want to divide a range, we can basically consider the icy wisdom of ancient people as the era of natural refrigeration. “Ice cellar” storage is one of the first methods of natural refrigeration, that is, ice cubes are stored in winter, placed in the ice cellar and enjoyed again in summer.
This refrigeration technique is primitive and simple, but it is easy to use. People have used it for thousands of years until the 19th century.
For ice cubes to melt, they must absorb heat. So, when building the ice cellar, it must be kept cool on the inside and sealed from the outside. Generally speaking, an ice cellar is much like a semi-basement, partially underground and built near natural ice sources such asfreshwater rivers and lakes to facilitate extraction and storage.
At the same time, people also cover the ice cubes with sawdust, which has poor thermal conductivity, and it can be regarded as a heat-resistant layer for the ice cubes. This will allow the ice cubes to last a few more months and even last until the following winter if handled correctly.
Many ancient civilizations will invariably use this method to store ice. China is one of them, and they did it around 1000 BC. There is a written record of "cutting ice in two days". the third day is accepted in the "Ling Yin" fragment.
In the Song Dynasty, there was also a special ice well department, responsible for storing ice. There are also many types of frozen treats, such as mixing sugar, fruit and juice with ice cubes. Under the dynastyYuan, some people added fruit pulp and milk.
The historical traces left by ice cellars are also found in certain street names:
It should be noted that in China, the equipment for storing ice cubes is very particular "Jian." is also often called an antique refrigerator:
(Bronze Ice Jian of the Warring States Period)
It has a simple and elegant appearance and a ingenious internal. Interestingly, in summer, people can put ice in the bronze ice bowl, so that the wine in the storage area will become cooler and it will become an iced drink to cool down;
But if that's the case, when winter comes, it will still be cold. You can heat the water, and the wine becomes mulled wine to warm your body...
In my opinion, this is not only wisdom, but also art.
The Romans and Jews also had a tasteespecially for the preparation of frozen drinks. The Romans collected snow from the mountains, stored it in pits, and covered it with similar insulating materials.
However, in areas with drier air, such as Egypt, people will choose another cooling method, the “evaporative cooling method”.
We know that evaporation can absorb heat and have a cooling function. This physical phenomenon was discovered by man a long time ago and used in refrigeration.
(Water on the ground evaporates)
In hot climates, foods do not stay fresh for long and some fruits and vegetables can barely last a week. So people will use this type of technology to make preservation tools for their own foods, usually called zeer.
This is a cooler made of two clay pots. Some people also call it plaisanting a can refrigerator.
zeer is very simple to use and small. The box is nested inside the larger box and the space between the two is filled with sand.
The next step is to add water to the sand to keep it moist.
At this point, the outer tank will usually have several holes to help vent air. The inner tank will generally be made of waterproof installations using some local materials, and the entire device will be placed in a ventilated and. dry place.
Finally, put vegetables, fruits and other foods that cannot be marinated into the internal tank, cover it with a damp cloth and switch to refrigeration mode.